16 Tex. Admin. Code § 65.611 - Heating boilers
(a) Steam Heating
Boilers.
(1) Safety valves.
(A) Each steam boiler must have one or more
safety valves, that are identified with applicable designator with the ASME
certification mark of the spring pop type, adjusted and sealed to discharge at
a pressure not to exceed 15 psig (103 kilopascals). Seals must be attached in a
manner to prevent the valve from being taken apart without breaking the seal.
The safety valves must be arranged so that they cannot be reset to relieve at a
higher pressure than the MAWP of the boiler. A body drain connection below seat
level must be provided. For valves exceeding 2 1/2 inch nominal pipe size (65
mm), the drain hole or holes must be tapped not less than 3/8 inch nominal pipe
size (10 mm). For valves 2 1/2 inch nominal pipe size (65 mm) or less, the
drain hole must not be less than 1/4 inch (6 mm) in diameter.
(B) Each safety valve 3/4 inch nominal pipe
size (20 mm) or over, used on a steam boiler, shall have a substantial lifting
device, which will positively lift the disk from its seat at least 1/16 inch
(1.6 mm), when there is no pressure on the boiler. The seats and disks shall be
of suitable material to resist corrosion.
(C) No safety valve for a steam boiler shall
be smaller than 1/2 inch nominal pipe size (15 mm). No safety valve shall be
larger than 4 1/2 inches nominal pipe size (15 mm). The inlet opening shall
have an inside diameter approximately equal to, or greater than, the seat
diameter.
(D) The minimum relieving
capacity of valve or valves shall be governed by the capacity marking on the
boiler.
(E) The minimum valve
capacity in pounds per hour shall be the greater of that determined by dividing
the maximum Btu output at the boiler nozzle obtained by the firing of any fuel,
for which the unit is installed by 1,000, or shall be determined on the basis
of the pounds of steam generated per hour, per square foot of boiler heating
surface as given in § 65.615, Exhibit 7. For cast iron boilers, the
minimum valve capacity shall be determined by the maximum output method. In
every case, the safety valve capacity for each steam boiler shall be such that
with the fuel burning equipment installed, and operated at maximum capacity,
the pressure cannot rise more than 5psig (35 kilopascals) above the
MAWP.
(F) Safety valve piping. No
valve shall be placed between the safety valve and the boiler or on the
discharge pipe between the safety valve and the atmosphere. When a discharge
pipe is used, it shall be full size and fitted with an open drain to prevent
water from lodging in the upper part of the safety valve or pressure relief
valve or in the discharge pipe. When an elbow is placed on the safety valve
discharge pipe, it shall be located close to the valve outlet. The discharge
pipe shall be securely anchored and supported, independent of the valve. 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.
(G) Safety
valves and pressure relief valves shall be installed on the boiler with
spindles positioned vertically. The opening or connection between the boiler
and any safety valve or pressure relief valve shall have at least the area of
the valve inlet.
(2)
Feedwater connections.
(A) Feedwater or water
treatment shall be introduced into a boiler through the return piping system or
through an independent feedwater connection which does not discharge 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
provided for inspection or cleaning, safety valve, surface blowoff, water
column, water gage glass, pressure gage, or temperature gage.
(B) Feedwater pipe shall be provided with a
check valve near the boiler and a stop valve or cock between the check valve
and the boiler or return pipe system.
(3) Low-water fuel cutoffs and water feeding
devices.
(A) 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 automatic
low-water fuel cutoffs installed in such a manner that they cannot be rendered
inoperative by the manipulation of any manual control or regulating
apparatus.
(B) The MAWP of all low
water fuel cutoff devices shall be set at or above the boiler stamped
MAWP.
(C) When low-water fuel
cutoff and feedwater pump controls are combined in a single device, an
additional separate low-water fuel cutoff shall be installed. The additional
control shall be wired in series electrically with the existing low-water fuel
cutoff.
