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ASME B31.3-2016 <br /> Table 331.1.3 Exemptions to Mandatory Postweld Heat Treatment (16) <br /> P-No.and Group No. <br /> (BPV Code Section IX, Control Thickness, Additional Limitations Required for <br /> QW/QB-420) [Note(1)] mm (in.) [Note(2)] Type of Weld Exemption From PWHT[Notes (3)—(5)] <br /> P-No. 1, all Group Nos. All All A preheat of 95°C (200°0 is applied <br /> prior to welding on any nominal mate- <br /> rial thickness>25 mm (1 in.) <br /> Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> P-No. 3, Group Nos. 1 and 2 <_16 mm (5/8 in.) All A preheat of 95°C (200°0 is applied <br /> prior to welding on any nominal mate- <br /> rial thickness>13 mm (1/Z in.) <br /> A specified carbon content of the base <br /> materials 50.25% <br /> Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> P-No. 4, Group No. 1 516 mm (5/8 in.) Groove Mandatory preheat has been applied <br /> Specified carbon content of the base <br /> materials 50.15% <br /> Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> <_16 mm (5/8 in.) except Socket and fillet welds Mandatory preheat has been applied <br /> the thickness of a Throat thickness of the fillet weld or the <br /> socket weld fitting or socket weld 513 mm (1/2 in.) <br /> flange need not be Specified carbon content of the pipe <br /> considered material 50.15% <br /> Nominal material thickness of the pipe <br /> <_16 mm (5/8 in.) <br /> Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> <_16 mm (5/8 in.) Seal welds and non-load-carrying Mandatory preheat has been applied <br /> attachments [Note (7)] Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> P-No. 5A, Group No. 1 516 mm (5/8 in.) Groove Mandatory preheat has been applied <br /> Specified carbon content of the base <br /> materials 50.15% <br /> Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> <_16 mm (5/8 in.) except Socket and fillet welds Mandatory preheat has been applied <br /> the thickness of a Throat thickness of the fillet weld or the <br /> socket weld fitting or socket weld 513 mm (1/2 in.) <br /> flange need not be Specified carbon content of the pipe <br /> considered material 50.15% <br /> Nominal thickness of the pipe <br /> 55 mm (3/16 in.) <br /> Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> <_16 mm (5/8 in.) Seal welds and non-load-carrying Mandatory preheat has been applied <br /> attachments [Note (7)] Multiple layer welds are used when the <br /> nominal material thickness <br /> >5 mm (3/16 in.) [Note (6)] <br /> P-No. 5B, Group No. 1 ... ... No exemptions from PWHT <br />