Eccentric Reducer

If a pump suction line approaches the pump vertically downward, then turns 90° with an immediate reducer, and finally goes straight into the pump suction; the reducer should be eccentric with the bottom flat.

If the suction line approaches the pump horizontally, or vertically upward and then a 90° ell, any reducer in the horizontal part should be eccentric with the top flat.

The purpose is to avoid any pockets of air or vapor that might accumulate in the suction line, and also to promote smoothness of flow.

Reducers in vertical lines are generally concentric.

Thank you for your valuable comment sir, till i need some more clarification. Is this reducer is for NPSH. I can't get you regarding that 90° turns. Why we shouldn't go to top flat for vertically downward and viceversa. You mentioned about concentric. I have seen this concentric reducers in the delivery line of pump. I thought it might be used for increasing the pressure(diagram shows like diffuser). Please clarify. Thanks in advance.

Pumps are generally manufactured with connection sizes as small as might be used on very short suction and discharge line connections. For reasons of pipeline pressure drop (pipe friction and NPSH), longer lines should be larger, with reducers near the pump.

If bubbles form in the suction line, they should not be allowed to accumulate. They should either return up any vertical lines to the fluid source, or pass through the pump as soon as possible. The reducer layouts I described facilitate this.

I have forgotten which is the best Website that shows drawings, but you can visualize this by sketching things out according to the descriptions.

When pump suction/dicharge nozzle size is small than suction/dicharge line sizes then the reducers or expanders are to be used. Generally, suction line size is larger than the pump scution nozzle and hence eccentric reducer is used. This eccentric reducers shall be installed with top side flat to avoid collection of vapor or gas (except for vertical inline pumps with suction line in the same plane as the pump shaft.

To provide an optimum flow patterns to avoid impeller disturbance, it may be necessary to have straight run of pipe as much as 5D to 8D immedietly prior to pump suction.

As said above if the disharge line size is larger than the disch nozzles then expanders with eccesntric or concentric type can be used. it has nothing to do with any pressure.

Thanks for your valuable comments....