(D) When a low-water fuel
cutoff is housed in either the water column or a separate chamber, it shall be
provided with a blowdown pipe and valve, not less than 3/4 inch nominal pipe
size (20 mm). The arrangement shall be such that when the water column is blown
down, the water level in it will be lowered sufficiently to activate the
low-water fuel cutoff device.
(E)
If a water feed device is utilized, it shall be constructed to prevent
feedwater from entering the boiler through the water column or separate chamber
of the low-water fuel cutoff.
(4) Pressure gages.
(A) Each steam heating boiler shall have a
pressure gage connected to the device exterior to the boiler. The gage shall be
of sufficient capacity to keep the gage tube filled with water and arranged so
that the gage cannot be shut off from the boiler except by a cock with tee or
lever handle placed in a pipe near the gage. The handle of the cock shall be
parallel to the pipe in which it is located when the cock is open.
(B) The scale on the dial of a steam heating
boiler pressure gage shall be graduated to not less than 30 psig (207
kilopascals) nor more than 60 psig (414 kilopascals). The travel of the pointer
from zero to 30 psig (207 kilopascals) pressure shall be at least three
inches.
(5) Stop valves.
(A) Single steam heating boilers. When a stop
valve is used in the supply pipe connection of a single steam heating boiler,
there shall be one used in the return pipe connection.
(B) Supply and return line. Each supply and
return line to a steam heating boiler, which may be entered while adjacent
boilers are in operation, shall be fitted with either two stop valves with
ample drain between or a stop valve and figure 8 blank. The blank shall be
installed between the stop valve and the boiler.
(C) Type of stop valve. When stop valves over
two inches in size are used, they shall be of the outside screw-and-yoke rising
stem type or of such other type as to indicate at a distance whether it is
closed or open by the position of its stem or other operating mechanism. The
wheel may be carried either on the yoke or attached to the stem. If the valve
is of the plug cock type, it shall be fitted with a slow opening mechanism and
an indicating device and the plug shall be held in place by a guard or
gland.
(6) Bottom
blowdown or drain valve.
(A) Bottom blowoff
valve. Each steam heating boiler shall have a bottom blowoff connection fitted
with a valve or cock, connected to the lowest water space practicable with a
minimum size as shown in § 65.615, Exhibit 8. The discharge piping shall
be full size to the point of discharge. Boilers having a capacity of 25 gallons
(95 liters) or less are exempt from these requirements.
(B) Drain valve. Each boiler shall have one
or more drain connections, fitted with valves or cocks connecting to the lowest
water containing spaces. The minimum size of the drain piping, valves, and
cocks shall be 3/4 inch nominal pipe size (20 mm). The discharge piping shall
be full size to the point of discharge. When the blowoff connection is located
at the lowest water containing space, a separate drain connection is not
required.
(C) Minimum pressure
rating. The minimum pressure rating of valves and cocks used for blowoff or
drain purposes shall be at least equal to the pressure stamped on the boiler,
but in no case less than 30 psig (207 kilopascals). The temperature rating of
such valves and cocks shall not be less than 250 degrees Fahrenheit (121
degrees Celsius).
(7)
Water gage glasses.
(A) Each steam heating
boiler shall have one or more water gage glasses attached to the water column
or boiler, by means of valved fittings not less than 1/2 inch nominal pipe size
(15 mm). The lower fitting shall have a drain valve of the straightway type,
with opening not less than 1/4 inch (8 mm) diameter to facilitate cleaning.
Gage glass replacement shall be possible under pressure.
(B) Transparent material, other than glass,
may be used for the water gage, provided that the material will remain
transparent and has proved suitable for the pressure, temperature, and
corrosive conditions encountered in service.
(8) Piping, Fittings and Valves.
(A) All piping, fittings and valves on the
steam line, shall have a pressure rating equal to or greater than the MAWP of
the boiler and a temperature rating of no less than 250 degrees Fahrenheit (121
degrees Celsius).
