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Pipe and Tube System Components - Minor (Dynamic) Loss Coefficients

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Minor or dynamic pressure loss in pipe or tube system components can be expressed as

Δ p minor_loss = ξ ρf v2/ 2                            (1)


ξ = minor loss coefficient

Δ p minor_loss = minor pressure loss (Pa (N/m2), psf (lb/ft2) )

ρf = density of fluid (kg/m3, slugs /ft3 )

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

Minor loss coefficients for commonly used pipe and tube system components:

Pipe and Tube System Fittings - Minor (Dynamic) Loss Coefficients
Type of Component or Fitting Minor Loss Coefficient
- ξ -
Tee, Flanged, Dividing Line Flow 0.2
Tee, Threaded, Dividing Line Flow 0.9
Tee, Flanged, Dividing Branched Flow 1.0
Tee, Threaded, Dividing Branch Flow 2.0
Union, Threaded 0.08
Elbow, Flanged Regular 90 o 0.3
Elbow, Threaded Regular 90 o 1.5
Elbow, Threaded Regular 45 o 0.4
Elbow, Flanged Long Radius 90 o 0.2
Elbow, Threaded Long Radius 90 o 0.7
Elbow, Flanged Long Radius 45 o 0.2
Return Bend, Flanged 180 o 0.2
Return Bend, Threaded 180 o 1.5
Globe Valve, Fully Open 10
Angle Valve, Fully Open 2
Gate Valve, Fully Open 0.15
Gate Valve, 1/4 Closed 0.26
Gate Valve, 1/2 Closed 2.1
Gate Valve, 3/4 Closed 17
Swing Check Valve, Forward Flow 2
Ball Valve, Fully Open 0.05
Ball Valve, 1/3 Closed 5.5
Ball Valve, 2/3 Closed 200
Diaphragm Valve, Open 2.3
Diaphragm Valve, Half Open 4.3
Diaphragm Valve, 1/4 Open 21
Water meter 7

Example - Minor Dynamic Pressure Loss in Waterflow a Ball Valve 1/3 Closed

The minor loss a ball valve with flow velocity 2 m/s with water with density 1000 kg/m3 can be calculated as

Δ p minor_loss = (5.5) (1000 kg/m3 ) (2 m/s)2/ 2

= 11000 Pa

= 11 kPa

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