(a) Safety valves and pressure relief valves.
(1) The use of weighted-lever safety valves, or safety
valves having either the seat or disk of cast iron, is prohibited.
(2) Each boiler shall have at least one safety valve
and, if it has more than 500 square feet (47 square meters) of bare
tube water heating surface or has electric power input more than 1,100
kilowatts, it shall have two or more safety valves. These valves shall
be "V" stamped per ASME Code.
(3) Safety valves or pressure relief valves shall be
connected so as to stand in the upright position, with spindle vertical.
The opening or connection between the boiler and the safety valve
or pressure relief valve shall have at least the area of the valve
inlet.
(4) The valve or valves shall be connected to the boiler,
independent of any other steam connection, and attached as close as
practicable to the boiler without unnecessary intervening pipe or
fittings.
(5) Except for changeover valves as defined in §65.2(14),
other valve(s) shall not be placed:
(A) between the required safety valve or pressure relief
valve or valves and the boiler; or
(B) in the discharge pipe between the safety valve
or pressure relief valve or valves and the atmosphere.
(6) When a discharge pipe is used, it shall be:
(A) at least full size of the safety valve discharge;
and
(B) fitted with an open drain to prevent water lodging
in the upper part of the safety valve or discharge pipe.
(7) When an elbow is placed on a safety valve discharge
pipe:
(A) it shall be located close to the safety valve outlet;
and
(B) the discharge pipe shall be securely anchored and
supported.
(8) In the event multiple safety valves discharge into
a common pipe, the discharge pipe shall be sized in accordance with
ASME Code, Section I, PG-71.
(9) All safety valve or pressure relief valve discharges
shall be located or piped to a safe point of discharge, clear from
walkways or platforms.
(10) If a muffler is used on a pressure relief valve,
it shall have sufficient area to prevent back pressure from interfering
with the proper operation and discharge capacity of the valve. Mufflers
shall not be used on High-Temperature Water Boilers.
(11) The safety valve capacity of each boiler must
allow the safety valve or valves to discharge all the steam that can
be generated by the boiler without allowing the pressure to rise more
than 6.0% above the highest pressure to which any valve is set, and
to no more than 6.0% above the MAWP. For forced-flow steam generators
with no fixed steam and waterline, power-actuated relieving valves
may be used in accordance with ASME Code, Section I, PG-67.
(12) One or more safety valves on every drum type boiler
shall be set at or below the MAWP. The remaining valve(s) may be set
within a range of 3.0% above the MAWP, but the range of setting of
all the drum mounted pressure relief valves on a boiler shall not
exceed 10% of the highest pressure to which any valve is set.
(13) When two or more boilers, operating at different
pressures and safety valve settings, are interconnected, the lower
pressure boilers or interconnected piping shall be equipped with safety
valves of sufficient capacity to prevent overpressure, considering
the maximum generating capacity of all boilers.
(14) In those cases where the boiler is supplied with
feedwater directly from water mains without the use of feeding apparatus
(not to include return traps), no safety valve shall be set at a pressure
higher than 94% of the lowest pressure obtained in the supply main
feeding the boilers.
(b) Feedwater supply.
(1) Each boiler shall have a feedwater supply, which
will permit it to be fed at any time while under pressure, except
for automatically fired miniature boilers that meet all of the following
criteria:
(A) the boiler is "M" stamped per ASME Code, Section
I;
(B) the boiler is designed to be fed manually;
(C) the boiler is provided with a means to prevent
cold water from entering into a hot boiler; and
(D) the boiler is equipped with a warning sign visible
to the operator not to introduce cold feedwater into a hot boiler.
(2) A boiler having more than 500 square feet (47 square
meters) of water heating surface, shall have at least two means of
feeding, one of which should be a pump, injector, or inspirator. A
source of feed directly from water mains at a pressure of at least
6.0% greater than the set pressure of the safety valve with the highest
setting may be considered as one of the means of feeding. Boilers
fired by gaseous, liquid, or solid fuel in suspension may be equipped
with a single means of feeding water, provided means are furnished
for the immediate shutoff of heat input if the feedwater is interrupted.
(3) Feedwater shall not be discharged close to riveted
joints of shell or furnace sheets or directly against surfaces exposed
to products of combustion or to direct radiation from the fire.
(4) Feedwater piping to the boiler shall be provided
with a check valve near the boiler and a stop valve or cock between
the check valve and the boiler. When two or more boilers are fed from
a common source, there shall also be a stop valve on the branch to
each boiler between the check valve and the source of supply. Whenever
a globe valve is used on the feedwater piping, the inlet shall be
under the disk of the valve.
(5) In all cases where returns are fed back to the
boiler by gravity, there shall be a check valve and stop valve in
each return line, the stop valve to be placed between boiler and the
check valve, and both shall be located as close to the boiler as is
practicable. Best practice is that no stop valve be placed in the
supply and return pipe connections of a single boiler installation.
(6) Where deaerating heaters are not used, best practice
is that the temperature of the feedwater be not less than 120 degrees
Fahrenheit (49 degrees Celsius), to avoid the possibility of setting
up localized stress. Where deaerating heaters are used, best practice
is for the minimum feedwater temperature be not less than 215 degrees
Fahrenheit (102 degrees Celsius), so that dissolved gases may be thoroughly
released.
(c) Water level indicators.
(1) Each boiler, except forced-flow steam generators
with no fixed steam and waterline, and high-temperature water boilers
of the forced circulation type that have no steam and waterline shall
have at least one water gage glass.
(2) Except for electric boilers of the electrode type,
boilers with a MAWP over 400 psig (three (3) megapascals) shall be
provided with two water gage glasses, which may be connected to a
single water column or connected directly to the drum.
(3) Two independent remote level indicators may be
provided instead of one of the two required gage glasses for boiler
drum water level indication, when the MAWP is above 400 psig (three
(3) megapascals). When both remote level indicators are in reliable
operation, the remaining gage glass may be shut off, but shall be
maintained in serviceable condition.
(4) In all installations where direct visual observations
of the water gage glass(es) cannot be made, two remote level indicators
shall be provided at operational level.
(5) The gage glass cock connections shall not be less
than 1/2 inch nominal pipe size (15 mm).
(6) No outlet connections, except for damper regulator,
feedwater regulator, drains, steam gages, or apparatus of such form
as does not permit the escape of an appreciable amount of steam or
water there from, shall be placed in the pipes connecting a water
column or gage glass to a boiler.
(7) The water column shall be fitted with a drain cock
or drain valve of at least 3/4 inch nominal pipe size (20 mm). The
water column blowdown pipe shall not be less than 3/4 inch nominal
pipe size (20 mm), and shall be piped to a safe point of discharge.
(8) Connections from the boiler to remote level indicators
shall be at least 3/4 inch nominal pipe size (20 mm), to and including
the isolation valve, and at least 1/2 inch (13 mm) OD tubing from
the isolation valve to the remote level indicator. These connections
shall be completely independent of other connections for any function
other than water level indication.
(d) Low-water fuel cutoff and water feeding devices.
(1) All automatically fired steam boilers, except boilers
having a constant attendant, who has no other duties while the boiler
is in operation, shall be equipped with approved low-water fuel cutoffs.
(A) These devices shall be installed in such a manner
that they cannot be rendered inoperative by the manipulation of any
manual control or regulating apparatus.
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