All Pumps Machinery Company Limited.

Preventive Measures for Avoiding Self-priming Pump Intake Air

Self-priming pump relies on the high-speed rotation of the impeller to create a low-pressure zone inside the pump for pumping, so the self-priming centrifugal pump must ensure that its inlet pipe does not leak, that is, the outside air cannot enter the inlet pipe. Otherwise, it will not only affect the pump efficiency, but also cause severe vibration and noise during pump operation.

In work, if the pump does not have enough water output or no water output, the first consideration should be whether the inlet pipe has air entering due to sand eyes, cracks, or loose joints, and observe it to find the air intake. Some defects are very subtle and difficult to find directly with the naked eye, often causing laborious and time-consuming efforts with no results.

1. The installation position of the self-priming pump should be as close to the water surface as possible to ensure that it does not suck in air when the water level drops.

2. When installing the suction pipeline for the self-priming pump, the inlet horizontal pipeline should be slightly inclined towards the incoming water direction or horizontally installed, and any point of the inlet pipe should not be higher than the inlet of the pump, otherwise the air inside the pipe cannot be completely removed.

3. The self-priming pump should prevent leakage of filler gas. The tightness of the filler cover should be appropriate. If it is too loose, tighten the filler pressure cover; if the filler is damaged or ineffective, it should be replaced in time; if the water seal pipe at the filler cover is blocked and heated, it will cause the filler cover to leak gas, so the water seal pipe should be cleaned.

4. Before installing the inlet pipe connected by the flange plate of the self-priming pump, the two flange plates should be cleaned on the contact surface, and a 3-5mm thick gasket should be added in the middle. The bolts should be tightened symmetrically and gradually several times.

5. The bottom valve of the self-priming pump should have sufficient immersion depth. The immersion depth from the valve plane should be equal to 1.5-2 times the outer diameter of the bottom valve, at least not less than 0.5m. If the immersion is too shallow, it is easy to form eddies, sucking in air, causing cavitation and damaging the impeller and pump casing. If the water level drops rapidly during pump operation, you can place some wooden planks on the water surface to reduce eddies and prevent air from entering the pump casing.

6. The self-priming pump body is equipped with an air release plug. In order to facilitate air release, a water tap with the same thread size as the air release plug can be used instead of the air release plug. When venting, simply open the water tap.

7. The vacuum degree at the suction port of the self-priming pump is limited. If the vacuum degree is too high, the water inside the pump will vaporize, which is not conducive to the operation of the self-priming pump. Therefore, each self-priming pump has its maximum allowable suction distance, generally between 3 and 8.5m, which should be controlled during installation.

8. Pay attention to exhaust of the self-priming pump. Before starting the self-priming pump, sufficient water should be added to eliminate the air inside the pump; normally, the air release plug on the pump cover should be opened regularly to discharge the accumulated air therein.