Inherent SHE - 20 years of evolution

ICHEME SYMPOSIUM SERIES NO. 141

INHERENT SHE - 20 YEARS OF EVOLUTION

Malcolm L Preston, Process Safety and Systems Consultant ICI Technology, The Heath, Runcorn, Cheshire WA7 4QD

John L Hawksley, SHE Manager ICI Group Headquarters, Millbank, London, SW1P 3JF ©ICI Technology 1997

This paper describes the evolution of thinking and application of inherent SHE principles in ICI from the pioneering post Flixborough 1970's, through alignment with Hazard Study and Hazard Assessment development in the 1980's, to new methodologies including Health and Environment as well as Safety in the 1990s.

Particular reference is made to the use of these principles at all stages from process conception to commissioning and operation, together with some case studies where significant benefits have been achieved. An outline is given of how requirements for the application of inherent SHE principles are being incorporated into the ICI SHE Management System. Some "tools" to help the application of the principles are also described. Finally, the paper identifies issues and needs both for research and industry into the 21 st century.

INTRODUCTION

The concept of "Inherent SHE" is that we should strive to minimise Safety, Health, and Environmental (SHE) impact (i.e. reduce risk) primarily by eliminating or minimising hazards rather than reducing the likelihood of hazardous situations arising. The more inherently safe or inherently clean a process the less reliance has to be placed on extrinsic (add-on), usually expensive, protective systems.

Inherent SHE has its roots in the concept of inherent safety first widely promulgated in the late 1970's by Trevor Kletz. His original booklet "Cheaper, Safer Plants or Wealth and Safety at Work - notes on inherently safer and simpler plant" (Ref. 1) has been recently updated and republished as "Plant Design for Safety : A User Friendly Approach" (Ref. 2). Both of these publications and the wide range of supporting papers (e.g. Ref. 3) are recommended reading.

Inherent Safety can be readily extended to embrace Health and Environment protection so that we can speak of "Inherent SHE". The basic principles are common sense and include avoiding the use of hazardous materials, minimising the inventories of hazardous materials and aiming for simpler processes with more benign and moderate process conditions.

As we shall show there is nothing new or particularly original in these basic principles - indeed that is their strength and magic - and we should always give these some thought when designing our processes and plants. However, do we always do as much as we could (as far as reasonably practicable)? We will also show several

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good examples of application of Inherent SHE principles. However, with ever-increasing emphasis globally on SHE issues ICI felt that a more systematic and comprehensive approach was called for. This has now become a formal requirement of the ICI Group Safety, Health and Environment standards.

For best results, Inherent SHE thinking should start early, ideally during the research and development stages of a project. It is only then that more fundamental opportunities for exploiting Inherent SHE concepts exist. It is then that alternative options to minimise SHE impact can be exploited without unreasonable time or cost penalties. Nevertheless the concepts and principles do cover the whole life cycle of a process or project right through into the later stages of operation and eventual decommissioning. Figure 1 shows this life cycle together with some of the Inherent SHE related ICI methodologies.

Figurel

THE WIDE SCOPE FOR APPLYING INHERENT SHE CONSIDERATIONS Product Selection Process Selection Process Spec. Project Spec. Design Cons t Operation Termination

Product Stewardship Guidelines (G010)

Hazards Studies for SHE (PSHEG13)

Inherent SHE In Process Selection and Development (PSHEG16)

SHE Assurance PSHEG13.PHR

HISTORY

In 1971 ICI set up its Process Safety Panel (later to become Process Safety Interest Group) following a series of inter-Business (then called 'Divisions') meetings of hazard practitioners/research specialists that had taken place in the 1969/71 period. Its formation was a recognition that the Company needed a formal mechanism for identifying areas of concern in Process Safety and for converting research into design procedures. Networking between professionals in different departments and locations was also part of the remit.

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It is no coincidence that at this time ICI was also developing its pioneering Hazard Study Process (Ref. 4) which has now been adopted globally by the process industries as a best practice approach for process hazard analysis.

In its first five years, the Process Safety Panel produced a number of Process Safety Guides (clear guidance) and Process Safety Reports (state-of-the-art) and perhaps most importantly for the time a series of Process Safety Seminars. The first 5 such seminars were:

June 1974 Hazard and Operability Studies April 1975 Evaluation of Risk December 1975 Control over Minor Plant Modifications October 1976 Development of Intrinsically Safer Plants and Processes. November 1977 Process Safety in the Next 5 Years.

