Zerk
A zerk is a small fitting used to inject lubricants, typically grease, into various mechanical components on semi-trailers and other equipment. It acts as a one-way valve, allowing grease to enter while preventing contaminants from getting inside.
On semi-trailers, grease zerks are commonly found in areas such as wheel ends, hinge or pivot joints, fifth-wheel plates, steering linkages, drivelines, clutch linkages, and brake systems.
Using
To use a grease zerk, a grease gun is attached to the fitting and grease is pumped into the mechanism. The fitting has a small ball and spring that opens under pressure, allowing grease to flow in while preventing contaminants from entering.
History
The lubricant fitting was patented (U.S. 1,697,217) by Oscar U Zerk in 1929.