Pulsation Dampers are sometimes needed at the outlet of positive displacement pumps. In positive displacement pumps such as reciprocating pumps, the output of the pumps is not steady but is pulsating.These pulsations are caused by the nature of the pump itself, which sucks water and expels it. The velocity of the fluid discharged from the pump is thus constantly changing. The acceleration and deceleration of the fluid are converted to fluctuations in pressure due to the momentum of the fluid.
Pulsation Dampers are devices which absorb the fluctuations. They are usually constructed as a container which contains a gas such as nitrogen. The container is connected to the line carrying the fluid. When the pressure of the fluid increases in the line, the nitrogen in the damper gets compressed and absorbs the pressure. Thus, there is a compression and decompression of the gas for every stroke of the pump.
The nitrogen gas is separated from the medium by means of a membrane. This prevents the gas from being absorbed by the fluid.