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Anonymous Poster

Concentric and Eccentric Reducer

08/18/2010 2:30 AM

What is the difference between Concentric and Eccentric Reducer and where can be used?
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user-deleted-1105
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#1

Re: Concentric and Eccentric Reducer

08/18/2010 2:42 AM

I have no idea of the context. But I'd guess the clue is in the name.
With the concentric one, the two 'whatever it is we are talking about' will be on the same axis or centre. In the other case, the 'whatever they are' are offset relative to eachother for some reason, possibly ease of manufacture, or to route the whatever around a thingummyjig.

KrisDelTM virtual products have a whole range of suitable thingumyjigs which can be used in various applictions.
Del

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#5
In reply to #1

Re: Concentric and Eccentric Reducer

08/18/2010 3:06 AM

Concentric reducers are capable of concentration, whereas eccentric reducers are as dotty as the aunt in the attic. Sorry, couldn't resist.

More seriously, imagine two different diameters of pipe laid horizontally end-to-end, and joined with a reducer. A concentric reducer tapers equally in all directions, like a cone, with the center lines of the two pipes at the same height throughout. An eccentric reducer is flat on one side, with all the taper on the other. In this way, a pipeline can be made so that the bottom is flat throughout, which is good for drainage; or the top can be flat throughout, which is good for venting vapor.

Books on pump piping or sewage piping would add more to this description, and would most likely show sample drawings.

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#2

Re: Concentric and Eccentric Reducer

08/18/2010 2:55 AM

The Eccentric ones are usually used in pipelines where water flows under the influence of gravity. The eccentric condition means that (when properly installed) the bottom level of the pipe can maintain a constant grade and there is no accumulation of fluid.

If you use concentric reducers, then there will be ponding of fluid upstream of any reducer.

They are also very handy when you want to put in a vertical line against a building. The eccentric set means that the pipe can be fitted against the vertical without the need for spacers as you go further up the building.

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#3
In reply to #2

Re: Concentric and Eccentric Reducer

08/18/2010 2:57 AM

Ah, so we're talking pipes not gear boxes.
Nice answer...
Del

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Just an Engineer
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#4
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Re: Concentric and Eccentric Reducer

08/18/2010 3:04 AM

I hope that's what they were talking about, otherwise I've put my foot in it.

What's the weather like over there? Late winter here, 23 degree days, down to 3 in the mornings. Great for BBQ with no insects to bother us.

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#7
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Re: Concentric and Eccentric Reducer

08/18/2010 3:29 AM

I'm reliably informed it "Summer" but it feels more like October, 8/8th cloud cover yesterday, lookin' sunnier today.
Del

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#9
In reply to #4

Re: Concentric and Eccentric Reducer

08/18/2010 5:42 AM

.......and an unseasonably high amount of rain which is draining away nicely due to the use of eccentric reducers in the drainage pipework.

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#11
In reply to #9

Re: Concentric and Eccentric Reducer

08/18/2010 5:58 AM

Must see if eccentric reducers could help drainage here in essex, with 200ft of clay beneath us.

In the meantime, the sun yet again pokes it's head between the rain clouds just to taunt us. But...two hours of continuous sunshine earlier this morning...TODAY must be summer! Don't miss it!
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#12
In reply to #11

Re: Concentric and Eccentric Reducer

08/18/2010 5:42 PM

Sorry to all for distracting the thread, but seems we all are impacted by the weather.

I know of many places that would gladly swap our winter for their summer, but there is one "down side". Major parts of Aus suffer significant nagging windy weather (Westerlies) through August/September. We often get days where the minimum wind speed is 50 kph and gusts to 100.

We have nearly 50 sq m of glass in the Western wall of the house. Great for the view, but gets concerning when trees are shedding branches and leaves.

There's a longer story behind this.

Everyone, enjoy the weather that you have, it does provide us with some variety in our lives that provides interest and a reason to communicate.

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#6

Re: Concentric and Eccentric Reducer

08/18/2010 3:27 AM

On the suction side of a pump air would be trapped if there is any higher point in the suction line.

The (eccentric) reducer is made flat on the top to prevent this.

Ignore the sketch on the right - Not decided on by CR4 yet - but it do make sone sense to get rid of air .

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#8

Re: Concentric and Eccentric Reducer

08/18/2010 3:45 AM

I believe an eccentric reducer, when used just before the pump suction, will also reduce or eliminate the risk of vortexing at the pump inlet.
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Anonymous Poster
#10

Re: Concentric and Eccentric Reducer

08/18/2010 5:55 AM

Wiki is some times right though a bit succint.

An eccentric reducer is useful at the suction side of a pump when the fluid the pump drives could contain another substance with different density, for example, water with air bubbles or oil with water.

If the secondary substance has a smaller density, (like air in water) the straight part of the reducer must be put on the top, thus, there are no "corner" where the air accumulates in a large bubble that could cause the pump to stall or cause cavitation.

If the secondary substance has more density (like water in oil) the straight part of the reducer must be put on the bottom, thus, there is no possibility that the heavier substance accumulates as a bubble that could cause a shock to the pump when absorbed.

Retrieved from "http://en.wikipedia.org/wiki/Eccentric_reducer" and CR4
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#13
In reply to #10

Re: Concentric and Eccentric Reducer

08/20/2010 9:35 AM

Suction lines of centrifugal pumps are nearly always larger than the pump suction. (Smaller pump and low resistance in suction line). This then requires a reducer at the suction side of the pump. In all but very few instances an eccentric reducer should be used with flat on top.

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Shavessels
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#14

Re: Concentric and Eccentric Reducer

07/07/2012 11:33 PM

Well noted and other than above points,

Is there any difference between concentric reducer and eccentric reducer in terms of pressure changes, velocity-rate of flow changes, energy loss/change?
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#15
In reply to #14

Re: Concentric and Eccentric Reducer

07/07/2012 11:48 PM

Little if any difference in those respects (maybe slightly less ΔP for concentric).

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