These values vary from about 40 cSt for some low-torque instruments up to 50,000 cSt and more for gearboxes and high-torque equipment.Ĭorresponding pour point temperatures and viscosity limits for representative mineral oils in Table 2 provide a basis for matching low-temperature needs. Table 1 provides approximate limiting viscosities for low-temperature operation of various machinery. At temperatures below this limit, the elevated oil stiffness interferes with adequate lubrication and related hydraulic functions in a machine. This viscosity limit represents the highest viscosity at which oil flows and properly lubricates in a system. While pour point establishes one low-temperature operating limit, other demanding requirements for low viscosity appear in critical machinery and lube system flow areas such as suction and drain piping, pumps and filters.
At this point the viscosity becomes so high (usually about 100,000 centistokes, cSt) it will eliminate any visible oil flow in the pour point test.
#OIL VISCOSITY CHART FREE#
With their low paraffinic content, wax free synthetic and naphthenic mineral oils can be further cooled to a lower pour point. Although gelling is reduced by these long-chain additive molecules, individual wax particles separating out of oil at low temperatures may still plug filters and impede circulation. Pour point additives that suppress this gelling effect of the wax are used in many automotive oils as well as in industrial lubes. With most mineral-based industrial oils (designated as turbine, hydraulic, industrial and machine oils), this pour point corresponds to the temperature that freezes the paraffin molecules of the oil into a white crystalline wax that will eventually immobilize the overall oil. This is the lowest temperature at which oil will flow when chilled under prescribed laboratory conditions (ASTM D97). The low-temperature limit for starting an oil- lubricated machine is often specified by the pour point of the oil. In other cases, grease or self-lubricating materials may reduce or even eliminate troublesome low-temperature problems. Avoiding high churning and splash losses at low temperatures in gear boxes developing remedies for more efficient lubrication of bearings and lubricated joints and implementing a reliable and low- maintenance technology that enables vehicle wheel bearings to safely operate over wide temperatures require careful lubricant selection.įortunately, specially compounded mineral oils or synthetics are available that match cold flow requirements.1 In difficult cases, heating is needed for piping, reservoir and filters. Industries and transportation in northern parts of the United States, Europe and Canada are vulnerable to harsh outdoor conditions during winter months. As a result, machines often cannot start or excessive friction causes a complete failure. Dropping below the pour point and the higher viscosity not only restricts oil flow to bearings and other machine elements, but also translates into high startup torque.
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