(B) All piping,
fittings and valves other than the steam line, shall have a minimum pressure
and temperature rating equal to or greater than the maximum expected pressure
and temperature that may be reached.
(b) Hot Water Heating Boilers.
(1) Pressure relief valves.
(A) Each hot water heating boiler must have
at least one pressure relief valve, of the automatic reseating type, identified
with the ASME certification mark with the "V" or "HV" designator ASME Code
Symbol, and set to relieve at or below the MAWP of the boiler.
(B) When more than one pressure relief valve
is used on a hot water heating boiler, the additional valve or valves shall
have a set pressure within a range not to exceed 6 psig (42 kilopascals) above
the MAWP of the boiler up to and including 60 psig (414 kilopascals), and 5.0%
for those having a MAWP exceeding 60 psig (414 kilopascals).
(C) Pressure relief valves shall be spring
loaded and shall be set and sealed, so that they cannot be reset without
breaking the seal. A body drain connection below seat level shall be provided.
For valves exceeding 2 1/2 inch nominal pipe size (65 mm), the drain hole or
holes shall be tapped not less than 3/8 inch nominal pipe size (10 mm). For
valves of 2 1/2 inch nominal pipe size (65 mm) or less, the drain hole shall
not be less than 1/4 inch (6 mm) diameter.
(D) Each pressure relief valve shall have a
substantial lifting device, which will positively lift the disk from its seat
at least 1/16 inch (1.6 mm) when there is no pressure on the boiler.
(E) Seats and disks of pressure relief valves
shall be made of a suitable material to resist corrosion. No materials likely
to fail due to deterioration or vulcanization, when subjected to saturated
steam temperature corresponding to capacity test pressure, shall be used for
any part.
(F) No pressure relief
valve shall be smaller than 3/4 inch nominal pipe size (20 mm) nor larger than
4 1/2 inch nominal pipe size (115 mm) except that boilers having a heat input
not greater than 15,000 Btu/hr (4.4 kilowatts) may be equipped with a rated
pressure relief valve of 1/2 inch nominal pipe size (15 mm). The inlet opening
shall have an inside diameter approximately equal to, or greater than, the seat
diameter. In no case shall the minimum opening through any part of the valve be
less than 1/4 inch (6 mm) diameter or its equivalent area.
(G) The required steam relieving capacity, in
pounds per hour, of the pressure relieving device or devices on a boiler shall
be the greater of that determined by dividing the maximum output in Btu at the
boiler nozzle obtained by the firing of any fuel for which the unit is
installed by 1,000 or shall be determined on the basis of pounds of steam
generated per hour per square foot of boiler heating surface as given in §
65.615, Exhibit 7. For cast iron boilers the minimum valve capacity shall be
determined by the maximum output method.
(H) In every case, the pressure relief valve
capacity for each boiler with a single pressure relief valve shall be such
that, with the fuel burning equipment installed and operated at maximum
capacity, the pressure cannot rise more than 10% above the MAWP. When more than
one pressure relief valve is used, the overpressure shall be limited to 10%
above the set pressure of the highest set valve.
(I) Pressure relief valve piping. No valve
shall be placed between the pressure relief valve and the boiler or on the
discharge pipe between the pressure relief valve and the drain. When a
discharge pipe is used, it shall be full size and fitted with an open drain to
prevent water from lodging in the upper part of the pressure relief valve or in
the discharge pipe. When an elbow is placed on the pressure relief valve
discharge pipe, it shall be located close to the valve outlet. The discharge
pipe shall be securely anchored and supported, independent of the valve.
Mufflers shall not be used on hot water heating boilers.
(J) Pressure relief valves and safety valves
shall be installed on the boiler with spindles positioned vertically. The
opening or connection between the boiler and any pressure relief valve or
safety valve shall have at least the area of the valve inlet.
(2) Makeup water connections.
