pressure gauge on positive displacement pump

[durcon]

Hi All:

I am using a PDP drawing a liquid from a tank. The pump center line is located below the bottom of the tank and there is always some liquid in tank. The pump works fine and moves liquid to a certain height without any difficulty. This pump is has magnetic drive.

Problem: The pressure gauge on pump discharge shows ZERO psi.

Question:
1. Why it is showing zero reading even everything is OK?

thanks.
Dur con

 

[JJPellin]

This positive displacement pump is designed to move a predetermined flow rate of product with very little affect based on the discharge pressure. The pressure at the discharge is dictated by the system, not the pump. The downstream pressure will be the combination of the head pressure needed to push the flow to elevation, the back-pressure in the downstream system or vessel and the head losses in the piping for a given flow rate. You should be able to pinch down on a valve in the discharge piping and see the discharge pressure of the pump build as it works to overcome the additional resistance.

 

[unclesyd]

That is just a pinch at a time. You have to make sure everything is in order on the discharge side. The valve and PSV have to in good working order.
One problem is that if a guage is stripped, quite common on PDPs you will not see the increase. Usually a PDP gauge will be liquid filled and the desired pressure in the midrange.
If there is a possibility that the pressure tap is plugged don't do it.
Just be careful around the discharge of PDP, stop and think before each step.

 

[durcon]

Thanks. I tried and it is working as mentioned in your trplies.