How to check if the inlet pipe of the self-priming pump leaks?

The self-priming pump relies on the high-speed rotation of the impeller to generate a low-pressure zone in the self-priming pump to absorb water. Therefore, the self-priming pump must ensure that the inlet pipe does not leak, that is, the outside air cannot enter the inlet pipe. Otherwise, it will not only affect the efficiency of the pump, but also cause severe vibration and noise when the pump is operating.

The technical requirements of the self-priming pump before installation are very critical
     1. Self-priming pump must ensure that the length and height of the inlet pipe cannot exceed the allowable suction range of the self-priming pump before installation.
     2, the imported pipeline must not have the phenomenon of air leakage, it should be guaranteed to be a fully sealed pipeline, even if there are small holes with pinholes will affect the self-priming capacity of the self-priming pump.
     3. The self-priming pump can't be cheap when it is installed. Some users put the wooden strip base of the factory-fixed self-priming pump and the self-priming pump on the ground and put it into use when the newly purchased self-priming pump is used. This method is not advisable, which can easily cause vibration and noise of the self-priming pump and cause mechanical failure of the self-priming pump. The correct way is to fix the pump base to a solid flat platform or to a hard floor.
    4. When installing the self-priming pump, try not to fix it on the bracket welded with channel steel. Because the surface of the channel steel is too close to the pump, it is easy to put a large part of the pump base while hanging the base screw. The base and the coupling are concentrically damaged, so the self-priming pump mounted on the channel bracket is the most prone to vibration and the coupling is easily damaged.
    In the work, if the pump water is not enough or does not produce water: First of all, it should be considered whether the inlet pipe is not tightly entered by the blisters, cracks or joints, and it is observed to find the air inlet. Some of the defects are very subtle, and it is difficult to find them directly by the naked eye. It is often time-consuming and ineffective.

Here are a few easy ways to check for leaks in the inlet pipe of the pump:
(1) Duck feather method: Use a duck down hair to get close to the suspected air intake when the pump is running, and observe the fluttering of the duck down hair. For the same reason, the ignited cigarette can be operated according to this method. Help the look by the fluffy direction of the duck down and the smoke.
(2) Oil method: For the inaccessible point that is difficult to ascertain, a small amount of oil can be applied to the determined intake portion, and the oil is quickly sucked away.
Measures to prevent self-priming centrifugal pump intake
     1. The installation position of the self-priming pump should be as close as possible to the water surface to ensure that the air is not sucked in when the water level drops.
     2. When installing the suction pipe, the inlet pipe should be inclined slightly downward or horizontally in the direction of the incoming water. The inlet pipe should not be higher than the water inlet of the pump, otherwise the air in the pipe can not be exhausted.
     3, to prevent leakage of the filler culvert. The tightness of the packing culvert should be suitable. If it is too loose, the packing gland should be tightened; if the packing is damaged or invalid, it should be replaced in time; the water sealing pipe at the filling area is blocked and heated, which will cause the packing to cover the leaking gas. The water sealing pipe should be cleaned. .
     4. Before installing the inlet pipe connected by the flange, clean the plane where the two flanges are in contact with each other, and add a 3~5mm thick rubber pad in the middle. Tighten the bolts symmetrically and several times.
     5. The bottom valve of the self-priming pump should have sufficient submergence depth. The submerged depth from the valve plane should be 1.5~2 times of the outer diameter of the bottom valve, at least not less than 0.5m. If the submersion is too shallow, it is easy to form a vortex, thereby sucking in air, causing cavitation and damaging the impeller and the pump casing. If you find that the water level drops quickly when the pump is running, you can put a few pieces of wood on the water surface to reduce the vortex and prevent air from entering the pump casing.
     6. The self-priming pump body is provided with a venting screw plug. In order to facilitate deflation, the faucet can be replaced by a faucet with the same thread size, and the faucet can be opened when deflated.
     7. The degree of vacuum at the suction port of the self-priming pump is limited. If the degree of vacuum is too large, the water in the pump is easily vaporized, which is unfavorable for the operation of the self-priming pump. Therefore, each of the suction pumps has its maximum allowable suction stroke, which is generally between 3 and 8.5 m, and should be controlled within this range during installation.
     8, pay attention to the exhaust. Before starting the self-priming pump, sufficient water should be added to eliminate the air in the self-priming pump; normally, the venting screw plug on the pump cover should be opened regularly to remove the air accumulated in the air.

      When starting the self-priming pump: Note that the steering of the pump shaft is correct. Pay attention to the abnormal sound and vibration when turning. Pay attention to the pressure gauge and vacuum gauge reading. After the start of the pressure gauge and vacuum gauge reading after a period of fluctuation indicating the stability, the self-priming pump has been filled with liquid and entered the normal infusion operation.

     In the self-priming process before the self-priming pump enters the normal infusion operation, special attention should be paid to the increase of the water temperature inside the pump. If the process is too long and the water temperature in the pump is too high, stop the pump and check the cause. If the temperature of the liquid in the self-priming pump is too high and it is difficult to self-prime, then it can be temporarily stopped, and the liquid in the discharge line can be  back into the pump or the liquid storage port can be directly added to the pump to make the pump The liquid inside is cooled and then started.

If the self-priming pump has strong vibration and noise during the working process, it may be caused by cavitation of the pump. There are two reasons for cavitation: one is that the inlet pipe flow rate is too large, and the other is that the suction stroke is too high. When the flow rate is too large, the outlet control valve can be adjusted to increase the reading of the pressure gauge. When the inlet pipe is blocked, it should be eliminated in time; when the suction stroke is too high, the installation height of the pump can be appropriately reduced.
The self-priming pump stops the pump during the working process. When it needs to be restarted, the outlet control valve should be slightly opened (not fully closed), which is beneficial to the gas from the discharge port during the self-priming process, and the tip is lighter. The responsibility is under the start. Pay attention to check the piping system for leaks.

Self-priming pump stop precautions and operation sequence:
1. First, the gate valve on the discharge line must be closed.
2. Stop the pump from rotating.
3. In the cold season, the liquid in the pump body and the water in the cooling chamber of the bearing body should be emptied to prevent the pump parts of the cracking machine.
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