Detect and Defeat - the Root Cause

Pinaki Roy

There was a big hen that climbed up a tree by eating bull droppings & was proudly perched at the top of the tree & showing off by crowing loudly.

Soon it was spotted by a farmer, who shot the hen.

Moral of the story: Bullshit might get you to the top, but

you won't be there for longThere is no alternative to – HARD WORK - but it should be supplemented with a

positive attitude & correct approach

Now to business

What is Maintenance? Maintenance describes the

management, control, execution and quality of those activities which will reasonably ensure that design levels of availability and performance of assets are achieved in order to meet business objectives.

Maintenance is a Risk Control activity Risk = Consequence x Probability =

Consequence x (Opportunity x Chance)

If maintenance expenditure is viewed as the premium to be paid for reliability insurance, then it follows that all maintenance activities should be directed towards maximum returns on that investment, i.e. improved reliability. However in reality this is rarely found to be the focus.

The emphasis is only on returning the machine to service as quickly as possible without serious consideration of reliability improvement, even when the opportunity is presented.

CORE MAINTENANCE ACTIVITIES ARE DEFINED BY DESIGN AND PROCESS.

Additional maintenance activity results from premature

equipment failure. Unexpected failures may incur other costs or losses - such as

loss in production, diversion of planned maintenance resources, loss of reputation, penalties for late delivery, etc. These are usually very much greater than the actual repair costs of the failure.

The focus of Maintenance should be to maintain the

overall ‘well-being’ of the plant – but when the task is just to ‘fix it’ then Maintenance has failed in its basic mission - through no fault of its own.

Much has happened in the area of maintenance since the industrial revolution began - a few hundred years ago, but the changes especially in the last fifty years have drastically affected the industrial maintenance systems worldwide.

Prior to the Second World War, machinery was mostly rugged and relatively slow running having only basic instrumentation and control systems. The demands of production were not severe and downtime was not a critical issue and so it was enough to maintain plant and equipment on a ‘breakdown – repair it’ basis. But those machines were very reliable.

Even today we can see some machines made in that period, which have worked continually, are almost as good today as on the day they were made.

From mid 50's after the world war with the rebuilding of industry, there developed a much more competitive marketplace with an increasing intolerance to downtime. The cost of labour increased leading to more mechanisation and automation. Machinery became lighter, ran at higher speeds but also wore out more rapidly and was less reliable, as they were utilised more. Production then demanded time based maintenance which led to the development of Planned Preventative Maintenance.

The involved planning for timely plant overhauls at which the failure rate of a group of similar machines became unacceptable.

This in turn lead to the basic assumption that the older an equipment gets the more likely it is to fail.

Thus evolved the ‘Bathtub Curve’ concept.

The Bathtub Curve was presumed applicable to All Machines There were 3 identifiable phases within the Bathtub Curve: Running In (also known as the Infant Mortality) phase. This

recognised the premature failure of components and was often seen in the first few days or weeks after overhaul.

Normal Operating Life phase. This showed a relatively constant probability of failure. Failures within this phase were usually referred to as Random.

Wear Out phase. There was an increasing probability of component failure between equal and successive time intervals. Somewhere within this phase the failure rate would become unacceptable and total maintenance would be carried out on equipment still in its “normal operating life”.

This was like carrying out open heart surgery on healthy machines.

This intrusive scheduled maintenance would lead back to the beginning of a new bathtub curve and the phase of Infant Mortality with its increased probability of failure.

Effectively, the process of Planned Preventative Maintenance gave rise to a series of mini-bathtub curves, each with their initial period of increased high risk

Within Planned Preventative Maintenance the challenge became one of choosing the best point in the Wear Out phase at which to perform maintenance - all other factors considered.

With the Bathtub curve often giving disturbing results it required further investigation.

In the 1960’s with the introduction of the Boeing 747, the aviation industry questioned the prevalent maintenance strategies and the long established basic assumption that the older an equipment gets its more likely to fail.

At that time aviation accident rates were in the order of 60 per million takeoffs. 20,000 hours flying time required some 2,000,000 man-hours of maintenance.

The bath tub assumption was questioned and the failure process researched. Various patterns of failure were identified and only three showed some relationship of increased probability of age related failure totaling only 11% of the failures. The remaining 89% showed no age relationship, but a period of constant probability of failure.

This proved that failure is a random event having the potential to warn of a developing failure through changing levels of some measurable parameters, indicating a change in condition of the component, machine or system.

The aviation industry made major changes to its maintenance practices and the results were dramatic; maintenance time for 20,000 hours flying time went from 2,000,000 man-hours down to 66,000 – a 30:1 reduction.

There was a dramatic improvement in safety and effective reliability. Design and technology improvements were made and condition based maintenance techniques became the provider of information to assist development.

