Principles of Hygiene in the Beverage Industry ISBN 0-620-3

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The Institute of Brewing and Distilling (IBD)

(Previously, The Institute & Guild of Brewing: IGB)

Africa Section

“Principles of Hygiene

in the

Beverage Industry”

First Edition, November 2003 ISBN 0-620-31335-8. Printed by Supreme Printers

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ACKNOWLEDGEMENTS This book has been prepared by the following:

• John Cluett, MPhil, (Mechanical Engineering), F.I.Brew, PrTech(Eng). • Dave Rowlands, BSc. Eng, M.I.M, CEng. • Dumisani Khanyile, BSc(Hons) (Chemistry) • Gavin Hulse, BSc(Hons) (Microbiology), MSc, Pg.Dip.Malt.Brew.

Material used in compiling much of the content of this book has been sourced from the following, whose contribution is gratefully acknowledged:

• South African Breweries, Ltd. • Southern Africa Stainless Steel Development Association. • Columbus Stainless. • EHEDG (European Hygienic Engineering &t Design Group). • GEA Tuchenhagen. • Toftejorg A/S. • Loctite. `

Photographs and drawings of specific suppliers’ equipment shown in this book are only used to demonstrate a particular feature related to the principles of hygiene. Special acknowledgement is also made to the following who have contributed to the presentation of this book.

• Mike Norton, Mike Williams, Bob Stafford, Tim Ellis Cole and MZ Pienaar of South African Breweries.

• Anne Schamotta for assisting the final presentation of the manuscript. • IGB Africa Section Committee for their encouragement and endorsement of the learning

solution.

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PREFACE The aim of this book is to compile a holistic approach to ‘Hygiene Engineering in the Beverage Industry” that can be used by the industry at large at different Management and Operational levels. This book is also compiled as a learning solution for “Hygiene Engineering in the Beverage Industry” course that the IGB Africa Section is offering to its members and non-members. The structure of this learning solution is designed to satisfy the following outcomes; • Recognise the current knowledge and competence of the learners before they come on the

course. • Through group work and stepwise interventions of the facilitators, introduce the learnings from

the Modules so that it raises the competence of the learners. • Apply the new acquired knowledge to measure the competence of the learners at their work

environment, in cooperation with their managers. In the compilation and design of this learning solution, care has been taken to apply the principles of competency acquisition as defined by the South African National Qualification Framework (NQF) which is aligned to other similar programmes in Europe, Australia and New Zealand. We encourage all relevant persons to use this book in their studies and research. Any part may be used or copied (but not in whole) in the furthering of knowledge in this vital mission to ensure safe and healthy practices for the manufacture and distribution of food and beverages. We now add to the global effort of the WHO and other international bodies and organization that strive for the same mission. We also request comments on the content that should be directed to: The Secretary of The Institute and Guild of Brewing, Africa Section, P.O. Box 26907 HOUT BAY 7872 SOUTH AFRICA Email address: [email protected] Website: www.igbafrica.co.za The Institute and Guild of Brewing, Africa Section (now the Institute of Brewing and Distilling) accepts no responsibility and no liability for the statements, opinion or other material contained in this publication.

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Learning Solution Course Material

for

“The Principles of Hygiene in the Beverage Industry”

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Course material has been compiled by John. D. Cluett of IGB Africa, Dave Rowlands of Southern Africa Stainless Steel Development Association, Dumisani Khanyile of P.Curate and Gavin Hulse. References to bibliography are made extensively from various sources and are acknowledged from:

• South African Breweries, Ltd. • Southern Africa Stainless Steel Development Association. • GEA Tuchenhagen. • Toftejorg A/S. • EHEDG (European Hygienic Equipment Design Group) `

Special acknowledgement is made to the following who have contributed to the compilation of the information and final presentation of this document.

• M Z Pienaar of South African Breweries. • John Tarbaton of Columbus Stainless. • Anne Schamotta for assisting the final presentation of the manuscript. • IGB Africa Section Committee for their encouragement and endorsement to

proceed on this project.

The design of the course material has been done to conform to the extent possible with the guide lines of the National Qualification Framework in South Africa.

Index

Learning Solution Course Design

Module 1 “Define Food Safety Legislation and how it applies to the brewing/beverage industry” Module 2 “Identify the principles applied to plant design, materials of selection, environmental conditions, and how they impact on hygienic levels and corrosion.” Module 3 “Describe the use of stainless steel as the material of choice in a hygienic environment Module 4 “Identify the factors that impact on the cleaning of the surfaces” Module 5 “Describe the methods to measure and inspect the surfaces”

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Module 1

Objective: “Define Food Safety Legislation and how it applies to the brewing/beverage industry”.

Outcomes

• Define Food Safety Legislation at international level and how it is applied in your plant

• Explain the importance of Due Diligence within the Food Safety Legislation when a

Consumer Product complaint is recorded at your plant.

• Define and apply HACCP to identify and analyze a problem in the plant.

Food legislation.

International regulations

The World Health Organisation (WHO) / Food and Agriculture Organisation (FAO) Codex Alimentarius Commission states “People have the right to expect the food they eat to be safe and suitable for human consumption” This implies that the consumer is not expected to check for foreign objects, chemical or biological contamination before consuming the product. The product should be safe by default. The World Trade Organisation (WTO) Sanitary and Phytosanitary (SPS) Agreement, states “Members have the right to take SPS measures for the protection of human life” Countries who are members of WTO are allowed to legislate for the purpose of protecting their citizens. In case of developed world they will have to help the developing nations to comply. The international food safety legislations have been tied to HACCP to bring focus on preventive measures. HACCP was adopted by WHO in 1969 as part of Food Standard Programme. Also part of this programme is Food Hygiene principles or food industry GMP. The 1993 EU (European Union) Directive on Food Hygiene put the momentum around the World on promulgation of food safety regulations that are in line with HACCP principles. This EU Directive required EU member countries to have HACCP type legislation in place by 1995. Because of the size of the European market, most countries outside Europe had to follow suite in order not to lose out. In the United States, FSIS (Food Safety Inspection Services) of US Department of Agriculture guide the implementation of HACCP in identified food related industries. The UK Food Safety Act of 1990 hinged around companies who manufacture or handle food to be able demonstrate due diligence. In South Africa, the HACCP legislation NR 495 was promulgated as part of Foodstuffs, Cosmetic and Disinfectant Act. HACCP is meant to be system that manages or control food safety hazards but it is important for manufacturers or food handlers to design out these hazards. This means that the location, premises, equipment and practices should be in such a manner that they do not introduce hazard e.g. locating premises in an area prone to floods or using equipment not designed for cleanability will result into unmanageable hazards. Because of this requirement, HACCP legislations included the application of good hygiene principles as an “infrastructure” for HACCP system.

Company policies and procedures

The company policy on food safety are developed and aligned with the organisation’s vision, mission statement and values. The policy should be consumer focused. It should spell out the product safety system that will be used and how it will be regularly reviewed for continual improvement and to guarantee effectiveness.

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Other product safety policies and procedures are integrated with quality assurance measures like documentation and record keeping, corrective and preventive action, management reviews and managing consumer satisfaction.

Risk Management

Food safety measures are part of risk management of an organization. The failure to produce safe and suitable food product will affect the brand, which in turn reduces revenues, which results into losses and profit warnings. When this occurs, the company value is negatively affected and shareholders’ worth is reduced. Turnbull’s requirements on risk management or Cadburys and King’s reports on Corporate Governance requires that Board members should do everything possible to protect shareholders’ funds. A functional food safety management system reduces the risk of losses that might be incurred due to product recalls; litigation or civil law suites above all protect the brand integrity. Risk assessment of all potential hazards should be conducted to establish the risk level as low, medium or high. Appropriate control measures should be instituted where risk is too high, measures of designing out the hazard should be considered.

HACCP

HACCP stands for Hazard Analysis and Critical Control Point. This a food safety management system which was developed by NASA in the late 60’s to ensure the safety of food that was going to be consumed by Astronauts during the space mission. The HACCP system was later adopted by WHO as part of Food Standard Program. Since then, HACCP has been legislated in many countries as a consumer safety or system to demonstrate due diligence.

HACCP system is implemented by applying six internationally recognized principles, which are: Identify hazards in very process step;

• Determine critical control points; • Establish critical limits for control points; • Establish critical control point monitoring procedure; • Establish documentation and record keeping procedure; • Establish HACCP review system.

The implementation of HACCP system is a team effort therefore the failure or success of the HACCP system will rely on the composition of the team that did the HACCP study with respect to expertise in product, process, technology, etc. and the quality of facilitation. A HACCP facilitator should be appropriately trained in GMP and HACCP system and the implementation thereof. A HACCP system should be deployed and managed according to company policies and reviewed regularly for continual improvement and effectiveness.

Security in the plants and in the manufacturing process.

Food and beverage industry is sometimes faced with tempering of product with the intention to injure or render consumer sick. This may be done by employees of the company or external persons or extortionist. HACCP is product safety management system, which focuses on the hazards associated with the production processes. HACCP is not intended for product tempering or preventing malicious damage to product. However, some of the HACCP principles can be adapted to identify potential modes of tempering with the product and risk analysis conducted. The focus on potential tempering can be internal and or external. The security measures put in place should cater for both. Special security measures are put in place to guard against internal tempering, which

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include structural redesigns in manufacturing processes to eliminate potential areas of tempering. External or market place intervention will require using packaging that is temper proof. Analytical tests are also used to check for indicators that will tell whether the hazard was introduced during manufacturing or in the trade e.g. enzymic test for pasteurized product used to pick up whether a cockroach got into the product during processing or after manufacturing.

Due Diligence.

Due diligence is a method of defence used by business to demonstrate that they took all reasonable and humanly possible steps to prevent an offence from happening. From the food safety point of view, due diligence defence will relate to manufacture, sale or distribution of unsuitable and unsafe food, incorrect labeling or description of food, inappropriate consumer related information about product storage and preparation and non-compliance with food safety standards. In the case of beer it will mean putting together a system that will ensure that physical or chemical hazards that will negatively affect the safety of the beer drinker are not present in beer.

Contamination prevention

A contamination of food from can render food unsafe and unsuitable for human consumption. Preventing contamination in a food product is the key to consumer safety. The prevention of contamination requires focus on all components of production; raw materials quality assurance, plant location, plant hygiene, the design and layout, process control that includes temperature and moisture control, plant maintenance, waste management and pest control. To prevent contamination, a systematic approach is required. Most of the prominent cases of reported contaminations or food safety incidents in beverage products have been linked to raw materials (1.2.3). The HACCP system focuses on preventing contamination by adopting systematic approach to food safety management. Contamination of beverage products like beer comes in three forms, chemical contamination due to cleaning product residues, or formation of carcinogenic compounds due to the presence of nitrate reducing bacteria, physical contamination due broken glass or other solid objects and lastly microbiological, like the presence of pathogenic bacteria. Fortunately beer does not support growth of pathogens, the only concern is spoilage microorganisms.

Showing how Due Diligence has been practiced.

The Due Diligence requires a company to demonstrate that they are doing everything possible to safeguard the safety of consumers. The adoption of a food safety system like HACCP helps in due diligence defense.

Case study of Due Diligence

There are a couple high profile cases of product contamination that have resulted in huge financial losses due to product withdrawals and recalls. When these cases occur, they result into losses in revenues, profit warnings and subsequent collapse in share price.

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CASE 1 Incident Bass Breweries recalled beer due to contamination by glycol. This incident occurred during World Cup in France, 1998. This resulted into profit warning and collapse of the share price. The loss was estimated at $20m. Cause This was caused by leak of glycol at the paraflow.

CASE 2 Incident Budweiser recalled beer packaged in twist off from ten European countries after glass complaints. The cost of recall was not disclosed. Cause The problem was caused by moulds used in producing bottles in Spain and Portugal. This resulted into oversize neck, which made bottles prone to breakage when opened

CASE 3 Incident In Belgium in 1999, school kids got sick after drinking Coke. Coca Cola had to withdraw Coke in Belgium, France and The Nederlands. The total cost was estimated to $70m. Subsequent to this Coca Cola learnt that they were not geared for quick response for incidents like these. Cause The problem was due to contaminated CO2, which was linked pesticide migration from the pallet.

Not related to these beverage cases was Ford and Firestone saga. Ford Blazers were in accidents caused by back tyre burst. These tyres happened to be Firestone tyres. The matter ended up with laws suite from the victims and the intervention of US Congress. Obviously in these cases we can put the blame on the failure of supplier quality assurance systems and poor maintenance plan.

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HACCP Plan

HACCP team

The purpose of having a HACCP team is to ensure that the HACCP studies are conducted by a competent multidisciplinary team. The team comprises of technology, process and product experts including quality assurance and microbiology experts. Heading the team is the HACCP facilitator who reports to the executive representative on product safety matters. Since HACCP is legislated in many countries, team members should be officially appointed by the most senior person on site like General Manager, CEO or Managing Director. The responsibilities of the team members should be spelled out and their duties included in agreed performance measures.

HACCP Organogram

ExpertTechnology

ExpertProduct

ExpertProcess

ExpertMicrobiology

ExpertQA

HACCPFacilitator

ManagementRepresentative

(Executive)

MD, CEO, GM

HACCP Scope and Product description

HACCP study will start and end at a certain point. It is preferable to scope the HACCP study in a manner that will allow to conduct HACCP study in areas that the team has control e.g. from manufacturing (brewing, packaging) to distribution warehouse. The product is described fully by including physical and chemical properties. The properties that will affect the consumer safety are highlighted. Beer is described as an alcoholic drink made fermenting the wort of malted barely. The product has pH between 3 and 5 and made bitter using hop alpha acids. The presence of hop alpha acids and low pH will render growth of microorganisms difficult in the product

Identify product use

The use of the product is identified to gauge the consumer safety risk associated with the target market. For instance when the product is used by infants or elderly, the risk would be high.

Process flow diagram (PFD)

The process flow diagram is used to describe how the product is made. A good PFD will include inputs, sub processes, process and bye-products. This will sound too detailed but when HACCP is integrated with system like ISO 9000 and 14000, it works very well.

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Process Area: HACCP Plan: REV NO. Inputs Sub-Process Process Bye-Product

Managed through Managed by Raw Materials QA ISO 14001 and part of GMP System

PFD Verified by: Job Title: Signature: Date:

On site investigation of PFD

It is important for the HACCP team to walk the plant and verify the process flow diagram. Once verified it should be signed off by a relevant person like Engineering Manager as the true reflection of the process flow. The signing off should be treated as a control document to cater for process modifications that may happen in future.

Identification of hazards

Hazard identification is the step in HACCP study that is very important and its effectiveness relies on the composition of the HACCP team. Any under representation of disciplines will show by missing some of the hazards that are critical for consumer safety. The hazard identification process involves the identification of all hazards that may affect consumer safety in every process step. For HACCP purposes hazards identified should be limited to those that may affect consumer safety otherwise the process losses focus. Hazards that may come with the raw materials should be handled by raw materials quality assurance system. The raw materials specifications must comply with food grade requirements as indicated elsewhere. Food Chemical Codex 4th Edition is good source of information of food grade specifications. It is an internationally accepted document put together by Codex Alimentarius Commission (Food Code Commission), which is Joint Committee of WHO and FAO. Sometimes the Joint Committee of Food Additives (JECFA) specifications are used. Individual countries sometimes prefer to use specifications from their own local regulating body like USFDA in the USA or relevant EU Directives in Europe. In South Africa, regulations from Foodstuffs, Cosmetics and Disinfectants Act are used as well. These regulations, codes or directives will cover food grade specifications of every material, water, additives, ingredients, colourants, water treatment chemicals, flavourants, grease/oil/ lubricants including hoses. There are also codes governing the use of cleaning and sanitizing chemicals. In other words, raw materials quality assurance is very important for food safety from specifying correctly and regular supplier surveillance.

Determination of CCP’s

Once hazards have been identified, critical control points (CCP) are determined using a decision tree. The definition of a critical control point is a process step or procedure where significant

Milling

Mashing

Malt

Premixing

Bottle

Water

Steam Lautering

Spent Grain

CO2

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control can be exerted to prevent or eliminate a food safety hazard or reduce it to an acceptable level. The decision tree goes through four questions, which should be answered to determine whether the hazard identified has a critical control point. If the hazard has no critical control point, the process step or procedure should be modified to either control the hazard or design out the hazard. A hazard can have more than one CCP. If the decision tree is not used properly, an organization may end up with too many CCPs, which can be difficult to manage or have too few CCPs, which will compromise consumer safety. Below is an example of the decision tree.

CCP Decision Tree

Does a control measure exist ?Q1

Is the step or procedure specifically designed to reduce or

eliminate the likely occurrence of a hazard to an

acceptable level?

Is the control at

this step necessary

for consumer safety

Is the control at

this step necessary

for consumer safety

Modify

step or

process or

product

No

YesYes

Q2

Not CCP- StopNo

Could contamination with identified hazard

occur in excess of acceptable level or could it increase to

unacceptable level?Q3

Will a subsequent step eliminate identified hazards or

reduce likely occurrence to an acceptable level?

Yes

No

Not CCP- StopNo

Q4

CCPNot CCP- Stop

No No

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Targeting levels & critical levels

Critical or targeting level is the minimum or maximum level the control parameter is set at in order to control the hazard e.g. let’s say 600C is the critical temperature that needs to be achieved in order to kill a certain pathogenic microorganism in a specified process step; 600C is the critical level of temperature. These levels should be established and validated to ensure that the CCP is effective in reducing the hazard to acceptable level.

CCP Monitoring Procedures

The CCP should be monitored appropriately to ensure effective control of the identified hazards. The monitoring procedure should spell out what is being monitored at what critical level, to control what hazard, what is the frequency of monitoring and who is responsible for monitoring the CCP. The record keeping of the CCP monitoring should be described. As part of monitoring procedures, verification procedure should be in place to ensure that CCP monitoring is always working.

Corrective/Deviation Action

Corrective or deviation action procedure describes what will be done to the product or process if there was an incident of exceeding the critical limit of the CCP. This is normally linked to the company correction/preventive action system. Records of deviation or corrective actions should be kept as per company recording keeping procedure.

HACCP Review

Regular review of HACCP system will ensure that the system is effective in providing consumer safety and that the system is continuously improved. The regular review of the system is done through internal audits, management reviews and HACCP certification programme. HACCP plan review triggers should be in place to ensure that the HACCP system is updated whenever necessary. These HACCP review triggers include, change in product formulation, change in raw materials, plant modification, increase in specific consumer complaints related to safety and change in food safety legislation.

Documentation

To maintain the HACCP system will mean proper document control and record keeping system. HACCP document control procedures should be integrated with the procedure used for ISO or any other quality assurance system. Record keeping procedures should comply with legal requirements with respect to duration.

Consumer complaints related to product safety

The consumer complaint system for the HACCP purposes should allow the separation of quality related complaints from the safety related complaints. The complaints should be analyzed for trends to be able to take appropriate corrective action.

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Module Two

Objective: “Identify the principles applied to plant design, materials of selection, environmental conditions, and how they impact on hygienic levels and corrosion.”

Outcomes

• Define the key principles applied in the design of warm and cold process plant, their materials of construction and the environment to which they are subjected.

• Identify the key factors that ensure optimum hygiene in the plants. • Identify the key factors that prevent surfaces from corroding so enhancing levels of hygiene.

Process Environments

Process

Underlying Principles

In the food and beverage industries the process is defined by the raw materials that have to be converted to the finished product for human consumption. The processing techniques and hygiene requirements have to be developed over time to ensure a reliable and efficient manufacturing operation that has to conform to the required Food and Safety regulations and Good Manufacturing Practices. The key principles applied to the manufacturing processes are as follows; • Design of plant to meet process requirements to ensure optimum transformation of the raw

materials. • Fabrication of plant and equipment to meet the design specifications and fabrication codes of

practice. • Plant and equipment must be maintained to industry standards to reduce the risk of failure,

safety incidents and product contamination. • Quality control of all materials, processes, product and services are aligned to company and

acceptable industry standards. • Management of hazards in the manufacturing and distribution chains meets national and

international standards. • Training of all operational personnel and stakeholders achieves the required competency

standards in the specific functional areas. In the process design of the plant, the transformation of raw materials into the final product falls into two categories:

o Hot processes. o Cold processes.

