In what circumstance, the reducer of a pump suction piping will be in bottom flat position. Explain why the reducer should be so.

Sravan,
There is a lot of information already on this forum about reducers in a pump suction line. Next time please try the "Search" command before you post a question.

The only time you should install an eccentric reducer with the top flat in a pump suction line is if:
- The suction source is from above the pump
and
- The pump is an end suction or side suction pump
and
- The commodity is a Slurry

Here is a related question from a previous posts.

Pump Cavitation
The question:
I have gotten information that there is a usage of avoiding cavitation and maintaining bop in piping system with an eccentric reducer? I can’t understand how cavitation is formed in a concentric reducer and avoided in an eccentric reducer. Please explain.

My answer:
First of all I think the person who told you this or wrote it did not make the point correctly or you misunderstood what was being said.
Concentric or Eccentric Reducers do not "cause" cavitation. Cavitation occurs naturally in all pump suction lines. The suction of a pump is the lowering of the pressure in the suction line to the pump. The lowering of the pressure of the line fluid lowers the vapor pressure in the line. The lowering of the vapor pressure allows the fluid to "Boil" at a lower temperature. When a fluid boils it starts to form bubbles. As the bubbles form they will join and become larger. These large bubbles create "cavities" in the suction fluid. When these cavities come in contact with the pump impeller they cause cavitation erosion.
You cannot prevent the formation of these tiny cavitation bubbles. What you can do is reduce the potential for the build-up of larger bubbles and therefore reduce the impact of cavitation erosion.
A reducer installed in the line does not cause or prevent the formation of the tiny bubbles or cavitation. What it can do, if improperly installed is to provide a place where the tiny bubbles can collect, build bigger bubbles and then be sucked into the pump.
An Eccentric Reducer properly installed, with the Flat-On-Top (FOT) in a pump suction line does not provide a place where these bubbles can collect. They are swept right through the pump while they are small and insignificant. On the other hand a Concentric Reducer or an Eccentric Reducer installed improperly (Flat-On-Bottom) in a pump suction line will provide a place for the tiny bubbles to collect and build. Then you have a higher effect of cavitation erosion.

Thnx for the explaination Jop..!

I had a line service as slurry (liquid + solid) & i was thinking of FSD Eccentric Reducer & thnx a lot for confirming this with your post.

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Another query I would like to know about reducers...

I wnt to reduce the line size from 12" x 4" as per the PID. I can use concentric reducer here considering routing/supporting/service etc.

Now as per ASME 16.9 I have multiple options of combination of concentric reducers to reduce the line size from 12" to 4". When we have multiple options I want to know which one to finalize?

I can do 12 x 8 x 4
I can do 12 x 6 x 4

or others.....

what governs making this selection? Cost? operation? anything else?

Pls advice / help!

You have not given enough information to be able to make a recommendation.
Is this a Pump Suction line?
Is this a line that is running horizontal?
Is this a line that is running vertical with the flow: up? or down?
Is the flow from larger to smaller?
Is the flow from smaller to larger?
Is the commodity a liquid?
Is the commodity a vapor?
Please describe the situation.

This is not a Pump Suction line.

This is a line that is running horizontal.

The flow is from larger to smaller.

The commodity is a liquid from an exchanger shell side.

Thanks for asking clarifications....now pls advice the logic behind a selection?

Also it will be interesting to know the effects of all of the other situation than mine which can affect the reducers selection. You can exclude the Pump situation as you have already told us the same.

Pls tell us more on the other situations ...thnx

How far does the 4" travel after the reduction (from 12") before it changes direction?
And which direction does it go?

just 1.5meters horizontal travel after the 4" reduction....& is going down!.............curious to know...the reasons

Here is my recommendation:

Option "A"
Continue the 12" pipe 2'-0" past the point where the 4" turns down. Place a 12" Weld Cap on the end of the pipe. Place a 12" x 4" WOL (Weld-O-Let) on the bottom of the 12" pipe and then attach the 4" pipe and continue the 4" run.
Reason: "Cost"! The Weld Cap and a few feet of pipe is cheaper than the two reducers and the extra welds.

Option "B"
Continue the 12" pipe 2'-0" past the point where the 4" turns down. Place a 12" Weld Neck Flange & a 12" Blind Flange on the end of the pipe. Place a 12" x 4" WOL (Weld-O-Let) on the bottom of the 12" pipe and then attach the 4" pipe and continue the 4" run.
Reason: "Future expansion"! The Weld Neck flange allows for the extension of the 12" header for future connections to other equipment. The cost of the flanges is possibly the same as the reducers and the welds.