Uranium Corporation of India Ltd.

A CASE STUDY IN

PINAKI ROY

A BRIEF RE-CAP of MAINTENANCE

MAINTENANCE is the act of maintainingor the state of being maintained. It denotes the work undertaken for keepingsomething in proper condition i.e. upkeep.It can be machines, household goods or evenyourself !!

Basics of MaintenanceMaintenance technology comprises of technical knowledge plus experience and their application in identifying and implementing the best possible maintenance and repair techniques for all maintainable items, in line with organizational policy.

• It provides a means to maintain the plant and equipment in a high state of operating efficiency and enhance its productivity.

Two Keywords of Maintenance

• CLEANING &• LUBRICATION

• CLEANING PHILOSOPHY: • IF YOU CAN’T SEE IT, • YOU CAN’T FIX IT

• So use: • High pressure water jets• Anti-Rust & Grease removal

compounds• Scrape, clean & re-paint regularly

LUBRICATION• Dictionary defines lubrication

as the application of some oily or greasy substance in order to diminish friction. Though a valid definition, it fails to realize all that lubrication actually achieves.

• Many different substances can be used to lubricate a surface. Oil and grease are the most common. Grease is composed of oil and a thickening agent to obtain its consistency, while the oil is what actually lubricates. The application determines which oil, commonly referred to as the base oil, should be used.

STATUS of GREASE- General Perceptions

Isn’t it true that of all types of lubricants in use, onlyGrease is looked down upon & treated with disdain. While pouring engine oil in your car is considered

normal, greasing is generally given to the mechanic or his assistant, as its supposed to be a menial & dirty

job.

LETS UNDERSTAND GREASE & GIVE ITS DUE

Grease – A Case Study in UCIL

• UCIL stands for Uranium Corporation of India Ltd, a modern Indian Public Sector Undertaking, involved in mining & processing of Uranium Ore. A few years back, a sudden spurt in equipment breakdowns made us go in for a detailed root cause analysis to study the failures. Many factors surfaced but what was shocking was that in most cases the lack or improper method of greasing was the culprit.

• This presentation highlights the steps taken to address the problem and also makes an effort to educate the viewers on the importance of Greasing by explaining its various facets.

TRAINING – The key to changeThe analysis highlighted that most workmen (even some engineers) hardly had any knowledge of lubrication and greasing. So the first challenge was to impart training in this domain.While this challenge involved imparting technical awareness regarding Lubrication, it was also an exercise in changing sleepy and often rigid Mind Sets.

Evolutionary Change – The Model Adopted

• A team of related engineers were selected & sent for a lubrication training course which involved both theoretical and practical training. On return they were assigned the following responsibilities:

• Create a broad based site specific pictorial awareness manual on lubrication in english and the local language as a handbook for the workforce

• Evolve a mechanism to train identified personnel• Demonstrate and bring pride to the persons involved in

lubrication and greasing

Evolutionary Change – The Line of Action

• A list of personnel from various maintenance sections was prepared by taking their education, age & experience.

• A short objective test of such personnel was conducted in order to asses their basic I.Q. & grasping potential.

• The top eight were short listed & trained in house on the basics of lubrication by theoretical and practical on equipment coaching and thereafter assigned exclusive lubrication responsibilities

Training Content• In order to provide training relevant to the

Equipment in use & the grasping power/education levels of those persons, course material was formulated.

• A broad scheme of the training material which became the foundation for understanding lubrication in general & grease in particular, is given in thefollowing slides:

A Layman's DEFINITION of LUBRICATION

““To make smooth or slippery To make smooth or slippery with oil, or other matter to with oil, or other matter to overcome friction”.overcome friction”.

TECHNICAL DEFINITION OF LUBRICATION

• LubricationLubrication– any procedure that reduces friction

between two moving surfaces.• LubricantLubricant

– Any material that reduces friction.– The main function of a lubricant is to

separate two moving surfaces and make their relative movement easier.

– Liquids used as lubricants achieve this by substituting low fluid friction in place of high solid-to-solid friction.

