This is more conservative and then helps in estimating max shut of pressure. Max suction pressure (in pump data sheets) is considered here at shut off, which means no consideration of friction losses in suction line (no flow). Elevation difference of tank HHLL has to be taken from pump suction center up (not from bottom up).ģ. Max operating pressure over liquid is 0 psig, in case of an atmospheric tank.Ģ. I think following is useful concerning post No 9 (clarifications).ġ. Supposing that pump suction nozzle (center) is 3 ft below tank LLLL (while HHLL 33 ft above it), head corresponding to max suction pressure is 33+3 = 36 ft of water (sg~0.978). For friction losses in the suction line consider the lowest operating viscosity of the liquid at the highest operating temperature.Įdited by ankur2061, 29 April 2012 - 12:41 PM.Ĭoncerning post No 8, it is clarified that the tank is considered atmospheric, as in post No 4. Max operating liquid level could be at High High Liquid Level (HHLL) signal from the Level Indicator of the vessel or upto the overflow nozzzle of the vessel whichever is higherģ. If the maximum operating pressure in the vapor space of the vessel cannot be ascertained and if there is a relief valve in the vapor space or vapor dome of the vessel then use the set pressure of the relief valve as the maximum pressure of the vapor in the vapor space of the vessel.Ģ. Operating pressure of the vapor in the vessel vapor space + Static Height from the Maximum Operating Level of the Vessel upto the pump suction nozzle centerline - Friction losses in the Suction Lineġ.
The maximum suction pressure can be defined as follows:
( *) PRV at pump discharge is not judged to be proper in this case.Įdited by kkala, 27 April 2012 - 03:18 PM. Note: A pump per API 610 has casing design pressure much higher than 122.7 psig, to my information from office. If a value of max allowable shutoff pressure is written, it must reflect one of the two, being higher than 122.7 psig. Max shut of pressure shall be not higher than design pressure of pump casing or of downstream piping ( *). Then max shut off pressure corresponds to 250+33 = 283 ft of water = 122.7 psig (suction tank is assumed atmospheric).Ĥ. Suppose that HHLL (high high liquid level) of the tank is 33 ft above LLLL. Nevertheless design point is usually considered at low low liquid level (LLLL) of suction tank. Exact value can be seen on the performance curve, given by pump supplier.ģ. Shut off head under above conditions is the head developed by the pump at zero flow, let us assume it as 250 m of water (sg~0.978). At the design point flowrate= 101 GPM and head = 207.57 ft of water.ĭifferential pressure 90+1.97=91.97 psi = 6.4662 kgf/cm2 = 212.1 ft of water of sg=1.0. Some probably useful notes in addition to the above.ġ.
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