10 replies to this topic

[PENGG]

I have querry w.r.t. Pump max. suction pressure.
Which is the right way to calculate pump max. suction pressure among below two formula.
1. Suction vessel Design Pressure plus suction static head w.r.t. high high liuid level in suction vessel.
2. Suction vessel Design Pressure plus suction static head w.r.t. high high liuid level in suction vessel plus suction vessel internal delta P.

If second is the right way why it is so?

[bhalchandra1986]

Dear PENGG,

Pump maximum suction pressure = Vessel fluid surface pressure + Hydrostatic pressure at high high level in vessel - Pressure loss in suction line of pump

regards

[PENGG]

Mr. BC,
I am talking abt MAX suction pressure whill will be either of two mentioned in my question.

[markymaark]

PENGG:

Not sure why you're worried of the Design Pressure of the Tank.

Otherwise, what BhalChandra said is the same as your 2). He is also taking into consideration of pressure losses as well from pipes, fittings, valves etc.

If you are talking theoretical max, then yes you are right it would be the max pressure the tank is designed to withstand + a high-high level of fluid in the tank.

Mark

[PENGG]

Max suction presure is necessary to find max discharge pressure i.e. Design pressure of down stream system.

[S.AHMAD]

1. The maximum suction pressure of a pump = PSV set pressure + Highest static head due to liquid overfilling
2. However, if liquid overfilling is unlikely e.g. enough vapor space and independent HHLA, then use static head based on the HHL.

[fallah]

PENGG,

Maximum suction pressure of a pump: 1.1* vessel's PSV set pressure +pressure due to static head of HHL of liquid column inside the vessel.

[PENGG]

Dear Mr. Fallah and Mr. S.Ahmad,
Few organization add delta P DUE TO VESSEL/COLUMN INTERNALS TO VESSEL DESIGN PRESSURE AND STATIC HEAD DUE TO HLL. Why so?

[fallah]

PENGG,

Add or subtract? Please clarify "delta P DUE TO VESSEL/COLUMN INTERNALS"...

[S.AHMAD]

"Few organization add delta P DUE TO VESSEL/COLUMN INTERNALS TO VESSEL DESIGN PRESSURE AND STATIC HEAD DUE TO HLL. Why so?"

The pressure at the bottom above HLL is higher than the top by the pressure drop of the internals.

It seems that there is no standards w.r.t. to the method of determining the maximum pressure at pump suction but my company's practice is currently to use PSV relieving pressure which is 10% of set pressure plus the static head due to liquid overfilling. However, in the situation where there is enough vapor space above HLL coupled with an independent HHLA, then the static head at HLL shall be used instead.

Edited by S.AHMAD, 01 January 2013 - 03:53 AM.

[sheiko]

PENGG,
The right way is the one specified in the Design Basis of the project you are involved in.