Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Steam Pipes - Sizing

Sizing of steam pipe lines - major and minor loss in steam distribution systems.

Sponsored Links

The pressure available for distribution of steam is the pressure difference between the initial pressure at the boiler, and the required final pressure at the end of the line - at the steam consumer.

The pressure difference available for the distribution system can be expressed as:

p = pj - pk                                    (1)


p = available pressure drop (Pa (N/m2), psi (lb/ft2))

pj = initial or boiler pressure (Pa (N/m2), psi (lb/ft2))

pk = final pressure (Pa (N/m2), psi (lb/ft2))

The total pressure drop in the distribution system is a result of friction (major loss) and pressure loss in fittings (minor loss), and can be expressed as:

pt = pmajor + pminor                               (2)


pt = total pressure drop in the system (Pa (N/m2), psi (lb/ft2))

pmajor = pressure loss in pipes due to friction (Pa (N/m2), psi (lb/ft2))

pminor = pressure loss in fittings (Pa (N/m2), psi (lb/ft2))

Friction - Major Loss

Major loss - the pressure loss due to friction in a low pressure steam distribution system can be expressed as:

pmajor = pa l                                (3)


pa = pipe friction resistance per unit length of pipe (Pa/m (N/m2/m), psi/ft (lb/ft2/ft))

l = length of pipe (ft, m)

The pressure drop in a steam pipe can be expressed as

pa-100 = 0.01306 q2 (1 + 3.6/di) / (3600ρ di5)                                      (3b)


pa-100 = pressure drop per 100 ft pipe (psig / 100 ft)

q = steam flow rate (lb/h)

di = inside diameter of pipe (in)

ρ = density of steam (lb/ft3)

Loss due to Fittings - Minor loss

Loss due to fittings - minor loss can be expressed as:

pminor = ξ 1/2ρ v2                                 (4)


ξ = minor loss coefficient

pminor = pressure loss (Pa (N/m2), psi (lb/ft2))

ρ = density (kg/m3, slugs/ft3)

v = flow velocity (m/s, ft/s)

Equivalent length

Minor loss - loss due to fittings can also be expressed as equivalent length:

pminor = pa le                                (5)


pt = pa(l + le)                                 (6)


le = equivalent length of the fittings (ft, m)

As a rule of thumb the total pressure drop is about 5 -10% of initial pressure per 100 m pipe.

Typical Steam Velocities

  • Exhaust steam - 20 to 30 m/s (70 - 100 ft/s)
  • Saturated steam - 30 to 40 m/s (100 - 130 ft/s)
  • Superheated steam - 40 to 60 m/s (130 -200 ft/s)
Sponsored Links

Related Topics

  • Pipe Sizing

    Sizing of steam and condensate pipe lines - pressure loss, recommended velocity, capacity and more.
  • Steam and Condensate

    Steam & condensate systems- properties, capacities, pipe sizing, systems configuration and more.

Related Documents

Sponsored Links


Search is the most efficient way to navigate the Engineering ToolBox.

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about


This page can be cited as

  • The Engineering ToolBox (2003). Steam Pipes - Sizing. [online] Available at: [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter


Sponsored Links