Book Bits

From "Filtration Technology":

Water absorption filters usually have an element that combines a particle removal media with water absorption material. The water absorption material may be something as simple as cornstarch, or as complex as a polyacrylate material. The latter is the type of material used in babies' diapers to absorb water. Typically, these filters are used to remove small amounts (less than 1% by volume) of free water from hydrocarbon fluids in circulating systems.

Most water absorption media are sensitive to flow rate, and their efficiency improves as flow velocity is lowered. It is common for these filters to be used on off-line circuits where the flow rate can be controlled by pump selection.

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Today's Tip

• There are two types of desiccants used to dry air, for example, in a reservoir breather:

  1. Deliquescent Type—Absorptive, the salt and water become dissolved in each other. Examples include calcium chloride and sodium chloride.

  2. Adsorptive Type—Regenerative, can be reused. Examples include silica gel, molecular sieves and activated alumina.

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Q & A

"We have recently noticed a significant increase in foam in one of our lube systems. A supplier recommended adding an after market antifoam agent, is this a good idea?"

While in some circumstances, adding an antifoaming agent may resolve the issue, it in generally not a good idea to add any aftermarket additive to a lube system. If foam has traditionally never been a problem, but has suddenly started, think about treating not the symptom (the foam), but the cause.

If nothing has changed with the design of the lube system or reservoir, it is likely that this sudden increase in foaming tendency is caused by contamination. Because foam suppression in a lubricating oil is closely related to the air/oil surface tension, any contamination that can result in either an increase in air entrainment, such as solid particles, or a decrease in surface tension can causer this type of effect. Common contaminants that can decrease the surface tension include water, grease and surfactants, such as soaps and detergents used during machine wash down.

To diagnose the root cause of your problem, try looking for significant increases in water or particle contamination or the appearance of unexpected elements in your spectrometric analysis data, such as lithium, calcium, aluminum or barium that may signal some other ingested grease or chemical contaminant.

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