The design, fabrication and maintenance of the operations in either the hot or the cold environments requires specific attention to ensure the cycles can be maintained to specification in all working conditions. The key factors are as follows:

• Defining the capacity of the plant is dependant on the batch sizes and the annual through put. • Materials used in the fabrication of equipment have to withstand all process and cleaning

conditions without impairing the product. Corrosion of the equipment must be prevented. • Due to different environmental temperatures, the implication of microbiological spoilage of the

product or attack of the surface material is possible. All precautions must be taken to understand both the nature of the microorganisms and how these can be eliminated.

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• All surfaces of the equipment have to be accessible for inspection and cleaning either by automatic cleaning systems (CIP), or by hand as required.

• All heating and cooling media used in the process must be safe for the product being manufactured and for the operators and maintenance personnel that work in the plant.

Figure 2.1 “EHEDG Concentration of microbes in a manufacturing and distribution chain” shows the relative changes in the microbe concentration in the overall chain.

09.08.200112/08/2003Knuth Lorenzen, EHEDG Executive Committee

raw

materials

P

processing heat

treatment

processing

packagingstorage

distribution & shelf life

concentration of

microbes

acceptable at

time of:

consumption

production

cleaning &

sanitation

required

ultimate time

of consumption

19.10.2001 Knuth Lorenzen, GEA & EHEDG Executive Committee Figure 2.1 “EHEDG Concentration of microbes in a manufacturing and distribution chain”

Practical Considerations

The process of producing beer is taken as the example throughout this module to demonstrate the practical consideration, given the demanding requirements on plant design, detailed biochemical and biological processes, as well as the extensive international manufacturing infrastructure of this industry. Added to this is the worldwide acceptance of beer as a beverage with a long tradition, now manufactured and consumed extensively in all parts of the world. The standards set for the brewing and sale of beer can be considered as a benchmark for most food and beverage industries. The brewing process is based on the transformation of raw materials rich in sugars and protein (i.e. malt, maize, rice and liquid sugars that can be produced from either maize or barley) in a “hot” process. Hops are added to this extract (wort), to give the characteristic flavour and aroma of beer. The wort is cooled and fermented with a specific strain of yeast to convert the extract to alcohol and carbon dioxide, followed by a natural subzero centigrade stabilization process, and then filtered prior to packaging. The final product is packaged in bottles, cans or kegs, or transported in bulk for further processing. The mass balance of the brewing process can be expressed in terms of “kilograms of dry matter per hectoliter finished beer”, and given the importance of water in the process, its usage can be measured in “water expressed in cubic meters per hectoliters of finished beer”. Figure 2.2 shows this process mass balance of beer production.

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Figure 2.2 “Process Mass Balance’

Both of these measurements demonstrate the strict economic management that is exercised in the process and the plant used in the production of beer. The factors are as follows: • Extract from raw materials has to be transformed to alcohol and carbon dioxide under strict

conditions, given the cost of raw materials and the implication on Customs & Excise duty levied on the alcohol content of the packaged product.

• Solids have to be removed from all surfaces to ensure that optimum hygienic conditions are achieved and corrosion is prevented.

• Effluent discharges are strictly monitored to reduce costs and to prevent contraventions of environmental regulations.

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The “Hot & Cold Processes” as shown in Figure 2.3 and “Packaged Product Processes” as shown in Figure 2.4, define the manufacturing chain of beer production.

Figure 2.3 “Hot & Cold Processes”

Figure 2.4 “Packed Product Process”

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Process Plant


Mills

Mills crush the malt and separate the husk from the endosperm that contains the extractable sugars and protein. Milling can be performed either in dry or wet conditions. In both case care must be taken to keep the equipment clean from dust and infestation in the dry mills and free from microorganism in the wet mills. In the case of wet mills, spray balls are fitted to allow for CIP of the internal surfaces.

Vessels

All vessels used in the hot processes are constructed in stainless steel. Previously they were constructed from copper, but this material is rarely used now due to the greater adaptability of stainless steel to the higher hygienic conditions now required in the food and beverage industries. These vessels are all equipt with spray balls or rotary jet cleaners for CIP. Effective access to vessels for cleaning, inspection and sample taking is critical to ensure optimum operations. This aspect is assured at the time of design and fabrication. Examples of this can be seen in the photographs of brewhouse vessels and fermenting vessel shown in Figures 2.5, 2.6 and 2.7. These photographs also show the environment around the vessels that allows good access for cleaning in the work area.

Figure 2.5 “Brewhouse work area”

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Figure 2.6 “Brewhouse vessel”

Figure 2.7 “Vessel in cold cellar area”

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Where agitators are required, these are designed to give the correct mixing action and to facilitate cleaning of all the surfaces. Vessels are designed with specific height to diameter ratio and with falls toward the outlets to allow for effective drainage. Inlets and outlets of vessels are also designed to prevent undue turbulence to the product and to prevent vortexing when emptying. Both of these conditions cause excessive aeration of the product that is detrimental to its quality. A good example is a whirlpool used to separate the hot trub (protein coagulated during wort boiling) from the wort after boiling. The photo shows a clear ring around the sediment in the centre, demonstrating the effective operation resulting from an optimum vessel design and good boiling process of the wort. The rotating cleaning jets, which can be seen in the centre of the sediment, ensure that it is rinsed out effectively before the next brew enters the vessel. The vessel is also fitted with spray balls at the top so that the entire surface is cleaned effectively between each brew.

Figure 2.8 “Whirlpool vessel”

Temperature probes, level probes and sample cocks are fitted to the vessels to allow for control of the process. The attachment of fittings to all vessels requires careful fabrication to ensure hygienic standards are maintained. In the case of vessels used in the hot processes, special shrouds are fitted to ensure that there is no moisture ingress at the area where the fittings are welded onto the vessel. The following picture in Figure 2.9 shows the correct design and fabrication of the shrouds for temperature probes and sample cock

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Figure 2.9 “Vessel in hot process with correct shroud details”

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Pipes

All pipes are made of stainless steel to allow for effective cleaning with hot chemicals used in the CIP systems. The correct layout and diameters of these pipes is critical to maintain the required falls and flow rates for the process and for cleaning. Figure 2.10 “Process piping installation” shows an example of a piping system in a cellar area. Where pipes are insulated to prevent heat loss or uptake, the correct insulation procedure is critical to prevent corrosion as well as to prevent a hazard for the operating personnel.

Figure 2.10 “Process piping installation”

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Valves

Process valves are made from stainless steel to allow for effective cleaning with hot chemicals used in the CIP systems. The design of these valves and seats allows for minimum entrapment of microorganisms as shown in Figure 2.11 “GEA Type EL valve”

12/08/2003 Page 12 Hygienic design of process lines and valve-matrix Knuth Lorenzen, EHEDG Executive Board

Hygienic

metal stop

No gap to product side

Figure 2.11 “GEA Type EL valve”

Fittings

Fittings to vessels and pipes perform specific duties such as control or monitoring of temperatures, pressure, flow or conductivity. These fittings must be fabricated and then welded to the plate so that there are totally smooth internally and externally to prevent any entrapment of soil or microorganism. Figure 2.12 “Pressure Gauge” shows an example of how a fitting is design for optimum hygiene requirements.

Figure 2.12 “Pressure Gauge”

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Pumps

The transfer of liquid products from one step to the other is carried out by means of pumps within a totally enclosed environment to achieve the required level of hygiene. There are different designs of pumps to fit the consistency and fluid characteristics of the product. Their correct selection is critical for the process in question. Figure 2.13 “Centrifugal Pump and impellor for Hygienic requirements” shows the design of a pump commonly used in the brewing environment.

Figure 2.13 “Centrifugal Pump and impellor for Hygienic requirements”

Heating & Cooling Surfaces Vessels used in the hot or cold processes are fitted with surfaces that either contains a heating medium or cooling medium dependant on the purpose of the vessel. Brewhouse vessels have heating surfaces welded onto the outside of the bottom or sides of the vessel. The heating medium is supplied at a temperature that ensures an effective transfer of heat into the filled vessel. Dissipation of the heat into the product is assisted by an agitator or through natural convection. The surface has to be kept clean at all times to ensure an effective heat transfer and avoid scale or soil burning on or accumulating over time. This scale or soil impacts on the product quality and causes corrosion of the surface over time. The welding of the heating or cooling jackets on to the vessels requires strict fabrication procedures to prevent failures and corrosion that ultimately lead to failures and hazards to the operating personnel and the product in the vessel. There are numerous examples documented of such failures in the food and beverage industries. Figure 2.14 “Dimple weld on brewing vessel” and Figure 2.15 “Design of cooling coil for fermenting vessel” show examples of the type of coils used in these applications.

Figure 2.14 “Dimple weld on brewing vessel” Figure 2.15 “Design of cooling coil for fermenting vessel.

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Heat exchangers Heating or cooling processes are enabled by the use of heat exchangers that are positioned on the outside or the inside of the vessels. They are also positioned in a piping system to heat or cool the product on transfer. The surface of these heat exchangers (plate or bundle design) is susceptible to build up of scale or soil on both sides of the heat exchange surface. Care must be taken to eliminate these scales or soils as they reduce the effectiveness of the heat exchange process, cause corrosion or even give rise to off flavours and infection of the product. Figure 2.16 “Heat exchange pipe bundle in wort boiler” shows the pipes in the heat exchanger clear of any scale as a result of effective CIP.

Figure 2.16 “Heat exchange pipe bundle in wort boiler” Should heat exchange surface corrode or fracture, the product and or the cooling/heating medium can be contaminated depending what side the higher pressure is. The heating or cooling media traditionally used in the brewing industry are:

• Heating media: Steam or high temperature water • Cooling media: Ammonia as direct cooling of process vessels and heat exchangers, glycol

solutions, alcohol solutions, brine solutions, dry ice (solid CO²), chilled water 1°C. Although all media must be approved for use in the Food and Beverage industry, the operating pressures are such that they may cause hazards to operating personnel and cause serious effluent spills in case of plant failure. Continuous maintenance and cleaning of all heating and cooling systems is critical for the safe operation of the plant. There are examples of serious incidents with financial implications arising from failures to heating and cooling systems.

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Agitators Agitators are used to mix solid materials with water or to mix various liquid products together. In the design of agitators, excessive turbulence must be avoided to prevent air being drawn into the mixture, as this is detrimental to the product. A good example of a complex design of an agitator is the rake of a lauter tun. This rake cuts the thick mass of grains (350 to 400 mm thick) to allow for filtration of the strong wort and then assist in the sparging or “washing out” of the extract in the grains. The rake is also used for discharging the spent grains at the end of the filtration process. The vessel is then cleaned of all residual solids by means of spray balls that are positioned at the top and bottom of the vessel under the false plates. Figure 2.17 “Lauter Tun” shows the inside of the vessel with the raking mechanism and the grains.

Figure 2.17 “Lauter Tun”

27

Fillers

Fillers for bottles, cans or kegs are designed for maximum hygienic conditions during the filling and sealing or crowning process. CIP of fillers with or without tube “bottles” inserts is carried out at regular intervals. Seamers or crowners are jetted with sterilants to prevent contamination. In some cases of aseptic filling, the entire filler crowner-seamer unit is enclosed in an airtight room that has an over pressure and fitted with UV sterilizing units. Aseptic filling is preceded by strict quality control on the incoming product, cans/bottles/kegs, and can be followed by pasteurization of the product in the can or bottle. Figure 2.18 “Filler crower unit” and Figure 2.4 “Packaged Product Processes” below show the details.

2.18 “Filler crowner”

28

Figure 2.4 “Packaged Product Processes”

CO

2to

pp

res

su

re

Dra

inc

he

mic

als

Pasteurizer

Filled bottles or cans can be tunnel pasteurized after filling. Beer can by flash pasteurized prior to filling by pumping it through a heat exchanger to raise the temperature and obtain the same effect to kill the beer spoilage organisms as done in a tunnel pasteurizer. This process requires an effective CIP process as the beer must then have the same high standards as in ascetic filling. Control of the pasteurization process is done by means of calculating the Pasteurization Units. Product exposed for one minute at 60°C = 1PU. A critical part of the pasteurization plant, is the treatment of the water recovered from the pasteurizer baths to reduce the water usage in this process. In this water recovery, the over flows from the water baths (at 50°C to over 60°C) have to be cooled and returned to the pasteurizer. During this process, bottles and cans leak or break spilling beer into the water. This makes the water acid (beer p H 4.0) and also contaminates it with a medium that is rich in sugars that creates a heavy biofilm in the water recovery system. Corrosion of bottle crowns and the stainless steel sections of the pasteurizer and water recovery plant structure are also affected. Figure 2.3 shows the principle flow of the recovery system. Maintenance of the water recovery plant through chemical additions is a key factor in operating the pasteurizer. Figure 2.19 “Pasteurizer plant” shows the layout of this equipment within a packaging hall environment.

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Figure 2.19 “Pasteurizer plant” (pasteurizer on right of the picture) Kegs: dispensing product to the customers When dispensing product to the customers in draught, the beer is stored in kegs (stainless steel or aluminum) previously washed, steam sterilized and filled at the brewery. When the keg arrives at the sales outlet it is connected to the dispensing system that allows for beer to be pushed out under pressure of CO², and in some cases nitrogen, to maintain its quality in the glass. Between the keg and the dispensing tap, a cooler is located to lower the temperature of the beer. This system requires regular and careful cleaning with water and chemicals to ensure the biofilm build up in the entire system with small bore pipes is totally eliminated. This is the last chance to safeguard the product against bacterial or yeast infection that impacts on the flavour of the beer. Figure 2.4 “Packaged Product Processes” above shows the principle layout of this process.

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Surfaces


Surfaces on the inside of process equipment have a major impact on hygienic levels that can be achieved during the process and during the cleaning regimes. The materials used to fabricate equipment and piping is generally divided into two main categories:

• fabricated surfaces (e.g. stainless steel, aluminum, copper, plastic glass) • coated surfaces (e.g. epoxy or glass coated carbon steel, galvanized steel)

The surface must be resistant to all products, cleaning chemicals and heating and cooling medium used in the service of the equipment and those used in cleaning of the work environment. The metallurgical aspects of stainless steel are detailed in Module 3, but in this Module we look at the surface from a hygienic perspective. Stainless steel surfaces are determined at the mill during the manufacturing process and later changed during the fabrication process by mechanical polishing or electro polishing. The original surface after milling is generally considered too rough for plant used in the food and beverage industry, unless the thin gauge sheets or rolls from the mill have a roughness that is acceptable. In all cases great care must be taken to conserve the thin (1µm) passive oxide layer that is formed as part of the pickle and passivation process during milling and fabrication. Electro polishing increases the passive layer ten times to that achieved in the chemical pickling and passivation process. The passive layer is the key factor that determines the corrosive resistance of that stainless steel.

Mechanical polishing and electro polishing reduces the undulations of the milled finish to achieve what is generally considered a “smoother finish”. The expression of surface texture has been traditionally expressed in Ra units, this being the “Average Roughness” or the “Average deviation of the profile from the mean line”.

The validity of Ra as an expression of the surface texture has been questioned by a number of authors on the basis that it does not reflect the real characteristic of the surface profile. Expression such as Rz (DIN) that show the “mean to valley heights) and Sm that show the “mean peak spacing” demonstrate the profile in a manner that visual appraisal of the surface can be expressed with a number that can be measured on an instrument. This subject is covered in more detail in Module 5.

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At this stage we can look at SEM photographs magnified 1000 times of surfaces of stainless steel and epoxy lined carbon steel that give a sense of the relative difficulty of removing scale, biofilm, yeast cells or bacteria from the surfaces. Figures 2.20 “10 mm plate with No 1 finish, 2.21 “1 mm plate with 2B finish”, 2.22 “10 mm plate polished to 220 grit, 2.23 “Stainless steel polished to 220 grit finish with yeast cells superimposed”, Figure 2.24 “Electro polished stainless steel with yeast cells superimposed”, 2.25 “Epoxy coated carbon steel with yeast cells superimposed”.

Fig 2.20 10 mm No 1 finish Fig 2.21 1 mm 2B finish Fig 2.22 10 mm 220 grit

Fig 2.23 22O grit finish Fig 2.24 Electro polished finish Fig 2.25 Epoxy lined finish

The risk of biofilm build up and irreversible adhesion of bacteria physically attaching the surface sites by means of extra-cellular polymer fibrils, pill pr flagella, is a danger to the hygienic condition of the plant. Biofilms are described as a group of organisms that have attached themselves to the surface and enveloped themselves in an impenetrable polysaccharide (sugar) layer. The formation of biofilms in brewery installations has been extensively researched and the learnings can be summarized as follows:

• Biofilm build up occurs within hours of product circulation through pipes. • CIP chemicals, temperatures, flow rates and cycle times are effective only when all these

relevant factors are optimized. If any of them fail, biofilm starts to form in piping and at the bottom of vessels where flow is lowest and chemicals have lost their original strength, and where temperatures are below the optimum required. All this happens after ONE process and CIP cycle. The biofilm on surface of the cone in Figure 2.27 could only be removed rubbing manually with a 30% caustic solution. A 30% acid (used for vessel CIP) did not take off the biofilm off. Arrows show where the manual treatment was carried out.

• CIP of fittings in pipelines and vessels is generally poor due to ineffective design and fabrication. Surfaces are rarely in direct contact with all factors required to ensure effective cleaning.

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• Insufficient inspection of surfaces results in excessive accumulation of biofilms or scale that are difficult to clean and in some cases start corroding the surface. This is called MIC or Microbiologically Induced Corrosion. This phenomenon is also found in water reticulation pipes in industry and municipal installations.

The following pictures, Figure 2.26 “Pipe (outlet) at FV”, Figure 2.27 “Low level sensor at (the outlet of FV”, Figure 2.28 “Cone of FV”, show examples of biofilm build up in brewery installations.

Fig 2.26 Pipe at FV Fig 2.27 Level sensor at FV Fig 2.28 Cone of FV Where epoxy lined surfaces are used, care must be taken to ensure that the coating application is carried out correctly. Although the surface texture is smooth and therefore apparently easier top clean, breakdown of the coating causes serious infection and ultimately contaminates the beer with iron. Figure 2.29 “Epoxy coating from fermenter” shows a magnified cross section profile of the coating (750 µm thick) and the parent carbon steel surface of the vessel the coating has been applied to. Air bubbles (350 µm diameter) in the coating were caused by poor application of the coating application, that ultimately broke through and caused pin holes in the coating eventually resulting in large section delaminating from the vessel as shown in Figure 2.30 “Delaminated epoxy coating from fermenter”.

Figure 2.29 “Epoxy coating from fermenter” Figure 2.30 “Delaminated epoxy coating from fermenter”.

AcidAcidCausticCaustic

FV ConeFV Cone

33

Insulation

Underlying principles

Insulation of hot and cold process plant is required to maintain safe working conditions and keep the product at the required temperature. In the last 20 years serious failures caused by stress corrosion cracking (SCC) in food and beverage process equipment has given rise to a greater awareness of the specifications required in the design, fabrication and maintenance of the plant. The key aspects which are now considered to address the failures are as follows: • Specifications of the insulation material from the manufacturers (foam, glass wool). Chloride

present in the traditional materials range from 5 to 1000 ppm Chlorides. A maximum of 15 ppm is considered critical in this material.

• Specifications of the application of insulation systems onto the vessels or pipe surfaces are as important as the material itself. No additional chlorides must be allowed to contaminate the insulation during its application to the surfaces. A drop of perspiration from the installation crew gives a concentration of 1000 ppm chlorides or 1g/m2 that severely accelerates corrosion of the metal surface.

• Design of the installation system must include an external; coating (cladding) that prevents any moisture from entering the insulation throughout the life of the plant. Moisture in the insulation will leach out the chlorides in the insulation, concentrating them onto the surface of the vessel or the pipe.

