Vapour Pressure = Rated Suction pressure of the pump
Vapour Pressure = Rated Suction pressure of the pump
(OP)
In one of the Process data sheet for a closed drain drum vertical pump - Amine service ( handling water ( case 1 ) and Hydrocarbon ( case 2), it has been indicated that the vapour pressure of the Hydrocarbon is 1.23 kg/cm2 (a) and the suction pressure ( rated) is 0.2 kg/cm2 (g). If both these pressures are same , how will be the pump performing? Is there any mistake in the spec? The Pump capacity is 10 m3/hr and the diff pressure is 81 Metres head. The temperature of the Hydrocarbon is 41deg C. Another question is, for this application , the spec indicates VS4 type pump whereas one of the pump vendor has selected Vs1 type pump. Which is better. Thanks to clarify.





RE: Vapour Pressure = Rated Suction pressure of the pump
The temperature as such is of no importance unless that referenced vapour pressure is measured at a different temperature.
Don't wast any more time here - set up your NPSHa calculation and compare it to your NPSHr value!
Best regards
Morten
RE: Vapour Pressure = Rated Suction pressure of the pump
RE: Vapour Pressure = Rated Suction pressure of the pump
Read that statement carefully. If the vapor pressure is 1.23 kg/cm2 at 410C then you have trouble with cavitation, as you expect.
RE: Vapour Pressure = Rated Suction pressure of the pump
If this is the case you may be OK, but I would still prefer some margin (liquid level above inlet flange) for reliability.
RE: Vapour Pressure = Rated Suction pressure of the pump
My comment about the temperature refers to the fact that we are only given tidbits of information - e.g. the HC vapour pressure is 1.23 kg/cm2 (a) and that the temperature is 41ºC - but not a clear indication that the referenced vapour pressure is measure at the same temperature as the HC actual operating temperature. Should the referenced vapour pressure have been measured (or calculated) at a different temperature then the vapour pressure may be different.
Last rzrbk spotted that the pump may actaully be a submerged pump and then there may be no problem at all if you can submerge it enough.
Best regards
Morten
RE: Vapour Pressure = Rated Suction pressure of the pump