Common header for suction

[Geo3131]

Good day.

Hi. I would like to ask your opinion with regarding this kind of setup for the suction of the pump.

The pump is CNP vertical pump. (I can upload the performance curve if needed) . The way the pipe goes is they interconnect the suction side of the pump. Then three pipe coming from that interconnected pipe(common header suction) goes to cistern tank with each foot valve.

The problem is the pump can't reach the target pressure of 120 psi. Pump can only reach 100psi fluctuating, but the design head of the pump can reach up to 150psi.(the valve going to the distribution system at the discharge commmon header are close).Then when the pump stop manually. The pressure at the discharge side of the pump suddenly drop to zero. Then the suction side pump get pressurized around 100psi. I'm 100 percent sure that the check valve are ok and no passing.

Before all of that happen. That suction common header was connected only to one foot valve and the system was kinda running okay.

Now I need to explain to my senior that there a problem with the suction.(is the suction really the problem?) I'm no expert to this field so I'm asking your help. Any comment or suggestions are greatly appreciated. Thanks.

 

[1503-44]

What is the fluid?
Can you make a schematic type sketch of that. Not clear where those lines come from, the flow rates, lengths or diameters.

Sure. Upload the curve. All information helps.

 

[LittleInch]

I agree - Needs a good schematic from the tank through and beyond the discharge section with all valves and some pressures / flows as required.

That is one weird inlet header though. Never seen anyhting like it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

Before all of that happen. That suction common header was connected only to one foot valve and the system was kinda running okay.

Did it mean that the system was operated per design, i.e. flow rate, pressure of such & Disch, etc., as running with a single pump?

Did you confirm if the system has proper pump hydraulic for running two or three pumps simultaneously?

 

[Geo3131]

Thanks for the reply. Really appreciated.

Fluid - Water.

I'm gonna go the office today. I'll get the pump curve, design plan, schematic diagram and upload it here.

Yeah this one is really weird inlet. I'm kinda clueless where they get the idea for that inlet.

I know pump with negative suction should have 1 foot valve per pump and should be properly aligned for less friction loss. But this one really weird.

I'll upload everything here. Thanks. I really appreciate that somebody answer. I feel lost actually . Thanks guys.

 

[JJPellin]

The last time I worked on a pump similar to yours, it had very confusing markings. There were two arrows on the side of the pump that pointed in opposite directions. The upper one pointed right to left and indicated the rotation of the motor (clockwise). The lower arrow pointed left to right and indicated flow direction through the pump case (which flange is suction and which flange is discharge). These arrows were not labeled. Our electricians misinterpreted the arrows and wired the motor for counter-clockwise rotation because that is much more common for vertical pumps. I suspect that one or more of your pumps are spinning in reverse and your unusual piping arrangement is causing the strange performance. Verify motor rotation and do not trust any markings on the pumps to tell you which rotation is proper. A full system schematic or P&ID would help to disprove my theory.

Johnny Pellin