Q:
the Expert
Q: Can you provide an explanation regarding the What types of greases are used in the following mills: temperature capability of some standard high temperature steel mills, lumber mills, sugar mills & paper mills? greases and how to interpret and compare the values typically listed for each product? Drop point, Flash point, A: maximum operating temperature. There is some debate Steel mills – The steel industry originally used clay here about how to apply a product and what the different greases, as they were the only high-temperature products product descriptors indicate. of the time. The industry moved to aluminum complex when it was introduced. Some steel mills continue to use A: aluminum complex grease, while others have moved to The maximum operating temperature of lubricating greases is reported differently by different suppliers. First, lithium complex products for general lubrication. Some applications use polyurea greases with synthetic base fluid. we will discuss the terms that you have listed: Dropping Point is basically the temperature at which the thickener in a grease melts, as determined in various test methods. The melting of the thickener results in the grease becoming fluid enough to run out of the dropping point test cup. Greases should not be used at temperatures approaching the dropping point. Flash Point is a property of the fluid component of a grease. The flash point is the temperature at which the vapors of the fluid momentarily ignite when an ignition source is applied. The flash point is typically well above the operating temperature of the grease. The maximum operating temperature of a grease is typically determined by how the grease performs in bearing tests at elevated temperature. Such tests include ASTM D3336, ASTM D3527, FAG FE-9, etc.
Lumber mills – This application does not have the extreme conditions found in the steel or paper industries. The lumber industry has typically used lithium, lithium/ calcium, or lithium complex greases. Sugar mills – The sugar industry is characterized by heavy-loaded, slow-moving plain bearings. The greases used in the sugar industry have historically been calcium soap or clay thickened, with high (ISO 1000 or higher) base oil viscosity and lubricating solids, such as molybdenum disulfide. Paper mills – The typical paper machine has both high water (wet end) and high temperature (dry end) applications. In general, lithium complex greases are used, while some specialized applications require products such as polyurea grease with a synthetic base fluid.
Q: It is recommended that you discuss the specific What type of grease is the thickest but still is a lubricant application and temperature range with your grease to take up or make up the gear mesh? supplier so that the supplier understands the requirements and can supply a product with the appropriate A: temperature range capabilities for the operating The use of a grease in place of gear oil in a worm gear conditions. will not make up for excessive slack in the gear set. - 24 VOLUME 80, NUMBER 1
