What is the formula used to determine the minimum wall thickness after bending a boiler pipe?

Answer 1

See ASME B31.3 for low pressure boilers. For power boilers use ASME B31.1

Specifically Paragraph 304 where the following formula is found: t= PD/ 2[(SEW/I)+PY] Where: I= [4(R/D)+1]/[4(R/D)+2] for the extrados of the bend and

I= [4(R/D)-1]/[4(R/D)-2] for the intrados of the bend

t= minimum wall thickness required at design pressure

P= design pressure required

D= Pipe diameter (outer diameter)

S= allowable stress at temperature (20,000 psi for A269 TP304 SS at 300 degrees Fahrenheit)

E= quality factor (0.85 for fusion welded ). See B31.3 for other values.

W= Weld joint strength reduction factor (1.00 for non welded) see B31.3 for specific values - if you do not have welds in your bend then use 1.00

Y= 0.4 for Ferritic Steels at 900 degrees Fahrenheit or lower. See B31.3 for other values.

Cheers!