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High-temperature chain oils are used in the plasterboard industry, insulation material industry and in all other industries where conveyor and drive chains are exposed to high temperatures. This article covers only the most important and common requirements and test methods. Additional specific tests can be conducted if required.
In general, requirements for high-temperature chain oils are the same as for standard chain oils that are used at room temperature. Friction and wear have to be reduced to a minimum. However, special base fluids and specific additives must be used in order to achieve optimum performance at elevated temperatures.
Good penetration ability and adhesiveness are basic requirements for chain oils. Both properties are often in contradiction to each other and need to be balanced according to the individual application. The inner parts of the chains must be lubricated to not wear out, while the adhesion must be excellent to avoid centrifugal or drip-off losses. This is especially relevant for high-temperature chain oils because of the viscosity-temperature dependency.
Particularly for high-temperature applications, evaporation losses and the appearance of residues are important. Low evaporation losses allow longer relubrication periods and less contamination in exhaust filter systems. However, the residues after evaporation must still be smooth and capable of flowing to prevent the single chain links from blocking. In addition, the smooth residues must be able to redissolve in fresh oil.
The flash points of high-temperature chain oils play a decisive role. There should be a safety gap between the flash point and maximum operating temperature of the chain to avoid ignition and fire.
To describe the performance of chain oils, standardized methods are used, such as the well-known four-ball test, which reveals the extreme-pressure properties and wear performance of the oil. Flash point is measured by the Cleveland open-cup method.
Friction and anti-wear properties of chain lubricants subjected to oscillating movements are tested on SRV (oscillation, friction, wear) equipment, where a wide range of test parameters can be adjusted in terms of load, frequency, amplitude, contact geometry and temperature. High-temperature applications can be simulated up to 300 degrees C (572 degrees F).
One of the most important specifications for high-temperature chain oils is evaporation loss. Basically, two methods are used to determine this parameter: the standard evaporation test, in which the chain oil is exposed in a cup to higher temperatures for a defined time period, and the thermogravimetric analysis (TGA) method, which determines the weight loss as a function of temperature across a wide range, thus providing very reliable results with regard to practical relevance.