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Pump Performance curvePump performance curves are the least used,least consulted, least appreciated, and leastunderstood aspect of the world of industrialpumps.

In reality, the performance curve is easy to

understand. It isnt rocket science.

The performance curve indicates that the pump

will discharge

A certain volume or flow (m3/hr) of a liquid,At a certain pressure or head (H).

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By definition, the pump is a machine designed toadd energy to a liquid with the purpose ofelevating it or moving it through a pipe. Thepump can elevate a liquid in a vertical tube up toa point where the weight of the liquid and gravitywill permit no more elevation.

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Theres a language barrier between the pumpmanufacturers and the pump users.

They use different terminology.

Pump users, operators and mechanics, use

pressure gauges that read in bar, kg/cm2 etc.

The pump manufacturer denotes pressure inmeters of head ( mlc).

mlc : meters of liquidcolumn

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Therefore when we operate a centrifugal pumpwe have to calculate the Total head of the pump.

HOW ?Using the following formula

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Manometric pressure is the difference ofdischarge and suction manometers.

Keep in mind always :

If suction gauge is below zero (vacuum)Manometric pressure = Discharge + suction

If suction gauge is above zero (positive suction)Manometric pressure = Discharge - suction

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Easy formulas

But in LPGs things are WORSE

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[ (PD - PT) + PL] x 10,2SG

H = + HM - HLTotal head calculation in LPG ship

Pump discharge pressure calculation

in LPG ship

[ (TH - HM) + HL] x SG10,2D=

+ PT - PL

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Given :PD = Discharge gauge pressure ( bar ) = 7,5 barPT = Tank pressure ( bar ) = 0,03 bar

PL = Pump column losses ( bar ) = 0,2 barSG = Specific gravity ( kg/dm3 ) = 0,6815 @ -33,2 CHM = Discharge pressure gauge height ( mtrs ) = 18,3 mtrsHL = Tank Sounding level ( mtrs ) = 13,5 mtrs

Required :

TH= 120mlc

TH = Total Head ( mlc )[ (PD - PT) + PL] x 10,2

SGTH = + HM - HL

[ (7,5 0,03) + 0,2] x 10,2

0,6815TH = + 18,3 13,5

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BEP

Q= m3 /hr

TH

=mlc

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The pump is designed for a discrete value offlow rate, differential head, and speed.

This is the Best Efficiency Point of operation.

B E P

However,in practical applications, the pumps are rarelyoperated at the operating parameters for which

the pump has been designed.

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Given :TH = Total Head ( mlc ) = 120 mlcPT = Tank pressure ( bar ) = 0,03 bar

PL = Pump column losses ( bar ) = 0,2 barSG = Specific gravity ( kg/dm3 ) = 0,6815 @ -33,2 CHM = Discharge pressure gauge height ( mtrs ) = 18,3 mtrsHL = Tank Sounding level ( mtrs ) = 13,5 mtrs

[ (TH - HM) + HL] x SG

10,2+ PT - PL

Required :

PD =PD = Discharge gauge pressure ( bar )

[ (120 18,3) + 13,5] x 0,6815+ 0,03 0,2D =

10,2

PD= 7,53bar

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In the final analysis,

Pumps should be operated at or near

theirBEP.

These pumps will run for years without

giving problems.

The pump curve is the pumps control

panel, and it should be in the hands of

the personnel who operate the pumpsand understood by them.

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In case you have understand what we just saidThen you can use my application to calculate the

Total head and required gauge pressure.

Thank you

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