If moisture is >300ppm, BAD things are happening in Your lube system
If you have ever worried about moisture levels in your lubrication oil, you are rightly concerned. Waters interaction with oil, at any contamination level, is harmful to plant and machinery. It will shorten the service life of your machinery, as well as the life of the lube oil protecting your sensitive components. Moisture is an exponentially damaging contaminant!
Left Unchecked, Moisture Will Affect Your System
Compressors handling natural gas with higher levels of Hydrogen sulphide can strike real problems if the oil interacts with the product gas and any moisture is present. The result is an attack on the compressor alloys called sulphide stress cracking, a form of hydrogen embrittlement. In extreme cases this can cause a compressor casing to split.
Hydrogen embrittlement is not limited to just compressors though, as electrolysis or corrosion will split a water molecule releasing hydrogen atoms to react. Unfortunately, this effect is self-amplifying.
Put simply, what rust does is impair the bearing surfaces and denies the oil a chance to form that critical elastohydrodynamic (EHD) film that separates the bearing surfaces.
Impaired Film Strength
Similar to corrosion, the oil is denied the opportunity to lubricate and separate the surfaces. This occurs when dissolved water affects the viscosity of the oil and allows the load zone to force the lubricant aside and bump.
Did You Know?
An amazing and very damaging event can occur when water is present in the bearing load zone.
The effect produces super-heated steam which creates a mini explosion inside the oil, similar to micro-dieseling, that will damage the oil & work harden, fatigue and crack the bearing surfaces.
Water (especially chemically treated water) can have an adverse effect on the ability of the lube oil to dissipate foam and separate from water. Excess foaming (aeration) will lead to sluggish response from hydraulic control systems, cavitation in pumps and bearings, and wear.
Lube Oil Additive Depletion
Additives are designed to be a sacrificial product. They are consumed as the additive pack anti-oxidant neutralises unwanted chemical contaminants. However, if additives such as demulsifiers (which help shed water) are exposed to large amounts of water contamination, the demulsifiers can be stripped from the oil very quickly leaving the oil at risk.
Other additives like Extreme Pressure (EP) and Anti-wear (AW) can be hydrolyzed (broken down into acids) by water and deny your Equipment the protection those additives are designed for. If left unchecked the by-product is sludge and varnish.
Water, being polar has an affinity with other contaminants in the lube oil such as soot, resin, spent additives, oxides and dirt. These agglomerate into a sludge that will overwhelm strainers, filtration and eventually restrict oil flow in the system.
For microbes to thrive and grow within lubrication oil or diesel then the presence of water is a great promotor. Eventually this biomass or bug will grow to interfere with lube circuits and can plug fine lube capillaries and filtration. Microbial contamination is also corrosive and can be carcinogenic.
Dry Oil Equals Extended Life of Oil & Machinery
A trial of machines by the BHRA compared equipment life to moisture contamination. They found the correlation between dry oil and oil with high moisture content. Oil with a moisture level of 5,000 ppm was dehydrated and trialled to measure equipment life. The results show that equipment with oil drier than 100ppm has three times the life of a machine with oil of 450ppm moisture.
Resolving the Problem of Moisture
There are many solutions on the market today to mitigate moisture and particulate contaminant. BioKem uses a range of units and for the best results you may want to consider a vacuum dehydrator VDOPS type unit. They are effective at removal of dissolved, free and emulsified water, entrained gas, and particulate for heavy gear oils right down to very light oils of any Group. They are the Gold Standard of the filtration industry. These VDOPS units have class leading microglass filtration media to remove particles as small as 2l¼m.
If you want some advice on specifying or sizing a suitable unit for your Plant, then let us know.
If you can keep your lube oil moisture levels under 300ppm then you will increase equipment life and prolong the life of your lube oil.
Next Article – Why and when should you Hot Oil Flush (HOF)?
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