3-point Pump Curve
3-point Pump Curve
(OP)
How can I generate a 3-point pump curve from the TDH I have for the pump?
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RE: 3-point Pump Curve
Hope this helps.
saxon
RE: 3-point Pump Curve
the three points should bracket the point of maximum efficiency of the pump. If you are specifiying the pump, you should also bracket the minimum, maximum and average design flows expected in your system. Therefore, assuming you are pumping into a transmission main which is interconnected with your distribution system,
Point 1 - low demand, high system pressure
Point 2 - average demand, average system pressure
Point 3 - high demand, low system pressure
RE: 3-point Pump Curve
And the three points are really the controlling factor...instead of the TDH?
RE: 3-point Pump Curve
HL = static head
Hf = friction head loss
Hv = velocity head
in order to specify a pump, you need to know the complete range of conditions that the pump will operate in. Normally a system curve(s) is generated for the pumping system being studied. This defines the full operating range of the pump. As stated before, you need to specify points on the curve to define the range of pressures and flow rates that the pump will be operating at.
RE: 3-point Pump Curve
The pump should have a plate stating the TDH at a particular flow. This is the design point of the pump. It can produce x gpm at the stated TDH. This was estimated by overlaying the system curve on the pump curve as CVG was stating.
A pump curve is typically generated using the pump, a pressure gauge, a flow meter, and a throttling valve. The pump is run against a closed valve where flow is zero and the pressure read. This will give you one point on the curve. By the way, the pressure gauge is on the pump side of the valve.
The valve is open allowing flow. Again the pressure and the flow are read. This is another point.
This is repeated until several points are generated and a curve is then drawn.
What CVG was trying to say in his first post is you want one point near zero flow, one near the midpoint of the flow, and one near the high end of the pumps capacity.
If you have the pump manufacturer and model number, you can probably obtain the curve from a local sales rep or possibly the internet. Otherwise you might have to generate one in the field.
RE: 3-point Pump Curve
You could obtain a group of pump curves from a supplier of similar pump models and extract a typical pump curve shape -above and below TDH.
If you really want to go into it, a whole range of dynamically typical pump curves have been produced for a whole range of specific speeds - "Pump Characteristics for Transient Flow" ARD Thorley and A Chaudry - Pressure Surges and Fluid Transients Conference 1996 - BHR Group.
Obtain paper from BHR (British Hydraulic Research)
Search for BHR in the internet.