Current through Register Vol. 43, No. 12, March 20, 2024
(a)
(1) Each hot water heating boiler shall have
at least one ASME-certified or national board-certified safety relief valve set
to relieve at or below the maximum allowable working pressure of the boiler.
Each hot water supply boiler of the water tube or coil type shall have at least
one safety relief valve that is approved and certified by ASME or the national
board. The safety relief valve shall be of the automatic reseating type and
shall be set to relieve at or below the maximum allowable working pressure of
the boiler. If the capacity of the safety relief valve is certified by the ASME
or the national board, the safety relief valve shall have pop action when
tested by steam.
(2) If more than
one safety relief valve is used on either a hot water heating boiler or a hot
water supply boiler, the additional valve or valves shall be ASME-rated. The
additional valves shall be set to relieve at or below the maximum allowable
working pressure of the vessel or any component in the system.
(3) Each safety relief valve shall be
spring-loaded. A safety relief valve shall not be capable of being reset at a
higher pressure than the maximum allowable working pressure of the boiler or
pressure vessel.
(b)
Materials that can fail due to deterioration or vulcanization when subjected to
saturated steam temperatures corresponding to the maximum capacity test
pressure shall not be used for safety relief valves.
(c) A safety relief valve shall not be
smaller than 34 inch or larger than 412 inches standard pipe size, except that
boilers having a heat input not greater than 15,000 BTUH may be equipped with a
safety relief valve of 12-inch standard pipe size. The inlet opening shall have
an inside diameter that is approximately equal to or greater than the seat
diameter. The minimum opening through any part of the valve shall not be less
than 12 inch in diameter or its equivalent area.
(d) The steam-relieving capacity, in pounds
per hour, of each pressure-relieving device on a boiler shall be the greater of
the steam-relieving capacity determined by either of the following methods:
(1) Dividing the maximum output in BTUH by
1,000, where the maximum output is the output obtained at the boiler nozzle by
the firing of any fuel the unit is capable of using; or
(2) using the number of pounds of steam
generated per hour per square foot of boiler heating surface as specified in
the table in K.A.R. 49-52-5 (d)(1).
(e) If operating conditions are changed or
additional boiler heating surface is installed, the valve capacity shall be
increased, if necessary, to meet the new conditions in accordance with
subsection (f). The additional valves required because of the changed
conditions or additional heating surfaces may be installed on the outlet piping
if there is no intervening valve.
(f) The safety relief valve capacity for each
boiler shall be sufficient to prevent the pressure from rising more than 5 psig
above the boiler's maximum allowable working pressure with the fuel-burning
equipment installed. Each storage water heater and each hot water supply boiler
shall have T & P relief valves with a relieving capacity and an American
gas association rating that is equal to or exceeds the burner BTUH input or the
electrical power kilowatt input. Each hot water supply boiler that is of the
coil or water tube type shall be equipped with a safety relief valve. The
connecting hot water storage tank shall have a pressure and temperature safety
relief valve with a temperature-relieving capacity equivalent to the total
burner BTUH input.
(g)
(1) Each safety relief valve shall be
installed in a vertical position, except for T & P relief valves that are
installed on storage water heaters equipped with side tappings to accommodate
the insertion of the T & P valve thermostat. The T & P valve thermostat
shall be immersed in the water and located in the top six inches of the vessel.
No valve of any type shall be placed between the safety relief valve and the
boiler or on the discharge pipe between the safety relief valve and the
atmosphere.
(2) The diameter of
the discharge pipe shall not be less than the diameter of the safety discharge
opening and shall be fitted with an open drain to prevent water from lodging in
the upper part of the safety relief valve or in the discharge pipe. Horizontal
discharge piping that provides adequate gravity drainage shall not require the
fitting of an open drain, except as specified in this paragraph. If an elbow is
placed on the safety relief valve discharge pipe, the elbow shall be located
close to the safety relief valve outlet, or the discharge pipe shall be
securely anchored and supported.
(3) All safety relief valve discharges shall
be located or piped in a manner that does not endanger persons working in the
area. If discharge piping is directed downward, the pipe shall terminate no
more than six inches above floor level. Plastic discharge piping shall not be
used on any safety relief valve discharge line, including discharge lines for
domestic hot water heaters of any size.
(4) If two or more safety relief valve
discharge lines are connected together, the cross-sectional area of the common
discharge line shall equal or exceed the combined cross-sectional areas of all
of the connected safety relief valve outlets.
