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In This Issue:

• Up Front: Localized Temperatures Cause Varnish

• Book Bits: Inspect New Oil Deliveries

• Today's Tip: Sources of Copper in Oil

• Q & A: Can Sump Headspace Fumes Ignite?

Readers Challenge

Hydraulic Temperature Affects Performance

In colder weather, be careful of your hydraulic oil temperature as the operation of machinery can be severely affected if the oil is too cold.

The effects of high temperatures are usually of greater concern, especially when electronic systems are involved, as these are adversely affected by too much heat. Oil that is too cold, however, is much more insidious.

In one case, a hydraulic tensioner was operating erratically on an umbilical loading vessel. We lost considerable time changing components and ensuring that we had plenty of cooling for the oil. After much wasted time, we learned that for winters in Norway, the oil may be too viscous to flow as well as it should.

Normal hydraulic systems should operate around 50 degrees C and if fitted, cooler bypass valves should operate around 47 degrees C. If the temperature drops too much below this (in practice I've found it to be around 30 degrees C), then a hydraulic control system may not work properly. The difficulty that this causes is that all of the parameters for a correct working system are probably being met - the pressures will be fine and the flow rates OK. This can lead to an initially incorrect diagnosis.

So when checking a system, in addition to looking at filtration, pressure and flow, make sure that your oil is running at the correct temperature. Make it part of your routine! (Submitted by Mark Chisholm, Chief Engineer, Stolt Offshore. Thanks Mark!)

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Book Bits

Inspect New Oil Deliveries

From the paper "How to Inspect New Oil Deliveries" from the "Lubrication Excellence 2003 Conference Proceedings".

Inspecting your new bulk oil delivery is important to the end user for several key reasons. A new oil fill for a turbine reservoir will be a significant investment for the plant. Volumes of up to 10,000 gallons are common and can reach costs exceeding $30,000. It will also be the lifeblood of the components for which it lubricates. In this regard, inspecting the new oil should be considered a critical first step in assuring the best service performance is achieved from your new oil product.

Some key reasons for inspecting your new oil delivery include: 1. Assurance that you received the correct product. 2. Assurance that the product was not compromised during handling and delivery. 3. Product warranty.

More information about the "Lubrication Excellence 2003 Conference Proceedings"

Today's Tip

Sources of Copper in Oil

• Typical sources of copper within an engine include: wrist pin bushings, thrust washers, oil pump, governor, valve train bushings, cam bushings, oil cooler and bearings. Copper can also be an antiwear additive in some oils. Additionally, high copper readings may occur during the run-in of a new engine (say after 500 to 1000 hrs of service) and when changing from one brand of an oil to another.

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Q & A

Can Sump Headspace Fumes Ignite?

"I've heard that oil fumes and mist in the headspace of a machine's oil sump or reservoir is at risk of exploding if temperatures are high or there is an ignition source. Is this true?"

In order for spontaneous combustion to occur, the temperature in the headspace must rise to approximately 270 degrees C (518 degrees F) and the oil content of the oil/air mixture has to reach 13 percent by weight.

An automobile crankcase constitutes an enclosed tank containing a lubricant, as does an automobile transmission. As a practical matter, there is minimal risk of explosion of a tank or gearbox that holds or has held a lubricant. With rare exception, the vapor space above the lube oil in properly operating industrial machinery is not combustible. Unless contaminated with a flammable substance (or the oil has cracked), the partial pressure of a lubricant will not lead to this event.

An explosion will result if two conditions are met:

a) The temperature is allowed to rise to levels considerably higher than normally encountered in oil-containing areas of automobiles or industrial machinery.

b) The oil/air weight ratio is not too lean and not too rich, perhaps 13 to 17 percent.

Answered by: Heinz Bloch

Submit your question here.

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