Page 14 - Demo

ASME SECTION VIII DIV 1 KS B ISO 4126For the homogenized wet steam of 90% or more drynessnote) For pressure up to 1500psig apply the above equation, and for dry saturated steam pressures over 1500psig and up to 3200psig, the value of WT, calculated by the above equation, shall be corrected by being multiplied by the following factor.Dry saturated steamGas/AirLiquidWTPdPAMTKCZ(lb/hr)(psia)(psia)(R)(in2)Constant for gas or steam based on specific heat ratio(k=CP /CV)1.001.021.041.061.081.101.121.141.161.181.201.221.243153183203223243273293313333353373393411.261.281.301.321.341.361.381.401.421.441.461.481.503433453473493513523543563583593613633641.521.541.561.581.601.621.641.661.681.702.002.20366368369371372374376377379380400412k C k C k C... ...(lb/ft3 %u03c9 )Mass flow ratePractical outlet area in opening rupture disc Whichever is greater in %u2018(Set pressure %u00d7 1.10) + atmospheric pressure%u2019 or %u2018set pressure + 3psia + atmospheric pressure%u2019Back pressure(pressure at outlet)Mol weightAbsolute temperature at valve inlet,%u2109+ 460%u2109Release coefficient (design coefficient, in general apply 0.62 for rupture disc and practical measure %u00d7 0.9 in real measurement, but it shall be less than 0.875.)Compressibility coefficient related to P and T(if there is no available data, Z=1.0)Specific weight of liquid under the condition for valve inlet Gas/steam at critical flowGas/steam at subcriticalflowLiquidA0CQm%u03b1V0Z0MKbKvRePbXT0P0(mm2)(kg/h)(m3/kg)(psia)(bar)(bar)(K)0.500.600.700.800.820.840.860.880.900.920.940.960.981.811.962.082.202.222.242.262.282.302.322.342.362.381.0011.021.041.061.081.101.121.141.161.181.201.221.241.521.541.561.581.601.621.641.661.681.701.802.002.202.402.412.432.452.462.482.502.512.532.552.562.582.592.782.792.802.822.832.842.852.862.872.892.943.043.131.261.281.301.321.341.361.381.401.421.441.461.481.502.612.622.632.652.662.682.692.702.722.732.742.762.77k C k C k C k CRe= 0.3134QmA0P%u00b5Minimum required flow cross sectional areaMass Flow rateFunction for isentropic exponent k(Refer to table 1. Physical properties of gas)Specific volume at practical release pressure and temperatureRelease pressureRelease coefficient (In general, apply 0.62)Release temperatureCompressibility coefficient at practical release pressure and temperature (If there is no available data, Z0=1.0)Mol weightDryness of wet steamCorrection factor for reduction in the theoretical capacity as increase of the back pressure in subcritical flow (Refer to table 3. Capacity correction factor for back pressure)Viscosity correction factor related to Reynold's number(Re) If the liquid viscosity is less than that of water at 20%u00b0C, kv=1.0 (Refer to Table 2. Capacity correction factor for viscosity)Reynold's numberViscosity of the liquid( P=Po -Pb)differential pressure released through rupture discBack pressure (pressure at outlet)RUPTURE DISCSIZING51.5KPWT A=0.1906P-1000 ( )0.2292P-1061WT A=ckp tmWT A= 2407 . k . (p-pd ). %u03c9A0 = 3.469 C . kb . %u03b1qmp0v0A0 = C . kb . %u03b1. p0qmmt0 .z0orA0 = 3.469 C . %u03b1qmp0v0A0 = C . %u03b1. p0qmmt0 .z0orA0 = 3.469 p0v0C . %u03b1qm . xWT A0 = 0.621kv . %u03b1 p . p