Problem of the shielded pump not starting
Thread Content
There is a problem with the unit: there is an outlet manual valve at the outlet of the shielded pump. When the pump is started, the manual valve opens, but the pump does not operate. The equipment replied that it was due to the pump outlet being too close to the outlet manual valve. Solution: There is another valve on the pump outlet pipe, located further away from the pump outlet. As a result, we opened the manual valve at the pump’s outlet; after starting the pump, we opened the manual valve on the outlet pipe that was located further away from the pump’s outlet, and the pump began to operate. Excuse me, what is the cause of this?
This is due to air in the shielded pump, which prevents it from pumping. The shielded pump is equipped with its own cooling and flushing system. Before startup, there is air at the pump outlet (at the outlet valve side); after startup, as the fluid reaches the outlet valve, the short distance between the pump outlet and the valve causes the compressed gas to enter the cooling and flushing system, and eventually reach the pump impeller, resulting in air entrainment. If the outlet valve is placed far from the pump outlet, the air inside will be pushed towards the inlet of the cooling and flushing system (of course, it isn’t completely expelled all at once; this is why the pump needs to be started first before the outlet valve is opened). In that case, there will be no air left inside, and no air bubbles will form.
It is necessary to vent the shielded pump before starting it! If the flow rate is not sufficient, it can easily burn out the sliding bearings of the shielded pump. It is recommended to study the operating procedures for shielded pumps carefully and follow them strictly.