6.1.1 Grey
cast iron valves and fittings will, in general, be accepted in Class
III piping systems except as stated in Pt 4, Ch 4, 6.1 General 6.1.6.
6.1.2 Consideration
will be given to the acceptance of grey cast iron for valve bodies
and parts in Class I hydraulic oil piping systems where failure would
not render the system inoperative or introduce a fire risk.
6.1.3 Spheroidal
or nodular graphite iron castings for valves and fittings in Class
II and Class III piping systems are to be made in a grade having a
specified minimum elongation not less than 12 per cent of a gauge
length of 5,65 
, where S
o is the actual cross-sectional
area of the test piece.
6.1.4 Proposals
for the use of spheroidal graphite iron in Class I piping systems
will be considered, but in no case is the material to be used in systems
where the design temperature exceeds 350°C.
6.1.5 Where
the elongation is less than the minimum required by Pt 4, Ch 4, 6.1 General 6.1.3, the material is, in general,
to be subject to the same limitations as grey cast iron.
6.1.6 Grey
cast iron is not to be used for the following:
-
Valves and
fittings for piping systems subject to shock or vibration.
-
Shell valves
and fittings.