Issue with cryogenic pump

[entropy99]

I have a cryogenic pump at one of my industrial gas fill plant locations that is having an issue pumping. An 11,000 gallon nitrogen tank is connected to two liquid cryogenic pumps. The pumps are piped in together in an A and B configuration. The issue is that when the tank is full (at 260 inches) the pumps work fine. But once the tank level has reached 100 inches, the pumps cease to operate. The NPSH for the pumps is adequate for this installation. The tank is even on 4ft elevated legs. So my question is this a tank issue or a pump (npsh) issue?

 

[iainuts]

Recips? If so,
- What make & model?
- Can you post a photo of the liquid line and vapor return? Provide diameter and look for anywhere there is a liquid trap.
- How long has it been since they were rebuilt? By who?
- Is the tank horizontal or verticle?

 

[EdStainless]

First check to see if the pumps are making rated flow and pressure with full tanks.
Then examine the vapor and liquid return lines.

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