WearCheck LUBE TIPS: Volume 6

25. Lube tip: saturation levels in fluids

The saturation level of a fluid describes the amount of water that can dissolve in that fluid. There are certain factors that determine the amount of water that a fluid will absorb – these include the fluid’s temperature, viscosity, base stock, and what additives have been added. Generally, for a synthetic fluid, the saturation level is much higher than for a mineral base fluid. When oil is above its saturation level, it has a cloudy appearance. 

26. Lube tip: oil-sample-taking essentials

One of the most critical parts of oil analysis is the correct taking of the oil sample. If mistakes are made while taking a sample, it could create problems for the entire oil analysis process. Two fundamental objectives must be met in order to obtain a truly representative oil sample:

Maximising density of data - the oil sample should be collected in a way that provides the highest possible amount of information per millilitre of oil. Factors that provide information about the oil’s condition include the oil’s dryness and cleanliness, additive depletion, and the amount, if any, of wear particles that are being generated by the component. For example, an oil sample that is taken downstream of a filter would not be beneficial,  as most of the information about the oil’s condition would already have been removed by the filter.

Minimising data disturbance - the sample taker should ensure that the concentration of information about the oil’s condition is uniform, consistent and not altered by the actual sampling process. Crucially, the sample must not be contaminated during the process of taking the sample.  If it is contaminated, this can distort the data, making it hard to establish what contamination was already in the oil, and what entered the oil during the sampling process. Using a dirty sample bottle, for instance, will add contaminants to the oil sample, resulting in data disturbance. In this scenario, it would result in a false positive.

27. Lube tip: understanding particulate contamination in oil 

     

Clearance-sized particles

One of the most important size particles to control in lubricants and hydraulic oils is clearance-sized particles. Larger particles cannot get between moving surfaces and smaller ones pass right through.

Clearance-sized particles usually get in and do the most damage. The clearance refers to the film of separation provided by the lubricant or hydraulic fluid.

Contamination control starts by keeping contaminants out of the equipment from the beginning. The costs associated with keeping the contamination out from the beginning are much less than cleaning a system once is has been contaminated. 

Once the contamination is introduced to the lubricant, the lubricant can start to degrade, and internal components can deteriorate prematurely. Implementing a few good maintenance practices can provide the reliability needed to keep equipment running in optimum condition.

How particles affect the oil

Particles, especially catalytic metal particles like copper, iron and lead, increase the rate at which oxidation occurs. Particles also strip the oil of its polar additives, including anti-wear additives, extreme pressure additives, rust inhibitors and dispersants. Also, numerous very small particles in stable suspension can cause the oil’s viscosity to increase. 

Visit www.wearcheck.co.za for more condition monitoring information.