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In This Issue:
Up Front: Integrating Technologies Equals Success
Book Bits: Water Exclusion is Difficult
Today's Tip: Oil First
Q & A: Eye on Crackle Test
Many companies are discovering the benefits of fully integrated condition-based maintenance. Taking a holistic approach we can now make much better informed decisions on the maintenance requirement of our machinery. Here's a recent success story.
An emergency diesel fire pump fitted to an oil production platform was identified as having excessive vibration at half order during the monthly survey. A combustion problem was suspected and the following recommendations made.
Perform oil analysis
Check lube oil discharge pressure
Perform stethoscopic survey of injectors and cylinders
Perform temperature survey of cylinders
We found that the oil sample had a strong smell of diesel. Flash point was 47 degrees lower at 143°C than the new oil sample. Viscosity was reduced to from 99 cSt to 77 cSt. The lube oil discharge pressure reduced from 4.8 to 4.2 bar (recommended minimum pressure being 4.5 bar).
Cylinder A5 had the highest overall level of vibration. The next highest levels of vibration were measured at cylinders A1 and B1. A5 was identified both in terms of noise and of having the lowest temperature, and was therefore assessed as being the faulty cylinder. A recommendation was issued to replace the injector of cylinder A5. (Submitted by John March, RC Consultants. Thanks John!)
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From "Filtration Technology":
Water is a common contaminant in hydraulic and lubricating systems. Moisture can enter these systems at several points:
Through reservoir breather caps in humid air. System fluid absorbs some of this moisture, while some is condensed on the inside surfaces of the reservoir.
Through worn seals. Besides humid air, coolant and cutting fluid sprays can enter hydraulic systems through worn rod seals as the cylinder moves. In lubricating systems, these water-based fluids can enter through rotating shaft seals on pumps, machine tool spindles and gear boxes.
Through heat exchangers. Worn and damaged heat exchangers can allow cooling water to leak through seals and ruptured lines into the oil system, and vice versa.
In new oil. An oil barrel stored outside in a vertical position is likely to collect rainwater around its bung. With changes in temperature, some of this moisture will be sucked into the barrel. Eventually, this water enters the system fluid when the reservoir is filled.
here for more information about "Filtration Technology".
When replacing top-suspended spin-on or threaded canister-type filters, fill them with fresh oil before installation. This will reduce the amount of time that the engine or machinery undergoes dry start-up by having that extra available amount of oil available. In some cases, it could also prevent filter damage when a gush of high-pressure fluid hits a dry element. (Submitted by Dave Oh, Powertrain Design/Development Engineer, FEV Engine Technology, Inc. Thanks Dave!)
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"I've tried using the visual crackle test to detect water in our lubricating oils. I'm having a hard time seeing the bubbles through my safety glasses. Any suggestions?"
The hot-plate crackle test is used worldwide as a preliminary screen for water. The test can be performed by simply dropping a few drops of oil onto a hot plate set at 150°C to 160°C.(300°F - 320°F.) and watching for the crackling, or sputtering of any water that is present as it vaporizes. The test is simple and reliable, but audible crackling occurs only where the oil is contaminated well above its saturation point. An experienced analyst, however, can detect water at very low levels of concentration by looking closely at the drop of oil for the formation and disappearance of non-scintillating vapor bubbles. The number of bubbles, the size of the bubbles, the duration of bubble life and of the bubbling itself provide clues to the analyst about the moisture level.
Try using an electrician's magnifying glass, the kind used for soldering printed circuit boards, to perform visual crackle tests. The magnifying glass will direct light onto the hot-plate and make the small transient vapor bubbles in which we are so interested much easier to see and analyze. These devices are inexpensive and widely available.
For more information on using this test, check out the article: Revisiting the Visual Crackle
Drew Troyer, Noria Corporation
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