Nfpa 20 is clear on the need for an eccentric reducer before the firepump when it is splitcase horizontal. What I am confused about is why is there the same need for ecentric reducer on a vertical pump? Since the pump rotates 90 degrees different, why is there still required to have an eccentric reducer to prevent air pocket and why would it be oriented the same as a horizontal installation with the flat side on top?
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REDUCER BEFORE FIREPUMP
- Thread starter coarts
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pipesnpumps
Mechanical
For the same reason... In the common vernacular, it's called air binding. Flow into the pump keeps air bubbles pulled towards the pump so they can't vent out backwards. A concentric reducer will trap these bubbles at the reduction and build up. I've seen pumps perform very poorly in these type situations. Even 3% air by volume will greatly degrade performance of a centrifugal pump. I don't see why it matters if a pump impeller is horizontal or vertical. Either way air will degrade it's performance..
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