Pump Startup Sequence
Pump Startup Sequence
(OP)
My question is about the sequence used in starting a pump.
My customer is using a vertical-shaft pump with a 6" outlet. 800HP motor The outlet piping goes through a check valve and an automated ball valve.Then the line rises 1100 feet.
When they start the pump, the ball valve is closed. They then open the ball valve slowly. It takes over a minute for the valve to reach full open.
The valve is showing signs of cavitation, and the seats are being eroded. I keep wondering why they would start the pump deadheaded, as that MUST cavitate the impeller, too.
Should they not open the ball valve first, then start the pump, allowing the pump to come up to speed initially without load and protected from reverse flow by the check valve? Note again that it is a vertical shaft pump and there is no possibility that it could lose prime.
My customer is using a vertical-shaft pump with a 6" outlet. 800HP motor The outlet piping goes through a check valve and an automated ball valve.Then the line rises 1100 feet.
When they start the pump, the ball valve is closed. They then open the ball valve slowly. It takes over a minute for the valve to reach full open.
The valve is showing signs of cavitation, and the seats are being eroded. I keep wondering why they would start the pump deadheaded, as that MUST cavitate the impeller, too.
Should they not open the ball valve first, then start the pump, allowing the pump to come up to speed initially without load and protected from reverse flow by the check valve? Note again that it is a vertical shaft pump and there is no possibility that it could lose prime.





RE: Pump Startup Sequence
The pump will be spinning with no flow passing through it for a very short time period using this technique. I've never known this to be a problem. The time period is short - very short if you consider that the discharge valve will start to open very soon after the motor starts to spin. Also, the motor speed is initially low as it must accelerate up to operating speed.
Doug
RE: Pump Startup Sequence
There can also be negative water hammer consequences of starting pump with valve wide open.
=====================================
Eng-tips forums: The best place on the web for engineering discussions.
RE: Pump Startup Sequence