Steam Pipes  Online Pressure drop Calculator
Calculate pressure drops in steam distribution pipe lines.
The pressure drop in a saturated steam distribution pipe line can be calculated in metric units as
dp = 0.6753 10^{6} q^{2} l (1 + 91.4/d) / ρ d^{5 }(1)
where
dp = pressure drop (Pa)
q = steam flow rate (kg/h)
l = length of pipe (m)
d = pipe inside diameter (mm)
ρ = steam density (kg/m^{3})
The Unwin formula can also be expressed in imperial units as
dp = 0.0001306 q^{2} l (1 + 3.6/d) / (3600 ρ d^{5})^{ }(2)
where
dp = pressure drop (psi)
q = steam flow rate (lb/hr)
l = length of pipe (ft)
d = pipe inside diameter (inches)
ρ = steam density (lb/ft^{3})
Use values for the specific volume corresponding to the average pressure if the pressure drop exceeds 10  15 % of the initial absolute pressure.
Note that for elevated velocities the Unwin's formula is known to give pressure drops higher than the actual.
Example  Pressure Drop in a Steam Pipe
A steam flow 4000 kg/h with pressure 10 bar (1000 kPa) and density 5.15 kg/m^{3} flows through a schedule 40 ND 100 steel pipe with inside diameter 102 mm and length 100 m. The pressure drop can be calculated as
dp = 0.6753 10^{6} (4000 kg/h)^{2} (100 m) (1 + 91.4/(102 mm)) / ((5.15 kg/m^{3}) (102 mm)^{5 } )
= 36030 Pa
= 36 kPa
Steam Pressure Drop Calculator  Metric Units
Steam Pressure Drop Calculator  Imperial Units
Pressure Drop Diagrams  metric units
The diagrams below can be used to indicate pressure drop in steam pipes at different pressures. The calculations are made for schedule 40 pipe.
 1 bar = 100 kPa = 10,197 kp/m^{2} = 10.20 m H_{2}O = 0.9869 atm = 14.50 psi (lb_{f}/in^{2})
 1 kg/h = 2.778x10^{4} kg/s = 3.67x10^{2} lb/min
Steam  pressure 1 bar gauge
Steam  pressure 3 bar gauge
Steam  pressure 7 bar gauge
Steam  pressure 10 bar gauge
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