The transactions of these seminars are all fully recorded themselves as Process Safety Reports and as such part of ICI Corporate memory.

It is therefore fitting that exactly 20 years on from Id 's internal seminar on intrinsically safer plants and processes we should be reviewing progress and achievements during 20 years of evolution. We have chosen "evolution" rather than "revolution" as the journey towards Inherently Safer, Healthier and Environmentally more acceptable processes and plants has been one of gradual improvement interspersed by plateaux of quiescent activity.

In early 1979 there were two key meetings. The first in February was a symposium organised by Trevor Kletz for his home Petrochemicals Division on "Simpler Plants". The second was the twentieth meeting of the company Process Safety Interest Group of which Trevor was a key member, which established the ICI Intrinsic Safety Panel and in particular initiated thinking towards what have become accepted Inherent SHE principles and use of indices for ranking and early stage process decision making.

It was in March 1983 that the panel adopted the more appropriate nomenclature of 'Inherent Safety' to avoid confusion with the intrinsically safe designation applied to some electrical equipment. In 1984, Trevor Kletz, by then retired from ICI, published his seminal booklet "Cheaper, Safer Plants or Wealth and Safety at Work" which encapsulated much of Id ' s thinking to this date with Trevor's own particular added value and style.

The mid 1980's were the heyday of development of aligned methodologies in the area of Process Integration, and incorporation of Inherent Safety thinking was trialled in ICI 's internal courses on preliminary flowsheeting and associated process evaluation and preliminary design procedures. The summary table of guidelines from this evolutionary period has survived with little modification through to our current guidance. (Figure 2).

The five year period 1986 - 1991 are somewhat the 'Wilderness Years' for the development of Inherent Safety methodology in ICI. The history shows there had

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been uncertainty over how best to incorporate the principles further into the design methods. Also many of the key players had retired, few new plants were being built and at the end of this period another cyclic downturn had arrived. But, more particularly, that period saw the implementation of the Seveso Directive in Europe and process safety activity was dominated by burgeoning developments in risk assessment as applied to major process hazards. Despite the hiatus in development activity on Inherent Safety methodology, the principles were being applied in practice; a survey at that time revealed almost a hundred examples of hazard reduction. Also

the major hazards legislation encouraged reviews of inventories of hazardous substances and in many cases significant reductions occurred.

Figure 2

Guidelines for improved inherent safety, hygiene and environmental protection

PRINCIPLES 1 Avoid

processing or using toxic, flammable or environmentally hazardous materials

2 Reduce the inventory of hazardous material

3 Reduce the potential for surprise

4 Separate people from chemicals

CONSIDERATIONS • THE CHEMISTRY OF THE PROCESS

Feeds Intermediates Products By-products Impurities

• PROCESSING AIDS Heat transfer fluids Refrigerants Recycles

• WHERE THE MATERIAL IS Stock tanks In process In transport

AS ABOVE PLUS: • Unit operations and equipment • Continuous rather than batch • Possibility of faster reaction • Hazard Density

Spread over large area Sub-divide inventories

• Keep simple • Avoid runaways, explosions and

detonations • Moderate the operating conditions • Continuous rather than batch

operation • Big heat sinks, small amount in

process • Dynamics

High inertia, hazards slow to devleop Low inertia, deviations quickly corrected

• Integrity of containment Design strength Joints Seals Moving parts

• Minimise corrosion and wear • Operability and layout • Remote control • Beware vents and drains

KEYWORDS ELIMINATE

SUBSTITUTE Avoid Combine

INTENSIFY Combine Reduce Divide

ATTENUATE bimpnry Avoid Dilute Reduce

SEPERATE Contain Remove Enclose Reinforce

M


THE PRESENT

Paradoxically at the onset of the downturn ICI had responded to an internal 'crie de coeur* from its Process Safety community that it needed to revitalise spending on development of process safety tools, techniques and methodologies as well as networking and training.

Under the leadership of ICI Group SHE the individual businesses of ICI at the time (Chemicals and Polymers, Explosives, Materials, Paints, Pharmaceuticals and Tioxide) agreed to fund an ambitious 3 year programme of activity. Amongst the topics to be pursued, ranging from Hazard Study and Risk Management, through Fire and Explosion, Gas Dispersion to Pressure Relief, was Inherent SHE. (Importantly, now Inherent Safety, Health and Environment (SHE) not just Safety). This reflected a progressive integration of S, H and E considerations when managing the risks from process hazards. But also it was recognised that conflicts could arise. Sometimes what was good for inherent safety might not be best for reduced environmental hazards - the demise of CFC's as inherently safer refrigerants is a prime example.

