The following has been reported to me. Can anybody there confirm this.

The Australian Standard, AS 4458 specifies the following: "The distance between the edge of two circumferential butt welds shall be not less than four times the pipe wall thickness or 30 mm, whichever is the greater, unless the first weld is post weld heat treated (PWHT) before the second weld."

I can confirm the first half of the statement as being correct although we use 25.4mm (1"). I can't confirm the PWHT part.