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Pump Suction Diffuser Technical InformationHelpful Member! 

ColonelSanders83 (Mechanical) (OP)
15 Oct 09 17:43
Hello All,

I have recently been tasked with creating a white paper at my company. The subject is the use of suction diffusers on pump inlets and the benefits thereof vs an elbow straight into the pump suctions.

All of our pump are centrifugal water pumps running between 1000-6000 gpm. Most commonly vertical split case double suction.

I am well aware of the fact that one should have 10D of straight pipe and a minimum of 5D before entering a pump.

In order to properly complete my task I need real comparison information on pump inlet piping configurations. The information cannot come from a manufacturer of suction diffuser as this would be a conflict of interest (you can never fully trust the salesman on how good his product is).

Centrifugal/Vertical Pump Intake Design (ANSI/HI 9.8) looks like a likely source of information, but the description is a little lacking. Can anyone tell me if this spec will have what I am looking for? I would also appreciate any additional sources of good suction diffuser information.
 
Helpful Member!  BigInch (Petroleum)
15 Oct 09 19:12
I'd think you'd want to have a look at this anyway
http://www.metraloop.com/pdf/whitepapers/Metraflex_CRV_FlowAnalysis.pdf
even if you just look at the pictures.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

Artisi (Mechanical)
16 Oct 09 9:33
You could always trust me on how good our products were, I found you couldn't trust the customer to give to straight truthful information of what they were pumping, the actual duty and following correct installation proceedures.

Anyway, it sounds to me you are trying to re-invent the wheel and why would there be a conflict of interest in obtaining info. from  manufacturers?
BigInch (Petroleum)
16 Oct 09 10:07
Right.  It all depends on how you use it.

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

ColonelSanders83 (Mechanical) (OP)
16 Oct 09 10:41
Big Inch:

Thank you for that information, very interesting. I would like to find a similar CFD analysis for flow in a standard 90 degree elbow (no CRV) for comparison.

Artisi:
We pump water, sometimes water with glycol. No mystery fluids here.

I am asking for the information so I don't have to re-invent the wheel. I always take vendor and manufacturer information with a grain of salt. My experience has been that the full story is never given i.e. all of the good none of the bad. Therefore I would like to find technical papers (the type that must go through peer review) or known industry standards on the subject, the information must be out there, I am just asking were to find it. I don't mind buying standard or papers, I just want to make sure they contain the information I want before I do.
 
BigInch (Petroleum)
16 Oct 09 14:41
Do a CFD on a 90.

openflower.com

**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/

MartinSr00 (Mechanical)
16 Oct 09 21:27
I did a lot of work on this in the 1980's for a very expensive high end Department of Energy contract with view ports in the suction of a pump, pitot probes, etc.

Our task was to simulate 10 diameters of upstream piping after an elbow.  The elbow had turning vanes and 3/16 cell-sized honey-comb flow straighteners, 2 inches thick, on the inlet and outlet of the elbow.  Traversing pitot probes were used to get the velocity profile.

The profile was kind of OK, but didn't simulate 10 diameters.  And what was just described seems way way fancier than a suction diffuser.

Even so, unless you're on the ragged edge of NPSH performance for the pump, there's a good chance it would work fine with even the elbow (I'm not suggesting that you do this straightaway).  If the diffuser makes the situation better for a reasonable cost, even better.  Conical reducers with an included angle of 7 degrees or less on the downstream side would tend to stabilize flow, as does small pipes tapping off a large plenum.

You can do CFD if you wish.  But the problem with CFD is, when you get a flow pattern, how will you assess it?  What is the pass/fail criteria?

It also depends on how much money you want to spend.

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