FRICTION• Always exists where there is sliding contact

between two surfaces• Always consumes power• Always produces heat• Is independent of contact area and sliding

speed• Is dependent on surface roughness and contact

pressure• Represented by COEFFICIENT OF

FRICTION

TYPES OF FRICTION

SLIDING FRICTION(most)

ROLLING FRICTION

FLUID FRICTION(least)

LUBRICATION, FRICTION AND WEAR

SIMPLE REPRESENTATION

UNLUBRICATEDMETAL SURFACES

PRESSURE ANDSLIDING MOTION

FRICTION ANDHEAT

(ENERGY LOSS)

CATASTROPHICFAILURE

SEIZURE

LUBRICATION, FRICTION AND WEAR

LUBRICATION: “MAKES SURFACES SLIPPERY”

LUBRICATEDMETAL SURFACES

PRESSURE ANDSLIDING MOTION

OIL FILMPREVENTS CONTACT

FLUID VISCOSITY: “RESISTANCE TO FLOW”FLUID VISCOSITY: “RESISTANCE TO FLOW” or “INTERNAL FRICTION” or “INTERNAL FRICTION”

FULL FILM, or FULL FILM, or HYDRODYNAMICHYDRODYNAMIC LUBRICATION LUBRICATION

FRICTION• Always exists where there is sliding contact

between two surfaces• Always consumes power• Always produces heat• Is independent of contact area and sliding

speed• Is dependent on surface roughness and contact

pressureRepresented by COEFFICIENT OF FRICTION

THE LAWS OF FRICTION

There are two laws of physics that govern sliding friction:

1. The friction between two solid bodies is independent of the area of contact.

2. The friction between two solid surfaces is proportional to the load by one surface on another.

COEFFICIENT OF FRICTION

F / Wwhere F = frictional force opposing motion

And W = the load

Frictional Conditions CoF (Fluid Friction 0.001 - 0.005Rolling Friction

• Ball 0.002• Roller 0.004

Sliding Friction• Mixed Film 0.02 - 0.08• Boundary 0.08 - 0.10• Dry 0.15 -

0.40

LUBRICATION CONDITIONSLUBRICATION CONDITIONS

CONDITIONS LEADING TO BOUNDARY LUBRICATION

• STATIC LOAD

• SLOW SPEEDS

• HIGH LOADS

• ROUGH SURFACE FINISH

• SMALL CLEARANCES

• SHOCK LOADING

region of boundary lubrication

partial fluid film lubrication

full fluid film lubrication

TYPES OF OF FRICTIONTYPES OF OF FRICTION

• Modes of lubrication• Hydrostatic• Hydrodynamic• Elasto-hydrodynamic• Boundary

• Regime depends upon• Design• Speed• Load• Materials• Viscosity• Operating conditions etc.

LUBRICATION CONDITIONSLUBRICATION CONDITIONS

A solid to semi-fluid product of dispersion of a thickening agent in

a liquid lubricant. Greases consist of the following:

1. Additives 2. Thickener 3. Base oils

COMPONENTS OF GREASE• LUBRICATING FLUID• THICKNER SYSTEM• ADDITIVES

LUBRICATING OIL(Pet./SYN. 4-20%)+THICKNER(SOAP/NON-SOAP 75-96%)+ADDITIVES(0-5%) = GREASE

Mineral Oils( Paraffinic or Naphthenic Hydrocarbon Based)

Synthetic Oils(Chemically Synthesised Oils and Esters)

Silicone Oils(Polymerised product of Silicon Oxide)

LUBRICATING FLUIDS

Soap based thickener system ( Product of reaction between fats and

alkalis)

Non-soap thickener systems

THICKENING SYSTEMS

Anti-oxidantsAntirustAntiwear

Extreme PressureTackifiers

Solid LubricantsFriction Modifiers

Structure ModifiersMetal Deactivators

ADDITIVES

GREASE- CLASSIFICATIONTHICKENERS SOAP SIMPLE SOAP COMPLEX SOAP LITHIUM LITHIUM COMPLEX CALCIUM CALCIUM COMPLEX ALUMINIUM ALUMINIUM COMPLEX BARIUM BARIUM COMPLEX SODIUM TITANIUM COMPLEX STRONTIUM MIXED SOAP

NON SOAP INORGANIC ORGANIC ORGANOPHYLIC CLAY POLY UREA, etc Silica Based, etc

The interactions between thickener The interactions between thickener and lubricant (Base oil +Additive) and lubricant (Base oil +Additive) together with the manufacturing together with the manufacturing process constitute the major part of process constitute the major part of grease performance grease performance

PROPER GREASE SELECTION PROPER GREASE SELECTION Due to the lack of specificity in most grease Due to the lack of specificity in most grease

recommendations, it is important to learn how to properly recommendations, it is important to learn how to properly select greases for each application in the plant or select greases for each application in the plant or equipment. equipment.

