ASME BPVC 2023 Section VI

5.9.3 Steam Boiler Return Pipe Connections
5.9.3.1 The return pipe connections of each boiler
supplying a gravity-return steam-heating system shall
be so arranged as to form a loop similar to that shown
in Figures 5.9.1-3 and 5.9.1-5 so that the water in each
boiler cannot be forced out below the safe water level.
5.9.3.2 For handfired boilers with a normal grate line,
the recommended pipe sizes detailed as “A” in
Figure 5.9.1-3 are as follows:
a NPS 112 DN 40 for 4 ft2 0.4 m2 or smaller firebox
area at the normal grate line
b NPS 212 DN 65 for areas larger than 4 ft2 0.4 m2
up to 15 ft2 1.4 m2
c NPS 4 DN 100 for 15 ft2 1.4 m2 or larger
5.9.3.3 For automatically fired boilers that do not have a
normal grate line, the recommended pipe sizes detailed as
“A” in Figure 5.9.1-3 are
a NPS 112 DN 40 for boilers with a minimum safety
valve relieving capacity of 250 lb/hr 113 kg/h or less
b NPS 212 DN 65 for boilers with a minimum safety
valve relieving capacity of 251 lb/hr 114 kg/hr to 2,000
lb/hr 900 kg/h, inclusive
c NPS 4 DN 100 for boilers with a minimum safety
valve relieving capacity greater than 2,000 lb/hr 900
kg/h
5.9.3.4 Provision shall be made for cleaning the interior
of the return piping at or close to the boiler. Washout openings
may be used for return pipe connections and the
washout plug placed in a tee or a cross so that the
plug is directly opposite and as close as possible to the
opening in the boiler.
5.9.4 Feedwater and Makeup Water Connections
5.9.4.1 Water Connections. Proper and convenient
water-fill connections should be installed, and provisions
should be made to prevent boiler water from backfeeding
into the service water supply. Provision should also be
made in every boiler room for a convenient water
supply that can be used to flush out the boiler and
clean the boiler room floor. Water piping should be
installed such that the boiler is not supporting the
piping. Refer to the Manufacturers instructions for information
regarding required water flow rates and supply
pressure so that piping is sized accordingly.
5.9.4.2 Steam Boilers. Feedwater or water treatment
shall be introduced into a boiler through the return piping
system or through an independent connection. The water
flow from the independent connection shall not discharge
directly against parts of the boiler exposed to direct
radiant heat from the fire. Feedwater or water treatment
shall not be introduced through openings or connections