Oil bleed is something that all industrial grease suffer from. The bleeding or separation of oil from the thickener is a normal occurrence that can happen during service or storage. The bleeding that happens during service is what is known as dynamic oil bleed and happens due to mechanical stresses that the grease is exposed to. This type of bleeding is necessary for the grease to perform its lubrication duty. The movement of the bearings causes the oil to flow out of the thickener and into the surfaces that requires lubrication.
The bleeding that happens during storage is known as static bleeding. During storage, the weight of the grease creates a stress that causes the thickener to release oil. The less dense oil travels to the top of the grease and forms a puddle on the surface.
The separated oil can be removed or mixed back into the grease. The amount of oil that separates during storage is inconsequential to the performance of the grease. However, certain storage conditions can aggravate the bleeding to a level in which the performance of the grease is jeopardize.
Factors that can worsen static oil bleed are vibrations and temperature. The mechanical and thermal stress caused by these two activates the grease into releasing oil. Proper storage practices must be observed to prevent excessive oil bleed and protect the performance of the grease.