• A barrier coating of anti stress corrosion cracking paint or lacquer must be applied directly onto the metal surface. On top of this a sacrificial layer (aluminum foil) is placed that will corrode first before the vessel or pipe surface. The insulation material of the correct thickness is then applied, followed by a coating onto which is applied a totally enclosed and welded stainless steel cladding. Failure to follow these strict specifications will result in early corrosion of the equipment that will prove both costly and hazardous.

• On insulation systems used on cold vessel and piping, a vapour barrier is also fitted under the outside cladding to ensure that no moisture enters the insulation. This can cause ice build up on the cooling jackets and physically destroy the insulation making it worthless for its function.

• As corrosion starts on the metal surface in the areas of maximum stress, special care must be taken where welding has taken place or where the material has undergone stress through forming or bending and has not been stressed relieved.

Figure 2.31 “Details of insulation” and Figure 2.32 “Insulation integrity”. Both of these explain the importance of a sound insulation system and the importance of maintaining these specifications throughout the life of the plant. Re-insulation of repaired or damaged areas is possible to prevent the entire vessel or piping from failure.

34

Figure 2.31 “Details of insulation” Figure 2.32 “Insulation integrity”.


Examples of good and poor insulation details are shown in Figure 2.33 “Good insulation detail on piping “and in Figure 2.34 “Poor insulation detail on vessel”. A fitting has been welded on to a hot vessel without placing a shroud around it to prevent water ingress into the insulation. This is the most common fault found.

Figure 2.33 “Good insulation on piping Figure 2.34 “Poor insulation on vessel”

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Internal and external corrosion


Module 3 addresses the key aspects of corrosion, but in this section we review the main underlying principles. • Material selection is one of the more important aspects that determine the life of the

equipment. Care must therefore be taken during the design phase to select the correct grade for the process in question. This alone will not guarantee corrosion free life of the plant.

• Fabrication of the equipment can influence the life cycle of the equipment, as damage to the surface often results in a latent defect developing over time. The correct fabrication techniques must also be applied depending on the material being fabricated, such as welding codes of practice. Strict specifications and quality control procedures must be in force during this phase of the life of the plant.

• Inspection and maintenance of the plant during its entire life cycle must be exercised. Well trained personnel in the operational and maintenance departments that are fully aware of all the factors that contribute to corrosion, is one of the most effective guarantees for a long life cycle of the plant. This practice also assures the prevention of serious financial loss due to hazardous incidents to personnel and plant, and to losses caused by product failure and customer complaints.

36


Stress corrosion cracking (SCC) has been experienced in stainless steel and carbon steel plant in all food and beverage industries where plants have not followed the specifications indicated above. Examples of serious product spoilage and plant failures are recorded in the brewing, dairy, soft drinks and yeast industries in South Africa and around the world. Examples of some of these incidents are shown below.

• Figure 2.35 “Lauter tun pressure sensor”. The SCC crack under the sensor (↑) started from the out side of the shell. Cause: chlorides in insulation. Age of vessel 10 years.

• Figure 2.36 “SCC on plate”. SCC cracks seen from insulation side. Caused by chlorides in insulation. Age of vessel 10 years.

• Figure 2.37 “Composite photo of crack through SS plate”. Top is the insulation side where SCC started, bottom is product side.

Top; direction of crack↓

Bottom: product side

Fig 2.35 LT with crack Fig 2.36 SCC on plate Fig 2.37 SCC crack

• Figure 2.38 “SCC of mash vessel”. Stress corrosion coating applied on vessel under insulation contained excessive chlorides causing SCC. Age of vessel 6 weeks. Vessel replaced.

• Figure 2.39 “Pit corrosion on external piping surface”. 40% surface corroded. Cause: chlorine sterilizers used in cellars. Age of piping 6 years.

• Figure 2.40 “Crevice corrosion”. Crevice corrosion of welds on fermenters’ cooling coils caused excessive glycol leaking. Root cause: chlorides in water used for diluting the glycol. Age of vessels 10 years.

Fig 2.38 SCC Fig 2.39 Pitting on pipe Fig 2.40 Crevice corrosion

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Inspection and maintenance


To ensure an effective inspection programme, all stakeholders must be involved in the original design of the plant to the extent possible. These must include the operational, quality, maintenance, and HR staff, as well as design engineers and supplier of equipment. This team will ensure the following outcomes are achieved with specific reference to the maintenance of hygiene standards. • Product quality can be analyzed at all times required by company standards, and at any other

time to analyze and resolve problems. • Access to equipment is easy and safe to inspect the plant and takes samples. • Ergonomic considerations are implemented in the plant layout to facilitate the tasks of the

operational and maintenance personnel. • Inspection (physical and condition monitoring) and analytical facilities and equipment are

available and reliable at all times. • Inspection and analytical personnel are competent in all their relevant tasks.

Summary The following diagram summarizes the key aspects of “Understanding the process environment”.

Process

Environment

Understood

Equipment People

MaintenanceProcess

Training & assessment

Problem solving teams

Manuals

Stakeholder

involvement

StakeholderTraining

Inspection & visits

Captureall data

Design

to specification

Planned maintenance

& conditionmonioting

Repairs

Specifications

Specificationsdefining

potential

problems

Incident

reports

Asset register

Hgyiene implications

on plant design

Hygiene implicationon plant failures

Process impacton hygiene factors

Optimize

equipment life cycleFeatures of equipment

that assure

hygiene standardsImportance

of corrosionon hygiene

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Cleaning System


The underlying principles that determine the need for a cleaning system are as follows:

• Understanding the levels of cleanability and hygiene required in the plant producing food or beverages.

• Determine the composition of the soils, scale or biofilm accumulating on the surfaces of the plant.

• Recognize the factors that contribute to a balanced cleaning system • Identify the equipment to achieve the required level of hygiene.

In Module 4, the levels of cleanability are presented with details of the microbiology that defines levels of hygiene. The Table 2.1 “Soils, biofilm and scale on brewery process plant” shows where these accumulate on the surface of equipment and piping. This information determines the type of cleaning system that has to be designed in each of these areas. Table 2.1 “Soils, biofilm and scale on brewery process plant” Location & Equipment Level of

organic soil or biofilm

Level of inorganic scale

Temperature of the process. (Hot =100 to +40°C) (Cold = 5 to -2°C)

Brewhouse Mill Medium Hot Cereal cooker Medium Medium Hot Mash Vessel Medium Medium Hot Wort kettle + HE High High Hot Whirlpool Medium Low Hot Liquid sugar tanks High Low Hot Hot water tanks Low High Hot Cold water tanks Low Low Cold Hops, acid & salt tanks Medium Medium Cold CIP vessels Medium High Hot & cold Heat exchanger; wort High High Hot & cold Piping High Medium Hot & cold Cellars Ferment & storage vessels High Medium Cold Yeast plant High Low Cold CIP plant Low High Hot & cold D Plant + HE Medium High Hot & cold Filter plant & additives Medium Medium Cold Pipes + HE High Medium Hot & cold Bright Beer Tanks High Low Cold Packaging Filler & crowner/seamer/keg plant

Medium Low Cold

Pasteurizer & water recovery plant

High High Hot

Pipes Low Low Cold CO2 recovery lines High Medium Cold Compressed air lines: process Low Low Cold

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The underlying principles of a balanced cleaning system are based on the following:

• Mechanical force for a determined time period • Chemical composition at a determined temperature • The synergistic effect of the above factors

The balanced application of these factors will determine both the design and effectiveness of the cleaning system. As each of the factors influence cost of the initial plant (vessels, pumps, piping, heat exchangers instrumentation and the area occupied by the cleaning station with upgraded building finishes), as well as the running costs (chemicals, water, heat, effluent, power, spares), the optimum balance must be achieved to obtain the required levels of hygiene. The four factors have to be optimized during the operation of the cleaning system, as inefficiencies will become evident as soon as one or two of them falls below their effectiveness level. For example, a CIP system to clean process pipes in the cellar area with low temperatures will not be effective, even though the flow, time and chemical concentration are within the specification. Figure 2.41 “Graphical representation of balanced cleaning factors” shows the principle of balanced cleaning factors.

Cle

an

ab

ilit

y i

mp

rovem

en

t

Increase in velocity of CIP in pipe line m/s

Chemical + concentrationMechanical + tim

e

Chemical + concentration

+ Mechanical + tim

e

Effectiveness in Cleanability related to mechanical & chemical factors

and velocity of CIP in pipe line

Co

sts

of

cle

an

ing

Figure 2.41 “Graphical representation of balanced cleaning factors” The four factors impacting on the cleaning efficiency are influenced by conditions that are also important to consider. These are as follows; • Mechanical factor

o Quantity of the solids to be removed from the surface o Flow rates o Turbulence o Shear stress o Pressures & pressure drops

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o Water hammer (lifts seats on valves allowing CIP into product line) o Efficiency of flow and pressure meters

• Chemical factor o Quantity and quality of the solids to be removed from the surface o Initial concentration as measured & efficiency of conductivity meter o Topping up in the circuit o Presence of solids in solution o Dilution in circuit o Neutralization e.g. CO² for caustic o Return to holding vessel or drain in multiuse system

• Temperature

o Initial temperature as measured o Controlling in the circuit o Cooling in the circuit e.g. pass over cold surface of FV, SV or HE o Return to holding vessel or drain in multiuse system o Efficiency of temperature control

• Time

o Time for complete process as measured o Time to wash out or rinse the previous chemical or product o Time for chemical to react on surface soil o Time to drain the detergent in the bottom of the vessel o Time to sequence CIP and CIR pumps o Time to sequence opening and closing of automated valves o Efficiency of time control

In the selection of the correct equipment to be included in the cleaning system, the following principles must be considered: o A “multi use CIP system” requires that the capacity of the vessels in the CIP plant must be

sized to hold the required quantity of the chemicals and water for reuse and recirculation. o The number of vessels is dictated by the type of chemicals to be used e.g. caustic hot and or

cold, acid, sterilant. o The level of instrumentation is defined by what parameters are required to be monitored e.g.

temperature, flow, pressure, level and conductivity. o The flow characteristics of the CIP for vessel and piping systems is determined by the

principles of fluid dynamics as follows: o Flow rates required to clean surfaces of vessels range from 1000 to 3510 litres per

hour per meter of vessel circumference. o The force from the spray ball or rotary jet on the vessel surface is only totally effective

at the point of contact; point of impingement. The fluid then runs down the side of the vessel wall by gravity to clean the rest of the surface. There are two schools of thought on whether flooding of all the surface with fluid from low pressure spray balls is more or less effective than rotary high pressure jets that work on the principle of maximum impingement of fluid directed at the targeted surface as it completes a rotation every 6 to 12 times a CIP cycle. There is no conclusive evidence that one system is superior to the other given all the factors that contribute to an effective cleaning system.

o The force of the fluid through pipelines determines the effectiveness of the cleaning of the surface. Turbulent flows, defined in Reynolds Number Re, have a direct relation to the shear stress on the side of the pipe, and this determines the mechanical force on the surface that helps to remove the soil or scale.

o Other factors that will influence the flow = cleaning effectiveness, are the pressure drop across the pipe lengths, the number of bends, fittings, roughness of the internal surface of the pipe and the pipe diameter. To optimize all these factors, a detailed hydraulics

41

study is required of the entire piping system. Figure 2.42 “Pipe flow velocity to achieve effective flow characteristics for CIP” is a guide to assess the relationship between the Reynolds Number Re (at turbulent flow levels) and the flow velocity in the pipes in meters/second. This shows the recommended CIP range for flow velocities in four different pipe sizes used in the brewing & other beverage industries.

The graph shows the flow rate of CIP in m/sec in different pipe diameters to ensure the flow characteristics are such that CIP is

mechanically effective.

Pipe flow velocity to achieve effective flow

characteristics for CIP

0

500

1000

1500

2000

2500

3000

3500

0 1 2 3 4Flow velocity in m/sec

Re n

um

ber x

100

Effective CIP range

50 mm

125 mm 80 mm

100 mm

Re = pVdµ

P = fluid (kg/m³) e.g. 1000

V = mean fluid velocity (m/s) e.g. 2d = tube inside diameter (m) e.g. 0.125

µ = fluid viscosity (Ns/m² =cP/1000) e.g. 0.001

Example 1000 x 2 x 0.125 = Re 2500000.001

Figure 2.42 “Pipe flow velocity to achieve effective flow characteristics for CIP”

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Spray systems: Spray Balls The choice of spray balls carried out for a research vessel followed the specifications required. Figure 2.43 “CIP flow rates in vessels expressed in litre/hour/meter of circumference” shows the flow rates for CIP spray balls used in different types of vessels at four operational breweries. These were compared with theoretical flow rates cited in the literature and two different flow rates that were evaluated in the research programme.

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Plant E Plant D Plant H Plant J

FV

FV

SV

SV

BBT

BBT

BBT

BBT

l/h/m

Literature

Research Upper limit

Literature

Research lower limit

CIP Flow rates in vessels expressed in

litres/hour/meter of vessel circumference

Low Test Flow Rate

High Test Flow Rate

Figure 2.43 “CIP flow rates in vessels expressed in litre/hour/meter of circumference”

In this same research programme, the research vessel (600 litre & part of a training brewery) fermented a number of brews to study the type of soil and the effectiveness of two different CIP flow rates. Figure 2.44 “FV before CIP” and Figure 2.45 “FV after CIP” show they type of soil (yeast ring) that accumulates at the top of all FV’s in the brewing process, and what the top of the vessel looks like if the CIP is effective.

Before CIPBefore CIP

240 Grit240 Grit EPEP

Dome after CIP

Figure 2.44 “FV before CIP” Figure 2.45 “FV after CIP” The choice of spray balls or rotary spray jets is a key factor in the effective design and operation of a CIP system. There are a number of reputed manufacturers of this equipment but we have chosen data from GEA Tuchenhagen and Toftejorg as they represent typical designs that could be chosen to achieve the required outcomes.

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The dimension of the vessel dictates the type of spray device required for an effective covering of the entire surface during the CIP cycle. Spray balls showers the entire surface all the time the pump is operational, by directing the impact flow of the fluid on the area where most of the soil is located e.g. at the yeast ring in the FV example above. The fluid runs down the side of walls of the vessel in a continuous curtain contributing to the effect of the chemical, timing and temperature to assure a clean surface. The following shapes of vessels can be fitted with the fixed spray balls with multiple holes or for two three or four jets. To cover the entire surface of the vessel, either one or multiple spray balls can be installed in one vessel to ensure that the spray diameter of each spray ball give total cover of the vessel surface. The spray angle can be chosen to give from 90° to 360°. GEA Tuchenhagen spray balls as installed in vessels

GEA Tuchenhagen vessel attachments

44

GEA Tuchenhagen data sheet for selection of spray ball for different vessel sizes

Selection of spray balls should be done in consultation with the manufacturers.

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Spray systems: Rotary Spray Cleaners Rotary spray cleaners require a high pressure to direct the fluid on to the surface of the vessel that has an impact effect at the point of contact. The fluid flows down the rest of the surface cleaning on its way. Rotary jet cleaners from two suppliers show the different applications when they are positioned on the floor of the vessel and when they are fixed at the top of the vessel. The rotating jets have a higher impact force on the surface exerting greater mechanical effect on the soil or scale, than the flooding low pressure system applied on fixed spray balls. The jets on a rotating mechanism directs the fluid at one point a specified number of times for a complete cycle, at the end of which all the surface will be covered.

Both GEA Tuchenhagen and Toftejorg rotating jet cleaners are shown below. GEA Tuchenhagen rotating jet cleaners placed on vessel floor

46

GEA Tuchenhagen Orbital Cleaner TS – T4 Orbital Cleaner M19

GEA Tuchenhagen Orbital Cleaner RH19G

47

Toftejorg Rotary Jet Heads

TRAX Validation of tank cleaning with rotary jet head.

Toftejorg cycles of rotary jet heads

Toftejorg TZ – 74 rotary jet head

Rotacheck sensors to check operation of rotary jet head

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Maintenance of spray cleaning devices The blockage of holes in the spray balls and rotary spray jet cleaners must be avoided at all times as this seriously impairs their effectiveness. The devices must be inspected on a routine basis to ensure they are clear of the debris and function correctly. Rotary jet cleaners are sometimes fitted with a sensor to check that the system is rotating: see Toftejorg Rotacheck above. A signal is sent to the control system if the sensor does not make the signal closing down the CIP cycle. Figure 2.46 “Blocked spray ball holes” shows the hole of the spray ball blocked that caused ineffective cleaning of the surface at the top of the vessel.

Figure 2.46 “Blocked spray ball holes”

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CIP of vessels and piping Vessels

The effectiveness of CIP over the entire surface of a vessel is determined by the flow of the fluid at its impingent area and as it flows down the walls of the vessel. However, the factors that assure an effective cleaning process are mechanical, chemical, time and temperature. The spray systems are most effective on those areas where the fluid impinges on the surface. Experience and research has shown that vessels have three zones with different levels of cleanability i.e. absence of soil, biofilm and scale. This is shown diagrammatically in Figure 2.47 “Areas of cleanability of vessels”.

Figure 2.47 “Areas of cleanability of vessels”.

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The top area where there is greatest impingement the surface is always clean provided the spray device holes are not blocked, As the fluid flows down the side walls and the rotary jets have the longest trajectory, the middle of the vessel tends to be less clean, In this area temperature probes are normally located. At the bottom of the vessel, whether conical or domed shape, there is clear evidence of biofilm and scale formation. In this area chemical effectiveness is at its lowest and the temperature may have been reduced by the cooling medium remaining in the cooling jackets that would cool the detergent as it flows down the wall. If the CO² has not been removed completely, caustic will be neutralized. Evidence has been seen of this in vessels that have completed the CIP cycle with caustic, demonstrated by a zero reading on the conductivity meter on the return line and by a distinct odour of CO² inside the tank. Low level indicators at the bottom of the vessels have to be totally reliable at all times. This will allow for effective sequencing of the CIP return pump and the supply pump to ensure that the bursts of detergents does not accumulate in the bottom of the vessel making the chemical effect on the biofilm even less effective. These low level indictors also indicate that the CIP cycle has terminated and the vessel is empty of detergent ready for filling with beer. Failures in these low level indicators have caused numerous incidents of vessels being filled with beer on top of detergent chemicals. In the case of cleaning vessels with flow rates specified for spray devices, care must be taken that those flow rates are also effective for cleaning the outlet pipes off the vessel, especially as those detergent are cold and often low in concentration. Flow rates for vessel CIP are frequently not sufficiently high to achieve an effective cleaning of the outlet pipes. In the case of fully piped up and automated systems where inspection of the pipes and vessel is rarely practiced, this problem requires careful consideration Beer pipes must be cleaned with hot detergents. Figure 2.48 “Vessel CIP” shows the layout for CIP of hot and cold vessels.

Figure 2.48 “Vessel CIP”

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To optimized fluid flows for the CIP of vessels, the following factors must be considered: • Spray devices define the volume and pressure required for effective cleaning depending on its

spray circle for the vessel in which it has been installed. • Supply CIP pumps will deliver the following flows:

o Spray balls example: 360 angle in a 5 meter diameter vessel: 350 hl/h at 1.5 bar pressure. Burst of fluid shower the entire surface, normally recommend with specific bursts of defined minutes on and off.

o Rotary jet cleaner example: 360 angle in a 5 meter diameter vessel: 240 hl/h at 6 bar pressure. Continuous flow of fluid to get the rotating cycles to obtain 100% coverage over the total time for CIP.

