HEAT TREATMENT OF PIPES III

If a weld is allowed to cool prior to the postweld heat treatment, the rate of uniform cooling must be controlled to prevent a detrimental effect in the piping.

Partial heat treatment of a piping assembly that cannot be fitted completely into a furnace is acceptable if there is at least a 300 mm (1 ft) overlap between successive heats and parts of the assembly outside the furnace are protected from harmful temperature gradients.

The local heat treatment of a weld is acceptable if the heat treatment is applied circumferentially on the run pipe and the branch. This section should be heated until the specified temperature exists over the entire pipe section and at least 25 mm (1 in.) beyond the section.