Pipe Elbows That Reduce Turbulence 2

[jgilmore]

We have several pump system installations with short radius 90deg. elbows attached to the suction of the pump casings. Does anyone have experience with an elbow designed to minimize turbulence which could be used as replacements and reduce the hydraulic imbalance at the pump inlets ?
JGilmore

 

[BobPE]

what are you pumping and what is the flow rate?

There are designs out there, but they are usually a big design nightmare and its almost break even installing these things vrs. straightning the suction out if you can.

BobPE

 

[quark]

Bob!

I know about flow straighteners. But elbows designed that way is rather new to me. Can you please give me some links?

Regards,

 

[MJCronin]

jgilmore,

You do realize, of course, that the suction piping for your pumps was configured by an idiot.....

Are your pumps located in some kind of pit or something where short radius "ells" were the only way to pipe up your system ? Was an MBA involved somehow in the layout or the general arrangement of the system ?

The CARDINAL rule for suction piping on centrifugal pumps is 5 diameters - staight pipe AND.... piping one size larger than the suction connection.

Additionally, you should know that "double suction" pumps are more susceptable to damage from elbows on the inlet than the more common "ANSI" type of pump. See the goulds pump manual, GPM6, for a discussion of this.

In my opinion, flow straighteners are a "maybe" solution.......and could be a "career buster" if you spend a lot of money and they don't work.

Is there any way to correct the piping layout ?

Tell us more about the type of pumps where this "installation error" exists.......

My opinion only........but check what a 30 year veteran has to say

http://www.mcnallyinstitute.com/14-html/14-07.htm

Come back and post your solution..............

MJC

 

[ccfowler]

I recall seeing some literature some ten years ago about a flow conditioning device that was to be installed immediately before an elbow. The device included a couple of curved vanes whose purpose was to induce swirling motions in the flow that would, in turn, be cancelled by the passage of the flow through the adjacent elbow. The flow leaving the elbow was supposedly inherently restored to a condition as though it had simply passed through a length of straight pipe.

It seemed like a very elegant solution to such a problem, but it would have required an orderly flow entering the conditioning device. Unfortunately, I can't remember the name of the device, but for some reason the name "Chang" comes to mind in association with it.

I've done some Internet searches for such a flow conditioner, but so far, I've had no success. Does anyone else know of such devices ever becoming commercially available?

I've never been much of a fan of flow straighteners. The only ones that ever made any sense always introduced significant pressure drops and risked (promised would be more accurate) plugging if the flow contained significant amounts of solids.

 

[davefitz]

The flow device you described was advertized as a "Chen " flow device, I think it was advertised 10-15 yrs ago as a means to reduce permanent pressure drop, but I am do not know if it was advertised for correction of pump suction issues.

 

[PUMPDESIGNER]

Victaulic manufactures "suction diffusers" that are claimed to straighten flow into a pump.
URL is:

http://www.victaulic.com

Richard Neff
Irrigation Craft

 

[piffer]

I recall a study/technical paper written by an engineer from HDR Engineering a few years ago. It suggested that atleast a 2-size reducing elbow will greatly help equalize inlet velocities at the impeller eye (vertical pumps w/suction elbows). I try to follow that guideline, but I am careful when pumping solids that require a min. transport velocity (to avoid settling/accumulation). Backman Foundry in Provo, UT has (almost) all sizes of reducing elbow patterns. Good luck!
-Piffer