Please join Jack Nicholas Jr., Author of Advancing Reliability and Maintenance (3rd Edition) in the 6th web workshop in a series of 12 workshop scheduled for 2008 for an informative discussion about at least 15 approaches to Reliability Centered Maintenance including those that follow the original intention of Nowlan and Heap as well as RCM Variations that have taken a slightly different or modified path. Also included in the review will be RCM Derivations, most of which claim to meet the original intentions of Reliability Centered Maintenance but have found ways to make the process quicker and less resource intensive.

Jack will also explain the definitive RCM Documentation that exists including works for the originators plus 2 early pioneers who brought their work forward to an industrial setting.

Please join us for a Web Workshop on July 18

The new online bookstore at MRO-Zone.com is asking maintenance and reliability professionals to post reviews and ratings for the books they have so other can act on their recommendation.

To write a review:

1) Visit the MRO-Zone.com Bookstore using the link below

2) Find the books that you have read

3) Write a brief review that will help other maintenance and reliability professionals select the best books for each topic

Write a book review at the MRO-Zone.com bookstore

Dependable electrical distribution is not an option – it is critical to corporate fiscal health in a world where “lean manufacturing” and “just in time” philosophies have made reliability and plant uptime into boardroom topics.

IRISS invites you to download your free case study detailing how one company saved millions of dollars with their Electrical Preventive Maintenance program.

Download Preventive Maintenance Pays

In a recent issue of Maintenance Tips, you published a Tip regarding the Slenderness Ratio.

This concept was developed over 20 years ago to make a point regarding the difference in shaft deflection of an end suction pump with a sleeved shaft and one with a solid shaft. The problem was excessively frequent and repetitive failures of mechanical seals and packing.

The Pump Tip incorrectly identifies the measurement of the “L” of the overhung length. The correct measurement should be from the centerline of the radial bearing to the centerline of the impeller, as that is the point through which the resultant of the unbalanced radial forces act. In some pump styles this difference can be dramatic, especially as it is calculated to the third power. However the actual number is of little importance.

For example, by suggesting that only those pumps with a slenderness ratio of less than 25 “should be able handle the unevenly distributed pressure in the pump volute caused by throttling without allowing shaft flexing”, the Pump Tip effectively eliminates the entire range of ANSI pumps, all of which have a Slenderness Ratios well in excess of 25.

Identifying the Slenderness Ratio as the source of the problem also ignores the fact that the Unbalance Radial Force in the impeller varies from practically zero at the Best Efficiency Point to as much as 800 lbs. at the Shut-Off condition. Consequently a pump with a very high Slenderness Ratio can run quite effectively and reliably when close to Shut-Off with no adverse repercussions.

A more constructive tip involving shaft strength would be to address a problem of excessively frequent and repetitive failures of mechanical seals and packing, by simply removing the sleeve arrangement on the shaft and opting for a solid shaft arrangement through the stuffing box. This will indeed lower the Slenderness Ratio by a considerable amount, but that would only be significant if the seals and packing were already failing on an excessively frequent basis.

Sincerely

--
Ross Mackay
Consultant in Pump Reliability
Author of “The Practical Pumping Handbook”
Creator of “The Mackay Pump School”
Tel: 1–800–465–6260
http://www.practicalpumping.com

Read the original Pump Tip

“To Listen or Not To Listen, That Is The Question” (From Ultrasonic War Stories by Jim Hall)

You and I when listening to our ultrasound instrument are hearing low-frequency sounds through the headphones. If your hearing is better than I mine for instance, then you may hear the sound of a bearing through the headphones better than I do, or vice-versa.

In the past you may have thought you heard a bearing that was bad and subsequently you removed the bearing. Did it really appear to be so bad that removal was the correct diagnosis? Or, could removal had waited several months or possibly years?

I have heard over the years from many technicians that have expressed doubt in the use of airborne ultrasound for determining bearing failure.

One such technician however told me about how he had been trending the bearings for several years, every 30-60-90 days depending upon criticality of the motor or bearing.

By trending, he was referring to decibels, numbers, collecting data and watching the bearing readings. The reading would stay relatively steady or indicate an increase over-a-period-of-time!

I personally have always taught that a bearing with a little wear on it and that has been starved a grease will sound as if its ready to come popping out of the motor at anytime.

I have always mentioned that you should lubricate the bearing when decibels exceed 8-10 decibels over the previous baseline. If after lubricating and the bearing does not return to a previous or near previous reading then you should watch the bearing by shortening your trending time from say, 60 days to every 30 days.

On certain bearings at low rpm’s, one might be able to diagnose a bearing by hearing the bearing. Maybe you can hear the repetitive clicking sound one could set his/her watch by, indicating a race problem. Or, the intermittent clicking sound indicating a ball defect that occurs as the ball turns striking the race or other balls. But this is more the exception to the rule than the rule! The majority of bearings being diagnosed using airborne ultrasound should be done by “Trending” over a period of time.

Just as vibration, a baseline and a 30-60 or 90 day reading should be done to determine degradation of the bearing.

The beauty of ULTRASOUND is that it is the earliest of all readings, prior to vibration and heat. Yes, it is so early that the findings can be very subjective.

However, the numbers do not lie when you are trending those decibels and reporting the differences over a period of time.

What is the magic number to removing the bearing? That’s a question to be answered for another War Story....

Find out more about Ultrasonic War Stories

Cantronic’s Academy of Infrared Training, Inc. (AIRT) has been training thermographers for 30 years. AIRT provides multi-level training across the U.S. and internationally—and custom on-site IR training!

Custom on-site IR training is available for companies with 5 or more technicians to be trained. AIRT offers an economical flat fee for Level I, II, or III training.

Call AIRT about on-site IR Training today: 1-866-391-6970

Find out more about on-site IR Training today

Gear Type coupling lubrication

Periodic lubrication of gear type couplings is critical to ensure longevity of the coupling itself and the associated drive train.

In harsh environments it can be difficult to remove a grease port plug in order to purge the coupling. Therefore this job can be overlooked due to task length and perceived lack of value.

By installing a grease relief valve in the lube port opposite the zerk couplings can be lubed in a fraction of the time it would normally take. An additional benefit is a smaller volume of grease is purged.

Less time, less cleanup and less waste makes performing this critical task efficient therefore more likely to get done.

Reader tip provided by Bob Burgoyne
RCM Specialist
Evraz Oregon Steel Mills
Portland, OR

Thanks Bob - Your stainless steel diamond plate Reliabilityweb.com coffee mug is on the way!

Send a Tip and get your own Stainless steel diamond plate Reliabilityweb.com coffee mug

From Which Reliability Tool should I use?
By H. Paul Barringer

Reliability tools exist by the dozens: what are the tools, why use the tools, when should I use the tools, and where should I use the tools?

Each week we will explain a reliability tool. The details about these tools will be brief as books are written about each item. Think of the presentations below as hors d’oeuvres (a little snack food or starters)—not the main course.

Bathtub Curves-

What: The concept is derived from the human life experience involving infant mortality, chance failures, plus a wear out period of life since data for births and deaths is accumulated by government agencies. Most equipment lacks the birth/death recording by government agencies and most non-human systems can be regenerated to live/die many times before relegation to the scrap heap.

Why: Failure rates are different for both people and equipment at different phases of operation and the medicine to be applied to both humans and equipment need to be considered for effectively treating the roots of the problem.

When: The concept is useful during design, operation, and maintenance of equipment and systems to understand the failure mechanisms

Where: It explains the human experiences to the ordinary person to relate equipment/system failures to those experienced in real life so as to coordinate the design, operation and maintenance of equipment.

Which Reliability Tool should I use?