Predictive/Preventive Maintenance - Who needs it?

Richard L. Harrison, Vibration analyst

Consolidated Diesel Company, Whitakers, NC ABSTRACT

For many years, maintenance departments commonly used two types of methods in the battle to maintain equipment, “Run Until Failure” and the all-famous “Fighting Fires”.

Either of these approaches proved to be extremely time consuming and costly, for they were and are still today directly and indirectly responsible for expensive machine repairs, downtime, lost production, & unnecessary overtime that is created in order to get back on schedule.

In order to avoid confusion, I should define two terms.

First, “Predictive Maintenance”, plainly put: The ability to detect & predict machine catastrophic failure.

Secondly, “Preventive Maintenance”: Performing the tasks necessary to avoid machine catastrophic failure.

These programs are ever evolving and have taken on a totally, workable solution for most professionals interested in maintaining their equipment in an “as new” as possible condition.

Preventive maintenance makes use of procedures to inspect for wear, lubricate, adjust & service equipment, in hopes of avoiding failure.

Predictive maintenance, makes use of Vibration Analysis, Oil Sample Analysis, & Infrared Thermography also known as Thermal Imaging, in order to monitor, detect, predict, and warn of impending failure, so that a proactive approach can be used.

This saves both time & money by avoiding untimely machine related failures.

Both programs are good, however “Preventative Maintenance” is used only to inspect a machine during a “Static” or off condition, and as we all know, machines run.

Predictive Maintenance, on the other hand uses many tools to determine machine condition in it’s “Dynamic” state or, to put it another way, “running in its natural condition”; which I believe is best suited to determine a machine’s health.

This paper has singled out the technology of infrared thermography, or thermal imager and will focus on its benefits.

Using my own case histories as examples I hope to answer the question: Who needs a predictive program?

Keywords: Infrared thermography or thermal imager, predictive & preventive maintenance.

1. INTRODUCTION When an industry falls on hard times and capital spending is reduced, preventive and predictive maintenance programs appear to be the first on the list to catch the volleys of the first shots, in the war on cost reduction.

It is ironic however that these programs which are praised during times of profit are ignored in bad times, when they are most needed.

It is therefore my contention that proof is needed, which produces visual, viable data that can show exactly what the industry is missing, when they neglect their cost saving/avoidance programs.

The following thermographic evidence presented will prove beyond a shadow of a doubt, that when the question is raised “Who needs predictive/preventive maintenance?” it can be answered with full confidence and satisfaction.

2. THE EVIDENCE WILL ASTOUND YOU Most preventive maintenance inspections or PM’s as they are called occur during scheduled downtime. The equipment is inspected in its unnatural state, that is to say, in a static state.

Not much is going to happen, except for the observance of possible lubrication or adjustments needs or replacement of visually worn parts, which most definitely extends the life of the equipment but does not take into account the natural state of the equipment, which is the dynamic state.

In addition, when the equipment is at rest, it may be difficult to detect any serious conditions that may appear during operation and cause catastrophic failure.

When equipment is in the dynamic state, most force, stress, and other laws of motion are being exerted on the equipment, which allows for a better barometer in which to access its condition.

Enter infrared thermography or thermal imaging cameras, an excellent, non evasive, non contact way to access machine condition.

Here are the examples:

Figure 1. A disconnect with an overheated phase, a 17 Deg F Delta “T” from the other two.

To some, these might not appear to be at a critical temperature however, when more demand is placed on this conductor, it will fail. A repair made to these disconnects included simple tightening of the lugs.

Figure 2. A loose lug on the middle phase of a disconnect.

Figure 3. A loose lug on the middle feed of a main disconnect.

Figure 4. This conductor had a Delta “T” of 17 Deg F through to the fuse block than the others.

The above examples were not caught during the normal PM inspection but were with the predictive PM using a FLIR PM290 cooled short wave camera.

The four examples had the typical potential fire & safety hazard, and if failed, would have cost the company approx.$4,000 apiece.

3. A PICTURE IS STILL WORTH A THOUSAND WORDS. As a thermographer, I find myself constantly having to justify my findings and convince not only the maintenance dept that what I have predicted is correct and in fact will happen but, also attempt to convince management that they are just prolonging the inevitable by cutting back on such a valued program as predictive maintenance.

This can be realized in then next set of thermograms, which show what happens when the predictions are ignored and, the saying we in predictive maintenance are so fond of “Pay me now, pay me later” comes to pass:

Figure 5. A loose lug and overheated wire which failed during peak production. Repair cost was $2k

Figure 6. Loose lug that caused heat build up, which melted the lug, peak production. Repair cost was $2k

Figure 7. A fuse in a main feed I suspected to be weak and suggested replacing. It was ignored, the panel blew

during startup crippling both the machine line and support offices for several hours until repairs could be made. Cost of repairs was $10k

Figure 8. A fuse block with several loose connections caused an overheated condition, which melted the

conductors and fuse block requiring replacement during peak production hours. Cost of repairs was $6k

4. IT’S NOT AS BAD AS YOU THINK. I know what you’re probably thinking; Infrared thermography works well to detect things that pretty much is already bad”

I would like to mention that there were prior thermograms taken and the responsible departments were warned, they just didn’t take action in time and you can obviously see what the results were.

The good news is, there is a silver lining at the end of the rainbow, for there are many successes as in the next examples:

Figure 9. A simple tightening of lugs on this fuse block avoided a dangerous condition & potential failure.