Over the years that followed, industry worldwide also followed this study and this became the principal foundation of Reliability Centered Maintenance.

Identifying Potential Machinery Failure

To understand the concept better, let us take a real life example.

In the above case of a pump & motor, a failure can occur due to many reasons. Let us firstly identify those reasons before going further.

OPERATIONAL Deposits, clogging Running dry Blocking Overloading, failure to

reach minimum discharge rates

Evaporation, cavitation Increased corrosion,

erosion, abrasion Wear and tear (floating

ring seal, plain and roller bearings, normal corrosion, erosion, abrasion)

HUMANWrong choice of pump

Incorrect assembly Mistakes in commissioning

(inadequate cleaning of the system, inadequate venting)

Mistakes during repair Incorrect start up Mistakes during cleaning

(steam on plastic, caustic solutions on stainless steel)

The direction of rotation of a dry pump is not checked.

The oil fill was forgotten.

Having identified the possible ways in which the system may fail, lets see if it is possible to detect and measure the failure process.

Firstly see if past failure history is available. Then use the information to analyse the cause for the failure.

If the answer is NO then use either Planned Preventative or Breakdown Maintenance, depending upon the Criticality or Risk - should the failure event happen.

If the answer is YES, the failure process can be observed, and the Criticality justifies it, then Condition Based Maintenance will be applied. If the answer is YES but Criticality does not justify it, then Planned Preventative or Breakdown Maintenance will be applied.

Its important to understand that Maintenance and Downtime are an effect and not a cause. The causes can be traced back to defects and errors from a variety of life cycle sources.

These failures can be design errors, material selection errors, fabrication errors, assembly errors and even transportation damages that may have happened to the items before they got to site. When installed, further causes of future failures arise from incorrect installation, incorrect site assembly, improper mounting practices, inadequate environmental protection and deficient foundations or supports.

Manufacturing, installation & commissioning errors result in early failures in the equipment’s operating life and are known as ‘infant mortality’ failures.

Errors in a machine that do not appear early in equipment infant-life will eventually surface randomly to cause failures sometime during its operating life.

These arise from operating errors, repair errors, abuse, management mistakes and even acts of Mother Nature.

The terminology for hidden errors and mistakes is ‘defects’, because they are present in the plant and equipment with the endless potential to one day become failures.

A part properly built and installed, without any errors, will operate in a machine at its designed level of performance. If looked after properly, it should ideally, deliver its design requirements through its operating life.

As a machine is operated any hidden manufacturing or installation errors in a part will start to make their effects shown. Not all defects will act at the same time, but some defects will cause a part to start to fail. Remember that defects can start failures at anytime.

It is thus essential to devise a systematic method of analysing the effects and the causes that create or contribute to those effects.

The Fish Bone diagram & FMECA are some such methods.

LETS TRY TO UNDERSTAND THEM

A Cause-and-Effect Diagram is a tool that helps identify, sort and display possible causes of a specific problem or quality characteristic. It graphically illustrates the relationship between a given outcome and all the factors that influence the outcome. This type of diagram is sometimes called an "Ishikawa diagram"because it was invented by Kaoru Ishikawa, or a "fishbone diagram" because of the way it looks.

When to use a Cause-And-Effect Diagram?A Cause-and-Effect Diagram is used when you need to:

Identify the possible root causes, the basic reasons for a specific effect, problem or condition.

To sort out and relate some of the interactions among the factors affecting a particular process or effect.

To analyze existing problems so that corrective action can be taken.

A Cause-and-Effect Diagram is a tool that is useful for identifying and organizing the known or possible causes of quality or the lack of it. The structure provided by the diagram helps team members think in a very systematic way.

The benefits of constructing a Cause-and-Effect Diagram are that it Helps determine the root causes of a problem or quality

characteristic using a structured approach. Encourages group participation and utilizes group

knowledge of the process. Uses an orderly, easy-to-read format to diagram cause-and-

effect relationships. Indicates possible causes of variation in a process. ! Increases knowledge of the process by helping everyone to

learn more about the factors at work and how they relate. Identifies areas where data should be collected for further

study

FISHBONE DIAGRAM

The fishbone diagram, also known as the Ishikawa diagram after the Japanese quality management innovator who created it, is a common tool used to help organizations solve problems by conducting a cause and effect analysis of a situation in a diagram that looks like a fishbone. The fishbone diagram helps you to identify the root cause of a problem. It is also possible to identify solutions that may help solve more than one problem. While carrying out this analysis, you may make further discoveries that will also help you remove other blocks.Basic steps:1. Define the characteristics of the problem and make it the “backbone” of the fish.2. Decide on the main causes of the problem. Divide the causes into the categories of: Staff, Machine, Material, Method and Environment (or Energy).3. Assign one “large bone” -- coming off the backbone of the fish -- to each category.4. For each main cause, think of an area that contributes to the problem e.g. lack oftraining might be a main cause in the Staff category. Write these on the horizontallines -- the “middle bones” -- that run out from the large bones.5. Analyse and define secondary causes and add them as “small bones”:For each cause, ask why does this happen? If there is another reason, include it on a branch of the horizontal line for that cause: e.g. why is there lack of training? The answer maybe may be lack of funding. This should be added to the diagram.