• Return CIP pump service o Low level probe senses flow and the pump starts o Low level probe senses no flow and the pump stops

There are some important considerations that need to be taken into account in the sequencing of the supply and return CIP pumps. • Avoid excessive back up of fluid over the require level to cover the low level probe in the outlet

pipe of the vessel. • Ensure the pipe has enough fluid to supply the required suction pressure on the return pump. • Avoid vortexing of the pump when it has no suction pressure, as it will cause cavitation of the

pump and result in mechanical damage to the impeller and the seal. In a domed bottom vessel vortexing is often a problem. A vortex breaker has to be fitted manually at the vessel outlet, most often positioned next to the man way, before CIP starts. Once CIP is complete, the vortex breaker is removed. If the vessel is a fermenter or a storage tank where a thimble is fitted in the vessel outlet to hold back yeast or tank bottom, this can be done at the same time, once the vortex breaker is removed. The following pictures show a manual CIP system with the vortex breaker in position next to the thimble which is also cleaned at the same time as the rest of the vessel (Figure 2.52). The photos also show the effectiveness of a manual CIP system where all the mechanical and chemical factors are optimized at the design and operational phase.

Fig 2.49 FV before CIP Fig 2.50 Manual CIP Fig 2.51 Clean FV Fig 2.52 Vortex breaker

Vortex breaker & thimble

52

The following figures represent three levels of CIP, from a manual process Figure 2.53, semi manual using pipe panels Figure 2.54 and a fully automated system Figure 2.54.


Manual System / “Open” Hose Connection

transfer to next process

Manual System

Figure 2.53 “Manual CIP system”


Semi Automated System / “Open” Fixed Piping

Figure 2.54 “Semi automatic CIP system”

53

Tank 1

Tank 2

Tank 3

Tank 4

Tank 5

Matrix Piping with Tank Bottom Valve

Figure 2.55 “Fully automated CIP system”

54

Piping

To ensure an effective cleaning of piping, all four factors must be optimized to ensure optimum hygienic conditions. The importance of flow characteristics has been discussed above under underlying principles. The use of the appropriate chemicals is addressed in Module 4. The monitoring of concentrations is done by means of a conductivity meter and adjustments are made either to the main CIP vessels in a multi use CIP system or by adjusting the dosing rate of the concentrated chemical in line when using a single use CIP system. Temperature and pressure indicators will monitor both these factors in line and corrections made automatically to meet the design specifications of the plant. To ensure that all these factors work according to specification, a detailed physical inspection and maintenance plan must be in place to ensure that these critical control points in the CIP system are attended to regularly. The correct welding of piping is very important to the overall level of hygiene in the system. Figure 2.56 “Welding details for piping” shows how pipe welding can cause hygiene problems and what the correct finish should be inside the pipe.


A - Plan and cross section showing misalignment and lack of penetration.Crevices will harbour micro-organisms

B - Plan and cross section showingeffects of lacking gas shielding.Roughened weld and heat affected zonepromote adhesion of soiling

Surface preparation

Hygienic installation of the segments to a functional system by welding

Gas shielding

Orbital vs. Manual

butt weld, no filler wire

Figure 2.56 “Welding details for piping”

Pumps & Valves The selection of pumps and valves for the Food & Beverage industry is very wide and reputed suppliers are available to recommend, supply and maintain them. In the design of the plant it is important that the final selection is made by both the user and the supplier to ensure a holistic approach to the life cycle cost and accountability in the operation of a hygienic plant. Selection must never be made on the relative cost of the individual pumps and valves. Equipment from GEA Tuchenhagen is shown as an example of the items manufactured with the highest specification in the Food & Beverage industry. Many of the items have been approved by the EHEDG (European Hygiene Engineering Design Group.).

55

Pumps. Centrifugal pumps are used for most of the hygienic requirements. Lobe pumps are used for yeast and other slurries and are designed for hygienic requirements. Liquid ring pumps can be used as CIP return pumps as they are not normally recommended for hygienic conditions. Dosing pumps meet hygienic requirements and are used for dosing additives. The following details cover some of the hygienic pumps in the GEA Tuchenhagen range GEA Tuchenhagen centrifugal pump and impellor used for all hygienic requirements

Performance curves for the above pumps

56

Exploded view of the above pumps, used for maintenance identification

57

GEA Tuchenhagen rotary lobe pumps: used for yeast and slurries

Exploded view of rotary lobe pumps used for maintenance identification

58

Valves Like in the selection of pumps, valves are likewise manufactured by a number of reputed suppliers. Examples of the GEA Tuchenhagen valves are shown below. GEA Tuchenhagen Shut off valves

Housing Combination


Hygienic

metal stop

No gap to product side

59

VARIVENT Butterfly valve, manual or with actuator

Fittings Like in the selection of pumps, fittings are likewise manufactured by a number of reputed suppliers. Examples of the GEA Tuchenhagen fittings are shown below.

Pressure gauge

Pressure transmitter

In line temperature gauge

60

Recommendations on features that assure hygienic conditions in the layout of piping and fittings in plant.


100bar

STATE OF THE ART

THE COMMON WAY

In-Line Instrumentation

Tuchenhagen Inline Access Unit


Non-hygienic versus Hygienic

WRONG CORRECT


Pipe Connection

Not recommended

EHEDG certified

•Easy in-place cleanable

•Sterilisable in place•Impervious to micro-organisms•Easy installation•Reliable

EHEDG Recommended Pipe Connection

61


Heat damage on o-ring gasket

20°C > 100°C 20°C

Expension of elastomers: 15 times higher than stainless steel

Drainability: transition of pipe diameter. The upper concentric method is used for horizontal piping and will hamper draining. The lower eccentric method will not effect draining in either direction.

Position of dead legs with reference to the flow of product and cleaning liquids.

.

62

Multi Use CIP v Single Use CIP In the design of the CIP system, there is a choice of incorporating either a multi use or single use system. In determining the choice of either of these two systems, the following factors need to be considered.

Multi Use System • High initial capital cost of the vessels, instrumentation, pumps, valves, piping and control

system. • Relative inflexibility of the CIP chemicals • Relative independence from the chemical suppliers • Complex control system and instrumentation • High maintenance • Control of chemicals requires complex instrumentation • High and variable effluent loads when discharging entire vessels with caustic, acid or sterilants • Central location with high grade building finishes that are chemical resistant Single Use System • Low initial capital costs: few to no vessels, short piping routes, simpler valving and

instrumentation • Relative dependence on chemical; supplier • Mobile unit • Simple controls • Medium maintenance • Simple detergent controls • Control of effluent discharges and smaller volumes • Reduced area for CIP station An economic justification for choosing either of the two systems is presented below:

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Using the formula below, a quantitat ive statement can be made about the cost of asingle use- and a recovery CIP system.

Single Use CIP System – Recovery CIP System

Fact is:

KVR = KSTR

KVR = KIST+KNA+KNS

(VKR x C x KRM x Ra) = (KIST x FA) + (VST x C x KRM x Na) + (VKR x C x KRM x FMV x Ra)

KVR = Cost for single use cleaning

KSTR = Cost for recovery cleaning

KIST = Cost / Investment for CIP-tanks including accessories and installat ion

KNA = Cost for CIP-tank filling with the detergent

KNS = Cost for re-concentrat ion

KRM = Cost for detergent (DM/kg)

FA = Write-of f factor

VST = Volume CIP-tank (m3)

VKR = Volume CIP-pipe circuit (m3)

C = Concentrat ion single use CIP (kg/m3)

C = Concentration recovery CIP (kg/m3)

CIP - System Calculation

FMV = Factor mixing zone losses

Na = New CIP-tank filling per year

Ra = Cleaning times per year

1 = KVR (Cost for single use cleaning)

2 = KSTRtotal (Cost for recovery cleaning, total)

3 = KSTRRM (Cost for recovery cleaning, only detergent)

X1 = KVR = KSTRtotal

X2 = KVR = STRRM

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1 = KVR (Cost for single use cleaning)

2 = KSTRtotal (Cost for recovery cleaning, total)

3 = KSTRRM (Cost for recovery cleaning, only detergent)

X1 = KVR = KSTRtotal

X2 = KVR = STRRM

KR (DM)

X2 X1 VKR (m3)

The graph shows the cost parameter in relation to the volume of the CIP-pipe circuit .The single use CIP is more price eff icient on the left hand side of the cross points X1 and X2.

1

2

3

CIP - System Calculation

Volume CIP-pipe circuit

Cost for CIP

65

Figure 2.56 “CIP Processes” shows the PFD of the two systems

Figure 2.56 “CIP Processes” Summary The following diagram summarizes the key aspects of “Optimizing a cleaning system”.

Cleaning System

Optimised

PeopleSpray devicesVessels

ProcessPumps

Valves

Fittings

Piping

Level of hygiene

defined

Composition of

soil determined

Equipment

identified

Hygiene contributing

factors identified

Mechanical

Chemical

Time

Temperature

International

Standards

Company standards

Biofilm

Scale

Angel of spray

Spray ball

Vesseldimensions

Rotaryjet cleaner

Maintaindevice clean

Spraypattern defined

Pressure

& flow

Soil

Location

Type

Fittings

Dimensions

Inlets &outlets

Dimensions

Mechanical

factors

Pipe spec

Length

Diameter

Internalroughness

Pressures

Velocity

TurbulenceShearstress

Pipe fall

Selectfor duty

Hygienic

design

Inspection

Hygienicinstallation

Optimise hygienic

contributing factorsMechanical

Chemical

Time

Temperature

Cleaning CIP

process

defined

& maintained

QC

standards

Spares &

service

Mechanical

performance

66

Corrosion prevention to enhance levels of hygiene


Breakdown of the surface through corrosion of internal and external surfaces has a significant impact on the hygienic condition of the plant. In the preceding section the underlying principles have been reviewed and practical consideration detailed Corrosion on the inside and outside of the surfaces of stainless steel and coated linings of vessels, stainless steel pipes, valves, heat exchangers and other process items are summarized as follows. Corrosion type Cause Effect

Inside Surface Stress Corrosion Cracking Stainless Steel hot water tanks

Accumulated scale build up concentrates biofilm and chlorides on the surface causes SCC to start

Total failure of tanks. SCC is not possible to repair. Scale and biofilm harbour bacteria.

Pitting corrosion Vessel, pipes, heat exchangers and fillers

Pits occur due to abnormal use of descaling or sanitizing chemicals with high chlorine levels, over 50ppm Cl.

Surface damaged with holes that harbour infection and is difficult to clean. Not usually seen as plant is nor inspected regularly

Pitting corrosion Stainless Steel product storage vessel

SO² in sugar solutions (200ppm) cause pits in pipes & vessel

Vessel wall pitted and made difficult to clean. Pits harbour bacteria.

MIC (microbiologically induced corrosion)

Stainless steel pipes left with water standing in them and contaminated with sulphate- reducing bacteria (SRB)

Holes starting from inside of pipes with potential for major failure in entire piping system.

Outside surface Stress corrosion cracking Stainless steel vessels and pipes.

Chlorides in insulation cause SCC due to poor initial specifications & fabrication or due to poor repairs and maintenance.

SS plate or weld of heating/cooling jacket with steam or ammonia breaks through to process side. Product contamination & risk to personnel

Stress corrosion cracking Stainless steel process heat exchanger plates

Scale on heat exchanger plates causes SCC and plates break through.

Product contamination with glycol cooling medium.

Carbon steel coated (epoxy) lined carbon steel process vessels

Misalignment of process vessel plates with defective seam weld under the ammonia cooling jackets causes failure on HAZ through corrosion.

Ammonia ingress into vessel with product contamination and hazard when personnel inspecting empty vessel.

Stress corrosion cracking Coated (epoxy) lined carbon steel process vessels

Chlorides in insulation cause SCC due to poor initial specifications & fabrication or due to poor repairs and maintenance.

CS plate or weld of cooling jacket with ammonia or glycol breaks through to process side. Product contamination & risk to personnel

Pit corrosion of process piping, heat exchangers and vessels

Pits occur due to chlorine based sterilants used in process environments

Surface damaged with holes that harbour infection and is difficult to clean. Not usually seen as plant is nor inspected regularly

Crevice corrosion of glycol piping systems

Chlorides in diluting water used for glycol solutions settle in crevices of welded coils on vessel external surface.

Coil welds corrode and glycol leaks out causing failure in system. Costly repair required.

Table 2.2 “Corrosion types: cause and effect”

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Module 3

Objective: “Demonstrate an understanding as to why stainless steel is the material of choice in an hygienic environment”

Outcomes

• Describe the reasons why stainless steel is the material of choice in the food and beverage industry • Explain the corrosion resistance of stainless steel • Describe the factors that are that must be considered during the fabrication of stainless steel to prevent damage to the surface and subsequent corrosion • Compare surface finishes from different materials (including stainless steel, lined surfaces, etc) and appraise their relative impact on hygiene

Stainless steel, the material of choice

Passivity ≡≡≡≡ Corrosion Resistance

A steel is only stainless if it contains more than approximately 11%Cr. This results in the built-in natural resistance to corrosion termed passivity, i.e. a state in which a metal or alloy loses its chemical reactivity and becomes inert to many corrosive solutions. Refer Fig 3.1

OXYGEN or

OXIDISING ENVIRONMENT

PASSIVE FILM Cr rich oxide

PARENT METAL

≥≥≥≥ 11-12% Cr

Fig 3.1: Schematic illustration of the formation of the passive film

on the surface of stainless steel

The Cr content of stainless steels renders them passive due to the formation of a Cr rich oxide film (termed the passive film) on its surface.

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• This passive film is � extremely thin (≈ 3-5x10-6mm thick) � uniform & continuous � stable & tenacious � smooth � self-repairing.

Corrosion Resistance

The corrosion resistance of stainless steel is totally dependent on, and directly related to, the integrity and the properties of the passive film, which are affected by • The alloy content � Chromium is the primary alloying element that renders stainless steel “stainless”. As stated above, a minimum of ≈11%Cr (free and un-combined in the microstructure) is required. At this level, a continuous passive film forms on the surface. Higher levels of chromium (up to ≈26%Cr in wrought stainless steel and ≈30% in cast stainless steel) result in superior corrosion resistance. However, with respect to each specific grade of stainless steel, it must be appreciated that it is not possible to simply increase the chromium content to attain a superior corrosion resistance, as this would adversely affect the related secondary properties. � Secondary alloying elements that have a positive influence in increasing the corrosion resistance (in general, in specific corrosive environments and/or to specific corrosion mechanisms) include nickel (Ni), molybdenum (Mo), copper (Cu), and titanium (Ti).

• The process whereby the passive film developed � Naturally by self-repairing, i.e. spontaneously (NB NOT instantaneously) on a newly created surface of stainless steel by reaction with oxygen in the air or dissolved in solutions. For this natural self-repairing to take place the surface MUST BE � clean, uncontaminated by and free of metallic particles, salts, dust, debris, polishing and/or adhesive residues, oil film, grease, paint, crayon marks, etc � chemically unaffected, i.e. oxidised (scaled) due to exposure at elevated and/or high temperature in an oxidising atmosphere.

Experience has shown that such self-repaired passive film has a lower resistance to discoloration, staining and possibly the initiation of corrosion. • Chemically treating by the use of acid solutions based on nitric acid (HNO3), viz Pickling and/or Passivating. These processes are covered in Section 3.4 The integrity and the properties of the passive film, and hence the corrosion resistance, are superior to those that result from a natural self-repairing process. • Electro-polishing. This process will also be covered in Section 3.4. This process develops a passive film with the best integrity and corrosion resistance.

Stemming from the corrosion resistance are the inter-related properties of hygiene, cleanability, product purity and factors associated thereto. • Hygiene – a surface that is clean, sanitary, aseptic, free of germs/bacteria, sterile, healthy. Associated factors being a surface that is � tolerant of both high and low temperatures, and resistant to thermal shock � unaffected (not roughened, pitted) by a wide variety of liquids encountered both in production (e.g. acids, juices, spices, salts) and also by the cleaning and sterilising solutions employed � non-porous and non-absorbent, thus prevents growth of germs and bacteria, and their carry over from batch to batch.

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• Cleanability - an expression of the ease, simplicity and rate of cleaning the surface; and the degree to which residues, germs and bacteria are removed. Associated factors being � CIP solutions applied through spray-balls or spray jets, and the subsequent easy and complete removal of the cleaning solutions � Cleaning is effected rapidly with little time loss between the processing of successive batches � 100% removal is attained (provided efficient contact of the cleaning solution with the surface occurs).

• Product purity Associated factors being � Non-porous and non-absorbent surface prevents tainting due to the retention of odours and flavours � No discoloration of the product due to corrosion.

Classification of Stainless Steel

Stainless steel is not a single material, but a FAMILY of different grades of stainless steels. • All grades can be logically grouped within five classifications (and related sub-classifications) as schematically illustrated in Fig 3.2

Fe + CrFe + Cr

NiPlain CrMn N

C Ti Mo Cu

MARTENSITIC

Stainless Steels

FERRITIC Stainless Steels

Utility

Ferritic

S/S

Conventional

Ferritic

Stainless Steels

Super

Ferritic

S/S

AUSTENITIC Stainless Steels

Cr Mn N

Aust S/S

Cr Mn Ni

Aust S/S

Conventional Cr Ni

Austenitic Stainless Steels

Heat Resisting

Aust S/S

Austenitic

Stainless

Alloys

DUPLEX

Stainless Steels

PRECIPITATION

HARDENABLE (PH)

Stainless Steels

Fig 3..2: Schematic representation of the different classifications within the FAMILY of STAINLESS STEEL

70

� Four classifications are named according to the inherent crystal structure (i.e. the atomic arrangement of the constituent elements) that results from the composition and the thermal treatment � These classifications are the MARTENSITIC, the FERRITIC, the AUSTENITIC and the DUPLEX stainless steels

� The fifth classification is named from the heat treatment required to develop the properties � This classification is the PRECIPITATION HARDENABLE stainless steels.

• The stainless steels within any classification have similar properties.

Grades of stainless steel

There are many different individual grades of stainless steel. Each is identified by a grade number (or a grade designation) in the different International and National Specifications (or Standards), e.g. USA ~ ASTM; Great Britain ~ BSI; Germany ~ DIN; France ~ AFNOR; Japan ~ JIS. • Some countries “adopt” the National Specifications of other countries, e.g. the South African stainless steel industry has traditionally made use of the American Specifications.

The ASTM (American Society for Testing and Materials) Specifications.

• The grades of stainless steel contained therein have historically been identified according to AISI (American Iron and Steel Institute), viz the familiar “200 Series”, “300Series” and “400Series” � “200 Series” include the CrMnNi (chromium/manganese/nickel) austenitic stainless steels, eg Grade 201 � “300 Series” include the CrNi (chromium/nickel) austenitic stainless steels, eg Grades 304(L), 316(L), 321 � “400Series” include the ‘plain chromium’ stainless steels, both martensitic and ferritic stainless steels, eg Grade420 and Grade 430 respectively.

• Newly developed grades could not be logically accommodated in these AISI “Series”, and therefore the UNS (Unified Numbering System) for grade identification was evolved. The UNS grade identification consists of a letter followed by five numerals � the letter denotes either a steel or an alloy type, eg Sxxxxx is a stainless steel grade, Nxxxxx is a stainless alloy or a nickel alloy grade � for stainless steels the first three numbers are often the same as the previous 200, 300 or 400 “Series Number” (if this existed), and the last two numbers are used for the different grades of the same basic type, e.g. S30400 = 304; S30403 = 304L; S30409 = 304H; S30415 = no previous grade; S30451 = 304N; S30452 = XM-21; S30453 = 304LN.

The New European EN Standard

Historically each country in Europe had their own National Standard and Specifications that applied to stainless steel and other materials. Consequently, a huge number of individual grade identifications existed that, although similar with respect to composition, were not exactly equivalent. National Standards and Specifications have been replaced by the new European EN Standards. Exactly the same Standard is used by all countries (eg by Great Britain as BS EN xxxxx; by Germany as DIN EN xxxxx; by France as AFNOR EN xxxxx; etc), the only difference being the language in which these Standards are written. • Grade identification is according to either a grade number or a grade designation (e.g. 1.4301 or X5CrNi 18-10 respectively)

71

� The grade numbers and grade designations in these new EN Standards appear to be the same as the old DIN Werkstoff numbers and Kunzname. � However there may be differences in the composition and/or properties. Therefore, care must therefore be taken not to confuse the two, nor to make unconsidered substitution.

