Chests etc., in General
||All chests and fittings
shall be smooth, sound and free from flaw, cracks or other
injurious defects. After completion, the chests shall
be tested hydraulically at the manufacturing works to
at least twice the working pressure of the boiler for
which they are intended.
Hydraulic test shall be made with water which may contain
a corrosion inhibitor, with kerosene or which other suitable
liquid provided its viscosity is not greater than that
of water at a test temperature not above 52 C.
||Valves may be fabricated
from seamless steel pipes of pressure not exceeding 250
pounds per square inch and temperatures not exceeding
800ºF. The welding should conform to Regulation
125 and valve chest should be stress relieved after
fabrication. Valves meant for use in pipe work may also
be fabricated by welding from seamless steel pipes but
no restriction as above regarding pressure and temperature
shall apply to them provided the welding complies with
all the relevant requirements of fusion welding such as
stress relieving and radio-graphic inspection of the weld
and the like prescribed in Chapter
V of these Regulations.
The working pressure of the chests shall be determined
by equation 91 or 91A, whichever is applicable, where
the term 2 Se shall be substituted by the
term 1.8 x S The wall thickness shall not
be less than 3/8. The fabricated valves with their
assembled fittings shall withstand satisfactorily a hydraulic
test to the same pressure as will be applied to the drum
during its registration.
||The working pressure
and the thickness of Bronze and Cast Iron Valve chests
shall be determined by the following formulae, subject
to minimum thickness as specified in regulation
||R x ( T - C )
|4.5 x D
||4.5 x WP x D
R is the minimum specified tensile strength of the grade
of the material.
D - is the external diameter of the chest.
T - is the minimum thickness of the chest, excluding tolerance
C - is the minimum positive tolerance as specified here
For Bronze Chests C = 1.5 mm
For Cast Iron Chests C = 5 mm