U-bend before pump suction inlet. 2

[danialzulkifli]

Hi,

I went for a site visit to an existing plant, and saw that there is this U-bend piping before the suction of a centrifugal pump for a sump pit. My question is, is this bending required and what is it for? Thank you.

 

[moideen]

It looks like an installation mistake. Why create a pressure drop in the suction line and resulting cavitation?

 

[goutam_freelance]

It introduces pressure drop as already been said. Which increases possibility of cavitation.

It introduces flow disturbances at suction increasing the propensity for cavitation again.

It provides a place for air to accumulate and thus may result in vapor lock and reduction of flow.

 

[pierreick]

Hi,
weird design, troubles for sure.
Pierre

 

[Compositepro]

It makes the pumps self-priming to some extent, in that it keeps water from draining completely out of the pump casing. There is a tee on the pump discharge with a ball valve for adding priming water (or pulling vacùum).

 

[TenPenny]

It looks like an attempt to help create a pseudo self-priming pump. It might actually work if the pumps are occasionally shut down, but I surely wouldn't rely on it.

 

[bimr]

It appears to be installed that way for 2 reasons:

1. To allow the drop pipe to be removed.
2. The drop pipe is not aligned with the centerline of the drop pipe. The piping allows the installation without elbows in the horizontal pipe.

The arrangement probably would cause operational problems with a larger pump.

 

[LittleInch]

Two options as most people say,

either the inlet gets clogged and the wanted an easier way to disconnect and flush out the gunk or someone thought it could be semi self priming.

Ask the operators....

 

[Artisi]

It's to make the pumps self-priming, nothing new.
If I was designing it, I would increase the suction pipe diameter to increased the retention volume.

Ask the people who own the system, "is it effective?"

 

[georgeverghese]

That is one way to keep the pump casing primed on shutdown, but I dont see a way to prime the suction riser going down to the cold well if it all dribbles out through a leaking foot valve.

 

[pierreick]

Hi,
I don't think the diameter of the pipe is big enough to be a priming pot!

Rhodek Pumps and Equipments

www.rhodekpumps.com

Pierre

 

[danialzulkifli]

It's to make the pumps self-priming, nothing new.
If I was designing it, I would increase the suction pipe diameter to increased the retention volume.

Ask the people who own the system, "is it effective?"View attachment 14649

Hi Artisi, thank you for sharing. My first thought was also for priming, but the pipe size maintains the same for the whole suction line which made me a bit confused. Will try to talk with the operators and see how effective this is.

 

[Artisi]

Hi,
I don't think the diameter of the pipe is big enough to be a priming pot!
Pierre

As I suggested to the OP, ask the user - does it work?

 

[moideen]

@Artisi , If a foot valve is present, is a priming tank necessary? Thanks

 

[TugboatEng]

That depends on how much you trust your foot valve.

That expansion joint straight up to unsupported PVC pipe is not ideal either.

 

[Artisi]

@Artisi , If a foot valve is present, is a priming tank necessary? Thanks

In theory no, but no harm if fitted.

 

[goutam_freelance]

In case it is a priming arrangement, there should be a water connection with a valve at the top for refilling the pipe(priming tank) in case it gets drained due to leakage or backflow.

 

[Artisi]

Hi Artisi, thank you for sharing. My first thought was also for priming, but the pipe size maintains the same for the whole suction line which made me a bit confused. Will try to talk with the operators and see how effective this is.

Would be great to hear their comments.

 

[Artisi]

In case it is a priming arrangement, there should be a water connection with a valve at the top for refilling the pipe(priming tank) in case it gets drained due to leakage or backflow.

There is a valve in the discharge pipe that would allow that.