The outcome in 1994 was a long awaited, much sought after, Process SHE Guide on "Inherent SHE in Process Selection and Development"; No 16 in a series that had started in 1974 immediately after Flixborough with No. 1 on "Emergency Isolation of Plant". There is a two-fold importance to this guidance. Firstly it focuses on activities that are upstream of Hazard Study 1 in the ICI six stage Hazard Study Process, and secondly its production and delivery continued across ICI's demerger in 1993 into Zeneca, (the Pharmaceutical and Specialities Group) and the new ICI Group.

We are pleased to see a resurgence in activity in the Inherent Safety arena : conferences such as this and the 1995 CCPS event, research projects such as the CEC "Inside" initiative (Ref. 5) and aligned activities such as that at Loughborough and Dow on indices and cost-effectiveness (Refs. 6,7), and renaissance of the twenty year old truths, updated, by Trevor Kletz (Ref. 3).

In ICI the strategy over the last three years since demerger has been one of focus on core businesses, core competencies and core values. As such our recently articulated vision includes these values:

• exemplary performance in safety and health • responsible care for the environment • relentless pursuit of operational excellence

Our strategic Inherent SHE theme has much relevance to putting these values into practice. Since 1994 we have continued to evolve the emphasis on the principles, guidance and recognition of best practice. In particular, we have organised internal process safety seminars, contributed articles to house journals and arranged awareness and training courses, i.e. publicity, promotion and technology transfer.

The response has been supportive although many of our experienced engineers and technologists say they have been aware of the principles and techniques for many years and apply them - so what is the fuss? Indeed the exercise has identified

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numerous examples of good practice in all branches of the ICI businesses, some of which are included in Case Studies below. Although Inherent SHE thinking is "alive and reasonably well" we believe that there is scope for a more systematic approach and are progressing towards establishing formal requirements in our SHE Management System. Our next step, as well as further awareness/training and outward expression such as this paper, is to completely integrate Inherent SHE thinking in our existing tools, techniques, methodologies and procedures, including a very early front end SHE impact review.

SOME CASE STUDIES

An important part of guidance in Inherent SHE is the provision of case studies and examples, both to illustrate and clarify the principles and for use in training sessions. The following are summaries of a few, drawn from each of the ICI International Businesses, to emphasise both the universal and the different aspects of Inherent SHE thinking.

Chemical or Physical Approach to Inherent SHE

a) Oxy-anion promoted catalysts have been developed in which the selectivity promoter is absorbed onto the catalyst to activate it. Any temperature excursion in the reactor results in desorption of the activator so the reaction runaway potential has been eliminated. ((ICI C & P).

b) For some explosives, mobile mixing plants have been developed to enable explosive mixtures to be made at the site of use and charged directly into a borehole. There is then no need for intermediate storage of the explosives mixture and the separate components are individually less hazardous than the mix to transport. (ICI Explosives).

Reduction of Inventories

a) By Process Selection/Development

The inherent safety of the chloride route for production of titanium dioxide pigment has been improved by increasing the pressure of the oxidation reactor from the traditional atmospheric pressure to a moderate pressure to enable the chlorine rich gaseous stream to be fed directly into the chlorinator to recover chlorine. This avoided the need for an absorption/distillation stage previously required to boost the pressure of the highly corrosive chlorine rich mixture using liquid titanium tetrachloride as the absorption medium. Inventory of titanium tetrachloride has been reduced one hundredfold. (Tioxide Group).

b) By "Just-In-Time" Production

In order to minimise intermediate storage of hydrogen cyanide, on new hydrogen cyanide and acetone cyanohydrin plants, the feed of hydrogen cyanide is taken directly from the distillation column reflux tank, on the

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hydrogen cyanide plant. This not only minimises the inventory of hydrogen cyanide, but also eliminates a hazardous storage installation. (ICI Acrylics).

Inherent SHE by Process Design

Ethylene oxide is purified from water solution by distillation, with heating by live steam injection. This avoids indirect heating of the EO containing solution in a reboiler and the higher temperature that could result from overheating. A known hazard with EO is that heating above 140°C can lead to internal deflagration. With live steam heating, the required capacity of the pressure relief system is reduced because the source of heat to the still stops if the still pressure rises to the level of the steam pressure. (ICI Polyurethanes).

