Eccentric reducer position at a pump 4

[stberry]

I have a problem. I know that top-flat position of a eccentric reducer is used at a pump suction when the pump is pulling water from a sump. However, I don't know which position of a reducer is correct between top-flat and bottom-flat when a pump is pulling water from a high level, higher than pump, vessel at a suction side.
I highly appreciate if anyone helps me.

 

[quark]

We had the same discussion sometime back. Refer thread407-133376 and thread378-16922

It seems to me that we engineers are more comfortable in maintaining status quo as far as this issue is concerned.

 

[Artisi]

The rational is to put the flat side up so that air / gas doesn't collect in the inlet pipe and my thinking is, there is the potential for air to collect if the flat side is down - whether the supply is lower than the pump or above the pump.
However, I have seen many trouble-free installations where the flat side was down - but for convention sake and peace of mind, I would always put the flat side up - unless there was a very good reason not to do so.



Naresuan University
Phitsanulok
Thailand

 

[25362]

Karassik's et al Pump Handbook has an additional comment on the subject:

Although installing eccentric reducers with the flat side top will eliminate a potential air pocket, too large a change in diameters -more than 4 in (10 cm)- could result in a disturbed flow pattern to the impeller and cause vibration and rapid wear. Pipe venting and a concentric reducer are preferred rather than an eccentric reducer.

From Sam Yedidiah's Centrifugal Pump User's Guidebook:

When the diameter of the suction line is more than a size or two larger than the bore of the suction nozzle, a section of straight pipe of the same diameter as the pump inlet should be installed between the reducer and the pump. This is necessary because the eccentric reducer may deflect the liquid stream toward one side of the impeller eye, reducing output and efficiency.

 

[Artisi]

25362 (Chemical) - good valid information - as this is usually over-looked when we pass on information.

Naresuan University
Phitsanulok
Thailand