Composition

Each grade of stainless steel has a unique composition as stipulated by the specification, i.e. the elements contained and the amount of each such element (often referred to by the term alloy content). • The composition is the primary determinant of the properties associated with each classification and each grade therein • The elements contained and their relative amounts have a major influence, and seemingly small differences can have a great effect. � The chemical composition is therefore carefully controlled to achieve not only the corrosion resistance, but also the desired associated properties that include, for example, strength, hardness, formability, weldability, machinability. To attain one such property may require that another property has, to some extent, be sacrificed.

The more important alloying elements in stainless steel, and their effects, are summarised below: - • Chromium (Cr) Chromium is the primary alloying element of stainless steel and its effect has already been outlined in §3.1.1.1 above. • Carbon (C) Carbon has a high affinity for Cr and will form chromium carbides which can be very deleterious to the corrosion resistance. Therefore, in most stainless steels C is kept to a low level, typically 0,08% max, or to a lower level of 0,03% max in the low-carbon “L” grades and other stainless steels which are utilised for the manufacture of welded fabricated components in thicker section. However, in the martensitic stainless steels C is the alloying element specifically added (in amounts varying from 0,15% to 1,2%). This renders these steels amenable to heat treatment by quenching and tempering to develop high strength and hardness. •••• Nickel (Ni) Nickel, when added to stainless steel in sufficient quantity, develops and stabilises the austenitic crystal structure. The hence the austenitic stainless steels as typified by Grade 304 [1.4301] (18%cr 8-10%Ni). Lower levels of Ni, insufficient to develop a fully austenitic crystal structure, result in a duplex (mixed) crystal structure of ferrite and austenite of the duplex stainless steels. •••• Molybdenum (Mo) Molybdenum enhances the properties (Passivity) of the passive film, and thereby renders those stainless steels that contain it more corrosion resistant, eg to reducing acids and to localised corrosion such as Pitting Corrosion. Higher levels of Mo enables more aggressive corrosion conditions to be handled. •••• Manganese (Mn) The normal content of Mn in stainless steels is typically 0,75% to 1,0%. It is similar to Ni in that it has the ability to promote the formation of the austenitic crystal structure, eg in the “200 Series Mn partly replaces Ni. However, Mn is only half as powerful as Ni in this respect and typically 2%Mn is needed to replace 1% Ni. •••• Nitrogen (N) Nitrogen is an alloying element which strongly develops and stabilises the austenitic crystal structure. Because of the pneumatic (gaseous) refining processes used in the manufacture of stainless steel N is a “natural” alloying element and has beneficial effects except in martensitic and ferritic stainless steels. It improves the resistance to Pitting Corrosion and the strength. In the duplex stainless steels it increases the austenite fraction of the crystal structure and thereby the weldability.

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•••• Titanium (Ti) and Niobium + Tantalum (Nb+Ta) These are stabilising elements, so termed because they are strong carbide formers. They will thus preferentially form carbides and thereby prevent sensitisation, ie the formation of grain boundary chromium carbide precipitates adjacent to the weld due to the high temperatures attained within this region. Sensitisation renders the stainless steel prone to Intergranular Corrosion (sometimes termed ‘weld decay’). The following table is included in order to give an appreciation of the composition of different grades of stainless steels.

TABLE 3.1

Nominal composition of some of the more common grades of stainless steel Similar grades (on the basis of composition only) from the ASTM & EN Standards are

grouped together NOTES: 1. Nominal compositions are given in this table. These must not be used for specification purposes. For the exact composition reference

must be made to the appropriate Specification 2. The % content is a maximum unless a compositional range is given 3. Al = aluminium ~ C = carbon ~ Cr = chromium ~ Cu = copper ~ Mn = manganese ~ Mo = molybdenum ~ N = nitrogen ~ Nb = niobium (as

Cb = columbium in American Specifications) ~ Ni = nickel ~ P = phosphorus ~ S = sulphur ~ Se = selenium ~ Si = silicon ~ Ti = titanium ~ V = vanadium

4. Only the primary alloying elements (C, Cr, Ni, Mo & N) are individually listed in the Table 5. All stainless steels contain Si, Mn, P & S. These are controlled to maximum % contents of typically 0.75% or 1.0%Si ~ 2.0%Mn ~ 0.015%S

~ 0.045%P. If these elements are intentionally added as alloying elements the higher % content is listed under “% Other” 6. The % content of any other alloying elements that are contained in some of the stainless steels is listed under “% Other” 7. Typical Proprietary Grades (which are commonly referred to in South Africa) are given for the purpose of example only. The inclusion of

any such Proprietary Grade must not be interpreted as an endorsement or recommendation; and vice versa, the exclusion of any such Proprietary Grade must not be interpreted as a non-recommendation

Grade Number

UNS Number Grade Designation

%C %Cr %Ni %Mo %N %Other

Austenitic Stainless Steels and Austenitic Stainless Alloys 201 S20100 0.15 16.0-18.0 3.5-5.5 0.25 5.5-7.5 Mn

1.4372 X12CrMnNiN 17-7-5 0.15 16.0-18.0 3.5-5.5 0.05-0.25 5.5-7.5 Mn

201L 20103 0.03 16.0-18.0 3.5-5.5 0.25 5.5-7.5 Mn 1.4371 X2CrMnNiN 17-7-5 0.03 16.0-17.0 3.5-5.5 0.15-0.20 6.0-8.0 Mn

202 S20200 0.15 17.0-19.0 4.0-6.0 0.25 7.5-10.0 Mn 1.4373 X12CrMnNiN 18-9-5 0.15 17.0-19.0 4.0-6.0 0.05-0.25 7.5-10.5 Mn

301 S30100 0.15 16.0-18.0 6.0-8.0 0.10 1.4310 X10CrNi 18-8 0.05-

0.15 16.0-19.0 6.0-9.5 0.80 0.11

1.4318 X2CrNi 18-7 0.03 16.5-18.5 6.0-8.0 0.10-0.20

303 S30300 0.15 17.0-19.0 8.0-10.0 >0.15 S (Free Machining properties) 1.4305 X8CrNiS 18-9 0.10 17.0-19.0 8.0-10.0 0.11 0.15-0.35 S (Free Machining properties)

303Se S30323 0.15 17.0-19.0 8.0-10.0 0.06 S & >0.15 Se (Free Machining properties)

304 S30400 0.08 18.0-20.0 8.0-10.5 0.10 1.4301 X5CrNi 18-10 0.07 17.0-19.5 8.0-10.5 0.11

304L S30403 0.03 18.0-20.0 10.0-12.0 0.10 1.4306 X2CrNi 19-11 0.03 18.0-20.0 10.0-12.0 0.11

304LN S30453 0.03 18.0-20.0 8.0-12.0 0.10-0.16 1.4311 X2CrNiN 18-10 0.03 17.0-19.5 8.5-11.5 0.12-0.22

304H S30409 0.04-0.10

18.0-20.0 8.0-10.5

1.4948 X6CrNi 18-10 0.04-0.08

17.0-19.0 8.0-11.0 0.11

305 S30500 0.12 17.0-19.0 10.5-13.0 1.4303 X4CrNi 18-12 0.06 17.0-19.0 11.0-13.0 0.11

309 S30900 0.20 22.0-24.0 12.0-15.0 1.4828 X15CrNiSi 20-12 0.20 19.0-21.0 11.0-13.0 0.11 1.5-2.0 Si

309S S30908 0.08 22.0-24.0 12.0-15.0 1.4833 X12CrNi 23-13 0.15 22.0-24.0 12.0-14.0 0.11

310 S31000 0.25 24.0-26.0 19.0-22.0 1.5 Si 1.4841 X15CrNiSi 25-21 0.20 24.0-26.0 19.0-22.0 0.11 1.5-2.5 Si 310S S31008 0.08 24.0-26.0 19.0-22.0 1.5 Si

1.4845 X8CrNi 25-21 0.10 24.0-26.0 19.0-22.0 0.11 1.5 Si

310MoLN S31050 0.02 24.0-26.0 20.5-23.5 1.6-2.6 0.09-0.15 1.4466 X1CrNiMoN 25-22-2 0.02 24.0-24.0 21.0-23.0 2.0-2.5 0.10-0.16

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316 S31600 0.08 16.0-18.0 10.0-14.0 2.0-3.0 0.10

1.4401 X5CrNiMo 17-12-2 0.07 16.5-18.5 10.0-13.0 2.0-2.5 0.11 1.4436 X3CrNiMo 17-13-3 0.05 16.5-18.5 10.5-13.0 2.5-3.0 0.11

316L S31603 0.03 16.0-18.0 10.0-14.0 2.0-3.0 0.10 1.4404 X2CrNiMo 17-12-2 0.03 16.5-18.5 10.0-13.0 2.0-2.5 0.11 1.4432 X2CrNiMo 17-12-3 0.03 16.5-18.5 10.5-13.0 2.5-3.0 0.11 1.4435 X2CrNiMo 18-14-3 0.03 17.0-19.0 12.5-15.0 2.5-3.0 0.11

316LN S31653 0.03 16.0-18.0 10.0-14.0 2.0-3.0 0.10-0.16 1.4406 X2CrNiMoN 17-11-2 0.03 16.5-18.5 10.0-12.0 2.0-2.5 0.12-0.22 1.4429 X2CrNiMoN 17-13-3 0.03 16.5-18.5 11.0-14.0 2.5-3.0 0.12-0.22

316Ti S31635 0.08 16.0-18.0 10.0-14.0 2.0-3.0 0.10 (5x[%C+%N])-0.7 Ti 1.4571 X6CrNiMoTi 17-12-2 0.08 16.5-18.5 10.5-13.5 2.0-2.5 (5x%C)-0.7 Ti

316Cb S31640 0.08 16.0-18.0 10.0-14.0 2.0-3.0 (10x%C)-1.1 Cb 1.4580 X6CrNiMoNb 17-12-2 0.08 16.5-18.5 10.5-13.5 2.0-2.5 (10x%C)-1.0 Nb

317L S31703 0.03 18.0-20.0 11.0-15.0 3.0-4.0 0.10 1.4438 X2CrNiMo 18-15-4 0.03 17.5-19.5 13.0-16.0 3.0-4.0 0.11 ~ ~ ~ S31726 0.03 17.0-20.0 13.5-17.5 4.0-5.0 0.11-0.20

1.4439 X2CrNiMoN 17-13-5 0.03 16.5-18.5 12.5-14.5 4.0-5.0 0.12-0.22

317LN S31753 0.03 18.0-20.0 11.0-15.0 3.0-4.0 0.10-0.22 1.4434 X2CrNiMoN 18-12-4 0.03 16.5-19.5 10.5-14.0 3.0-4.0 0.10-0.20

321 S32100 0.08 17.0-19.0

9.0-12.0 0.10 (5x[%C+%N])-0.7 Ti

1.4541 X6CrNiTi 18-10 0.08 17.0-19.0

9.0-12.0 (5x%C)-0.7 Ti

347 S34700 0.08 17.0-19.0

9.0-13.0 (10x%C)-1.0 Cb

1.4550 X6CrNiNb 18-10 0.08 17.0-19.0

9.0-12.0 (10x%C)-1.0 Nb

~ ~ ~ N08904 0.02 19.0-23.0

23.0-28.0 4.0-5.0 0.10 1.0-2.0 Cu

1.4539 X1NiCrMoCu 25-20-5 0.02 19.0-21.0

24.0-26.0 4.0-5.0 0.15 1.2-2.0 Cu

Typical similar proprietary grades:- 904L ~ Cronifer 1925LC ~ 2RK65 ~ Uranus B6

~ ~ ~ N08925/6 0.02 19.0-21.0

24.0-26.0 6.0-7.0 0.15-0.25 0.5-1.5 Cu

1.4529 X1NiCrMoCuN 25-20-7 0.02 19.0-21.0

24.0-26.0 6.0-7.0 0.15-0.25 0.5-1.5 Cu

Typical similar proprietary grades:- Cronifer 1925hMo ~ 25-6Mo ~ Uranus B26

~ ~ ~ N08028 0.03 26.0-28.0

29.5-32.5 3.0-4.0 0.6-1.4 Cu

1.4563 X1NiCrMoCu 31-27-4 0.02 26.0-28.0

30.0-32.0 3.0-4.0 0.11 0.7-1.5 Cu

Typical similar proprietary grades:- Nicrofer 3127LC ~ Sanicro 28

~ ~ ~ N08020 0.07 19.0-21.0

32.0-38.0 2.0-3.0 (8x%C)-1.0 Cb & 3.0-4.0 Cu

2.4660 NiCr 20 CuMo 0.05 19.0-21.0

36.0-39.0 2.0-3.0 (8x%C)-1.0 Nb & 3.0-4.0 Cu

Typical similar proprietary grades:- Alloy 20Cb3 ~ Nicrofer 3620Nb ~ Inco alloy 20 ~ ~ ~ N08825 0.05 19.5-

23.5 38.0-46.0 2.5-3.5 0.6-1.2 Ti & 1.5-3.0 Cu & 0.20 Al

2.4858 NiCr 21 Mo 0.025 19.5-23.5

38.0-46.0 2.5-3.5 0.6-1.2 Ti & 1.5-3.0 Cu & 0.20 Al

Typical similar proprietary grades:- Incoloy 825 ~ Nicrofer 4221

~ ~ ~ N08330 & N08332 0.10 17.0-20.0

34.0-37.0 0.75-1.50 Si & 1.0 Cu

1.4864 X12NiCrSi 35-16 0.15 15.0-17.0

33.0-37.0 0.11 1.0-2.0 Si

Typical similar proprietary grades:- Incoloy DS ~ Nicrofer 3718

~ ~ ~ N08800 & N08811 0.10 19.0-23.0

30.0-35.0 39.5 Fe(min) & 0.15-0.60 Ti & 0.15-0.60 Al

1.4876 X10NiCrAlTi 32-21 0.12 19.0-23.0

30.0-34.0 0.15-0.60 Ti & 0.15-0.60 Al

Typical similar proprietary grades:- Incoloy 800 & 800HT ~ Nicrofer 3220 & 3220H ~ Uranus 800 & 800H

Ferritic Stainless Steels

3CR12™ 0.03 11.0-12.0

1.5 0.03 0.6 Ti

1.4003 X2CRNi 12 0.03 10.5-12.5

0.3-1.0 0.03

~ ~ ~ S40910 0.03 10.5-11.7

0.5 0.03 (6x[%C+%N])-0.5 Ti & 0.17 Cb

1.4512 X2CrTi 12 0.03 10.5-12.5

(6x[%C+%N])-0.65 Ti

430 S43000 0.12 16.0-18.0

0.75

1.4016 X6Cr 17 0.08 16.0-

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18.0 1.4509 X2CrTiNb 18 0.03 17.5-

18.5 0.045 0.10-0.60 Ti & (0.3+[3x%C])-1.0 Nb

439 S43035 0.07 17.0-19.0

0.50 0.04 (0.2+4x[%C+%N])-1.1 Ti & 0.15 Al

1.4510 X3CrTi 17 0.05 16.0-18.0

(0.15+4x[%C+%N]) -0.80 Ti

444 S44400 0.025 17.5-19.5

1.0 1.8-2.5 0.035 (0.20+4x[%C+%N])-0.80 Ti+Cb

1.4521 X2CrMoTi 18-2 0.025 17.0-20.0

1.8-2.5 0.03 (0.15+4x[%C+%N])-0.8 Ti

446 S44600 0.20 23.0-27.0

0.75 0.25

1.4762 X10CrAlSi 25 0.12 23.0-26.0

1.2–1.7 Al & 0.7-1.4 Si

Martensitic Stainless Steels

410 S41000 0.15 11.5-13.5

1.4006 X12Cr 13 0.08-0.15

11.5-13.5

0.75

416 S41600 0.15 12.0-14.0

>0.15 S (Free Machining properties)

1.4005 X12CrS 13 0.08-0.15

12.0-14.0

0.60 0.15-0.35 S (Free Machining properties)

420 S42000 > 0.15 12.0-14.0

1.4021 X20Cr 13 0.16-0.25

12.0-14.0

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431 S43100 0.20 15.0-

17.0 1.25-2.50

1.4057 X17CrNi 16-2 0.12-0.22

15.0-17.0

1.5-2.5

440A S44002 0.60-0.75

16.0-18.0

0.75

440B S44003 0.75-0.95

16.0-18.0

0.75

1.4112 X90CrMoV18 0.85-0.95

17.0-19.0

0.9-1.3 0.07-0.12 V

440C S44004 0.95-1.20

16.0-18.0

0.75

1.4125 X105CrMo 17 0.95-1.20

16.0-18.0

0.4-0.8

Duplex Stainless Steels

3204 S32304 0.03 21.5-24.5

3.0-5.5 0.1-0.6 0.05-0.20 0.05-0.6 Cu

1.4362 X2CrNiN 23-4 0.03 22.0-24.0

3.5-5.5 0.1-0.6 0.05-0.20 0.1-0.6 Cu

Typical similar proprietary grades:- SAF2304 ~ 2304

~ ~ ~ S31803 0.03 21.0-23.0

4.5-6.5 2.5-3.5 0.08-0.20

2205 S32205 0.03 22.0-23.0

4.5-6.5 3.0-3.5 0.14-0.20

1.4462 X2CrNiMoN 22-5-3 0.03 21.0-23.0

4.5-6.5 2.5-3.5 0.10-0.22

Typical similar proprietary grades:- SAF2205 ~ 2205 ~ Uranus 45N

2507 S32750 0.03 24.0-26.0

6.0-8.0 3.0-5.0 0.24-0.35

1.4410 X2CrNiMoN 25-7-4 0.03 24.0-26.0

6.0-8.0 3.0-4.5 0.20-0.35

Typical similar proprietary grades:- SAF2507 ~ 2507 ~ Uranus 47N 255 S32550 0.04 24.0-

27.0 4.5-6.5 2.9-3.9 0.10-0.25 1.5-2.5 Cu

1.4507 X2CrNiMoCuN 25-6-3 0.03 24.0-26.0

5.5-7.5 2.7-4.0 0.15-0.30 1.0-2.5 Cu

Typical similar proprietary grades:- Ferralium 255-3SF ~ Uranus 52N

Precipitation Hardenable (PH) Stainless Steels

630 S17400 0.07 15.0-17.5

3.0-5.0 3.0-5.0 Cu & 0.1-0.5 Cb

1.4542 X5CrNiCuNb 16-4 0.07 15.0-17.0

3.0-5.0 0.6 3.0-5.0 Cu & (5x%C)-0.45 Nb

Typical similar proprietary grade:- 17-4PH

631 S17700 0.09 16.0-18.0

6.5-7.75 0.7-1.5 Al

1.4568 X7CrNiAl 17-7 0.09 16.0-18.0

6.5-7.8 0.7-1.5 Al

Typical similar proprietary grade:- 17-7PH

632 S15700 0.09 14.0-16.0

6.5-7.75 2.0-3.0 0.7-1.5 Al

1.4532 X8CrNiMoAl 15-7-2 0.10 14.0-16.0

6.5-7.8 2.0-3.0 0.7-1.5 Al

Typical similar proprietary grade:- PH 15-7Mo

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Associated properties and applications

Stainless steels have an extensive variety of associated properties which results in their application in a diversity of industries. • For any application the full spectrum of the desired properties must be considered • In the beverage and food industries the desired properties include � Corrosion resistance and the associated properties of hygiene, cleanability and product purity � Strength that will enable components to be manufactured that will be � of an acceptable mass to size ratio � able to contain the required process pressure � have the required temperature associated properties, eg strength at elevated and high temperatures, unaffected by temperature fluctuations (often rapid), tough (ie not brittle) at sub-zero and cryogenic temperatures � have good formability � Formability is a qualitative expression of the capability of a material to be plastically deformed without fracture, eg to be formed by bending, pressing or deep drawing into the required shape

� have good (even excellent) weldability � Weldability is a qualitative term that implies the ability of a material to be joined by standard welding processes so that the resultant mechanical, physical and chemical properties of the weld zone (ie both the weld metal and the adjacent heat affected zone within the parent material) are at least equivalent to the parent metal. In the design of welded components a weldability factor is used to impose a prescribed lower stress value than that as specified in the material specification � Good weldability enables

= the fabrication of complex items of plant and equipment (eg pressure and process vessels, heat exchangers) = joints to be effected without associated laps and crevices = maintenance, repairs or alterations to be carried out (if necessary) in situ

� be resistant to accidental mechanical damage � be able to be restored to a fully corrosion resistant condition should impairment of the corrosion resistance occur by accident or during repair The conventional austenitic stainless steels fulfil to an excellent degree all such desired properties and are thus utilised to the greatest extent, specifically Grades 304/304L [1.4301/1.4306], and to a lesser extent Grades 316/316L [1.4401/1.4404] if a higher corrosion resistance is required. • Duplex stainless steels fulfil a necessary role in applications where process conditions involve high chloride concentrations and thus require a high resistance to chloride induced mechanisms of corrosion, viz Pitting Corrosion and Stress Corrosion Cracking. • Utility Ferritic Stainless Steels are not suitable for components or equipment in direct contact with the food or beverage being processed � However, they are definitely worthy of consideration in peripheral applications where lower levels of maintenance are of benefit (eg ducting, stairways and walkways, pipe racks and supports, cable trays, gullies and drains)

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CONVENTIONAL (CRNI) AUSTENITIC STAINLESS STEELS

Nickel (Ni) promotes the formation of an austenitic crystal structure, and if sufficient Ni is contained a wholly austenitic crystal structure results. The stainless steels in this classification have both excellent corrosion resistance and associated secondary properties, and account for the greatest usage of stainless steel.

