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.

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.
   

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.

Daily Tips

Keeping oil clean involves two different processes:

* EXCLUSION (keeping contaminants from getting in the oil)
Sources of contaminants can include:

• New oil
• Ventilation and breathers
• Seals
• Wear generation
• Service and manufacturing debris
• Filter dumping
• Wash-down sprays and solvents

The cost of excluding a gram of dirt is probably only 10% of what it will cost you once it gets into your oil.

* REMOVAL (getting contaminants out of the oil)Areas to consider:

• Proper filters for circulating systems
• Off-line filters for some splash/bath lubricated machines
• Portable filters for other machines
• Proper sump and reservoir management
• Timely filter servicing

Foaming is often overlooked as a lubrication problem. However, foaming is a problem when:

* The oil level in the sump or reservoir becomes impossible
to control

* The oil spills onto the floor creating a safety hazard

* The foam leads to air locks and inability to effectively
supply oil to lubricated components

* The foam inhibits heat transfer and encourages oxidation and thermal failure of the oil

* The equipment is lubricated with foam instead of oil

More Great Tips

Today we are going to look at an excerpt from the book "Hydraulic Fluids."

"Flushing may often be required when the system is new or during subsequent service, particularly after repairs, if significant contamination has occurred. Large systems assembled on site frequently incorporate components treated with temporary corrosion protectives. Unless such materials are removed prior to filling the system with a clean hydraulic fluid, they will gradually dissolve in the working fluid and may detract from its performance in several respects, e.g. by promoting emulsification.

"If flushing is required, it is preferable to utilize the grade to be used in service or a lower viscosity grade of similar composition. Critical components (valves, hydraulic pumps and motors) should preferably be isolated or by-passed during the flushing operation to avoid harmful accumulations of particulate contaminants, thus defeating the purpose of the treatment. A minimum charge of flushing oil should suffice, this being circulated through the system and adequately dimensioned supplementary filter(s) by a suitable external pump. Filters should be checked periodically and flushing continued until particle counts on the fluid returning to the filters decrease
to a satisfactory level.

"The temperature of circulation should preferably be around 40 degrees C; if necessary the flushing medium should be heated, but local overheating must be avoided. If electrical heaters are used they should be of liberal surface area."

Book Bits

"Since synthetic oils get contaminated with wear metals, carbon soot, combustion residue, and by products of fuels, such as acids and sulphur compounds, in much the same way as petroleum base oils, it may be unreasonable to expect synthetic oils to last longer than petroleum base lubricants.

"Oil levels must be checked periodically, filters serviced or replaced on a regular basis and above all, oil samples should be taken regularly and sent to a competent used oil analysis laboratory for analysis."

This passage comes from the book "The Practical Handbook of Lubrication" by Lloyd Leugner.

Today's Tips

The pour point is the lowest temperature at which an oil will flow. This property is crucial for oils that must flow at low temperatures. A commonly used rule of thumb when selecting oils is to ensure that the pour point is at least 10 degrees C (20 degrees F) below the lowest anticipated ambient temperature.

Consider system design in filter selection. If the application has cyclic flow rates, the increase in flow can dramatically alter the efficiency of the element during the surge. If this cylinder cycles at a fast rate, the filter is subjected to extremely high flow rates as the equipment cycles. This can cause leakage past the filter and over the bypass valve as the pressure drop increases, perhaps inducing element collapse.

More Great Tips

Today we are taking a passage from the book "Synthetic Lubricants and High Performance Functional Fluids."

"The use of PAO-based gear oils in industrial settings can lead to important savings in energy consumption, as well as decreased downtime and lower maintenance requirements. The wide range of operating temperatures allows the use of less viscous oils, which results in greater energy efficiency. The relatively low coefficient of friction for PAOs reduces the amount of internal friction created by the normal shearing of an oil film during operation.

"Improved scuffing performance for gear/circulating oils has been demonstrated by Jackson et al., who studied the influence of lubricant traction characteristics on the load at which scuffing occurs. The study compared low traction PAO-based lubricants with mineral oils in additive-free, antiwear, and extreme pressure (EP) formulations. Benefits of 25-220% were observed for the PAO-based synthetic lubricants over mineral oils. The investigators found that low traction PAO-based lubricants uniformly gave higher scuffing loads per unit width than the mineral-based fluids tested at both high and low specific film thickness. PAO-based gear and circulating oils outperformed mineral oil based gear and circulating oils, respectively. PAOs were also shown to be very responsive to additives.

"The advantages of PAOs as lubricants in conveyor applications has been demonstrated by Paton et al. Gearboxes lubricated with a fully synthetic poly(a-olefin)-based gear oil (75W-90) was studied. An all-season PAO-based fluid was chosen for pulley shaft bearing lubrication.

"In wind turbine gearboxes, the high viscosity index of a synthetic fluid would ensure that the change in viscosity with temperature would be less than with equiviscous mineral oils. A further advantage of a synthetic fluid for applications of these types is that synthetics have lower pour points than mineral oils. PAOs provide both excellent viscosity index and low pour point. These properties make them a fluid of choice for applications characterized by wide ranges of operating temperatures."