allflo specs and formula e-guide

E-GUIDE

Specs and FormulaCheat Sheet

1800 333 424 l www.allflo.com.au

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Vol. Flow (L/s) = 1.002 x Mass Flow (kg/s) Volumetric ?ow from mass ?ow and density

Power (kW) =Volumetric Flow (l/s) x Head (m)

102.2 x ef?ciency (decimal)Pump input power from pump performance

Motor input energy per volume of liquid pumped Energy/Volume =Head (m)

368.0 x motor ef?ciency (dec) x pump ef?ciency (dec)

Flow velocity in pipes Flow velocity (m/s) =1273 x Flow (L/s)

(pipe diameter in mm)²

Through any area normal to the direction of ?ow: Flow velocity (m/s) =1000 x Flow (L/s)

area (mm²)

NOTE: Coefficients are based on:

1. Density of water at 20°C of 998.2042 kg/m³

2. Gravitational acceleration of 9.8 m/s²

Head of liquid from pressure and density

1. Head (m) = 0.1022 x Pressure (kPa)

2. Head (ft) = 0.3354 x Pressure (kPa)

PUMPING FORMULA

FOR WATER

NPSH OR NET POSITIVE SUCTION HEAD

IS A TERM THAT IS USED TO DESCRIBE THE AMOUNTOF HEAD, OR PRESSURE, THAT IS AVAILABLE TO PREVENTVAPOURISATION OR CAVITATION IN THE SYSTEM.

E-GUIDE Specs and Formula Cheat Sheet


SUCTION HEAD AS AFFECTED

BY TEMPERATURE




NET POSITIVE SUCTION HEADFOR PUMPING WATER

BASED ON THE TABLE

4 POLE DUTY FROM 2 POLE CURVE

CALCULATIONS



ENGINEERING DATA

NOTE: The information provided is for guidance only. Allflo Pumps & Equipment accepts no responsibility for the misuse or misapplication of this information.


Quantity Various units Pumping units (SI)

Name Symbol Name Symbol Conversion

factors

Length andhead of liquid

Foot ft Metre m

Area Acre

Hectare

ac

ha

Square metre m2

Volume Imperial gallon

Cubic foot

gal Litre L3ft

Power Horsepower

Foot pound-force per second

Kilogram-force metre per second

hp

ft.lbsf/s

kgf.m/s

Kilowatt kW

Density Pound per cubic foot

Pound per imperial gallon

Pound per US gallon

3lb/ft

lb/gal

lb/US gal

Kilogram per cubic metre kg/m3

Concentration Part per million ppm Milligram per litre mg/L 1.000

Dynamic viscosity

Centipoise cP Millipascal se c ond mPa.s 1.000

Kinematic viscosity

Saybolt second universal

Centistoke

ssu

cSt

Square millimetre per second mm /s2 0.2165 *1.000

0.3048

4047

10,000

4.546

28.32

0.7457

0.0014

0.0098

16.02

99.78

119.8

Torque Foot pounds ft.lbs Newton meters Nm 1.355

Temperature Centigrade °C °F °C x1.8 + 32Farenheit °F Centigrade °C (°F - 32) x 0.55

Farenheit

* Approximate conversion factor for use above 250 SSU

NOTE: The information provided is for guidance only. Global Pumps accepts no responsibility for the misuse or misapplication of this information.


CONVERSION UNITS


GLOSSARY


CAVITATION

When the pressure of liquid flowing is reduced to equal or below the vapour pressure.

This creates small pockets or bubbles of vapour and rapidly collapse under pressure of surrounding liquid.

It may be heard as grinding or ‘marble’ noise and if it continues may cause serious pitting to the metal and represents unstable conditions.

Often mistaken for corrosion.

FLOW

Flow means the quantity of liquid to pass across a surface, such as the delivery aperture of a pump or a cross section of a pipe, in a unit of time.

This can be measured in litres per minute (I/min), litres per second (1/s), cubic meters per hour (m3/h) etc.

It should be noted that there is a close analogy between the flow of water in a pipe and the flow of electricity in a wire. Hy draulic head is equivalent to electrical potential or voltage and hydraulic flow is equivalent to electrical current.

