Pipe Wall Thickness Calculator

Pressure design of straight pipe per ASME B31.3, para. 304.1.2 (Eq. 3a / 3b).

Inputs

Unit system

Pipe material

Design temperature

Dimension input

NPS size

Quality factor E

Weld joint reduction factor W

Design gage pressure P

Total allowance c (corrosion + mechanical + erosion)

Results

Computed values

t (design thickness)

–

Eq. 3a

t\u2098 (min required)

–

t + c

Outside diameter

–

Allowable stress S

–

Coefficient Y

–

t / (D/6)

–

< 1 required

Results

Computed values

Maximum allowable pressure

–

Outside diameter

–

Wall thickness

–

Allowable stress S

–

Coefficient Y

–

P / SE

–

< 0.385 recommended

Formulas (ASME B31.3 para. 304.1.2)

For t < D/6, minimum required thickness (Eq. 3a):

t = P·D / [ 2(S·E·W + P·Y) ]

P·D = –2(S·E·W + P·Y) = –

Where: D = outside diameter; P = design gage pressure; S = allowable stress; E = quality factor; W = weld joint reduction factor; Y = coefficient (Table 304.1.1-1); c = sum of allowances.

Table 304.1.1-1 — Coefficient Y (valid for t < D/6)

Material	Temperature, °C (°F)
Material	482 (900) & below	510 (950)	538 (1000)	565 (1050)	593 (1100)	621 (1150)	649 (1200)	677 (1250) & above
Ferritic 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	0.4	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

Y may be interpolated for intermediate temperatures. Y = 0.4 is typical for most operating temperatures.

Reference data

Allowable stresses are reference values for common materials; always use the value for the specific spec/grade in the current code edition.