Proper grease specification requires all the components of Proper grease specification requires all the components of oil selection and more. Other special considerations for oil selection and more. Other special considerations for grease selection include thickener type and concentration, grease selection include thickener type and concentration, consistency, dropping point and operating temperature consistency, dropping point and operating temperature range, worked stability, oxidation stability, wear resistance, range, worked stability, oxidation stability, wear resistance, etc. etc.

Understanding the need and the methods for appropriate Understanding the need and the methods for appropriate grease selection will go a long way toward improving grease selection will go a long way toward improving lubrication programs and the reliability of lubricated lubrication programs and the reliability of lubricated machinery.machinery.

Let’s go through the grease selection process step by step, Let’s go through the grease selection process step by step, starting with the most important starting with the most important

Additives and Base Oil Type Additives and Base Oil Type The additive and base oil types are other The additive and base oil types are other

components of grease that should be components of grease that should be selected in a fashion similar to that used for selected in a fashion similar to that used for oil-lubricated applications. oil-lubricated applications.

Most performance-enhancing additives Most performance-enhancing additives found in lubricating oils are also used in found in lubricating oils are also used in grease formulation and should be chosen grease formulation and should be chosen according to the demands of the application. according to the demands of the application. However, there are applications that might However, there are applications that might benefit from the use of a synthetic base oil. benefit from the use of a synthetic base oil. Such applications include high or low Such applications include high or low operating temperatures, a wide ambient operating temperatures, a wide ambient temperature range, or any application where temperature range, or any application where extended re-lubrication intervals are desired. extended re-lubrication intervals are desired.

Base Oil ViscosityBase Oil Viscosity The most important property of any lubricant is viscosity. The most important property of any lubricant is viscosity. A common mistake when selecting a grease is to confuse A common mistake when selecting a grease is to confuse

the grease consistency with the base oil viscosity. the grease consistency with the base oil viscosity. The majority of grease-lubricated applications are element The majority of grease-lubricated applications are element

bearings, one should consider viscosity selection for those bearings, one should consider viscosity selection for those applications. applications.

There are several common methods for determining There are several common methods for determining minimum and optimum viscosity requirements for element minimum and optimum viscosity requirements for element bearings, most of which use speed factors, commonly bearings, most of which use speed factors, commonly denoted as DN or NDm. denoted as DN or NDm.

Speed factors account for the surface speed of the bearing Speed factors account for the surface speed of the bearing elements and are determined by the following formulas: elements and are determined by the following formulas:

DN = (rpm) * (bearing bore) DN = (rpm) * (bearing bore) NDm =rpm * (bearing bore + outside diameter)/2) NDm =rpm * (bearing bore + outside diameter)/2)

Grease Consistency and Grease Consistency and Thickener Type Thickener Type

Now for that extra step: • The consistency of grease is controlled by the

thickener concentration, thickener type and the viscosity of the base oil. Even though base oil viscosity affects consistency, it is important to note that a grease can have a high consistency and a low base oil viscosity or vice versa.

• Higher speed factors require higher consistency greases. Grade based on speed factor and operating temperature.

Greases stay putGreases seal out contaminantsGreases do not need circulation systems Greases decrease dripping, splattering and leakage Greases suspend solid additives easily Greases are suitable for intermittent operations Greases work under extreme operating conditions Greases seal for life Greases reduce noise Greased machinery tends to need less power

• REMAINS AT APPLICATION POINT & ADHERES TO SURFACE• LESS FREQUENT APPLICATION NEEDED• SEALS OUT CONTAMINANTS• REDUCES NOISE AND VIBRATION• MAINTENANCE COSTS REDUCED• OPERATES OVER WIDE TEMP. RANGE• WATER RESISTANT • MORE EFFECTIVE FOR EXTREME CONDITIONS SUCH AS SHOCK LOADING, REVERSING OPERATIONS, LOW SPEED & HIGH SPEEDS HOWEVER BECAUSE OF THE SEMI-SOLID NATURE OF GREASES, THE COOLING AND CLEANING FUNCTIONS OF A FLUID LUBRICANT ARE NOT PERFORMED.

