Common Faults of the Drilling Pump 1. Pump pressure drop and insufficient displacement: Mostly caused by damaged and washout pistons, failed sealing of the suction and discharge valves, and liner wear. 2. Severe pressure fluctuation and heavy pump vibration: Caused by incorrect pre-charge pressure in the air chamber (pulsation dampener), or cavitation due to poor suction. 3. Valve knocking and abnormal noise: Caused by worn or damaged valve flaps (valve plates) and valve