In a Hydraulic Shock Absorber, mostly oil contained in one side of the cylinder is used to a pass through constricted spaces/valves to the other side of the cylinder,Thus converting the kinetic energy of the shock to the heat since the fluid is viscous in nature, which is then dissipated. This method is dually effective as it does not produce further vibration (as spring) and also works as a damper at the same time.Industrial shock absorbers are used in conjunction with the spring loaded check valves, to control the flow of oil and put the system back in initial state.
