VELOCITY IN PUMPING

For new pumps and piping projects , especially for high viscous products it is necessary to
working out the velocity of flow before deciding on the pipe size (most will straight away decide on the pipe size )
The ideal velocity for discharge line should be between 1 to 3 meter per second
and suction between 0.5 to 1.5 Meter /sec

Higher velocity means smaller pipe being used ,thus higher head loss and this mean pump
operates at higher pressure , and higher head means higher Kw of drive or bigger size of pump

On the cost factor , the piping cost will be lower but power cost will be higher
Work out total cost of piping for different size and compare with power cost and see the saving achieveable
This is applicable to high capacity pumping rate . small pumps will not affect much

Suction line is usually more critical .There is one bulking plant where suction line diameter
is to small and pump located far away from tankyard , all these resulted in extremley low NPSH
avialable , at 0.20 meter . Any upgrading of pump is not possible to achieve the required capacity as any pump will be operate in cavitating condition . Replacing the suction line system will cost a bomb .

Looking at this comparison , a pump operating at 9 bar and another at 6 bar

model : 200-500 -------------------------200-500
capacity : 450 m3/hr at 9 bar ------------450 m3/hr at 6 bar
motor Kw : 150 Kw ----------------------95 Kw


See the huge difference in motor kw ( 60% )?