Valve Sizing for Gas and Steam
Gas Flow Rate Formula
| \(\large{ Q_g = 59.64 \;C_{vl}\; p_i \;\sqrt {\frac {\Delta p} {p_i} } \; \sqrt {\frac {520} {SG\; T_a} } }\) |
Where:
\(\large{ Q_g }\) = gas flow rate, SCFH (Use only at very low pressure drop \(\large{\left( \frac {\Delta p} {p_i} \right)}\) ratios of 0.02 or less)
\(\large{ C_{vl} }\) = liquid sizing flow coefficient
\(\large{ p_i }\) = valve inlet pressure, psia
\(\large{ \Delta p }\) = pressure differential, pressure drop across valve, psi
\(\large{ SG }\) = gas specific gravity (air = 1.0)
\(\large{ T_a }\) = absolute temperature absolute temperature of gas at inlet, degrees Rankine
Critical Flow Rate Formula
| \(\large{ Q_{cr} = C_{vg}\; p_i \;\sqrt { \frac {520} {SG\; T_a} } }\) |
Where:
\(\large{ Q_{cr} }\) = critical flow rate, SCFH (Use only to determine critical flow capacity at a given inlet pressure)
\(\large{ C_{vg} }\) = gas sizing flow coefficient
\(\large{ p_i }\) = body inlet pressure, psia
\(\large{ SG }\) = specific gravity of fluid (water at 60°F = 1.0000)
\(\large{ T_a }\) = absolute temperature of gas at inlet, °R
Universal Gas Sizing Formula
| \(\large{ Q_g = \sqrt { \frac {520} {S\; T_a} } \; C_{vg} \;p_i\;sin \left[ \left( { \frac {59.64} { c_i} } \right) \; \left( \sqrt { \frac {\Delta p} { p_i} } \right) \rightarrow \right] rad }\) | |
| \(\large{ Q_g = \sqrt { \frac {520} {SG \;T_a} } \; C_{vg} \;p_i \;sin \left[ \left( { \frac {3417} { c_i} } \right) \; \left( \sqrt { \frac {\Delta p} { p_i} } \right) \rightarrow \right] deg }\) |
Where:
\(\large{ Q_g }\) = gas flow rate, SCFH
\(\large{ SG }\) = specific gravity of fluid (water at 60°F = 1.0000)
\(\large{ T_a }\) = absolute temperature of gas at inlet, °R
\(\large{ C_{vg} }\) = gas sizing flow coefficient
\(\large{ p_i }\) = body inlet pressure, psia
\(\large{ C_i }\) = \(\large{\frac {C_{vg}} {C_{vl}} }\)
\(\large{ \Delta p }\) = pressure differential, psi
Steam or Vapor Flow Rate Formula
| \(\large{ Q_{sv} = 1.06\; \sqrt { \rho \;p_i } \; C_{vg} \; sin \left[ \left( { \frac {3417} { c_i} } \right) \; \left( \sqrt { \frac {\Delta p} { p_i} } \right) \rightarrow \right] deg }\) |
Where:
\(\large{ Q_{sv} }\) = steam or vapor flow rate, lb/hr (use to predict flow for perfect or non-perfect gas sizing, for any vapor including steam, at any service condition when fluid density is known)
\(\large{ \rho }\) = density of steam or vapor at inlet, lb/cu ft
\(\large{ p_i }\) = body inlet pressure, psia
\(\large{ C_{vg} }\) = gas sizing flow coefficient
\(\large{ C_i }\) = \(\large{\frac {C_{vg}} {C_{vl}} }\)
\(\large{ \Delta p }\) = pressure differential, psi
Steam or Vapor Flow Rate 1000 psig or Less Formula Formula
| \(\large{ Q_{sv} = \left[ \left( \frac { C_{vs}\; p_i } {1\;+\;0.00065 \;T_s } \right) \right] \; sin \left[ \left( { \frac {3417} { c_i} } \right) \; \left( \sqrt { \frac {\Delta p} { p_i} } \right) \rightarrow \right] deg }\) |
Where:
\(\large{ Q_{sv} }\) = steam or vapor flow rate, lb/hr (only to determine steam flow when inlet pressure is 1000 psig or less)
\(\large{ C_{vs} }\) = steam sizing flow coefficient, \(\large{\frac {C_{vg}} {20}}\)
\(\large{ p_i }\) = body inlet pressure, psia
\(\large{ T_s }\) = degrees of superheat, °F
\(\large{ C_i }\) = \(\large{\frac {C_{vg}} {C_{vl}} }\)
\(\large{ \Delta p }\) = pressure differential, psi
Tags: Steam Gas Valve Sizing