April 2013 FAQ
Q: One of my customers has been experiencing significant foaming and loss of oil pressure running the Gear Oil 150 in a Striker HP300 (Concrete Cone Crusher), and I'm looking to rule out contributing factors. The oil in the machine was only four hours old, and the machine has recently had a brass brushing replaced, so we suspect there may be some other mechanical factor contributing to the foaming. In addition, the machine should automatically shut off if the fluid heats up beyond 65°C. I would like to know the acceptable temperature working range of the various gear oils for future reference.
A: The most common causes of foaming are contamination, over-filling, air leakage, poor reservoir design and lubricant additive depletion. Since the oil is relatively new, contamination is most likely causing the foaming.
A 65°C temperature shut-off limit is not normal in industrial gear boxes. Does the unit have a heat exchanger to keep it cool? If yes, check for water or coolant leaks. For every 10°C rise in temperature, the rate of oxidation doubles. Thus, OEMs stipulate the minimum viscosity of the gear oil at operating temperature. This will be your guide on whether the product is still appropriate. Check the manual to confirm the minimum viscosity. If the OEM says 25 cSt at operating temperature, Gear Oil 150 is still good - it has a kinematic viscosity of 26 cSt at 80°C. When the operating temperature is above 80°C, it is advisable to use synthetics to reduce viscosity loss and lessen the rate of oxidation.