To get a holistic and logical representation of a problem broken down into a pictorial format

To get a holistic View

Need to study a problem

Need to ArriveAt a solution

Process Simplification

To Enhance a Process

Need to study a problem/issue to determine the root cause?

Need to Arrive at a Solution to any problem

Need to Simplify a process flow

Want to study why a process is not performing properly or producing the desired results

Use an idea-generating technique (e.g., brainstorming) to identify the factors within each category that may be affecting the problem/issue and/or effect being studied

Idea-generating technique (e.g., brainstorming)

Analyze the results of the fishbone after team members agree that an adequate amount of detail has been provided under each major category.

Analyze the results of the fishbone

Repeat this procedure with each factor under the category to produce sub-factors. Continue asking, "Why is this happening?" and put additional segments each factor and subsequently under each sub-factor.

Repeat this procedure with each factor

For those items identified as the "most likely causes", the team should reach consensus on listing those items in priority order with the first item being the most probable" cause.

“Most Likely Causes",

Continue until you no longer get useful information as you ask, "Why is that happening?"

“Continue until "

What is a FMECA?FMECA is an analysis technique which

facilitates the identification of potential design problems by examining the effects of lower level failures on the system operation.

These are basically of 2 types: FMECA - Failure Mode, Effects and Criticality

Analysis. FMEA - Failure Mode and Effects Analysis

What are the effectsof part failures on the board?

What are the effectsof board failures on the box?

What are the effectsof box failures on the system?

Note: This is a bottoms up example. Top down examples are possible.

The flashlight below is used by special operations forces involved in close combat missions during low visibility conditions. The light is mounted coaxially with the individual's personal weapon to momentarily illuminate and positively identify targets before they are engaged. The exterior casing including the transparent light aperture have a rugged design and are to be considered immune to failure.

Item Failure Mode End Effect

bulb dim light flashlight output dimno light no flashlight output

switch stuck closed constant flashlight outputstuck open no flashlight outputintermittent flashlight sometimes will not turn on

contact poor contact flashlight output dimno contact no flashlight outputintermittent flashlight sometimes will not turn on

battery low power flashlight output dimno power no flashlight output

How can it fail?What is the effect? Notethat Next Higher Effect =End Effect in this case.

Part

SEVERITY classifies the degree of injury, property damage, system damage and loss that could occur as the worst possible consequence of a failure. For a FMECA these are typically graded from I to IV in decreasing severity.

CRITICALITY is a measure of the frequency of occurrence of an effect.May be based on qualitative judgment orMay be based on failure rate data

Severity

Severity I Light stuck in the ‘On’conditionSeverity IILight will not turn onSeverity III Degraded operationSeverity IV No effect

Can circled items be designed out or mitigated?(There may be others that need to addressed also.)

FMECAs should begin as early as possibleThis allows the analyst to affect the design before it

is finalised. Also if one starts early one can expect to have to redo portions as the design is modified.

FMECAs take a lot of time to complete. FMECAs require considerable knowledge of

system operation necessitating extensive discussions with software/hardware Design Engineering and System Engineering.

Time should be spent in developing ground rules with the customer, up front.

If you want your equipment to be truly reliable you must prevent the introduction of defects and errors at all stages of equipment life. By getting rid of the defects that generate failure modes you will reduce your future maintenance requirements.

The best maintenance strategy to adopt is to not let failure modes into the equipment from the start. Such strategies require that you put in place quality management controls and quality assurance to detect, control and stop the introduction of errors and defects into the equipment.

Select one failure and identify where defects and errors were first introduced by employing root cause failure analysis methods.

Use resources towards eliminating the root cause and action a plan to engineer-out the causes forever. Do not use work procedures to live with failures from bad engineering design or manufacture. Use work procedures to direct people’s attention to the right reliability practices but not to compensate for in-built equipment defects. If your equipment has engineering defects then engineer them out.

Introduce clear quality, production and engineering standards that contain Accuracy Controlled checks and tests to prevent the defects from repeating.

Train and re-train your people to meet the new quality and reliability standards.

Effective mechanisms must be introduced to combat and defeat the cause of the defects. Unless the causes are controlled and stopped you will be continually battling failures. They will never stop because they are forever being introduced and perpetuated by poor procedures and practices, poor quality control and poor management systems.

