Machinery Lubrication

Machinery Lubrication May June 2013

Machinery Lubrication magazine published by Noria Corporation

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LUBE OIL AND CIRCULATING OIL PS/M HYDRAULIC OIL PS/M Gear oil >2,000 Mobile hydraulics (Bio) 800 Steam turbine oil 13 Industry hydraulics (ZnDTP) 250-2,000 Gas turbine oil (PAO) 1,200 Industry hydraulics (ester) >2,000 Gas turbine oil (ester) 1,500 Phosphoric acid ester (airplane) >2,000 SAE 10W-40 >2,000 Airplane hydraulics synthetic 29 Manual transmission gear oil >2,000 Synthetic 9 Paper machine oil (Zn-P) 350 Aircraft PAO 70 Paper machine oil (S-P) 10 Silicate ester (refrigeration) 1,500 Insulating fluids 12 Table 2. Conductivity of oils and synthetic fluids at 23 degrees C (73 degrees F) • Oil purity requirements have increased. This in turn has led to higher filtration rates. conventional filter cartridges. These filters can discharge or even prevent the charge from occurring. • The filtration intensity and electrostatic charge properties of the oil (resulting from filtration) have increased. 2.Use an oil with a different makeup and poorer conductivity value. • The oils' low conductivity, which often is far below 1,000 pS/m in certain conditions, has resulted in an increased tendency for electrostatic charging. 3. Choose or modify the system's material combinations so microspark formation is prevented despite an electrostatic charge. Measuring Conductivity to Prevent Damage In order to prevent damage from electrostatic discharges, more than just the conductivity of new oil must be identified. The parameter is also important for older lubricants, especially when dealing with larger quantities, if nothing is known about the used oil or a burning smell or soot particles are noticeable. Therefore, some oil analysis laboratories now offer conductivity measurements at different temperatures. The process has been tested for several years and is conducted in accordance with ASTM D2624. It originally was developed for inspecting airplane kerosene to avoid accidents caused by jet fuel charging. As mentioned previously, oil's conductivity value is measured in pS/m. If the conductivity is more than 400 pS/m at 68 degrees F (20 degrees C), there is little risk of damage to the oil or the system from electrostatic charges. However, if the value is lower, there is a very real possibility that the phenomenon could occur. If an oil with an increased ESD risk is being used, grounding the entire system is not a viable option. The voltage inside the system cannot be discharged through a grounding wire. Fortunately, there are several other approaches for prevention. 4. Optimize flow diameter, tank hold times or tank volumes to minimize the charge potential. 4 Ways to Prevent Electrostatic Problems 1.Install special stat-free filters instead of www.machinerylubrication.com | May - June 2013 41

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