After a recent rebuild of a small, 500 HP steam turbine and gearbox that drive a cooling tower water pump, the first monthly oil sample results showed high water content. Rather than just use the 'shotgun' approach to eliminate all the potential sources of water, we attempted to identify the water source.

The gearbox serves as an oil sump for both it and the turbine, and has a shaft driven oil pump, external oil cooler, filter, and a small decanter settling pot. Small, 1 oz clear acrylic sight glasses were added to the drain ports on the turbine bearing housings and oil cooler drain without shutting the unit down. After just one day, the sight glass on the governor end turbine bearing housing showed 0.5 oz of free water along with 'milky' colored oil.

This narrowed the search for the water source considerably. The three possible sources were the housing breather, which was a desiccant type and not changing color, the bearing housing water jacket, which we valved out to test and still got water, and the labyrinth oil seal that faced the carbon rings that seal the 600 psig steam in the turbine casing. An upgraded bearing isolator has been ordered to replace the simple labyrinth oil seal and will hopefully eliminate the water contamination problem. (Kevin Bellamy, Reliability Engineer, Eastman Chemical Company)

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Achieving optimum benefit from lubrication and maximizing equipment uptime is more than just the correct lube application and monitoring. While these are essential components, getting the correct lubricant is the first step. This is not always as simple as it sounds because of multiple vendors, sole sourcing or variable and/or qualitative purchasing decisions.

It can also be exacerbated by a lack of understanding of the application and/or the significance of any changes to a lubricant. Even lubricants by the same name and from the same supplier can undergo formulation changes or changes in the place they're manufactured. Normally, this goes unnoticed with the recent proliferation of mergers, acquisitions and product dropping.

Read this article from Machinery Lubrication magazine.

Test your knowledge and prepare for ICML lubrication and oil analysis certification.

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"A mechanic asked us what he should use to take a quality sample from a crankcase on a diesel engine. He was concerned that draining the oil from the sump of a engine would negatively bias the sample toward a higher-than-normal wear debris analysis and or particle count. Your thoughts?"

The best way to sample a diesel engine is to install a sampling valve on the main pressure feed, somewhere between the oil pump and full-flow filter.

Many newer engines, particularly CAT, have these pre-installed. You didn't mention the engine types, but I know that CAT will provide engine specific recommendations, and I'm sure other OEMs would do the same.

There are several different types of valves available, however we prefer what is generally called a minimess in oil analysis, actually a Stauff series 20 hydraulic test fitting.

If you cannot install a sample valve, drain sampling is not recommended. Instead, use a vacuum sampling gun and nylon tube, and insert through the dipstick. To ensure you don't sample sludge from the bottom of the crankcase, we also recommend using the dispstick to measure the tube length - typically cutting the tube 10 inches longer than the dipstick and inserting 1/2 inch shorter than the dipstick length will give a correct measure.

We also suggest cutting the tube end at an angle, again to avoid bottom sampling. While this procedure works and will give reasonably reliable data, you did indicate you were doing particle counting, in which case I would strongly encourage you to install an appropriate sample valve.

Mark Barnes, Noria Corporation

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