# Steam Pipe - Pressure drop Calculator

## Calculate pressure drops in steam distribution pipe lines

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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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