Archive | April, 2013

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9:32 pm
April 24, 2013
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My Take: Job Satisfaction And You

newjaneresize2 thumb thumbBy Jane Alexander, Deputy Editor

It was a recent posting on 24/7 Wall St. (“Insightful Analysis and Commentary for U.S. & Global Equity Investors,” at www.247wallst.com) that put my column-writing brain into gear this month. Entitled “The Most (and Least) Satisfied Professions,” it discussed a 2012 telephone survey of 172,286 individuals over the age of 18 that was conducted by Gallup-Healthways. The findings were reported in something called the “Gallup-Healthways Well-Being Index” that tracks—tada!—well-being in the U.S. I was so troubled by the results noted below that I considered clicking on a link about miserable American cities just to make myself feel better.

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9:27 pm
April 24, 2013
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Uptime: Getting The Most From Your Reliability Consultants

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By Bob Williamson, Contributing Editor

This month’s column is dedicated both to consultants and their clients (with a bit more emphasis on the clients getting the most out of mutually beneficial client-consultant relationships).

Consultants abound. There are plenty of them (us) offering a range of just about any type of assistance and services your business might ever need. I’ve served as a consultant to hundreds of businesses and thousands of individuals for much longer than I care to add up. I have also rubbed shoulders with countless consultants in related and unrelated fields. You can trust me on this: All consultants are not created equal. Celebrate the differences!

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9:24 pm
April 24, 2013
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Compressed Air Challenge: VSD Compressors — Turn On Cruise Control

04cacAccurate control of pressure in compressed air systems is always of primary concern, but there are many ways to achieve it. Some are more efficient than others.  One of the biggest innovations in the field of compressed air efficiency is the invention of VSD-controlled compressors. VSD compressor control can put your air system pressure on “cruise control.” Let’s turn to an automobile analogy in comparing compressor control strategies.

One could use modulation control mode, which is similar to driving a car with the pedal to the metal and using the brakes to provide constant speed. Modulation control chokes off the inlet flow to the compressor to control the output pressure. This mode of operation is the least efficient way to provide constant pressure, with the compressor consuming 85% power even at only 50% output flow.

Another control mode involves loading and unloading a compressor between two set pressure points, with the average of the two readings providing the desired pressure.  This approach is similar to driving down the highway and controlling the speed by throwing the vehicle’s transmission alternately into drive and neutral. Air compressors in this mode of operation use less power than modulation—but can still consume between 70 and 85% power at a 50% loading level, depending on the frequency
of cycles.

A third mode is akin to a driver on a busy highway who repeatedly starts and stops his engine (slowing down or going faster) to reach a desired average speed. This method would be equivalent to a start/stop compressor operating mode: an efficient way to run small compressors, but hard on the motor.

In the three modes described above, average pressure could be adequately achieved, but it would come with either higher-than-desired energy consumption or wider pressure fluctuation. In a compressed air system, the desired result is a constant steady pressure—one set high enough to provide sufficient power to compressed air consumers, yet low enough to limit the energy consumption of the compressed air system.

Leveraging VSD control
VSD-controlled air compressors have accurate controllers on board that sense the actual pressure and speed up or slow down the compressor so as to keep a constant discharge pressure. The benefit is that the pressure can be set at a lower, more efficient level. Moreover, as the motor slows, the power consumption is almost linear to the speed reduction, saving even more. These units are more expensive and more complex than standard fixed-speed compressors but often, especially when an air compressor needs to be replaced anyway, the new VSD compressor will pay back the extra cost very quickly.

While these types of units are most appropriate for smaller single- and two- compressor systems, they can save significant energy in larger multi-compressor systems—if applied and controlled appropriately. To determine if VSD compressor control is appropriate for your plant, have an energy analysis of your system performed by a qualified compressed air energy-service company.

More information on this topic and many others can be found on the CAC Website (www.compressedairchallenge.org), in our online Library and our Best Practices for Compressed Air Systems Manual. MT

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224

9:12 pm
April 24, 2013
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For On The Floor: Is Benchmarking Part Of Your Strategy?

rick carter

When was the last time someone in your organization suggested a benchmarking study, for maintenance or any other company function? Here’s my guess: A long time, if ever. A chief exception: multi-site operations where cross-site benchmarking is policy. But that’s internal benchmarking, which was not the focus of this month’s questions for our MT Reader Panel. We were looking for Panelists’ experience with external benchmarking (where an organization’s cost and performance data is evaluated against that of the same function at a different, similarly sized company, especially one identified as best-practice).

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705

9:03 pm
April 24, 2013
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Lubrication Checkup: Sludge Prevention

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By Ken Bannister, Contributing Editor

Symptom:  

Dear Dr. Lube: While changing out unreadable sight-gauges on some large gearbox reservoirs, we discovered a wall of sludge in the tank bottoms. Is it preventable?

Diagnosis: 

Large gearboxes are almost always oil-lubricated, and typically employ a dual system wherein the reservoir is filled with oil to a determined level—usually designated on the sight gauge—to ensure partial lubricant coverage of lower mating gear teeth at all times. At speed, gears use surface tension on their teeth to “pick up” and transfer lubricant to other gears and bearings through “meshing” action and by “flinging and splashing” lubricant in all directions within the sealed reservoir. The “splash” method often involves a pressurized delivery system. An internal gear-driven pump picks up oil near the reservoir bottom and delivers it under pressure to bearings and gears that are difficult to service with traditional “splash” lubrication.

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Sludge is a “telltale” sign of a neglected gearbox. Neglected oil decomposes in the presence of oxygen, water and heat. This oxidation process is caused by depletion of the lubricant’s additive package for various reasons. The end result is deposits of varnish, tar and contaminants that thicken much of the oil into that gooey soup we call “sludge.” It sits on reservoir bottoms and deposits on mechanical internals, leaving a liquid with little or no lubricating properties.

Prescription: 

Reservoir sludge is most definitely preventable. Here’s how:

  • Mechanically remove as much sludge as possible and use a recommended solvent-based flushing fluid to clean the remainder.
  • Label the reservoir clearly to designate the correct lubricant manufacturer, product name and viscosity to be used, and indicate the same details on PM work orders.
  • If the reservoir exterior is regularly cleaned with water, ensure the fill cap and breathers (if applicable) are waterproof and always in place, or position a water-deflection shield over the reservoir.
  • Ensure the correct lubricant is used for the application ambient temperatures.
  • During change-outs, make sure the cap and breathers are reinstalled, and that the lubricant is transferred using dedicated clean equipment.
  • Always fill to the correct level; do not overfill!
  • Use regular oil analysis to determine when to change oil based on condition—and don’t forget to change it and the filter! MT


Dr. Lube, aka Ken Bannister, will present “Industrial Lubrication Fundamentals: Certification Preparatory Workshop,” a three-day, ICML-related Professional Development Course, at MARTS 2013. For details on this value-added lube-training opportunity, visit www.MARTSConference.com. E-mail: doctorlube@atpnetwork.com.

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