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[Mech.Engineer]

Hi everyone...!.

I would like to know How calculate GPM and Velocity at bottom of sphere?. and...(Please take a look on attached file...!)..

In advance...Thanks a lot..!

Attached Files

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•  QUESTION TWO.png   112.99KB   24 downloads

[kkala]

Liquid velocity in sphere is practically 0, in suction pipe it is calculated as in any other liquid.
E.g. suppose that rated flow of the pump (assumed the other one standby) is 40 gpm. So flow rate in suction line will be also 40 gpm, or (1gal=231 in3) 9240 in3/min=154 in3/s. 3" Sch80 pipe has 2.9 in internal diameter (tables), so cross section = 6.605 in2. Thus velocity in the pipe is 154/6.605 in/s = 23.3 in/s = 1.94 ft/s in this case.
NPSHa matters have discussed before,http://www.cheresour...ion-using-lpg/'> http://www.cheresources.com/invision/index.php?/topic/10528-npsha-calculation-using-lpg/.
Suction pressure at pump entry= NPSHa + LPG vapor pressure. This is for min liquid level in sphere, since NPSHa is considered for min level. Usually suction pressure at max liquid level is of interest (e.g. for max shutoff), so static difference between max and min liquid level of sphere should be considered (add corresponding static pressure).