Basic composition

• 18%Cr + 8-12%Ni • 2-3%Mo in some grades for increased corrosion resistance • Low carbon (<0,08%C) in the straight grades � extra low carbon (<0,03%C) in the “L” grades • Ti in the stabilised grades The “L” and stabilised grades are used to prevent the possibility of a mechanism of corrosion (viz Intergranular Corrosion), occurring next to the weld in thicker welded fabrications in some corrosive solutions.

Common Grades

304 304L 321 [1.4301] [1.4306] [1.4541] and the grades that contain Mo 316 316L 316Ti [1.4401] [1.4404] [1.4571]

Basic Properties

• Very good to excellent corrosion resistance • Excellent hygienic properties and cleanability, and therefore associated excellent product purity • Excellent formability and weldability, and therefore associated excellent fabricability • Moderate strength (in the annealed condition) � can be strengthened and hardened by cold work, not by heat treatment • Excellent mechanical properties at cryogenic (ie very low) temperatures • Good high temperature properties • Non-magnetic

Common Uses

• in thicknesses of 0,5mm or less to over 200mm; articles and components weighing but a few grams to over 100 tonnes; and from the mundane teaspoon to super-critical nuclear plant. � hollow-ware, tableware, cutlery, sinks (both domestic and commercial) � hospital and medical equipment � pharmaceutical � architectural (eg street furniture, facades, shop fronts, signs, balustrades, cladding, roofing) � builders’ hardware, masonry ties and anchors � reinforcing bar for concrete � food and beverage processing (eg abattoirs, dairy, beer, wine, soft drinks), and preparation (eg hotel, restaurant and fast food equipment) � transport (eg rail cars, tankers, ISO liquibulk “tanktainers”) � boat and yacht hardware, fittings and rigging � cryogenic equipment (eg manufacture, storage and transport of liquid gases)

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� pollution control and water treatment � at elevated and high temperatures � for plant and equipment in petrochemical, chemical, mineral extraction, pulp and paper, nuclear and other industries (eg as tanks, process & pressure vessels, heat exchangers, pipe-work).

Forms commonly available

� plate, sheet, coil, strip, bar, pipe & tube, forgings � castings (as similar cast grades) � also in product forms (flanges, fittings, fasteners, wire, rope, hollow bar, etc).

Duplex Stainless Steels

These stainless steels contain insufficient Ni to develop a fully austenitic crystal structure and therefore consist of a mixed ferritic-austenitic (ie duplex) crystal structure. Until the early 1980’s the crystal structure consisted of approximately 70% ferrite and 30% austenite. The associated weldability was, at best, moderate. N, a powerful austenite former, was then included in the composition (sometimes referred to as the “Second Generation Duplex Stainless Steels”) This resulted in a crystal structure of approximately 50% ferrite and 50% austenite, and a greatly improved weldability.

Basic Composition

• Higher Cr and lower Ni (ie compared to the Conventional Austenitic Stainless Steels) • Most contain Mo • Extra low C (<0,03%C) • N as an austenite former

Nominal composition of typical grades

Originally these stainless steels were developed as proprietary grades. The preferred, and therefore more often used, grades are now incorporated in different national specifications, for example 23%Cr 4%Ni 0,4%Mo 0,15%N [1.4362] 22%Cr 5%Ni 3,0%Mo 0,18%N [1.4462] 25%Cr 7%Ni 3,5%Mo 0,30%N [1.4410]

Basic Properties

• Excellent corrosion resistance. The higher Cr + Mo & N improve the resistance to Pitting Corrosion and Crevice Corrosion • a high resistance to Stress Corrosion Cracking due to the duplex ferritic-austenitic crystal structure • Strength ≈25% higher than the Conventional Austenitic Stainless Steels

• Good formability • Very good weldability

Common Uses

As welded process plant and equipment, heat exchanger tubing & panels � in the chemical and petrochemical industries for resistance to corrosive solutions that are likely to cause Pitting Corrosion and/or Stress Corrosion Cracking � in marine and off-shore oil applications � to handle chloride brine solutions.

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� plate, sheet, pipe & tube.

Utility Ferritic Stainless Steels

The initial breakthrough discovery of 3CR12 in the early 1980’s has lead to the development of these stainless steels. Their good weldability is the significant property that differentiates them from all other plain chromium stainless steels. They contain the minimum amount of Cr to render them “stainless” - ie preferably considered as corrosion resisting as opposed to corrosion resistant. Their main use has been as a cost effective material to replace un-coated and coated plain carbon steels in applications where these steels have inadequate corrosion resistance due to the environmental or operational conditions.

Basic composition

• Plain chromium stainless steels,11-12%Cr • Extra low C & N (both <0,03%).

Common Grades

3CR12 [1.4003]

Basic properties

• Good weldability (in thicknesses of up to ≈20mm) • Corrosion “resisting” (will stain and discolour, but suffer minimal metal loss even in polluted industrial and marine environments) • Good corrosion-abrasion resistance

Common uses

• In “rough and tough” applications (eg materials handling: eg ore cars, railway coal wagons, truck bodies, chutes, launders) • tanks, silos, hoppers, bins • pollution control, dust and fume extraction, ventilation ducting, chimney stacks. • To replace coated steel in applications in which � either, the coating is damaged/destroyed by the operational conditions � or, maintenance is difficult/costly (eg walkways, stairways and ladders, high level lighting masts, electrification masts, portals and transmission towers, bus and coach frames).

Potential uses

• As production of these stainless steels as a range of “long products” becomes more common, it is considered that there is a significant potential for their use � in structural steel work (ie as angles, channels and beams) � as reinforcing bar for concrete.


• plate, sheet and coil in thicker gauges • welded tube, fabricated large diameter pipe

• bar and sections (limited size range, but increasing)

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AVAILABILITY

Although a material may be an excellent choice from a theoretical point of view, it must further have, in the broadest sense, an associated availability for it to be a practical and useful choice.

Stainless steel has such an associated “Availability”. It is available in all product forms in a range of sizes and mass, and in different grades, that enables the manufacture of items of plant, equipment and related components, viz • Flat product as plate, sheet, coil and strip ∑ process and pressure vessels, tanks and tankers, heat exchangers, filters, hoppers,

conveyors, etc • Long products as bar (round, flat, square, hexagon) and sections (angles, channels, beams) ∑ shafts, spindles, bolts and nuts and other fasteners, etc ∑ pipe racks, cable trays, stairways and walkways, etc

• Forgings ∑ flanges, rings, tubeplates, larger shafts and spindles, etc

• Castings ∑ pumps, valves, tube and pipe fittings, etc

• Pipe and Tube (both welded and seamless) ∑ tube and piping systems, shell and tube heat exchanger bundles, hand railing, etc

Availability is further dependent on the existence of • fabricators with the facilities and capabilities to manufacture the required items of plant, equipment and related components • suppliers of services, equipment and products, eg � stockholding and distribution; profile cutting of blanks and shapes (plasma, laser, waterjet); polishing and polishing consumables; welding equipment and consumables (electrodes and gases).

Local availability

The South African Stainless Steel Industry has developed into a broad-based sophisticated industry. • With respect to the different product forms � Stainless steel flat product is manufactured by Columbus Stainless, the only producer of such product in Africa. A limited range of long product is produced by Iscor � There are several foundries and forge shops capable of producing a wide range of castings and forgings respectively � Further, there are several manufactures of welded pipe and tube.

• The availability of the broad range of required plant, equipment and components made from the respective product forms in then well catered for by the fabrication/conversion sector of the industry. Many individual companies exist in this sector that have the necessary facilities and proven capability. As such this sector of industry is able to supply, on a cost competitive basis, consumer, architectural and engineering products ranging from the simple/mundane to the high-tech critical plant and equipment as required by the chemical and petro-chemical industries.

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The above is but a brief outline of the “availability” that exists within the local Stainless Steel Industry. For a full review, it is advised that reference should be made to:- • The STAINLESS STEEL BUYERS GUIDE as published by SASSDA • SASSDA’s Internet <www.sassda.co.za>

International availability

Whereas there is an excellent local availability, supply ex-import must, in some cases and for different reasons, take place, eg • product forms not produced, or produced only in a limited range of sizes, eg � classifications or grades stainless steel, eg duplex stainless steels (except as castings) � seamless pipe and tube, and larger sizes of welded pipe and tube � long product as bar and sections (limited range only)

• ‘mass production’ items not produced because of low economies of scale related to local demand, eg � some bolts, nuts and other fasteners � some small size stopcocks and valves

With respect to many such imports, a local ‘ex-stock’ availability will often exist from the stockists and distributors where a regular demand has been historically shown to exist. International availability may have to be resorted to at times when the loading on the local fabrication/conversion sector of the industry is such that unrealistically long delivery times prevail.

“IF FOR SOME REASON ITS NOT AVAILABLE LOCALLY, IT WILL UNDOUBTEDLY BE AVAILABLE INTERNATIONALLY”

Life Cycle Costing (LCC)

Stainless steel is not a low cost material. Based on “first off installed price” plant and equipment manufactured from stainless steel is often perceived, and in fact may well prove, to be more expensive than that manufactured from other materials. However, the “fist off installed price” is not a truly valid base for comparison or decision making purposes. • It is far more meaningful to apply the principle of Life Cycle Costing. This takes into account all the estimated costs incurred (or saved) over the expected life cycle (ie future years of operation) of the plant or equipment manufactured from the different materials � The estimated costs should be as rational and justifiable as possible based on best applicable knowledge and experience

• For each material, the starting point is the “first off installed price”. Thereafter, either in tabular or graphical format, the estimated costs are entered at the time that they will occur to give both a progressive cost with elapsed time, and a total cost at the end of the life cycle (ie expected years of operation). • Costs that should be estimated and entered include, amongst others, � costs of scheduled maintenance (for each such maintenance, inflated if necessary) � costs of unscheduled shutdown for repair/maintenance (which may be reasonably expected based on historical experience) � cost of replacement of plant, equipment and components (either partial or complete) that will be necessary during the expected life cycle � costs associated with lost production during any of the foregoing

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� cost differences resulting from differences in production rates/volumes attained with the different materials � costs incurred by the necessity to discard “off-spec” product � obtainable value for plant and equipment, either sold as scrap or in working condition at the end of the life cycle.

The merit of LCC is recognised in all end-use sectors. In those instances where LCC indicated a preferred choice of high cost material with an associated high “first off installed price” it has, in the vast majority of cases, been proven as justified.

Industry AND Technical Support

SASSDA (Southern Africa Stainless Steel Development Association) was formed in 1964. • It offers members and the SA Stainless Steel Industry a wide range of services including education and training, skills upgrading, technical advice and information, industry and market support.. Further, SASSDA maintains strong links both nationally and internationally, viz • Columbus Stainless (being the primary producer) and technical institutions such as the South African Institute of Welding (SAIW), The South African Bureau of Standards (SABS), Mintek • The Nickel Development Institute (NiDI), the International Chromium Development Association (ICDA), and works closely with other Stainless Steel Development Associations.

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Module Four

Objective: “Identify the factors that impact on the cleaning of the surfaces”

Outcomes

• Describe how microbiology determines the level of hygiene on the surfaces.

• Describe the soils and scaling that build up on the surfaces of the plant.

• Define the cleaning systems as they are applied to different surfaces to ensure the

elimination of soils and scaling.

• Define cleaning chemicals and materials and discuss their comparative uses.

Microbiology defines levels of hygiene.

Why microbiology impacts on levels of hygiene?

What kills microorganisms?

Which microorganisms are detrimental to hygiene?

Which microorganisms do not impact levels of hygiene?

Description of soils and scaling build up Soils and scaling composition and why they build up in the process environment. In a brewery or beverage environment soil or dirt comes in two types, organic which include organic polymers like carbohydrates, proteins, organic acids, tannins, hop oils, etc. the type of dirt is mainly due to malt in a brewery. The second type of soil is inorganic which includes metal ions like magnesium, calcium, potassium, sodium, etc., anions like sulphates, phosphates, silicates, carbonates, oxalates, etc. The presence of inorganic soil is mainly due to the fact that malt is made from barley, which is an agricultural product. It is very important to know your soil very well in order to be able to know what type of detergent will be most appropriate to remove it.

When the scale is formed in a vessel or pipe, it will reflect the composition ratio of material used in production i.e. if the ratio of organic to inorganic is x in material used in production, this ratio should only change if there is conversion in the processing, biological or chemical. If a conversion is taking place in different area of the plant, theoretically ratios should be known. For scale to build up there should some movement of molecules, polymers and particles. This movement should be slow enough to allow adherence to the surface of a vessel or pipe. The movement can be provided by mechanical means like stirring or energy means like heating. Molecules, polymers or particles are sometimes charged which will result into polar or ionic interaction. Soils tend to build on a surface in layers. It has been observed especially in thick scales where layers are observed to be in different colours. Sometimes cleaning is not done every time the vessel is used. For instance, the mash tun cleaned after every eighth brew. This will allow some accumulation of dirt before it is completely removed.

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Impact on hygiene

A dirty surface will provide site for adhesion and nutrients for microorganisms. One indicator of scaled tank is microbial infection which refuses to go away which means bugs have logged themselves into scale and multiplying. Microorganisms found in brewing industry are mainly spoilage organisms, which affect beer quality rather than consumer safety. Infected beer will have to be dumped which cost money.

Impact on surfaces

The scaling and cleaning of a surface induce stress. The surface will show cracks and pitting. This later provides sites for easy adherence of dirt and microorganisms.

Cleaning systems and how they are applied to eliminate soils and scaling.

Manual cleaning

The manual cleaning system involves using a trolley, which has a mini tank and a pump. This means the cleaning system can be moved around from vessel to vessel. The mini tank on the trolley can be filled with detergent or sanitizer. To clean a vessel, the trolley is connected to a tank. The cleaning solution is pumped through the spray ball and circulated in the tank for a specified time. The same procedure is followed for rinsing and sanitizing. The manual cleaning system designed in this way, is the single use type of cleaning where after circulation the solution is dumped. The advantage of manual cleaning is the use of fresh detergent solution, which will minimize risk for microbial infection. There is also minimum water usage. The single use of detergent can be costly with respect to chemicals and environmental load.

CIP (multi use systems compared to single use systems)

A multi use CIP system will involve cleaning detergent that is recovered for re-use. A single use CIP system will involve the use and dump scenario.

COMPARISON OF THE TWO SYSTEMS

Single Use System

Advantages Disadvantages It is a versatile system High water use

Can handle multiple detergents High detergent use

/ concentration / temperature

Uses fresh water solutions

Uses low volumes

Less thermal shock

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Multi Use System

Advantages Disadvantages Multi use of solution; Using recovered solution

Optimal use of energy, water and may result to contamination

detergent;

Integrated CIP control systems within a process environment

The integrated CIP control systems have somehow taken over the control of CIP from the user. The system is closed, therefore the user assume that the sequencing and the switches are doing what they are suppose to do. When the low level switch says the tank is empty when it is not, contamination with detergent occurs. These types of contaminations are costly for big breweries where the fermenter can be 3200 hl. Again a close system makes it difficult to verify whether the sequence and the timing of cleaning steps are correct. The top pressure on the spray ball can be within specification but by the time water reaches the bottom of the tank, there is no turbulence. This can result into scale formation and infection without the brewer knowing. All in all integrated control systems make one lose control of a CIP system.

Cleaning chemicals and materials.

Safety requirements

Cleaning of tanks and mains require the use of harsh chemicals which are strong acids and strong bases. Sometimes, oxidizing compounds are used. Safety precautions as required by Occupational Health and Safety legislations (ISO 18000) have to be considered when using these chemicals. Components of these chemicals may have short or long-term effect on the health of the employees. Some component can affect the health of the consumer at parts per million levels. The safety of environment has to be considered as well, which means that the products used have to comply with environmental legislation with respect to handling of spillage. Every material used must be accompanied by Material Safety Data Sheet (MSDS). A MSDS should disclose the following: Manufacturer’s Details; Product Identification; Composition information on ingredient; Hazards identification; First measures; Firefighting measures; Accidental release measures; Handling and storage; Exposure control and personal protection; Physical and chemical properties; Stability and reactivity; Toxicological information; Ecological information; The MSDS information is meant to give enough information about the product that assist the user to make an informed technical decision. As a user, one will only know about this safety information if one reads the information provided and ask questions to the supplier to get clarity. There is still a culture of not going through the MSDS document before the product is used.

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Detergent and sanitizer chemistry

A detergent is a blend of chemicals, which are put together to solubalise soil and remove it from the surface and ensure that it does not redeposit itself back on the cleaned surface. Sanitizers are formulated to kill bugs and bring microorganism load to an acceptable level.

Properties

Detergent is made the base of acids or alkalis, therefore the chemical properties are acidic or basic. The sanitizers especially those for traditional non-rinse application are acidic when peracetic acid or hydrogen peroxide is used as sanitizer. When halogens like chlorine are used as sanitizer, the base material is made of alkali for stability. Alkaline detergents tend to work better for two reasons. Organic soil tends to be “acidic” in nature, organic acids, polyphenols, etc. Basic detergents can hydrolyze organic polymer chains, which add to the easy removal of soil as smaller molecules. Interestingly household detergents are alkaline as well because dirt like sweat is acidic. Ingredients Basically, detergents used in beverage industry have a base material, which is either alkali or acidic, surface active molecules as wetting agents, chelating agents or sequestrates and sometimes flocculating agents. The sequestrants or chelating agents are added in order to soften water by grabbing metal ions like calcium and magnesium. The presence of these metal ions tends to bond dirt together by providing multiple charges for multisite attachment. The surface-active molecules act as wetting agents that assist with penetration of dirt otherwise water clings to itself due to bipolar nature of water molecule. During cleaning of organic soil, like proteins, surface-active molecules are created out of hydrolyzed proteins hence observed foaming during cleaning. Flocculating agents are sometimes added to facilitate the easy removal of dirt by pulling dirt together into lumps, which are easily flushed away.

