6 steps to a healthy machine

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Six Steps to A Healthy Machineby James W. Taylor, MachineryManagement Solutions, Inc.

Introduction:Most condition assessment programs in industryconcentrate on one or two technologies. The people, proceduresand practices are tailored to those technologies. Application of thetechnology is optimized, rather than the results. This paperadvocates a machine centered, as opposed to a technologycentered, approach to the assessment of the condition of

machinery. Just as your physician uses a variety of tests andevaluations to assess your state of health, we should do the samefor our machinery. To do less means we make decisions based onincomplete information.

Many plants have a condition assessment program in place; usuallythose programs operate in relative isolation, concentrating on onlyone or two technologies. The people responsible for them work tomaximize the efficiency of the application of the technology.Therefore the application of the technology is optimized, rather thanthe results.

A machine-centered, as opposed to a technology-centered,approach to condition assessment will maximize the effectiveness oftechnology in improving machine reliability. This approach focuseson those tests and tasks that are cost effective when it comes tomachine reliability.

Background:A plants condition assessment program might includevibration monitoring, oil analysis and thermography. And they mayalso have preventive maintenance tasks calling for routine overhaulof some machines based on running time or calendar time. This hasthe potential to make major contributions to the reliability of themachinery. But usually, these various sets of data never meet. Andthe routine overhaul its not effected by collected data. So thepayback is never fully realized.

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Lets consider the typical vibration program. After some research, acost justification is made and approved to purchase vibrationequipment and software. Then one or two technicians are trainedand designated to manage the program. They are told to make thevibration program run. In the absence of any measure of

cost-benefit, they make the decision to apply the vibration to as

many pieces of equipment as possible. From their perspective, its asmart move: it spreads the cost of equipment and training over asmany pieces of equipment as possible, minimizes cost permeasurement, provides a full work load, and keeps the equipmentin use. It optimizes the individual technology program.

Is this the best strategy to improve machine reliability? Would yoube happy with your doctor if on your annual physical he only tested

your pulse rate? And then maybe he makes a decision on whetherto do surgery based on that? (That pump overhaul is surgery!)Probably not! Youd like to see him make a number of tests

blood work, EKG, chest x-ray, etc. Then hell get a complete pictureof your health. And have a lot better basis to make a decision onsurgery.

The same principle applies to machinery. To get a complete pictureof machine health, you need to run a number of tests. And whenthat PM for overhaul (surgery) comes up, you can make aninformed decision on whether to perform or defer it.

Condition assessment involves a lot more parameters than just

vibration, oil condition and IR. Process parameters such astemperatures, pressures, flow rates and operating speed all have

things to tell us about health of our machinery. For example, suctionand discharge pressure of a pump, along with motor amps, RPMand flow rate will give a good indicator of impellor condition. Basedon those, you may decide to defer that pump overhaul for anotheryear or two. Thats a big savings.

If you have a technician going to a machine to collect data for onetechnology, why not collect all the data you need? Instead of justvibration, how about trending bearing temperatures, fluid pressures,

RPM and other parameters that contribute to a complete picture ofthe machines health. It means that more time will be spent at eachmachine, and fewer machines will be assessed in a day. But youhave much more valuable information. You will also save transittime, prep time, and administrative time associated with multipletrips to the machine. And youll save time by just applying atechnology to those machines where its cost effective. You havent

optimized the technology, but you have optimized the machineshealthcare. And isnt that what we really want?

Proposal:I want to propose an approach thats not new or unique.

Many savy maintenance managers have done it for years. ReliabilityCentered Maintenance formalizes it. I call it Machine CenteredHealthcare.


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I believe that Reliability Centered Maintenance is the best approachfor critical machines. But not every plant can afford, can getapproval, or has the manpower for a Reliability CenteredMaintenance program. Its expensive in the short run. Im proposinga thought process that will help you decide how to maintain your

machines in a less formal manner with less paperwork than

reliability centered maintenance.

A machinery-centered approach looks at the machine first, and byasking a series of questions, helps you decide how to maintain themachines health. What tests should be done? What routine PMshould be done? How can we make the overhaul/no-overhauldecision?

First Ask, What Are The Possible Failures?:To ask what thefailure are, first we need to know what the machine is supposed todo. What is its primary function? At first glance, you might say that

a pumps primary function is to pump a liquid. In reality, its primaryfunction is to keep a supply tank full. As the process draws liquidfrom the tank, the pump replaces it. If the pump cant pump at asufficient rate, the supply tank will go empty. That minimum rate willvary from process to process. Look beyond the obvious to the realfunction of the machine.

Once youve decided what the machines function is, ask what canhappen to prevent it from meeting that function. In the case of the

pump, the answer might be the impellor wearing out reducing

available head, bearing failure causing low RPM, a crack in thecasing or worn-out seal causing liquid to be lost reducing flow, or anumber of other possible failures. At this point, youre justbrainstorming. Dont consider whether the failure is likely or hasmuch impact. Well do that in the next step. For now, just get acomplete list.