(A) Makeup water or water treatment shall be
introduced into a boiler through the return piping system or through an
independent makeup water connection, which does not discharge against parts of
the boiler exposed to direct radiant heat from the fire. Makeup water or water
treatment shall not be introduced through openings or connections provided for
inspection or cleaning, pressure relief valve, pressure gage, or temperature
gage.
(B) Makeup water pipe shall
be provided with a check valve near the boiler and a stop valve or cock between
the check valve and the boiler, or between the check valve and the piping
system.
(3) Low-water
fuel cutoffs and water feeding devices.
(A)
All automatically fired hot water heating boilers shall have an automatic
low-water fuel cutoff that has been designed for hot water service, and it
shall be so located as to automatically cut off the fuel supply when the
surface of the water falls to a level below the normal waterline
established.
(B) The MAWP of all
low water fuel cutoff and flow sensing devices shall be set at or above the
boiler stamped MAWP.
(C) When
low-water fuel cutoff and feedwater pump controls are combined in a single
device, an additional separate low-water fuel cutoff shall be installed. The
additional control shall be wired in series electrically with the existing
low-water fuel cutoff.
(D) When a
low-water fuel cutoff is housed in either the water column or a separate
chamber it shall be provided with a blowdown pipe and valve not less than 3/4
inch nominal pipe size (20 mm). The arrangement shall be such that when the
water column is blown down, the water level in it will be lowered sufficiently
to activate the low-water fuel cutoff device.
(E) As there is no normal water line to be
maintained in a hot water heating boiler, any location of the low-water fuel
cutoff above the lowest safe water level established by the boiler manufacturer
is satisfactory.
(F) All
automatically fired hot water heating boilers, when installed in a forced
circulation system and not under continuous attendance, shall be equipped in
the manner described in this subsection. A coil-type boiler or a water-tube
boiler requiring forced circulation to prevent overheating of the coils or
tubes shall have a flow sensing device which is listed by a nationally
recognized testing agency to prevent burner operation at a flow rate inadequate
to protect the boiler unit against overheating.
(G) If a water feed device is utilized, it
shall be constructed to prevent feedwater from entering the boiler through the
water column or separate chamber of the low-water fuel cutoff.
(4) Pressure and temperature
gages.
(A) Each hot water heating boiler shall
have a pressure or altitude gage connected to it or to its flow connection,
which cannot be shut off from the boiler except by a cock with tee or lever
handle placed in a pipe near the gage. The handle of the cock shall be parallel
to the pipe in which it is located when the cock is open.
(B) The scale on the dial of the pressure or
altitude gage shall be graduated to not less than 1 1/2 nor more than 3 1/2
times the pressure at which the pressure relief valve is set. The gage shall be
provided with effective stops for the indicating pointer at the zero point and
at the maximum pressure point.
(C)
Piping and tubing for pressure or altitude gage connections shall be of
nonferrous metal when smaller than 1 inch nominal pipe size (25 mm).
(D) Each hot water heating boiler shall have
a thermometer or temperature gage located and connected, that it shall be
readable, and shall be located so that it shall at all times indicate the
temperature of the water in the boiler at or near the outlet. If placed on the
outlet piping, it must be located between the stop valve and the
boiler.
(5) Stop valves.
(A) Stop valves shall be located at an
accessible point in the supply and return pipe connections near the boiler
nozzle of a single hot water heating boiler installation to permit draining the
boiler without emptying the system.
(B) When the boiler is located above the
system and can be drained without draining the system, stop valves may be
eliminated.
(C) Type of stop valve.
When stop valves over two inches in size are used, they shall be of the outside
screw-and-yoke rising stem type or of such other type as to indicate at a
distance whether it is closed or open by the position of its stem or other
operating mechanism. The wheel may be carried either on the yoke or attached to
the stem. If the valve is of the plug cock type, it shall be fitted with a slow
opening mechanism and an indicating device and the plug shall be held in place
by a guard or gland.
(6)
Drain valve.