Worth approx. 2k if failed.

These examples are small and seldom detected during a standard inspection, but appear to the most potential for being the root cause for many failures and unscheduled downtime.

I’ve heard on many occasions the familiar adage “ Its ok, the fuse blew, I’ll fix it”

The problem with this statement in most cases is, a new fuse is installed and considered repaired, but the reality is shown in the next example.

Figure 10. A loose knife blade was replaced during a scheduled downtime. Worth approx. $3k if failed.

In this example the fuse repeatedly blew, but only under certain conditions such as the seasonal change from spring to summer.

This brought about a temperature rise in the fuse panel where the already loose knife blade and terminations were expanding and contracting

The looseness combined with the demand, caused the circuit to overheat and fuse to blow then, each time the fuse was replaced, it was thought to be fixed.

After the maintenance department viewed the (Before) thermogram, they replaced the fuse holder and tightened the connections.

The resulting repair can be seen in the (After) thermogram. The mystery was solved.

Figure 11. A damaged conductor that runs 150 ft to control box on main floor was detected and repaired

during scheduled downtime. If failed during production, approx. cost to repair would have been $6k.

Figure 12. Here is a motor starter that was miss-wired by a contractor in such a way that the resets would not

work. Note the temperature was 600+F. This was detected during a routine infrared inspection and repair was made. Potential cost if this starter, adjacent wiring and boards had a meltdown would have been $20k.

5. WHAT’S THE GOOD NEWS? Infrared thermography also known as thermal imaging, is not just for electrical applications. There are other uses as you will see in the next examples:

Figure 13. Shows a thermogram taken to assist the engineering department in a special project that saved the

company thousands of dollars.

Figure 14. Shows a thermogram of a spindlehead which unknown to the maintenance department had a stuck

“low oil” meter. This caused heat at the spindle nose due to lack of lubrication.

Using infrared thermography or thermal imagers to detect lack of lubrication or over lubrication can be beneficial, but with one problem.

They both cause heat to be generated and appear very similar.

So whats a thermographer to do?

This should not discourage the thermographer because, just alerting the maintenance team to the fact that one or the other condition can be of great value to them, they can make the determination, inspection and correction..

Other uses and opportunities abound for infrared thermography; the sky is the limit.

I am often asked by both engineers and maintenance workers if I can do this or that with the camera.

My response is simple, I merely respond, “ Lets try it” and see what happens.

Here are some additional examples of uses for the infrared camera.

Figure 15. Shows a thermogram of a worn, misaligned coupler (left) and after repair was made (right). Based

on these thermograms, it is possible to detect misalignment.

Figure 16. A thermogram of a hydraulic tank fluid level.

According to the sightglass, maintenance assumed the tank was full, when actually it was only half full.

Figure 17. A failing bearing (left) and a normal bearing in a vertical pump.

In this example, opinions of the maintenance department as to the condition pump were satisfied when an infrared analysis was performed to compare the two pumps.

This proves the old saying, “without data, your opinion is just an opinion”

Figure 18. A routine scan from a catwalk across to another catwalk detected a 71degree F delta “T” (left) in

one of these identical fan blowers. It turned out to have severe belt wear and was repaired.

Right about now, I guess you might be asking yourself, “Maybe we do need to get or support predictive maintenance?”

But if you still are not convinced, perhaps some additional success stories are in order.

You can plainly see, I have shown the potential to save or cost avoid approx. $50k +

Please note, most of the data presented in this paper reflect only about ¼ of the potential savings of “one” technician using infrared technology, also known as a thermal imager. I think you can visualize what could be accomplished with a “team“ of technicians in the field.

6. LETS REVIEW Whatever you manufacture, maintain, research, test, monitor or service, predictive and preventive maintenance is the life’s blood of the company.

So in a time where companies need to tighten their belt, why does it make such great sense to cut off ones own circulation?

Without this type of maintenance, it is obvious what the outcome will be, “Total Chaos” and run till failure operations.

We know the monetary damage run until failure maintenance can cause because we spent years evolving away from it.

The following thermograms are additional successes that you may view and perhaps see something in them that you can identify with and use in your own program:

Figure 19. A thermogram of a fault heater on a motor starter, a simple 5 minutes to replace and avoid hours

of repairs.

Figure 20. A thermogram of a disconnect with a loose lug , a simple tightening of the lug and no more

problems.

7. IT’S ONLY MONEY. Properly trained predictive maintenance personnel can detect & report potential problems and as a by-product, they save money, avoid cost, reduce safety hazards & unscheduled downtime.

They are the unsung heroes of the maintenance field.

They work undetected and unrecognized.

The satisfaction is in the job, for their efforts, they must stand by and just visualize what might be, for they were responsible for it never coming to pass.

They must stand on the sidelines, never knowing the recognition, the feel of the slap on the back and a job well done.

For all their efforts they receive the satisfaction of knowing they saved the company money, even though their companies barely understands them or knows of their existence.

The term is used commonly, “Its Only Money”

To the infrared thermographer, that is what it’s all about, it is what they work for and understand.

8. SO WHO NEEDS IT? As you have seen, infrared analysis was an easy, non-invasive solution, for solving many of the variable problems that plague our equipment.

You can now realize the usefulness of infrared analysis as not only a predictive maintenance tool but in addition, a troubleshooting & engineering tool.

So who needs it?

Do you really have to ask?

InfraMation 2002 ITC 035 A 2002-08-01