Elimination of Hazardous Substances

A new generation of paints has been created which are water based, thus eliminating the need for expensive VOC treatments necessary when solvent based paints are used. Within the paint shop the hazards from flammable materials is considerably reduced. The quantities of flammable solvents to be handled and transported are virtually eliminated. (ICI Paints).

MANAGEMENT SYSTEM

The ICI SHE Management System with its "virtuous circle" of Policy, Standards, Guidelines, Procedures, Audit and Review has been described at a previous CCPS conference (Ref. 8). Within this system, the basic mandatory requirement with regard to Inherent SHE is set by a Group SHE Standard for "Product Stewardship" which states:

'There shall be arrangements to ensure that Safety, Health and Environment considerations are taken into account prior to the launch of new products and in the development of new processes. The Safety, Health and Environmental factors associated with any product from conception through to ultimate use and disposal shall be managed responsibly and ethically".

Meeting this Standard requires that there are procedures in place to address the relevant issues. For the consideration of processes, the procedures need to meet the requirements of the relevant Group Guideline, which calls for:

a) A formal, multi-disciplinary study of the SHE impact of each new process to be carried out at a suitable early point during research and development.

b) Systematic steps to be taken to reduce the potential for SHE impact to a practicable minimum.

c) Documentation of the study as a SHE impact statement for use at the Hazard Study 1 stage of any subsequent project.

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This multi disciplinary activity requires the collaboration of development, operations, safety, health and environment advisers. An objective is to consider the eight questions given in Fig. 3. The output from the procedure is documented evidence that alternative options of lower potential SHE impact have been considered (or reasons given if no alternatives feasible), an objective assessment of SHE impact and documented justification for the option selected.

Figure 3

Inherent SHE Process SHE Study Questions

(D

(2)

(3)

(4)

(5)

(6)

(7)

What alternative routes or processes can be used to allow substances or solvents of lower impact on man and the environment to be considered?

What alternative routes or processes can be used to minimise the inventories of hazardous substances?

What alternative routes or processes can be used to make process conditions as benign as possible?

What is the ultimate fate of all substances used in the process that are not part of the product?

How will processing stages permit internal recycles with minimum or nil purges?

Can the effluents be further processed to allow a recycle or a better means of disposal?

What are the consequences on man and the environment of the release of any of the materials during processing, transport and storage (including both normal and abnormal conditions)?

(8) What is the impact on capital and operating costs of lower SHE impact options and higher safety, health or environmental standards?

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During the study, there should be reviews by experienced "peers", independent of the research and development project team. A key function of the review is to act as a stimulus to ensure that adequate consideration is given to inherent SHE principles. Essentially the review is a questioning process. It can be structured around a few basic, but probing questions, for example:

•Why do it that way?

•Why is that necessary?

•Why that material?

•Why so much?

•Is it as simple as it could be?

•What changes have been made to improve inherent SHE?

•Why is the selected option considered the best?

•What is the impact of the selected option?

•What prevents the impact being reduced?

INHERENT SHE 'TOOLKIT'

Whilst there is a requirement for systematic consideration of inherent SHE during process selection and development, there needs to be a balance between structured and free thinking so as not to constrain the imagination of the process development team. Hence no rigid methodology has been laid down. Rather guidance has been assembled which includes a number of 'tools' for use where they seem helpful. Two of these, the Inherent SHE Flowsheet and Target Diagram are outlined below.

Inherent SHE Flowsheet

The 'flowsheet' given in Figure 4 is one suggestion to encourage broader and more structured thinking about inherent SHE. It is supplemented by a compilation of notes and examples to indicate and illustrate some of the many factors that may need to be considered. The well-established "guide word" tabulation (Figure 2) can be used in conjunction with the flowsheet.

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Figure 4

Inherent SHE Flowsheet

REACTION

PROCESS

INPUTS

i |

Consider all materials

What SHE issues are raised?

Raw material usage The effects of raw materials Reaction conditions Reaction profiles

PROCESSING

(including

purification)

^ 1

PROCESS OUT 3UTS

Process type Process conditions Process control Break-in requirements

Consider all effluents Consider properties What SHE issues are raised? Prevention and cure of effluents

Inherent SHE Target Diagram for assessing alternatives

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During process development the need will often arise to compare various options in order to select the preferred option. Often there will be significant factors in addition to SHE issues that will influence the decision, notably the process and business economics. Even within SHE, and particularly when it comes to inherent SHE, there is a range of factors to consider that includes the (possibly) separate S, H and E hazards, process complexity, siting considerations, energy considerations, transport and storage implications. There is no easy way to balance the various factors and there are many "apples and pears" comparisons so that judgements are inevitable. It is important though to try to make the judgements as objective as possible by assessing each factor in a rational way.

