Losses in Valves, Fittings, and Bends

Figure 1 – Typical Resistance Coefficients for Valves and Fittings [1],[2]

Approximate Range of Variation for K
Fitting Fitting Type Range of Variation
90 Deg. Elbow Regular Screwed ± 20 percent above 2 inch size
Regular Screwed ± 40 percent above 2 inch size
Long Radius, Screwed ± 25 percent
Regular Flanged ± 35 percent
Long Radius, Flanged ± 30percent
45 Deg. Elbow Regular Screwed ± 10 percent
Long Radius, Flanged ± 10 percent
180 Deg. Bend Regular Screwed ± 25percent
Regular Flanged ± 35 percent
Long Radius, Flanged ± 30 percent
Tee Screwed, Line or Branch Flow ± 25percent
Flanged, Line or Branch Flow ± 35percent
Globe Valve Screwed ± 25percent
Flanged ± 25percent
Fitting Fitting Type Range of Variation
Gate Valve Screwed ± 25percent
Flanged ± 50 percent
Check Valve Screwed ± 30 percent
Flanged + 200 percent, - 80 percent
Sleeve Check Valve Multiply flanged values by 0.2 to 0.5
Tilting Check Valve Multiply flanged values by 0.13 to 0.19
Drainage Gate Check Multiply flanged values by 0.03 to 0.07
Angle Valve Screwed ± 20 percent
Flanged ± 50 percent
Basket Strainer ± 50 percent
Foot Valve ± 50 percent
Couplings ± 50 percent
Unions ± 50 percent
Reducers ± 50 percent
Approximate Range of Variation for K
Fitting Fitting Type Range of Variation
90 Deg. Elbow Regular Screwed ± 20 percent above 2 inch size
Regular Screwed ± 40 percent above 2 inch size
Long Radius, Screwed ± 25 percent
Regular Flanged ± 35 percent
Long Radius, Flanged ± 30percent
45 Deg. Elbow Regular Screwed ± 10 percent
Long Radius, Flanged ± 10 percent
180 Deg. Bend Regular Screwed ± 25percent
Regular Flanged ± 35 percent
Long Radius, Flanged ± 30 percent
Tee Screwed, Line or Branch Flow ± 25percent
Flanged, Line or Branch Flow ± 35percent
Globe Valve Screwed ± 25percent
Flanged ± 25percent
Fitting Fitting Type Range of Variation
Gate Valve Screwed ± 25percent
Flanged ± 50 percent
Check Valve Screwed ± 30 percent
Flanged + 200 percent, - 80 percent
Sleeve Check Valve Multiply flanged values by 0.2 to 0.5
Tilting Check Valve Multiply flanged values by 0.13 to 0.19
Drainage Gate Check Multiply flanged values by 0.03 to 0.07
Angle Valve Screwed ± 20 percent
Flanged ± 50 percent
Basket Strainer ± 50 percent
Foot Valve ± 50 percent
Couplings ± 50 percent
Unions ± 50 percent
Reducers ± 50 percent

  1. The value of D given in the charts is nominal IPS (Iron Pipe Size).

Figure 2 – Resistance Coefficients for Miter Bends at Reynolds Number ≈ 2.25 x 105 [3]

Ks = RESISTANCE COEFFICIENT FOR SMOOTH SURFACE

Kr = RESISTANCE COEFFICIENT FOR ROUGH SURFACE, ε/D = 0.0022

Figure 3 – Resistance Coefficients for 90 Degree Bends of Uniform Diameter [4]

Figure 4 – Resistance Coefficients for 90 Degree Bends of Uniform Diameter and Smooth Surface at Reynolds Number ≈ 2.25 x 105 [5]

References

  1. Hydraulic Institute, Engineering Data Book, Second Edition, 1990, Table 32a.
  2. Hydraulic Institute, Engineering Data Book, Second Edition, 1990, Table 32b.
  3. Hydraulic Institute, Engineering Data Book, Second Edition, 1990, Table 33.
  4. Hydraulic Institute, Engineering Data Book, Second Edition, 1990, Figure IIB-5A.
  5. Hydraulic Institute, Engineering Data Book, Second Edition, 1990, Figure IIB-5B.

Last updated on May 12th, 2020