Ross Mackay Forum Moderator 94 Posts
Re: Why does our new pump have a lower flow rate?6 April 2011 at 1:29pm
Your new 2 pole speed pump obviously has a much steeper curve than the older 4 pole speed pump.
Your new piping on the discharge is causing more friction losses in a system that has significant friction losses already.
This would result in a higher head and lower flow. I suggest you fit a 2 x 3 increaser on the discharge of the new pump and refit all the rest to the existing 3-inch line.
We replaced an old horizontal multi-stage pump with a new vertical multi-stage pump. The new pump should have more flow rate than the old pump, but that did not happen. Let me explain the specification below. The old pump has piping details as such: Horizontal multi-stage pump with side suction. Gland packing seal Pump inlet-outlet = 2.5"-2.5" Piping installation for inlet-outlet = 3" - 3" There are three elbows used on the suction side as well as y-strainers, flexible joint and foot valve. Pipe length on the suction is approximately 5 meter (horizontal + vertical). Suction lift is approximately 1 meter to 2 meter measured from the suction flange to the surface of the water. Discharge piping is directly on top of the pump's discharge outlet. There are 3" NRV, gate valve, flexible joint on the discharge side. The new pump basically utilize the old piping without much change. The new pump has piping details as such: Vertical in-line multi-stage pump. Mechanical seal Pump inlet-outlet = 2"-2" Piping installation for inlet-outlet = 2" - 2" There are 1 elbows, 2" x 3" expander (so it can utilize the old 3" suction piping system), and foot valve on the suction side. Removed the old 3" NRV and flexible joint from the suction line. Pipe length on the suction is approximately 2.5 meter (horizontal + vertical). Suction lift is approximately 1 meter to 2 meter measured from the suction flange to the surface of the water. The discharge pipe is 2", goes straight for about 1 meter, then elbow upward to meet 2" x 2.5" concentric expander, after that connected to the old 3" fitting, valves and piping system. The new pump is wired correctly and operating not in reverse direction. We are confused with the pressure measured by the pressure gauge. The new pump register lower pressure than the old pump (3.6 bar compared to 5 bar).
Have an insight or suggestion?
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