The Shear Pin Cartridge coupling is a Series H type coupling. It is designed to physically disconnect the driving and driven equipment during torque overload. The purpose of the design is to prevent damage to the equipment- motor, gearbox, pump, etc. from torque overload. FAST’S® Shear pin couplings are used to limit the peak torque to a predetermined safe value. This value is greater than the normal starting torque of the system.