Ingredients of caustic or alkali detergents

Caustic detergents are made of caustic soda (sodium hydroxide) as the main ingredient with sodium gluconate / heptonate or amino tris(methylenephosphonic acid) as chelating agents. Other agents like EDTA, NTA, sodium polyphosphates, zeolites are sometimes used. Caustic or alkali detergent can be chlorinated. The choice of chelating agents or sequestrants depends on the pH of the working solution. Their effectiveness is pH dependant. These are typical ingredients of caustic detergents. Caustic detergents are not suited for the cleaning of aluminium tanks. To clean surfaces where caustic is not allowed, alkali detergents are used. These detergents use sodium metasilicates as a base. Sometimes soda ash or phosphates salts are used as alkali source with builder (sequestering) properties. Dealing with stubborn dirt found in paraflows (heat exchangers), chlorinated caustics or chlorinated alkalis are used. The amount of available chlorine of the working solution should not exceed 200 ppm to protect stainless steel from pitting. Sometimes, wetting agents are added to caustic or alkali detergent to improve penetration and rinsability of caustic.

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Ingredients of Acid Detergents

In beverage industry, acid detergents are use for descaling. The scale is made of metal salts of oxalates, phosphates, carbonates, silicates, etc. The acid detergent should be able to penetrate the scale, which means, a strong acid component and to facilitate the peeling of scale molecules, a component of acid that will attach itself to metal ions like sequestrant is required. Acid detergents are predominantly made of a blend of phosphoric acid and nitric acid. For an acid detergent, the ratio of phosphoric to nitric acid should be about 1.2: 1. Nitric acid is a strong acid, which is good for penetrating the scale, and phosphoric acid has sequestering properties for easy removal of scale. Acids with higher level of nitric acid than phosphoric acid are recommended for passivation of stainless steel. Adding wetting agents and flocculants in acid detergent improves penetration and removal of scale especially when the scale is not only inorganic soil.

Ingredients of sanitizers

There are different types of sanitizers for use in different areas of brewery and they are formulated differently to minimize negative effects they might have to beer.

Sanitizers recommended for non-rinse application

These are peracetic and hydrogen peroxide based sanitizers. They are made from the blending of acetic acid and hydrogen peroxide in the presence of stabilizing agent like 1 – hydroxyethylidene – 1, 1 – diphosphonic acid (Dequest 2010). When used, the break down products will be oxygen and water for hydrogen peroxide and acetic acid and oxygen for peracetic acid. These types of sanitizers breakdown in the presence of metal ions. Because peracetic acid based sanitizers are oxidizing they tend to affect flavour stability of beer if not rinsed. Except usage in vessel sanitation, they are also used in sanitizer baths and in environmental sanitizer formulation.

Sanitizers recommended for sanitizer baths

Iodophors are used in sanitizer baths because their presence can be easily be detected with brownish red colour. Iodophors combine elemental iodine with surface-active compound. Acid is added to ensure that the usage concentration is at lower pH. Iodophors can taint the product when not handled properly. Where a fear of tainting exists, peroxide / peracetic acid based sanitizers are used in sanitizer baths.

Environmental sanitizers

Environmental sanitizers are used in sanitizing floors, walls, external surfaces of tanks and pipes and cleaning of drains. For these sanitizers to work effectively on surfaces, they must be able to cling on the surface to allow for extended contact time. When rinsed of the walls, they must be easily removed. Because the risk of contact with the product is low, there is a wider choice of ingredients that can be used. Quaternary ammonium compound (QAC) sanitizers work by surface action. The QAC formulations contain nonionic surfactants like ethoxylated fatty alcohols to boost forming properties of the product. For QAC sanitizers to work effectively they need to be used in alternation with a sanitizer that has a different mode of action for the microorganisms not to develop resistance. Gluteraldehydes, are commercially available as acidic solutions and they are activated before use by making them alkaline. They have a wide spectrum activity against different microorganisms. For sanitizing purposes, 2% solution is recommended.

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Biguanides and Chlorhexidines have a wide spread bactericidal properties. For the product to foam, nonionic surfactants are added. Because of their cationic nature, anionic compounds deactivate these sanitizers. They are also not compatible with phosphate, borate, chloride, carbonates ions because they form salts, which are insoluble. This will make active ingredients unavailable.

Sanitizer for drains

Most popular sanitizer for drains is sodium hypochlorite solution that has been diluted to release about 5% available chlorine during use.

Sanitizer used in different areas of processing

Chlorine dioxide has gained popularity as an effective safe to use sanitizer. It is effective at low concentration and it is not affected by pH. Chlorine dioxide is effective against wide spectrum of microorganisms. It is effective in removing biofilms. Chlorine dioxide does not chlorinate, therefore there is no risk of forming trihalomethanes (THM) when coming across organics. Chlorine dioxide works by free radical electrophilic abstraction rather than oxidative substitution or addition like chlorine. The breakdown products are chlorite and chloride. Chlorine dioxide is used for disinfection in many areas, water disinfection, post or final rinse sanitizer, biocide for cooling tower and pasteurisers.

Factors effecting performances in plant hygiene (approval for use, concentrations, contact times, temperatures, hydraulics)

Approval for use The materials use for cleaning and sanitizing should be approved through a structured process to ensure that there are no negative effects to the product, the process, the consumer and the environment. To be able evaluate these materials; the supplier will have to disclose the ingredients used in manufacturing these products and possible impurities. This type of information can be obtained from MSDS under composition information on ingredients, provided the supplier has completed the MSDS fully. There are incidents where poor knowledge about ingredients used resulted into corrosion or pitting, safety of workers compromised, sometimes even the safety of the consumer put at risk.

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CONCENTRATIONS, CONTACT TIMES, TEMPERATURES, HYDRAULICS

Fig 4.1

The effective cleaning of any surface is the function of four factors: • Hydraulics or mechanical action; • Chemical action from detergent; • Time taken to clean and • Temperature

Mechanical action in beverage industry is about optimum spray pressure and flow rates in the mains or pipes that is turbulent. Chemical action is about appropriate cleaning chemicals used at required concentrations. Higher concentration means higher product usage and higher cost. Time to clean – the longer you clean the better but in a production environment time is money. Cleaning at high temperature is better than cleaning under cold temperature. The conditions in production facilities do not always allow cleaning at high temperatures. In a brewery, the brewhouse can be cleaned at high temperature but the fermenters cannot, due to cooling jackets. Table 4.1 :

Brewery Area Temperature Detergent

Concentration

Hydraulics

(Mechanical)

Time

Brewhouse Not restricted Restricted Restricted Restricted

Paraflow Not restricted Restricted Restricted Restricted

FVs Restricted Restricted Restricted Restricted

SVs Restricted Restricted Restricted Restricted

BBT Restricted Restricted Restricted Restricted

The table above shows how restrictive the brewery cleaning regime can be. Looking for optimum combination of factors for effective cleaning can be difficult. It will require the use of statistical techniques like Design of Experiments (DOE) to get the right combination and to understand which one of these four factors is the most important to control. Sometimes boosters like oxygen releasing compounds are used to improve the mechanical action. These compounds work by releasing oxygen at high temperatures, which results into vigorous movement of cleaning liquid. These have been used in cleaning wort kettles.

Effective Cleaning

Chemical Action Temperature

Hydraulics Time

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What will be the appropriate cleaning detergent to use in various areas of the plant? To answer this question, the soil composition in terms of organic to inorganic ratio should be known. If the soil is high on organics, caustic detergent is recommended for frequent use with occasionally descaling with acid. For soil with high inorganic component, acid detergent is recommended for frequent use with occasional use of caustic detergent. Sometimes the decision on the choice of detergent type is made with more cost in mind than effectiveness of cleaning. These decision results into heavy scaling of tanks with subsequent huge cost associated with microbial infection and the cost of descaling tanks. Water flush before cleaning with chemicals is required to avoid overload of the chemicals returning to the holding tank. Table: 4.2

Recommended Brewhouse FVs SVs BBTs

Water flush to clear soil Action Action Action Action

Caustic Frequently 4 4

Acid Occasionally 4

Acid Frequently 4 4

Caustic Occasionally 4 4

The table above is about recommended detergent use in a brewery. The recommendation for

cleaning SVs and BBT is based on cost rather than the effectiveness of cleaning.

Environmental cleaning & sanitizing

Environmental cleaning and sanitation is about ensuring that microorganisms load in the brewery environment is kept to a minimum or an acceptable level to reduce risk of product contamination. This involves cleaning of floors, walls, exterior of tanks and pipes and sanitation. Drains should be sanitized as well.

Choice of systems

The cleaning of environment will involve the normal cleaning steps of removing loose dirt first, followed by actual cleaning with detergent, then rinse and the last step will be sanitizing. Cleaning this way will take time and it will be complicated by some of the surface areas that are not easily accessible. The preferred cleaning system is the one where cleaning and sanitizing takes place in one step. This will require an environmental sanitizer, which contains detergent. The solution will be applied followed by rinsing. It is also preferable to use a product that will have the residual effect to kill bugs for some time after application.

Cleaning techniques

Manual In manual cleaning, the normal steps of cleaning are followed i.e. pre-rinsing by removing as much loose dirt as possible followed by use of detergent at the correct concentration and scrubbers. The scrubbing material should not be scratched the surface being clean. Therefore scrubbers or steel wools should be avoided. The surface that has been cleaned should be rinse thoroughly with potable water.

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High Pressure Cleaning

High pressure cleaning combines high pressure, high temperature and detergent. This cleaning technique allows effective cleaning of even difficult to assess areas. Since the process is more like a one short, it saves time. Cleaning at high pressure (high hydraulics) and high temperature will minimize the detergent usage. The use high pressure gun at appropriate pressure will ensure that even stubborn soil is removed. Foam Cleaning

In foam cleaning, the working solution is diluted with air. Strong detergent solutions can be used. Because of dilution with air, small quantities of water are used. The generated foam adheres to dirt, emulsify and loosen it. Cleaning In Place CIP

Cleaning in place is about cleaning a plant without dismantling it. Water flush, detergent, and sanitizer are sprayed and circulated in the vessel to remove soil and sanitise the tank. Four factors responsible for effective cleaning are combined with four steps of cleaning. The fluids are sprayed in a burst fashion to avoid flooding the pump and allow fresh liquid – soil contact. The mechanical action is delivered by spray balls at required top pressure for turbulence. The detergent at the right concentration delivers chemical action. The washing temperature depends on the area being washed e.g. brewhouse, FV, SV or BBT.

Cleaning mains

Mains or pipe are cleaned in two ways:

• Flooding, like in the brewhouse where the diameter of pipes is too big for achieving turbulence. Flooding works because of the use of hot caustic.

• In areas where cold CIP is used, mechanical action is important therefore the fluid flow

should be turbulent. In the cellars, turbulent flow is critical. In areas where turbulence cannot be achieved, cleaning tends to be poor.

Use in plant hygiene

Environmental cleaning and sanitizing is important for reducing microorganism level, which can lead into product microbial infection. It has been documented that high levels of microorganisms in the environment leads into product infection.

Cost of cleaning & sanitizing

To analyze the cost of cleaning, firstly it is important to look at four factors and four steps of cleaning and consider each individual element how it contributes to the overall cost of cleaning. Secondly, consider the cost of failing to clean effectively, the cost of descaling, the cost of microbial contamination, the downtime, etc. The mechanical action is dependent of the design of the plant with respect to pump sizing that will be enough to deliver the appropriate top pressure to the spray ball and enough turbulence in the

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mains. If the design is inadequate, scale will develop and the product will be contaminated with microorganisms. The chemical action comes from a detergent used at the right concentration. Using a chemical detergent has various cost implications. The cost of the chemical itself, the cost of environmental and occupational safety measures that need to be implemented when using the product. The assumption is the right product is used. If the wrong product is used, scale will form which will later require an expensive descaling process plus the cost already incurred by using an inappropriate product plus microbial infection that will require dumping of the beer. Cleaning at high temperatures like in the brewhouse will require fixed amount of steam if the cleaning is taking place at a fix temperature setting. In the cellars there is no need for manipulating temperature because there is no need for heating up. Therefore it is not much of a cost factor even in the case of steaming of kegs for draft beer. Contact time in cleaning or sanitizing is important for effective cleaning or effective sanitizing. Shortening cleaning time will result into scale buildup, which will be followed by infection and the need to descale. These will cost money. In sanitizing, if the contact time is not enough, microbial infection will occur which will spoil beer, which will need dumping. The four steps of cleaning take time. Sometime the temptation of reducing time of cleaning is there if there are pressures to improve efficiencies. To shorten time, a cleaning step is skipped or some steps are shortened which result into shortening of contact time. The microbial infection increases, which will cost the brewery money. To save money cleaning and sanitizing must be done properly any shortcuts taken to minimize cost will cost too much for the brewery in the long run.

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Module 5

Objective: “Describe the methods to measure and inspect the surfaces”

Outcomes

• Compare different methods to demonstrate if cleaning systems are operating

correctly. • Describe microbiological and chemical techniques to measure the surface for levels

of hygiene and residual cleaning chemicals. • Describe non-destructive testing (NDT) methods to measure the surface for

roughness and corrosion.

Different methods of inspection QC are compared.

Underlying principles In this section we look at ways in which the levels of hygiene are measured. Figure 5.1 “Inspection and QC Process Flow” shows the points in the manufacturing chain at which inspection of the plant and analytical methods are used to determine the hygienic condition of the process, plant, finished product and data related to customer complaints.

Figure 5.1 “Inspection & QC Process Flow

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Physical examination of the process and plant. HACCP procedures have identified CCP’s in the process. These have to be inspected and controlled at specific intervals using the documented procedures. When a process deviation or external customer complaint is reported, the required inspection is done of the process and plant, to assess the root cause of the incident and put in place the correct action required. Feedback to the relevant in-house or external customer is carried out through formal reports that are logged manually or electronically. Physical inspection Physical inspection carried out on routine plant walk abouts or on an ad hoc basis, must visit must address the following aspects related to plant hygiene: • What elements in the process or plant are inspected visually, electronically, audibility or

organoleptically? o Raw materials physical inspection, batch data from suppliers, storage area. o Process condition: step of the process, condition of the process. o Items of plant: monitoring devices (e.g. temperature, pressure conductivity, level)

functioning, condition of pumps, valves, heat exchangers, vessels and other relevant equipment.

o Hygiene, safety, process deviations, operating performance: are all these factors within specification?

Chemical Inspection The flowing chemical testing is carried out: • Deliveries of raw materials for infection and contaminants. • Deliveries of cleaning material, heating and cooling medium additives in bulk for MSDS

certification and manufacturers batch numbers and QC certificate. • Concentration of CIP solutions: caustic, acid, sterilants and other as required. • Temperatures of cleaning solutions during cleaning cycles • Residual chemicals in vessels, pipes and other relevant equipment. • Final product before dispatch to customer and samples from the trade or from Customer

Complaints. Surface measurement The following tests are performed on the surface to determine level of hygiene: • Microbiological testing by taking samples from:

o the surface or from solutions in contact with the surface (i.e. from vessels and pipes) o the environment i.e. surface of floor and walls, air, rinse water.

• Microscopic examination of samples of soil. • Surface roughness finish, presence of corrosion or metal fatigue cracks.

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Sampling programme to determine hygiene levels The samples are taken at the following stages of the process with the corresponding inputs: • Raw materials

o MSDS certificates for in coming cleaning chemicals and heating and cooling media additives e.g. boiler additives and glycol

o Batch ID of in coming relevant chemicals o Samples of in coming cleaning chemicals;

� check for active ingredients: caustic, acid, sterilant � stratification of chemicals in bulk vessel for incomplete mixing at producers

factory o Samples of packaging materials e.g. washed bottles, cans, kegs o Raw materials for presence of infestation o Taint net samples e.g. water, liquid sugars, malt, filter aids and final product. o Batch ID for raw materials for traceability

• Process

o Product contamination by relevant chemicals o Concentration and temperatures of cleaning chemicals in CIP tanks o Physical appearance of cleaning chemicals in CIP tanks: presence of soil from process

vessels o Micro of rinse water and cleaning solutions in CIP tanks o Pasteurization Units in packaged product o Trade complaints micro

• Plant

o Vessels, piping, fillers (i.e. bottles, cans, kegs), finished product o Welding quality of piping and water hammer: valves lifts & CIP enters product line o Bottle washer baths caustic strength o Pasteurizer water recover plant micro and chemical residue o EBI chipped bottle: breaks hermetic seal of finished product o Keg beer dispensing plant micro o Environmental micro samples: walls, floors, air, drains o CO2 gas micro o Compressed air micro o Concentration of additives to boiler feed water and glycol additive corrosion inhibitors to

cooling medium.

Analytical procedures The following analyses are performed to assess the level of hygiene in connection with the above sampling programme: • Caustic or acid determinations on the following;

o Raw materials, incoming cleaning chemicals o Bulk storage tanks o Solution in CIP vessels o Residual liquid after CIP of vessels, pipes, filters, fillers, keg dispensing plant

• Microbiological analysis on samples for: o Bacteria o Wild yeast o ATP swabs and liquid samples o Microscopic analysis

• Analysis of additives to boiler feed water and glycol and corrosion inhibitors to cooling medium.

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Non Destructive Testing (NDT)


Mechanical surface measurement: Roughness Parameters.

Ra - (CLA, AA) Average Roughness

The Ra or Average Roughness is the most widely accepted roughness parameter and accepted by international bodies such as ISO. The derivation of Ra is shown in Figure 5.2. It can be seen that Ra is the average deviation of the profile from the mean line. Ra does not differentiate between peaks and valleys.

Figure 5.2 “The derivation of Ra surface measurement”

Figure 5.3 shows three different profiles, each having the same Ra value and the profiles each have very different profile characters. Ra is unable to distinguish between the three profiles and the implication of this is important. The peaks and valleys are used for very specific purposes in such as to characterise the bearing loads, lubrication, oil retention, wear resistance, painting and optical properties. The implication of these peaks and valleys influences the retention of soil on the surfaces of vessels or pipes.

Figure 5.3 “Graphical comparison of Ra values for different profiles”

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Rz (DIN) (Rtm) - Mean peak-to valley height. Rmax (Rymax, Rma) - Maximum peak-to-valley height.

To determine the parameters Rz (DIN) and Rmax, the filtered roughness profile roughness is divided into 5 equal lengths. The maximum peak-to-valley height (Z1) is determined within each cut-off length as shown in Figure 5.4. Rz (DIN) is the average of the 5 peak-to-valley heights, while Rmax is the maximum peak-to-valley height within one cut-off. The use of these two parameters together is a valuable tool in monitoring the variations of surface finish in a production process.

Figure 5.4. “Derivation of the parameters Rz (DIN) and Rmax”

Rz (ISO) -Ten point height. Ry - Maximum roughness depth.

These two parameters are analogous to the DIN parameters Rz (DIN) and Rmax. Rz (ISO) is the average distance between the 5 highest peaks and the 5 deepest valleys within the assessment length. Ry is the distance between the highest peak and the lowest valley. The disadvantage of Rz (ISO) is that it is possible to have a number of high peaks or valleys located close to each other.

Waviness Parameters.

Wt - Total waviness depth.

The parameter Wt is analogous to the roughness parameter Ry. As shown in Figure 5.5, Wt is the maximum peak to valley height of the leveled and filtered waviness profile. This parameter is used to monitor a production process where waviness and not roughness alone is a critical of production variable. Figure 5.5 “Schematic drawing showing the derivation of the parameter

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Total Profile Parameters

Pt - Total profile depth.

Pt is the total peak-to-valley height or the unfiltered but leveled surface profile as shown in Figure 5.6. Pt is equal to the total roughness height Ry, plus the total waviness height, Wt. Pt is useful in finding defects such as scratches or pits.

Figure 5.6 “Schematic drawing showing the derivation of the parameter Pt”

Spacing Parameters

NR (Pc) - Normalized peak count

The appearance of a surface is dependent on both the profile depth and the spacing between its peaks. Surfaces with the same Ra and Rz (DIN) can vary greatly in appearance. Because of this, the peak count, NR shown in Figure 5.7, is often measured on surfaces where the appearance is critical. The number of peaks over the assessment length, Im, are counted and then normalized to give the number of peaks per 10 mm. A comparison of profiles with the same Ra profile and with different NR peak counts is shown in Figure 5.8. By measuring NR, the peak count and Rz (DIN), the mean peak-to-valley height, the appearance of the textured furnish can be closely monitored.

