ASTM A537 Class 1 Applied to ASME B31.3

Application & product forms in process piping

The ASTM A537 Class 1 steel plate with a thickness no greater than 64 mm [2-1/2″] can be applied to ASME B31.3 process piping. The plates shall be normalized with minimum yield strength and tensile strength of 50 ksi [345 MPa] and 70 ksi [485 MPa], respectively. The UNS designation of ASTM A537 Class 1 is K12437 and its P-Number is 1. The B31.3 Code has endorsed three other product forms equivalent to ASTM A537 Class 1 including ASTM A671 Gr. CD70 eletric-fusion-welded (EFW) steel pipes for atmospheric and lower temperatures, ASTM A672 Gr. D70 electric-fusion-welded (EFW) steel pipes for high-pressure service at moderate temperatures, and ASTM A691 Gr. CMSH-70 EFW steel pipes for high-pressure service at high temperatures.

Basic allowable stresses

*Temp.	*S
Min. ~100	23.3
200	23.3
300	22.8
400	22.7
500	22.7
600	22.4
650	21.9
700	18.3

*S & Temp.: basic allowable stress, S, ksi, at metal temperature, °F.
*All tabulated stress values are basic allowable stresses in tension; allowable stresses in shear shall be 0.80 times the basic allowable stress in tension and allowable stress in bearing shall be 1.60 times that values; allowable stresses in compression shall be no greater than the basic allowable stresses in tension.
*All stress values are applicable to ASTM A537 Cl.1, ASTM A671 Gr. CD70, ASTM A672 Gr. D70, and ASTM A691 Gr. CMSH-70.

Maximum & minimum use temperatures

The maximum use temperature of ASTM A537 Class 1 steel is 371°C [700°F]. According to ASME B31.3, the minimum use temperature shall be determined by a minimum temperature-thickness curve, Curve D. As illustrated in Figure-1, the left vertical axis is design minimum temperature in °C while the right vertical axis is design minimum temperature in °F. The horizontal axis represents nominal thickness T, in mm unit. If a design minimum temperature-thickness combination is on or above the curve, impact testing may be exempted. The tabulated values for minimum temperatures without impact testing for ASTM A537 Class 1 material are presented in the table below.

T mm	T inch	Curve D °C	Curve D °F
6.4	0.25	-48.3	−55
7.9	0.3125	-48.3	−55
9.5	0.375	-48.3	−55
10.0	0.394	-48.3	−55
11.1	0.4375	-48.3	−55
12.7	0.5	-48.3	−55
14.3	0.5625	−45.6	−55
15.9	0.625	−43.9	-47
17.5	0.6875	−41.7	-43
19.1	0.75	−40.0	-40
20.6	0.8125	−38.3	-37
22.2	0.875	−36.7	-34
23.8	0.9375	−35.6	-32
25.4	1.0	−34.4	-30
27.0	1.0625	−33.3	-28
28.6	1.125	−32.2	-26
30.2	1.1875	−30.6	-23
31.8	1.25	−29.4	-21
33.3	1.3125	−28.3	-19
34.9	1.375	−27.8	-18
36.5	1.4375	−26.7	-16
38.1	1.5	−25.6	-14
39.7	1.5625	−25.0	-13
41.3	1.625	−23.9	-11
42.9	1.6875	−23.3	-10
44.5	1.75	−22.2	-8
46.0	1.8125	−21.7	-7
47.6	1.875	−21.1	-6
49.2	1.9375	−20.6	-5
50.8	2.0	−20.6	-4
52.4	2.0625	−19.4	-3
54.0	2.125	−18.9	-2
55.6	2.1875	−18.3	-1
57.2	2.25	−17.8	0
58.7	2.3125	−17.2	1
60.3	2.375	−16.7	2
61.9	2.4375	−16.1	3
63.5	2.5	−15.6	4
65.1	2.5625	−15.0	5
66.7	2.625	−14.4	6
68.3	2.6875	−13.9	7
69.9	2.75	−13.3	8
71.4	2.8125	−13.3	8
73.0	2.8125	−12.8	9
74.6	2.9375	−12.2	10
76.2	3.0	−11.7	11

*All values are extracted from Table 323.2.2A of ASME B31.3; T: nominal thickness; Curve D: lowest exemption temperature.
*For blind flanges and blanks made from ASTM A537 Class 1, the T shall be 1/4 of the total thickness, where the total thickness is the thickness of the blind flange or blank including the thickness of the facing.