Next Ask, Which Of These Failures Are Significant?:Now thatyou have a list of possible failures, you want to decide which onesyou should worry about. Some failures are so unlikely that youwont worry about them; others have such a low consequence that

their impact and cost is minor.

Machinery history is the best way to determine how often a failureoccurs and what its impact is. You do have one, dont you?

However, we can do it without the history. Ive had success in the

past using a subjective evaluation. Make a list of the failures andask two questions: how often does this occur and whats the impacton production when it does. Make it up as a questionnaire. Possible

answers are in Table I below. This may sound simplistic but it works.

Table I

Score Frequency Effect

1 1/10 yrs None


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2 1/ yr A little

3 1/ month Some

4 1/ week A lot

5 1/ day Complete

Now send the questionnaires to a cross section of maintenance,production and management personnel. When you get them back,average the scores for each item.

The significance of a failure is the combination of two factors:frequency and effect. By taking the score for frequency score (1 to

5) and multiplying it by the score for effect (1 to 5) youll get acomposite score for each failure in the range of 1 to 25. Rank thelist by the composite score. The higher the composite score, thegreater the significance of the failure.

Now you have to make a judgment call which failures should youworry about? Often, only a few will have a high rank and you can

concentrate on them. Other times most will have a high rank. This iswhere your knowledge of the machine and professional judgmentcome into play.

Next Ask, How Can We Avoid These Failures?:Starting at the top

of the list, ask how can we avoid this failure? Is there some actionwe can take that will keep the failure from occurring? Can wechange the design? Can we replace a part that has a predictablewear-out period? Can we adjust or lubricate to avoid failure? The listyou make here should be the start of your preventive maintenancelist for that machine.

Then Ask, When We Cant Avoid Failure, How Can We Get An

Early Warning?:There will be some failures that we cant avoid.For those, we ask How can we detect the failure before it occurs?What are the symptoms of the failure? Most failures showsymptoms before they happen. A pump may have to be run faster

because of a worn impellor. A motor may draw more amps becauseof misalignment or a seal that is too tight. A coupling may be hotbecause of misalignment or lack of lubrication. Make a list for eachfailure.

Then, Tailor A Suite Of Tests To Detect Those Early Warning

Signs:With a list of symptoms, youre now in the position to selecttests that measure or detect that symptom. For each symptom, tryto get as many independent tests as possible. The more informationyou have, the more confident youll be in your call. You should haveat least two tests for each failure that can confirm each other andavoid false positives (or negatives).

As youre considering tests, dont limit yourself to high tech

methods. Process parameters are also valuable. And one of the

most valuable tests is the operator and maintainer. An experiencedperson, familiar with the machine, making a conscious effort tosense a particular effect, can be very effective at assessing thehealth of a machine.


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Finally, Collect The Results Of The Tests At One Decision Point:Doing the tests without putting all the information together is noteffective. I recommend that each machine have one or twoindividuals assigned to monitor its health. They should be trained inassessing all the information provided by the tests. Notice I didntsay, trained to evaluate the data. They dont have to analyze the

data (vibration spectra); they just have to understand the results(information) of that analysis.

They should receive the results of the tests along with any otherpertinent information on a regular basis. Then they can use thatinformation to manage the machine. They can use it to adjustlubrication intervals, decide when adjustments are needed or part

replacement is indicated. And that overhaul? They may decide itsnot needed after all.

Summary:Condition assessment programs are often structured tooptimize the application of the technology. This spreads the cost ofequipment and training over as many pieces of equipment as

possible, minimizes cost per measurement, provides a full workload, and keeps the equipment in use. But it means that we may bespending time and resources taking data that is not particularlyvaluable in improving reliability and reducing costs. And theinformation derived does not get integrated into overall machinehealthcare decisions.

What we want to do is to maximize the effectiveness of the

technology in improving machinery reliability. We need to assessmachine health based on several measures. And we should only dothose tests and tasks that are cost effective from the point of view ofthe machine. The question is, how do we decide what to do? Ipropose we follow a systematic process to identify that.

In summary, the process is:

First ask, what are the possible failures?1.

Next ask, which of these failures are significant?2.

Next ask, how can we avoid these failures?3.

Then ask, when we cant avoid failure, how can we get an early warning?4. Then, tailor a suite of tests to detect those early warning signs.5.

Finally, collect the results of the tests at one decision point.6.

For more information please contact the author:

James W. TaylorMachinery Management Solutions, Inc.

7724E 1100NClarks Hill, IN [email protected]

Editors note: Our thanks goes to James for this article - as the first

a what we hope is a long series of common sense "how to" articles.

Stay tuned. - Terry O


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