Table of Contents
How pump curves are generated?
How to Generate Pump Curves. Pump curves can be generated by reading measurements of pressure, NPSH, power, efficiency and others, while the pump is operating at different flow conditions. These results are then plotted against the flow rate to generate the pump characteristic curves.
How do you choose pump pump curve?
The best and easiest way: contact a pump dealer and give him/her the pressure you need (feet head or PSI), and the volume (GPM) you want to pump, they can figure out which pump you need. This is the best way to select a pump, as the dealers know their pump lines much better than you.
How does a pump curve change with specific gravity?
Pump curves are calculated based on water which has an SG of 1. If a fluid has a higher specific gravity than water, then the head will show the same, but the pressure will increase since Pressure is a function relative to fluid calculated by multiplying Head x Specific Gravity.
What is the significance of a pump curve?
Also called a pump selection curve, pump efficiency curve, or pump performance curve, a pump curve chart gives you the information you need to determine a pump’s ability to produce flow under the conditions that affect pump performance.
What happens when a pump runs off its curve?
If a pump is running out on the end of the curve it can cause cavitation inside the pump and result in premature wear of the impeller and bearings of the motor. It can also cause the motor to over amp and prematurely fail.
How does a VFD affect a pump curve?
A VFD can help here by raising the pump’s operating speed to a higher-than-standard rpm so the pump curve and system curve intersect at the desired flow rate — but at the expense of higher power requirements. Evaluating pump performance requires a BEP versus speed curve for the maximum diameter impeller.
How does viscosity affect pump curve?
As the viscosity increases, the pump performance has to be adjusted to account for the additional resistance to shear. Typically there is a small reduction in flow, a more significant reduction in head or pressure, and a substantial increase in power draw.
What are two of the three main items shown on a pump curve?
What does a pump curve show?
- Application.
- Liquid being pumped.
- Viscosity and temperature.
- Flow rate required.
- Pressure required.
- Voltage and frequency.
What happens if the pump is operating too far to the right on the curve?
When a pump operates too far to the right on the curve, this simply means that the pump is delivering a flow rate greater than that for which it was designed. In other words: The pump is too small for the volume flow needed by the system. Operating the pump in this range may cause damage to the pump and the motor.
What causes pump runout?
Runout is the maximum flow a pump can produce. When a pump manufacturer publishes a pump performance curve it is typically cut off at some point beyond the pump’s allowable operating range (AOR).
How do you read a water pump curve?
A PD pump curve indicates pump capacity, on the horizontal lines, in units per minute. In this example, the curve indicates gallons per minute (GPM) and liters per minute (LPM) in the left margin and the vertical lines indicates pump speed in revolutions per minute (RPM).
What happens at the end of a pump curve?
The pump curves suddenly stop at the right end of each curve. Beyond the end of the curve, the pump manufacturer is advising that the pump cannot be safely operated. Trying to run a pump off the right end of the curve will result in pump cavitation and eventually destroy the pump.
Why is your pump operating off the curve?
Causes for Operating Off Curve different or incorrect size impeller. different or incorrect speed. viscosity not corrected or accurate. net positive suction head (NPSH) margin insufficient.
What happens when pump runs off curve?
How does VFD affect pump curve?
What is head in pump curve?
Simply stated: a pump’s head is the maximum height that the pump can achieve pumping against gravity. Intuitively, if a pump can produce more pressure, it can pump water higher and produce a higher head.
What does the pump curve show?
The Pump curve shows the Flowrate range on the horizontal scale. As standard the Flowrate is from zero flow to 20% past the Best Efficiency Flow. The first point on the curve at zero flow is referred to as “Shut Off” and the last point at maximum flow is “Run Out”.
What are the factors that affect the pump curve?
These factors include Flow, Head, Efficiency, Impeller Trim Diameter, NPSHR, Power, MCSF (Minimum Continuous Stable Flow), and RPM. The Pump curve also represents the Pump model, the Pump size, and the number of stages for multi-stage pumps. The Pump curve displays the Flowrate range on the horizontal axis.
What are centrifugal pump curves and why are they useful?
Centrifugal pump curves are useful because they show pump performance metrics based on head (pressure) produced by the pump and water-flow through the pump. Flow rates depend on pump speed, impeller diameter, and head. What is Head?
How do you select a pump curve?
Years ago, making a pump selection meant sitting down with large printed catalogs and flipping through them until you reached a pump curve that fit a project’s hydraulic requirements. Today this process is made much easier through the use of electronic pump curve catalogs.