ADVANTAGES OF LUB. GREASE OVER OIL

Greases may not reach all places Greases may not reach all places in need of lubricationin need of lubrication

Greases do not have any Greases do not have any cleaning effectcleaning effect

Greases do not work as cooling Greases do not work as cooling agentagent

Greases cannot be used at as Greases cannot be used at as high speeds as liquidshigh speeds as liquids

• Viscosity - Know the viscosity of each grease and the machine requirements

• Grease base - Which greases are compatible with bearing requirements

• Is heat a problem - Grease life is halved for every 15 degrees C over 70 deg. C

• Question the grease supplied in new equipment . Standardize with existing equipment

• Location of grease fittings e.g. Center of pillow block for a W33 style bearing

• Grease path - Does the housing design allow grease to easily enter the bearing

Removal Clean Area Inspection of New

Bearings Alignment

Never assume the manufacturer has properly Never assume the manufacturer has properly lubricated the bearing from factory. The new lubricated the bearing from factory. The new bearing may have been shipped with a limited bearing may have been shipped with a limited amount of lubrication inside. This level may not amount of lubrication inside. This level may not be enough to form the necessary film between be enough to form the necessary film between the inner race and rolling elementsthe inner race and rolling elements..

Determine lubrication level by using sound Determine lubrication level by using sound analysis or vibration monitoring methods. analysis or vibration monitoring methods. Remember, a “dry” or under-lubricated bearing Remember, a “dry” or under-lubricated bearing will sound louder or “scratchier” than a “quiet” or will sound louder or “scratchier” than a “quiet” or “smooth” sounding properly lubricated bearing.“smooth” sounding properly lubricated bearing.

• Scoop or Paddle from a Container • Tube Refills • Refilling from a Storage Container using

Mechanical or Hydraulic Pumps

FAQ’sIn spite of covering most areas, there

were always plenty of questions.The common ones were:

How much grease to pump?In Grease, what actually lubricates?What to do if a grease drum is not

labeled?

HOW MUCH GREASE TO PUMP

Pumping grease into a well-sealed bearing until you see the grease leaving at the seal often

compromises the seal and assures that you have too much grease in the bearing.

A reasonable volume model to use is: V = D*B*.114, where V = Ounces per cycle, D =

Bearing OD” and B = Bearing width”.

In Grease,what actually lubricates?

It is the oil within grease that does the lubricating, not the thickener. The

thickener is an agent that holds oil like a reservoir. In many applications it also

allows oil to release slowly as it becomes required in bearings and

frictional machine surfaces

How to Prevent Mixing Greases "Is there a color and shape code used to

distinguish between different greases?”

Use tags to identify product type, quantity and interval. Colors and shapes can be used to tag grease guns and

transfer containers. Standardize lubricants. Instead of using a poly-urea and a lithium-based EM grease, consolidate so that all similar

machines receive the same lubricant. Use different grease fittings for different greases. This is

an effective way of reducing cross contamination. Training. Training is a most important component in

proper lubrication.

IMPROPER SELECTION AND APPLICATION OF GREASE

Grease lubricated failures fall in 4 categories• The selection and

application of the wrong type of grease

• Incompatibility resulting in excessive softening

• Contamination resulting in excessive wear

• Too much or too little grease applied

Points to remember• Do not mix greases of

different thickener types.• Keep similar thickeners in

the same application• Lack of grease can cause

failure, but too much grease is the primary cause of failure since the excess lubricant causes high temperatures, which in turn oxidizes the grease

IN CONCLUSION….• So the next time you hear

someone cursing this semi solid slimy lubricant please take a few minutes and tell him the true story of Grease.

• Whether he understands it or not is a different matter but in future he’ll think twice before ‘greasing any palms’!