5.7 “Schematic drawing showing the derivation of the parameter NR”

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Figure 5.8 “Graphical comparison of parameter NR and Ra for different profiles”

D Profile peak count. The parameter D is similar to the parameter NR in that it counts the profile peaks that exceed a pre-selected threshold. D is calculated over the entire assessment length and is not normalised to a standard length. Sm Mean peak spacing. The mean spacing parameter is the average distance between the peaks counted in the D or NR calculation. The parameter Sm conveys the same data as the parameters D and NR in a different form.

Measuring Equipment

Two Dimensional Measurements

There are many methods of measuring the surface texture but the stylus method is the most widely accepted. The diamond stylus is traversed across the work-piece, much like a household record player. The vertical displacement of the stylus is converted into an electric signal. The signal is amplified before being converted into digital information that in turn is transformed through a computer into the different forms of numerical analysis.

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The system consists of three sections; the stylus, the transducer and the skid. Figure 5.9 shows the electron microscope photo of a diamond stylus tip R = 5 µm. The geometry and the maintenance of the stylus play a key role in the reliable measurement of the surface.

Figure 5.9 “Electron microscope photo of a diamond stylus tip R = 5 µm”.

The surface tester comprises a battery operated display-traverse unit and the pick-up. A drive motor traverses the pick-up across the surface to be measured. The unit contains the electronic circuits for computing and displaying the values as described in “Mechanical Surface Measurement” above. Figure 5.10 shows the Surtronic 3 Display-traverse unit and pick-up in vertical use”. The pick-up is a variable reluctance type transducer that is supported on the surface to be measured by a skid, a curved support projecting from the underside of the pick-up in the vicinity of the stylus.

Figure 5.10 "Photograph of a Surtronic 3 Display-traverse unit and pick-up, also in vertical use”. Note: This instrument can also be used in the vertical position.

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Three Dimensional Microscopy and spectroscopy measurements.

Two dimensional measurements are used for evaluation of surfaces in many industrial applications, but it does not give the all important three dimensional perspectives that are required in the food and beverage industry, where the surface plays a critical role in the hygienic condition of the equipment. The three dimensional view of the surface is therefore presented. There are three forms of measurement that are reviewed: Optical Microscopy, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). All these techniques have been used in the food and beverage industry, including the brewing industry in Africa, to study the implication of surface conditions that are affected by biofilm and microscopic organisms that in one form or another have direct impacts on health and hygiene or corrosion.

Optical Microscopy

In the optical scan of the microscope, the polyvar optical system produces accurate images of extremely large object fields. Magnifications from 16 to 2000 are available to comply with DIN and ASTM standards. An example of photographs (500 magnifications) of stainless steel surface on an optical microscope can be seen in Figure 5.11 “Stainless Steel 120 grit polished surface: marker shows 100µm”.

Figure 5.11 “Stainless Steel 120 grit polished surface: marker shows 100 µm”

SEM (Scanning electron microscopy)

SEM has a resolution of up to 4.0nm and magnifications from 15 to 300,000. SEM has been used for evaluation of surfaces to detect microstructures of surfaces and evidence of corrosion on stainless steel. Example of an SEM image is seen in Figure 5.12 “SEM microphotograph of stainless steel 220 grit polish finish with yeast cells superimposed @ 1000 magnifications The depths of the pits or troughs on the surface are not measured in this procedure.

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Figure 5.12 SEM microphotograph of stainless steel 220 grit polish finish with yeast

cells superimposed @ 1000 magnifications AFM (Atomic Force Microscopy) The basic objective of the operation of the AFM is to measure the force (at the atomic level) between a sharp probing tip (which is attached to a cantilever tip) and a sample surface. Images are taken by scanning the sample relative to the probing tip and the measuring deflection of the cantilever as a function of later position. Examples of the use of AFM to view the surface profile of stainless steel surfaces are shown in the following; Figure 5.13 “Stainless Steel, 2B milled finish” Figure 5.14 “Stainless Steel 240 grit polished finish” Figure 5.15 “Stainless Steel electro polished finish” Figure 5.16 “Biofilm on top of fermenter before CIP” AFM can also be used to express roughness in the same terms as with the 2D Stylus instrument as above. The sample is prepared on the AFM and a computerized analysis function views the texture of the profile, as shown in Figure 5.17 “Image of replicating sample showing the analysis of trace”, and then reports the different figures in as table as shown in Figure 5.18.equivalent roughness. In the case of this example, the sample being shown is that of the replicated sample (see below) of a stainless steel surface. Figure 5.17 “Image of replicating sample showing analysis of traces” Figure 5.18 “Roughness measurements Ra, Rp, Rpm, Rtm”

Fig 5.13 “Stainless Steel, 2B milled finish” Fig 5.14 “Stainless Steel, 240 grit polished finish

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Fig 5.15 “Stainless Steel electro polished finish” Fig 5.16 “Biofilm on top of fermenter before CIP”

Figure 5.17 “Image of replicating sample showing analysis of traces used to analyse

the Roughness measurements shown in Figure 5.18”

Figure 5.18 “Roughness measurements Ra, Rp, Rpm, Rtm”

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Replicating the Surface Finishes The replicating system developed by Struers called RepliSet, is based on applying a fast curing 2 pack silicone material applied to the surface, and after 15 minutes, evaluating the replica sample under an optical microscope, SEM or AFM. The replicating sample can be

used to measure a resolution up to 0.1µm. This technique has been used in defining the measurement methods for the research test rig

Figure 5.19 “RepliSet sample of stainless steel surface 240 grit finish, compared to optical photograph of the stainless steel material”. This excellent reproduction of the surfaces makes the procedure valid as an NDT for surfaces over the entire life cycle of the equipment. Samples of replica can be kept for a number of years for reference.

Figure 5.19 “RepliSet sample of stainless steel surface 240 grit finish, compared to

optical photograph of the stainless steel material”

Camera and PC measuring surface of vessels.

Weinzierl and Wasmuht of Steinecker Germany investigated the application of a camera mounted on top of a tank that supplies images of the inside of the tank that are displayed on a PC. During the cleaning of the tank, the images are automatically evaluated and the processes are correspondingly automated. When the image analysis shows no further dirt, a safety interval of a few minutes is observed and the cleaning procedure ends. Because the adjustment of the cleaning programme is dependent upon the actual circumstances present, the process could be shortened and the use of cleaning chemicals minimised.

Vessel coating The coating of process vessels has to be carried out under a very strict procedure, so that the epoxy coating is anchored onto the profile of the carbon steel vessel. The epoxy is heated and sprayed onto the surface in a uniform manner either automatically or manually,

105

prior to polymerization to give a taste free and relatively chemical resistant surface. Special care is taken to ensure that no contamination of the surface is allowed during the coating application. This can occur in the following manner;

• Contamination of the steel surface by the shot blasting material when the anchoring

surface is prepared. • Contamination of the surface by any person entering the vessel during the lining

process: perspiration from a person has 1000 ppm of chlorides that can prevent the lining from adhering to the surface and cause pin holes.

• Epoxy temperature must be kept at 70°C for 12 hours prior to coating and the steel substrate must be more than 10°C.

• Spray equipment must be checked for correct operating parameters. • All circumferential and longitudinal welds are stripe coated prior to coating the rest of

the vessel. • One or two coats of epoxy shall be applied as specified to the required thickness

e.g.700 µm. • Carbon steel to stainless steel interfaces areas shall be prepared to ensure an

adequate overlap of the epoxy lining. The epoxy lining is tested for integrity to ensure that there are no pin holes that may give rise to delamination and eventually cause serious hygiene problems and contamination of the product with iron.

Lining integrity tests (Holiday Detector). Lloyd MK 6b brass or copper brush probe (3 – 4 mm flat faced) is placed on the surface of the lining, a current of 7KV is fed into the instrument and results will indicate if the instrument has detected a pin hole in the surface. This procedure is carried out after application of the lining, on receipt at the plant, after pressure testing and at regular intervals during the life of the vessel. Dye Penetrant Testing. Liquid penetratant testing as a NDT method is used to detect surface breaking of nonporous materials. The liquid penetrant (mesethyl oxide free) is applied to the surface and is drawn into the defect e.g. cracks or pinholes. Once a preset dwell time has passed, excess penetrant is removed and developer (e.g. chalk like suspension) is sprayed onto the surface. Visual inspection is then performed. The dye can be UV active so viewing under UV illumination also reveals cracks. The cracks arising from the following can be detected: Stress Corrosion Cracking, heat affected zone defects, poor weld penetration, fatigue, intergranular corrosion. Example of dye penetrant tests on a weld in a process vessel is shown in Figure 5.20 “Weld fatigue crack identified with dye penetrant”. Figure 5.20 “Fatigue crack identified with dye penetrant test”.

106

Figure 5.20 “Fatigue crack identified with dye penetrant test”.

Practical Implications A practical application of these testing techniques can be seen in the research done on vessel cleanability carried out since 2001 in the brewing industry in South Africa. The research set out to establish the relative cleanability of certain stainless steel surface finishes in the brewing industry. In this investigation four different surfaces were applied to one 600 litre test vessel in a training brewery. Tests were carried out using two dimensional and three dimensional profilometry, replicating material and ATP swab tests to assess the presence of organic material. The tests were also used on vessels in the operational plants to assess the validity of the research findings. The most important observations made are summarised by using graphic data compiled from the tests. Surtronic stylus instrument was used to compare the expression of the roughness measurement with the visual appraisal of the surface. Ra is not considered a true refection of the surface (the figures do not vary significantly between the different surfaces) but Rz (DIN) and Sm reflect the actual “look of the material” more effectively, as the measurements different more significantly over the range of surfaces. 2B finish is dull and electro polished surface is “bright and shiny”. This is also shown on the AFM scans of these surfaces.

107

Ra and Sm measurements compared Results are taken from readings from different levels of the surface of the test vessel during 4 weeks in 2001 and one set of samples in 2003.

Each of the surface finishes has had six readings, one at the start, four after each Brew & CIP in 2001

and the sixth on 15/4/2003. Each of these readings represents a different bar on the graph.

The finishes are as follows: High Polish at the top ring, 2B, 240 & 120 Grit and Electro-polish at the top and middle of the vessel cylinder and Electro-polish at the cone.

There appears to be no significant change in the Ra measurements over 20 months.

SAB TI Test Vessel Surface Roughness Scale Ra

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

1

Positions on the vessel.

Readings from 2001 & 2003

Ra

Valu

e

Middle Middle Middle MiddleTop Top Top Top

HP 2B 240 GRIT 120 GRIT EPEP

Bottom cone

Topring

AFM 2B surface AFM Electro polished surface

108

There appears a slight increase in the Sm measurements over 20 months.This is not reflected in the Ra and Rz(DIN) measurements.

Each of the surface finishes has had six readings, one at the start, four after each Brew & CIP in

2001 and the sixth on 15/4/2003. Each of these readings represents a different bar on the graph. The finishes are as follows: High Polish at the top ring, 2B, 240 & 120 Grit and Electro-polish at the

top and middle of the vessel cylinder and Electro-polish at the cone.

SAB TI Test Vessel Surface Roughness Scale Sm

0

50

100

150

200

250

300

1

Position on vessel. Readings from 2001 & 2003

Sm

Valu

es

Top Top Top TopTop

ring

Bottomcone

Middle Middle Middle Middle

EP EP2BHP 240 GRIT 120 GRIT

Use of RepliSet to assess the surface in conjunction with Optical Microscopy and AFM techniques Surfaces from test and operational vessels were subjected to RepliSet samples and then viewed under the optical microscope and the AFM. Samples where biofilm had accumulated were also viewed.

Repliset from swing cone outlet

Optical Photograph

Micron marker represent 100 microns

Repliset from FV pipe outlet

Optical Photograph

Micron marker represent 100 microns

Stainless Surface

Biofilm

AFM scan of RepliSet taken from 220 grit surface

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ATP swab investigation of vessels in operational area and at the Test Vessel. The ATP swab results showed significant levels of organic material at the bottom of vessels as indicated in the previously section of vessel cleaning in Module 2.

RLU VALUES AFTER CLEANING OPERATIONAL BREWERY FERMENTING VESSEL

0

100

200

300

400

500

600

700

800

900

1000

Weld

botto

m o

f 1st

can

above li

quid lin

e

liquid

interfa

ce

Weld

botto

m o

f 2nd c

an

Weld

botto

m o

f 3rd

can

botto

m o

f 3rd

can

Weld b

otto

m 4th

can

botto

m o

f 4th

can

Weld

botto

m 5th

can

bottom

of 5

th c

an

Weld

botto

m 6th

can

bottom

6th can

Weld

bot

tom

7th

can

Bottom 7

th can

Top o

f con

e

Bottom o

f cone

Bottom o

f cone

Swin

g co

ne

Top p

orthole

2nd porth

ole

Sight g

lass

in c

one

Insid

e to

p manh

ole

Low leve

l pro

be L

SL 1301

04

Back o

f sam

ple p

robe

SAMPLE POINT

RL

U RLU Weld Area

RLU Normal Finish

RLU Sight Glass

Test to show the relative presence of organic matter (cleanability)

using ATP Bioluminescence swab tests.

Acceptable

level of RLU

FOCUS OF HIGH LEVELS OF ORGANIC MATTER

= DIRTY SURFACE

TOP DOME

BOTTOM CONE

FITTINGS

INSIDE

VESSEL

BOTTOM OF FVTOP OF FV

TANK FITTINGS

VESSEL SHELL

INC

RE

AS

ING

LE

VE

LO

F O

RG

AN

IC M

AT

TE

R

ATP Swab RLU Process Vessel

10

100

1000

10000

100000

1000000

103910

4510

3010

3510

3410

2610

2910

3710

5210

6110

1410

5310

5410

4610

5910

6310

1310

2710

5010

4710

5810

5710

2210

5110

30

PV number

Series1

Series2

Series3

Series 1 =

Bottom PV

cone

Series 2 =

Outlet swing

cone

Series 3=

Outlet PV

20.03.2003

110

SAB TI ATP Swabs RLU

240EP

120EP

2402B

Temp probe upper

120

EP

2402B

Temp probe lower

Cone EP

1

10

100

1000

0 5 10 15 20

Location on FV

RL

U

Series1

Dome Lower cylinderUpper cylinder Cone

Observations

• Upper surface area of vessel cylinder has low FTU

• Upper temperature probe has high FTU

• Lower surface area of vessel cylinder and cone show increase in FTU over upper area of cylinder.

Note 1. The results show the relevant difficulty of having a “clean” surface under the temperature probe.

Note 2. Lower cylinder and cone show lower hygiene levels, following same trend as 2 years ago when research started.

20.03.2003

Stainless Steel surface finishes

2B,120 & 240 grit and EP.

Summary The following diagram summarises the key aspects of inspection and measurement of the surface.

Surface

inspected

& measured

Inspection

& QC

Sampling

programme

Practical

implications

NDT

Chemical

inspection

Surface

inspection

Physical

inspection

Analytical

procedures

Raw

materials

Process

Utilities

Contamination

Micro

Sample

MSDS

Plant

Appearance

Vessel, valves, fittings

heat exchangers

Packaging plantChemicalsSurface

micro

Taint net

Mechanical

surface

measurement

Roughness

SpacingWaviness

Measurement

equipment

2D stylus

Microscope OM, SEM, AFM

Camera

Lining detection

Dye penetrant

RepliSet

Surface Roughness

comparisons

RepliSet

samples

ATP swabs

Ra

SmMicroscopic

evaluation

Store

as record

Production

vessels

Test vessel

111

Further reading. • Biotrace, “Bioluminescence and Brewing Guidance Support Notes”, Lang G,

Biotrace Limited, Wales, UK. March 1996. • Campden & Chorleywood Food Research Association, “HACCP, A Practical Guide”,

(Second Edition) April 1997. Technical Manual No. 38. • Cluett J.D. “Cleanability of Certain Stainless Steel Surfaces in the Brewing

Process”, Dissertation for M.Phil. Mechanical Engineering, Rand Afrikaans University, Johannesburg South Africa, October 2001.

• Cluett J.D. “Chromium enhances an age old tradition and safeguards the quality of beer in a cost effective manner”. Chromium Review, March 1986.

• Curiel G.J, Hauser G, Peschel P, & Timperley D.A, “Hygienic design of closed equipment for processing of liquid foods”, Document 10, European Hygienic Equipment Design Group, October 1993.

• Czechowski F & Banner M, “Control of Biofilms in Breweries through Cleaning and Sterilising”, MBAA Technical Quarterly Vol. 29, No. 3, 1992.

• GEA Tuchenhagen “Hygienic Design of Process Lines and Valve- Matrix according to the EHEDG”. CD.

• Institute & Guild of Brewing, “An Introduction to Brewing Science & Technology Series II Volume 4, Engineering (including Distilling)”.

• Milledge J.J, & Jowitt R, “The cleanability of stainless steel used as a food contact surface”, Institute of Food Science and Technology Proceedings”, Vol. 13, 1980 p57-62.

• Mummery L, “Surface Texture Analysis – The Handbook”, Hommelwerke, GmBH, First Revision 1992.

• NiDI, “Stainless Steel: An introduction to their metallurgical and corrosion resistance”, Reprint Series No 14 056.

• Rowlands D, “Surface Finish for the Food & Beverage Industry”, published by Southern Africa Stainless Steel Development Association (SASSDA).

• Seiberling D.A, “Design Principles and Operating Practices Affecting Cleaning In Place Procedures of Food Processing Equipment”, ASTM STP 538, American Society for Testing and Materials 1973, pp 196 – 209.

• Struers, “RepliSet Introduction Manual”, January 2001. • Tuthill A.H, Avery R.E., & Covert R.A, “Cleaning stainless steel surfaces prior to

sanitary service”. NiDI Technical Series 10080.

112

PERSONAL HYGIENE An analogy to Hygiene Engineering

The IGB Africa Section Learning Solution has very specific parallels to Personal Hygiene. The holistic approach in the five modules draws analogies with Personal Hygiene.

Responsibilities for Personal Hygiene (Module 1) • “Natures Law”- natural habits of animals and birds to keep clean. • Prevents ill health and enhances a “sound way of life”. • Prevents failures to our bodies that may result in medical expenses, incapacity and

death. Know your body (Module 2)

• Different parts of your body are exposed to the sun and the cold. • Unexposed parts of the body and parts that is difficult to inspect. • Internal surfaces: mouth, ears, stomach, veins. • Cleaning systems:

o external washing, showering, brushing o baths: temperature, showers: pressure, grooming: types of brushes.

• Skin damage (internal & external) • Age, injury, infection, chemical attach.

The epidermis – nature’s material of choice (Module 3) • The epidermis

o Its natural protective characteristics o Its regenerating properties o The surface texture in different parts of the skin

• Medical support in the “wear and tear” of the body. • How do we prevent skin damage and harm to its integrity over the life time?

How do we clean our skin? (Module 4)

• The microbiology of the skin: knowing about the good and the bad microbes. • What types of soil affect the skin? • Microbial or non-microbial • How do we clean the surface of our skin?

o Mechanical methods: visual inspection, brushing, grooming. o Chemical methods: soaps, gels, creams, disinfectants. o What is the best way to clean different parts of the body?

• Cost of keeping clean.

How do we measure if our skin surface is clean? (Module 5) • Physical inspection: know what, when, where and why of inspection. • Checking the hygienic products: water, brushes, etc. • Test the skin surface for wear and tear: regular medical check ups.

• Check for cracks in the skin caused by age and injury: detailed medical tests.

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Outcomes of the Personal Hygiene programme

• Take personal accountability for your hygiene • Feel good for life.

• Pride in your self

• Low medical costs

• Smell good

• Taste good t

Outcomes of the Hygiene Engineering programme

• Take responsibility of the work place hygiene. • Feel good at the work place

• Have pride in the work place

• Low maintenance costs

• What ever you produce always smells and tastes great to you and your Customers

• Close cooperation between all stakeholders to achieve the optimum hygiene level.

Documents

Principles of Hygiene in the Beverage Industry ISBN 0-620-3