Alternatives may need to be assessed at various stages of the development process to guide the development. At an early stage there may be many unknowns and assessment of some factors may not be possible or can only be rudimentary. That may limit the confidence in the comparisons being made and any decisions should take account of that and be qualified as appropriate. Later, as more information becomes available, better comparisons should be possible with which earlier decisions could be checked, if necessary. At any event the basis for assessments and comparisons should be recorded so that the basis for decisions is clear.

From work done to evaluate options on one particular project, the idea of the 'target' diagram (figure 5) emerged. The sectors of the target cover the range of factors most or all of which will need to be considered when comparing options.

For each relevant sector each option is ranked on a scale 1 -5 in which:

1 is the better inherent SHE

5 is the worse inherent SHE

0 indicates insufficient data for assessment

The ratings are displayed on the diagram by masking the appropriate segments from the centre outwards, as shown for the example in figure 5. The format of the target diagram with sectors marked in this way means that an option that is best on all factors would show as a "bull's eye" on the target!

Ranking can utilise whatever approach seems appropriate and feasible for the options to be compared. The objective is to make rational comparisons. To that end, the ranking of different options should be on a consistent basis and should preferably be carried out by the same group of people. The objective is to achieve a ranking that is consistent for those options being.considered even though these are unlikely to be "absolute" values.

The diagram will not necessarily provide a clear indication of the best option and rarely will there be low scores for all sectors. Decisions will mostly be a matter of balancing the desirability of low scores in particular sectors against the ease of

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managing the hazards giving the higher scores in other sectors.

Figure 5

The Inherent SHE "Target" Diagram

ISSUES AND NEEDS

It is important that inherent SHE techniques become "recognised good practice". To achieve this continued promotion by industry and academia is needed. The thinking has clear applications throughout the asset life cycle for safety, health and environment. As such there is a need for better methods to resolve and balance conflicts between S, H and E, although a single criterion or inherent SHE index is neither likely to be desirable or in the limit feasible. Regulators need to influence not legislate for sensible adoption of inherent SHE : definition of 'best' inherent SHE option is problematic and there needs to be scope for judgement. A holistic approach ensuring all aspects and options have been duly considered at an early stage for SHE impact is a desired outcome. Neither S nor H nor E should obscure each other.

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CONCLUSION/SUMMARY

This paper has described a progressive evolution of inherent SHE thinking and application in ICI. The contribution it offers is to extend the original 'intrinsic'/inherent safety concepts into the broader SHE arena and across the project/process lifecycle. Progress in development and adoption compared to Hazard Study appears to be slow and sustained articulation and promotion is required. Nevertheless good guidance and excellent case studies exist to confirm that much has been achieved albeit in a quieter good practice, common sense way. Finally some issues and needs have been identified for further research, development and application.

ACKNOWLEDGEMENT

The authors would like to thank all their Process SHE colleagues who have helped the ICI Inherent SHE theme. They would also like to thank ICI for permission to present and publish this paper.

REFERENCES

1. Kletz, T A., Cheaper Safer Plants or Wealth and Safety at Work, I ChemE, Rugby UK, 1984 (2nd edition 1985).

2. Kletz, T.A., Plant Design for Safety - A User Friendly Approach, Hemisphere, New York 1991.

3. Kletz, T.A., Inherently Safer Design : The Growth of an Idea, Process Safety Progress No. 115, No. 1 pp5-8 Spring 1996

4. Swann, CD. and Preston, M.L., Twenty-five years of HAZOPs, J. Loss Prev. Process Ind. Vol. 8. No.6 pp 349-353 1995

5. Mansfield, D, Viewpoints on Implementing Inherent Safety, Chemical Engineering pp 78-81 March 1996

6. Edward, D.W. and Lawrence, D., Assessing the Inherent Safety of Chemical Process Routes, Trans IChemE vol. 71 Part B pp 252-258, November 1993

7. Gowland, R., Putting Numbers on Inherent Safety, Chemical Engineering 1996 pp 82-85 March 1996

8. Hawksley, J.L., A Multilevel Approach to Monitoring the Implementation of SHE Standards in the ICI Group, Proc. International Process Safety Manangement Conference and Workshop, pp227-240, San Francisco AlChE Sept. 1993

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Inherent SHE - 20 years of evolution