Ross Mackay Forum Moderator 94 Posts
Re: Does the velocity in the suction line need to be maintained?9 January 2012 at 1:29pm
The first thing we need to establish is whether or not the velocity in the suction line needs to be maintained above 1.5 m/sec. This will depend on the nature of the slurry.
If we really do need to maintain the 1.5 m/sec. velocity, then. . .
In a 3 inch suction line, that velocity will be maintained if the flow rate is maintained above 110 USGPM
In a 4 inch suction line, that velocity will be maintained if the flow rate is maintained above 190 USGPM
The industry standard sizing for a suction line on a pump with a 4 inch suction nozzle, would be 6 inch diameter, at which size the flow rate would need to be in excess of 440 USGPM in order to keep the velocity in that line in excess of 1.5 m/sec.
Further advice on pump piping can be found in my article "The Pitfalls of Pump Piping" on my website www.practicalpumping.com/articles.php
As the discharge piping is normally one size smaller than the suction piping, I can't help but wonder what size the discharge piping may be in your installation?
In a new installation, the supplier has erected a suction pipe of 3 inches connected to suction nozzle of 4 inches in the centrifugal pump for slurry application. The general engineering practice says the suction pipe should be the same or one size larger than the suction nozzle of the pump. As per supplier, this arrangement was made to maintain slurry speed of >1.5m/sec. With this condition, we are having frequent seal failures. Please suggest whether this type of suction pipe sizing is acceptable. And is it required to maintain slurry speed in the suction side as given by supplier?
Have an insight or suggestion?
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