Below is a list of Shaft Seals manufacturers from Union City, California. Shaft seals are simple devices that prevent the passage of fluids along a rotating shaft; they are necessary when a shaft extends from a housing that contains fluid. They are mostly seen in hydraulic cylinders, which produce linear motion by using pressurized hydraulic fluid. They are found in pumps and gear boxes, which provide the speed and torque from a rotating power source to another device.