Question: How Do You Read A PD Pump Curve?

What is pump efficiency curve?

Pump Efficiency The calculated pump shaft power has to be provided by an electric motor.

The efficiency curve typically has a maximum within the allowable operating range.

This maximum is also known as the Best Efficiency Point (BEP) as indicated in the sample curves..

How do you interpret NPSH curve?

Pump curves are essentially data about a given pump’s ability to produce flow against certain head. When you’re reading a curve, the pump’s flow rate will be on the top and bottom and its height to push is on the sides.

What causes a pump to over amp?

Excessively worn pump throttle bushing, impeller, and suction head – replace if standard tolerance is exceeded per the pump manual 3. Pump bearings worn out and rubbing 4. Motor windings bad.

How cavitation can be eliminated in a pump?

Vaporisation Cavitation Try the following: Reduce motor speed (RPMs). Note: Slowing the pump down will reduce flow rate and head pressure. Install an impeller inducer.

What is difference between centrifugal pump and rotary pump?

Centrifugal pumps differ from rotary pumps in that they rely on kinetic energy rather than mechanical means to move liquid. … Liquid is forced out of the pump by the energy it obtains from the rotating impeller.

What is NPSH pump curve?

NPSH stands for Net Positive Suction Head and is a measure of the pressure experienced by a fluid on the suction side of a centrifugal pump. … This can lead to greater maintenance costs and a higher incidence of pump failures. NPSH is normally considered in two forms: NPSH-R (NPSH Required) and NPSH-A (NPSH Available).

How pump curves are generated?

Pumps can generate high volume flow rates when pumping against low pressure or low volume flow rates when pumping against high pressure. The possible combinations of total pressure and volume flow rate for a specific pump can be plotted to create a pump curve.

How is NPSH calculated?

Explanation: To calculate NPSH Available, take the source pressure , add the atmospheric pressure , subtract the losses from friction within the pipeline and subtract the vapor pressure of the fluid . The result equals the NPSHA (or Net Positive Suction Head Available) of your system.

What is pump size?

Pump sizing involves matching the flow and pressure rating of a pump with the flowrate and pressure required for the process. The mass flowrate of the system is established on the process flow diagram by the mass balance.

Can positive displacement pumps Cavitate?

Positive displacement pumps can cavitate…but because of the difference in operation between positive displacement pumps and centrifugal pumps, they don’t normally see as great a reduction in fluid pressure while drawings fluid into the pump, and so are less likely to have the fluid pressure drop below the vapor …

What is the difference between a centrifugal pump and a positive displacement pump?

Positive displacement pumps capture confined amounts of liquid and transfers it from the suction to the discharge port. In short, with centrifugal pumps pressure is created and flow results, whereas with positive displacement pumps flow is created and pressure results.

Do positive displacement pumps have curves?

Positive displacement (PD) pump technologies vary, as do the curves for these pumps. A person without significant exposure to pump selection is often experienced only with centrifugal pump curves. Therefore, it can be frustrating to get the data required from a positive displacement curve.

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 do you increase pump flow?

PRIMING BEST PRACTICESPlace the pump as close to the water source as possible; minimal lift means better priming time.Fill the pump case completely with water (never operate a centrifugal pump without water in the pump casing).Start the pump engine.Partially restrict the discharge hose to improve priming time.More items…

What is difference positive and non positive displacement pump?

Pressure – Positive displacement pumps work for high pressure applications, pressure might be upto 800 bar. Non-positive displacement pumps are basically used for low pressure applications and are designed to work for a maximum pressure of 18 to 20 bar.

What does a pump curve tell you?

A pump performance curve indicates how a pump will perform in regards to pressure head and flow. A curve is defined for a specific operating speed (rpm) and a specific inlet/outlet diameter. … The curve also shows the shut off head or the head that the pump would generate if operating against a closed valve.

How does a PD pump work?

A positive displacement (PD) pump moves a fluid by repeatedly enclosing a fixed volume and moving it mechanically through the system. The pumping action is cyclic and can be driven by pistons, screws, gears, rollers, diaphragms or vanes.

How long can a centrifugal pump run dry?

45-60 secondsIf the pump is run dry for less than 45-60 seconds, the pump should not suffer damage. Dry running can be an expensive hazard on your equipment but with care and supervision, you can elongate the life of your machinery.

Can PD pumps Cavitate?

In positive displacement pumps, cavitation causes a reduction in flow rather than head or pressure because vapour bubbles displace fluid from the pumping chamber reducing its capacity. Power consumption may also be affected under the erratic conditions associated with cavitation.

What does a VFD do to 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.