Mud Pump Pulsation Dampeners

The speed of the piston is not constant during the suction and discharge strokes. During each stroke, the speed increases from zero to maximum at approximately the halfway position and then decreases to zero during the rest of the stroke (see Figure 20).

The change in piston speed and the fluid velocity causes the oscillating action shown in Figure 21. The effect is less severe for a single-acting  pump than a double-acting one.

Suction Dampener

The pump draws this from the dampener during the suction stroke when it requires more liquid. Once the suction stroke has been completed, the air chamber absorbs the flow from the tank and dampens the shock in the suction line.

The Discharge Dampener

Contrary to the suction dampener, the discharge chamber, or pulsation dampener, is partly pressurized with nitrogen gas. During the discharge stroke, the gas in the pulsation dampener is compressed. At the end of the discharge stroke, the compressed gas expands, sustaining a reasonable steady flow in the discharge line and dampening the peaks in discharge pressure.

Figure 22 shows a commonly used pulsation dampener. It consists of a steel spherical body in which a diaphragm is fitted. The diaphragm separates the gas (nitrogen) from the drilling fluid.

A charging valve and a pressure gauge are installed on top of the pulsation dampener cover to allow regular inspection and recharging. The pre-charge pressure should be 75 % of the minimum anticipated pump operating pressure to achieve a satisfactory dampening effect. The maximum pressure should not exceed 5250 kPa (750 psi).

WARNING: It is important that nitrogen only is used to charge the pulsation dampener. Serious accidents have been the result of using oxygen instead of nitrogen.

Dampener Location

The best dampening effect is achieved when the dampeners are installed close to the pump’s suction and discharge, as shown in Figure 23. The connection between the pump and the delivery line should include a hose to absorb vibration.