pump performance

[vjr0512]

Enclosed the snap shot of the suction piping arrangement of a centrifugal pump OH2 type. Pumping clear water...Our consultant is insisting to have a vortex breaker in the suction line...The pump rated flow is around 1100 m3/hr at 3 barg discharge pressure....Is this requirement is technically justified? Thanks to help with the criteria to provide a vortex breaker for such centrifugal pumps.

 

[Artisi]

1. Do you have any objection to a vortex breaker?
2. Why is the consultant spec. a breaker?
3.check with the pump manufacturer, some pumps already include a breaker in the inlet.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[vjr0512]

Thanks artisi for your reply. I do not have any objection...By the way, is the vortex breaker in the pump is providing strip(s) of metal plate (projection) before its suction nozzle?

 

[TenPenny]

If I interpret the drawing correctly, the arrangement is close to the minimum recommended submergence for that flow rate, so that's probably why the consultant wants a vortex breaker.

 

[Artisi]

Pumps with "built in" vortex breakers (or anti-rotation) is usually a cast-in fin like arrangement normally projecting from the outer diameter of the inlet to approx. the mid of the inlet.
TenPenny: I don't see the submergence playing any part in the need for a "vortex breaker" in this installation - maybe the consultant is covering his arse, or doesn't know what he's doing or has come across problems with this particular pump previously.

Of course the way to solve these problem is to always ask the consultant "why" or for justification.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[bimr]

The drawing appears to dimensioned in metric units so there would be adequate inlet submergence and no need for a vortex breaker.

The pump manufacturer will be a better resource as to whether a vortex breaker is necessary. Note that the vortex breaker is relatively inexpensive.

 

[DubMac]

If I recall rightly, a vortex breaker's purpose is not to "straighten" the flow profile into the suction case, it is a device used in the sump or the tank to prevent vortexes forming on the surface and drawing air bubbles down into the suction line and creating havoc when the bubbles "recollapse". Nothing shown in this installation would suggest the need for a vortex breaker.

Maybe the consultant is demanding a flow straightener, or as many in the HVAC market would call it, a suction diffuser. These are used on for installations such as a crowded mechanical room in a building with suction line dropping from ceiling and turning 90 degrees sharply into the suction inlet of the pump. MANY pump design engineers have questioned any benefit gained by these devices, but the manufacturers and the contractors who pad their bill like them a lot!

The pump manufacterer should definitely be asked their opinion.

I would absolutely have the consultant provide a technical justification for his demand. I would ask him to:
1. explain exactly what piece of equipment he is demanding, and what function it performs.
2. explain in detail what it is he sees in the system that requires needing this.

If he gives you some mularkey about swirling flow inside the pump causing cavitation or erosion, he either doesn't know what he's talking about, he's lazy, or he's on the take; possibly all three.

 

[Artisi]

DubMac : agree - terminology is a little vague, is it vortex or anti rotation device at the inlet or flow straightening in the inlet pipework - I just taken it as read "in the suction line" and assumed rightly or wrongly - straightening. Yes the consultant should justify what / where / why.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[vjr0512]

Thank you all for your replies. Actually consultant do have a concern on the vortex formation in the flow - inlet to the pump . As artisi had said, it is like to have a stop piece in the pump suction nozzle projection..and clarified with the consultant. Since the flow is high, consultant had raised this point. Hope the arrangement in the pump as said above should address the concern.

 

[pumpking]

A vortex breaker can certainly help especially at such high flowrates, i remember doing a cooling tower project many years ago at a previous company when i was an apprentice and installed for trial, a side on plank of wood - made things much better and followed on with a 'more engineered and permanent feature' (sometimes you look back at life and cringe...)

Ash Fenn

http://www.cdrpumps.co.uk

 

[Artisi]

For those interested Google vortices in pump inlet bays - lots of interesting information, note -not all vortices are surface generated.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)