reducers

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.

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.