Reg. 267 e, Reg. 267 f, Reg. 267 g
(e) For this heat treatment, the drum shall be placed in
a furnace sufficiently larger to accommodate the whole
drum. The furnace shall have proper means of temperature
measurement and control and shall be capable of heating
the whole of the drum to a uniform temperature. It shall
be so designed as to prevent direct impingement of flame
on the drum. The temperature of the furnace at the time
the drum is placed in it shall not be higher than 300°C.
For carbon steel a stress relieving heat treatment shall
be performed by heating the part to at least 600 ±
required by the characteristic of the material,
different temperatures may be necessary to obtain proper
The part to be stress relieved shall be brought
up slowly to the specified temperature and held at that
temperature for a period proportioned on the basis of at
least 2 ½ minutes per millimeter of the maximum
thickness of the part (approximately one hour per 25mm
of the thickness) and shall be left to cool in the
furnace to a temperature not exceeding 400°C.
For carbon steels and when stress relieving
temperature is at least 615 ±
the soaking time shall be 2 ½ minutes per mm of
thickness up to 50mm and 15 minutes for every additional
25mm thickness over 50mm and shall be left to cool in
the furnace to a temperature not exceeding 400°C
Reg. 267 f
Alternative procedure for the heat treatment of the
drum may be submitted to the Inspecting Authority for
Reg. 267 g
In special cases it may be permissible to heat treat
the test plates separately from the drum, provided the
Inspecting Authority is satisfied with the means adopted
to ensure that the following factors will be the same
for the drum as far the test plates.
|Rate of heating.
|Time held at maximum temperature.
|Conditions of cooling.