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Pipe Bends Minimum Wall Thickness Calculator per. ASME B31.3

Fluids Flow Design and Engineering
Hydraulic & Pneumatic Design Engineering

Pipe Bends Minimum Wall Thickness Design Calculator per. ASME B31.3

Thickness variations from the intrados to the extrados and along the length of the bend shall be gradual for curved and mitered segments of pipe.

Preview Pipe Bends Minimum Wall Thickness Design Calculator

Figure 1, Nomenclature Pipe Bend

The minimum required wall thickness, t_m of a bend, after bending, in its finished form, shall be determined as follows:

Eq. 1
t = P · D / ( 2 [ ( S · E · W / I ) + P · Y ] )

Eq. 2 Intrados (inside bend radius)
I_Int = [ 4 · ( R₁ / D ) -1 ] / [ 4 ( R₁ / D ) - 2 ]

Eq. 3 Extrados (outside bend radius)
I_Ext = [ 4 · ( R₁ / D ) +1 ] / [ 4 ( R₁ / D ) + 2 ]

Table 1, Values of Coefficient Y for t < D / 6

Material	Temperature, °C (°F)
	482 (900) and below	510 (950)	538 (1,000)	566 (1,050)	593 (1,100)	621 (1,150)	649 (1,200)	677 (1250) and above
Ferric Steels	0.4	0.5	0.7	0.7	0.7	0.7	0.7	0.7
Austenitic steels	0.4	0.4	0.4	0.4	0.5	0.7	0.7	0.7
Nickel alloys	0.4	0.4	0.4	0.4	0.4	0.7	0.5	0.7
Gray iron	0.0	-	-	-	-	-	-	-
Other ductile metals	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4

Where:

P = internal design gage pressure
D = Outside diameter of pipe
R₁ = pipe center line radius
S = Stress value for material
E = quality factor, typically 0.8, ranging from 0.6 - 1.0
W = Weld joint strength reduction factor, typically 1.0
I = Intrados Eq. 2 or Extrados Eq. 3
Y = coefficient from table 1

Thickness variations from the intrados to the extrados and along the length of the bend are gradual.The thickness requirements apply at the mid-span of the bend, γ / 2, at the intrados, extrados, and the bend center line radius.

Source:

• ANSI ASME B31.3 Process Piping, Page 50

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