As a common type of industrial pump, the air-operated diaphragm pump offers unmatched convenience and safety, as it is driven by an air source rather than an electric motor. However, like all positive displacement pumps, it has certain drawbacks—specifically, instability in discharge flow and head. How can this issue be resolved? Today, the pump experts at Shanghai Shenyin Pump Manufacturing Co., Ltd. will analyze how to stabilize the discharge flow and head of air-operated diaphragm pumps.
To stabilize the discharge pressure and flow of an air-operated diaphragm pump during operation, buffer tanks can be installed on the pump's inlet and outlet pipelines. These tanks require pre-charging with nitrogen; in principle, the pre-charge pressure should be no lower than 30% of the maximum operating pressure and no higher than 80% of the minimum operating pressure. While a higher pre-charge pressure yields a more significant buffering effect, it can cause fluctuations when the pressure drops, leading to frequent impacts against the tank bottom that damage internal metal components.
When the operating pressure range is wide, pre-charging to just 30%–35% of the maximum operating pressure is sufficient. Manufacturers typically recommend pre-charging the inlet buffer tank to 80%–90% of the inlet pressure and the outlet buffer tank to 60%–65% of the outlet pressure. In one actual case, excessive vibration in the inlet pipeline indicated an unsuitable pre-charge pressure; adjusting the inlet tank's pre-charge pressure down to 60%–65% of the inlet pressure eliminated the vibration immediately and restored the pump to normal operation.
During operation, the pressure in the buffer tank may gradually decrease due to factors such as leakage. Once the pressure drops to a certain level, the pump's flow becomes unstable and abnormal noises occur. Prolonged operation at low pressure causes the diaphragm to undergo wide-range fluctuations, leading to fatigue and a shortened service life. To prevent this, the buffer tank must be re-pressurized during operation. Based on experience gained during the commissioning and routine operation of the diaphragm pump, it was decided to pressurize the buffer tank while the pump was running under load; a stable pressure gauge reading served as the indicator of successful pressurization. Several trials yielded significant results, ensuring the long-term, safe operation of the diaphragm pump.
How to stabilize the discharge flow rate and head of a pneumatic diaphragm pump
We hope this proves helpful to you.