Even the behaviour of these properties is the same. Just as a thin wire restricts the flow of electricity more than a thick one, so a small bore pipe offers a greater resistance to the flow of a liquid than a large one.

In hydraulics this resistance is called head loss and is dependent on the quality of the pipe (e.g. material, shape, roughness etc.) and on its cross sectional area. The velocity of the liquid is also a factor.

HEAD

Head means height, difference in level, gradient. When it is said that a pump has a flow of Q litres per second and a head of 30 meters it means that the pump is capable of raising Q litres of liquid through 30 metres every second.

For any given pump, the head is determined by the details of its construction such as the external diameter of the impeller and the speed of rotation and is independent of the liquid being pumped. This means that the pump can raise through 30 meters, Q litres per second of water, petrol, mercury, etc. and only the power of the motor will have to be different for the three examples given .



HEAD LOSS Head loss is that part of the head, possessed by the liquid, which is lost in passing through a pipe or a valve or a filter etc. This loss is not recoverable as it is lost due to friction. Returning to the electrical analogy, just as the losses in a cable are propor tionately higher as the current increases, so the head loss is proportionately greater as the speed of the liquid increases. So the more the flow is restricted by scaled pipes, clogged filters, partially closed valves etc. the greater the head loss will be.

Hd = V2

2g

where: v = velocity of the liquid in m/s at the measuring point g = acceleration due to gravity (9.81) in m/s2

2g = 2 x 9.81 = 19.62 m/s2

The correction of the head is given by the difference between the dynamic head at the two connections. It is therefore clear that if the two readings for a pump have been taken on pipes of the same diameter, that as the liquid is at the same velocity, the correction is zero.

For submersible pumps it is sufficient to measure the head at the delivery connection. The head is then given by adding the head, the dynamic head (at the delivery connection) and the difference in level between the free surface of the liquid and the manometer.

NET POSITIVE SUCTION HEAD - (NPSH)

The total suction head of the liquid being pumped into the centre line or eye of the impeller less absolute vapour pressure.

NPSH

The amount of pressure that is available to prevent vapourisation or caviation of the liquid at liquid temperature.

NB: The pressure that a liquid exerts on the surroundings is dependent on its temperature. As liquid flows through the suction of the pump, the velocity increases and pressure decreases.

NET POSITIVE SUCTION HEAD AVAILABLE - (NPSHA)

NPSH must be equal or exceed the NPSHR.



NET POSITIVE SUCTION HEAD REQUIRED - (NPSHR)Insufficient absolute positive pressure available at the suction inlet, where vapour may occur and cause cavitation.

PRESSURE Pressure means weight per unit area (e.g. kg/cm2) and is a term which should not be confused with head. In the case of liquids, the pressure that the liquid exerts on a surface is given by the product of the height of the liquid and its specific weight. For this reason the column of several km of air on the earth’s surface produces at sea level a pressure of about 1 kg/cm2 (equal to approx. 1 atmosphere). If the same column were of water rather than air, the pressure would be some 700 to 800 times greater, due to the fact that water was a specific weight some 700-800 times greater than that of air.

Bearing in mind that a column of water 10m high is equivalent to approx. 1 kg/cm2 if placed a manometer on the outlet of our example pump (30m head) the following pressure increases would be measured:

a) with petrol (specific weight 0.7kg/cm3) = 0.7 x 0.001 x 30 x 100 = 2.1kg/cm2

b) with water (specific weight 1.0kg/cm3) = 1 x 0.001 x 30 x 100 = 3.0kg/cm2

c) with mercury (specific weight 13.6kg/cm3) = 13.6 x 0.001 x 30 x 100 = 40.8kg/cm2

SPECIFIC WEIGHT The specific weight of a liquid or fluid is the weight per unit volume of the liquid. Specific weight is usually measured in kg/cm3 remembering that 1cm3 = 1 litre.

VAPOUR PRESSUREPressure required to boil a liquid at a given temperature.


T E C H N O L O G Y l E Q U I P M E N T l S O L U T I O N S

Tel: 1800 333 424Tel: 03 5831 2220Fax: 03 5822 4160

Email: [email protected]: www.allflo.com.au


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