Every new piece of equipment, every new part and even every new person that joins the company will bring defects and errors with him & one day cause future failures.

How catastrophic those failures will be depends on your internal controls in place to prevent and control them and your ability to take proper & timely decisions!

Importance of Reliability

Reliability is a probability index, which indicates that a system will perform its required function without failure under given conditions for an intended operating period.

Reliability = MTBF/ (MTBF + MTTR

Identify the best line of action

Look for the relevant data & analysis

Aim for absolute clarity

Decision Making

Maintenance 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 the organizational policy.

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

To safeguard the investment.To keep the equipment in good working

condition.To prolong the life of the equipment.To assure optimum availability.

Types of MaintenanceBreakdown MaintenancePreventive Maintenance

Breakdown maintenance is

suitable for conditions where

Plant capacity exceedsmarket demand.Standbys are available andquick switching is possibleProcess is obsolete and

moremodern equipment is

underconsideration.For non critical equipment.

Preventive maintenance is different from Breakdown maintenance as

It is a systematic maintenance procedure wherein the condition of the plant is constantly watched through systematic inspection and preventive action is taken to reduce the incidence of breakdowns.

Fundamentals of PM

Periodical Inspection of plant and equipment to discover conditions of deterioration.

Upkeep of equipment to remove or repair such conditions while they are still in a minor stage.

Advantages of P.M Effective use of

manpower and material to attain greater efficiency in plant operation.

Planning of maintenance work and optimum inventory of spares and components.

Possible to synchronize the maintenance program so that there is least interruption to continuous operation and production.

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

Definition: ““To make smooth To make smooth

or slippery with oil, or slippery with oil, grease or other grease or other matter to overcome matter to overcome friction”.friction”.

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.

Lubricants achieve this by substituting low fluid friction in place of high solid-to-solid friction.

Prevent or Minimise FRICTION by: Providing a film to separate interactive surfaces Coating the rubbing surfaces with a protective

film Cooling

By reducing or removing excess heat Protection

By inhibiting the corrosive processes caused by air and water

Cleaning By flushing dirt particles away from lubricated

surfaces

Mineral oils carry out these functions effectively

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

The two well known laws of physics that govern sliding friction are:

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

Friction = Friction = Friction

1st Law

Friction Friction x 2 Friction x 3

2nd Law

SLIDING FRICTION(most)

ROLLING FRICTION

FLUID FRICTION(least)

Load

Direction of motion

Load

Direction of motion

sharp edge scrapes away oil - BOUNDARY LUBRICATION

bevelled edge rides over oil - FLUID FILM LUBRICATION

Modes of lubrication Hydrostatic Hydrodynamic Elasto-hydrodynamic Boundary

Regime depends upon Design Speed Load Materials Operating conditions Viscosity

LUBRICATION CONDITIONSLUBRICATION CONDITIONS

The viscosity of a liquid is the measure of its resistance to flow. Under the same conditions, a liquid with a low

viscosity will flow more readily than a liquid with a high viscosity. It is most commonly expressed in terms of Centistokes or SAE numbering.

Viscosity is the single most important property of a lubricant.

It is a major factor in the formation of a lubricating film and, therefore, determines the load carrying capacity of the lubricant, i.e. it indicates performance.

Why need maintenance performance indicators in the Mining Industry?

WHAT IS VISCOSITY?WHAT IS VISCOSITY?

Mining is a capital & labor intensive industry

Maintenance costs range between 20-50% of production cost.

Hence maintenance is an integral part of it’s long -term profitability

Maintenance can add value through equipment reliability and availability

In order to optimize maintenance functions it thus becomes imperative to have maintenance performance indicators in place.

In mining various indicators can be used for measuring maintenance performance

However, many managers still advocate that ‘performance measurement is not effective nor beneficial in mining companies’.Some maintenance managers still believe in the ‘let it work till it breaks’ syndrome commonly called - breakdown maintenance.

But in order to optimize maintenance performance one has to be different and have the DESIRE to go ahead –

like this Socrates anecdote

A young man asked Socrates the secret to success. Socrates told the young man to meet him near the river the next morning. They met. Socrates asked the young man to walk with him in the river. When the water got up to their neck, Socrates suddenly ducked the young man into the water. The boy struggled to get out but Socrates was strong and kept him there until the boy started turning blue. Socrates then pulled his head out of the water and the first thing the young man did was to gasp and take a deep breath. Socrates asked, 'What did you want the most when you were there?" The boy replied, "Air." Socrates said, "That is the secret to success. When you want success as badly as you wanted the air, then you will get it.“ There is no other secret.

A burning desire is the starting point of all accomplishments.

Just like a small fire cannot give much heat, a weak desire cannot produce great results.