The backup pump will not start. Urgent! !
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This post was last edited by yy1007 on 2010-11-10 00:55. Hello, everyone: Let me briefly explain the situation: It’s a vacuum distillation tower with a gauge pressure of 3 KPa and a medium temperature of 156 degrees. The pump at the bottom of the tower is working properly; currently, we want to switch to the backup pump (the pump in use has been operating for 3 months now, and it’s time to replace it). However, every time the inlet valve of the new pump is opened, the other pump immediately loses pressure and can no longer deliver fluid. 1. After connecting the hose and filling the pump, pressure is generated once the pump is started, but as soon as the inlet valve is opened, the above situation occurs immediately. 2. No problems were found after the pump was removed for maintenance, and the inlet pipeline is also unobstructed. 3. Even after the pump body has been preheated, the inlet valve still cannot be opened. 4. A leak test was conducted on the pump alone, and a leak was found at the mechanical seal; it was asked whether the insufficient suction at the inlet was caused by the leak in the mechanical seal 5. When the other operating pump stops, starting the backup pump still results in no pressure. (The pressure gauge is not faulty.) 6. Everything was normal before, and switching can also be done properly
It is likely that air has leaked in due to a leak in the mechanical seal; when you open the inlet valve of the standby pump, this air enters the inlet of the operating pump, preventing it from pumping properly. First, resolve the leak in the mechanical seal of the standby pump, and make sure to fill the pump properly before starting it
It is unknown what the medium in the distillation tower is; the standby pump has not been in use for 3 months, so it is possible that the impeller and flow channels could become clogged with scale (the medium)...
1. Please check whether the pump impeller is installed in the wrong direction or whether the motor is rotating in reverse. 2. As mentioned by the poster, if there is a leak in the mechanical seal during the airtightness test, it is necessary to determine the location of the leak by manually turning the shaft and starting up the equipment, so that it can be addressed as soon as possible.
1. The motor rotation direction is correct. 2. The mechanical seal leakage has been resolved. 3. The pump was inspected after being disassembled; it is in normal condition. It still doesn’t work yet
This post was last edited by luoheng116 on 2010-11-9 at 16:23. Could it be that when the inlet valve was opened, it was opened too quickly, resulting in a sudden increase in flow and preventing the pressure from rising? Mechanical seals inherently have a slight amount of leakage, which is normal, unless the leakage volume is very high. And why open the inlet valve? Do you open the outlet valve first, start the pump, and then open the inlet valve?
1. Please check whether the pump impeller is installed in the wrong direction or whether the motor is rotating in the reverse direction. 2. Pump startup: 1. Check that all valves and electrical components are in good condition. 2. Turn the drum. Check whether the pump is rotating properly. 3. Open the inlet valve fully and slightly open the outlet valve. 4. Start the motor. 5. Open the outlet valve and adjust it to the specified pressure range. 6. Observe the pump operation for 5 minutes. That’s it.
Reply to 1# wanghai127127: If the suction side of the pump is under negative pressure, there will be no pressure in case of air leakage or air present inside the pump
Mechanical seal leakage will only cause a decrease in the vacuum at the top of the tower, without affecting the pump pressure. Check whether the motor is rotating in the correct direction and whether the pump turns properly. Close the outlet valve, open the inlet valve fully, start the pump with air pressure, and then slowly open the outlet valve