(A) Each hot water heating
boiler shall have one or more drain connections, fitted with valves or cocks
connecting to the lowest water containing spaces. The minimum size of the drain
piping, valves, and cocks shall be 3/4 inch nominal pipe size (20 mm). The
discharge piping shall be full size to the point of discharge. When the blowoff
connection is located at the lowest water containing space, a separate drain
connection is not required.
(B)
Minimum pressure rating. The minimum pressure rating of valves and cocks used
for blowoff or drain purposes shall be at least equal to the pressure stamped
on the boiler, but in no case less than 30 psig (207 kilopascals). The
temperature rating of such valves and cocks shall not be less than 250 degrees
Fahrenheit (121 degrees Celsius).
(7) Provisions for thermal expansion.
(A) Heating systems with open expansion tank-
An indoor overflow from the upper portion of the expansion tank shall be
provided in addition to an open vent, the indoor overflow to be carried within
the building to a suitable plumbing fixture or basement.
(B) Closed heating system.
(i) If the system is of closed type, an
airtight tank or other suitable air cushion that is consistent with the volume
and capacity of the system shall be installed.
(ii) If the system is designed for a working
pressure of 30 psig (207 kilopascals) or less, the tank shall be suitably
designed for a minimum hydrostatic pressure of 75 psig (520
kilopascals).
(iii) Expansion tanks
for systems designed to operate above 30 psig (207 kilopascals) shall be
constructed in accordance with the ASME Code, Section VIII, Division 1, or
Section X, and the pressure and temperature ratings of the tank shall be equal
to or greater than the pressure and temperature ratings of the system pressure.
A pressure relief valve shall be installed with a set pressure at or below the
MAWP of the expansion tank. Alternately the boiler pressure relief valve may be
used provided the expansion tank's MAWP is equal to or greater than the set
pressure of the pressure relief valve.
(iv) Provisions shall be made for draining
the tank without emptying the system, except for pre-pressurized
tanks.
(v) If the expansion tank
was originally equipped with a sight glass, the sight glass and sight glass
valves shall be in working condition at all times, and the water level shall be
maintained as per the manufacturer's recommendations.
(8) Piping, fittings, and valves.
(A) All piping, fittings and valves on the
boiler supply and return lines shall have a pressure rating equal to or greater
than the MAWP of the boiler and a temperature rating of no less than 250
degrees Fahrenheit (121 degrees Celsius).
(B) All piping, fittings and valves other
than the boiler supply and return lines shall have a minimum pressure and
temperature rating equal to or greater than the maximum expected pressure and
temperature that may be reached.
(c) Hot Water Supply Boilers.
(1) Pressure relief valves.
(A) Each hot water supply boiler shall have
at least one pressure relief valve, of the automatic reseating type, identified
with the ASME certification mark with the "V" or "HV" designators, and set to
relieve at or below the MAWP of the boiler.
(B) When more than one pressure relief valve
is used on a hot water supply boiler, the additional valve or valves shall be
officially rated and may have a set pressure within a range not to exceed 6
psig (42 kilopascals) above the MAWP of the boiler up to and including 60 psig
(414 kilopascals), and 5.0% for those having a MAWP exceeding 60 psig (414
kilopascals).
(C) Pressure relief
valves shall be spring loaded. Pressure relief valves shall be set and sealed
so that they cannot be reset without breaking the seal. A body drain connection
below seat level shall be provided. For valves exceeding 2 1/2 inch nominal
pipe size (65 mm), the drain hole or holes shall be tapped not less than 3/8
inch nominal pipe size (10 mm). For valves of 2 1/2 inch nominal pipe size (65
mm) or less, the drain hole shall not be less than 1/4 inch (6 mm)
diameter.
(D) Each pressure relief
valve shall have a substantial lifting device which will positively lift the
disk from its seat at least 1/16 inch (1.6 mm) when there is no pressure on the
boiler.
(E) Seats and disks of
pressure relief valves shall be made of a suitable material to resist
corrosion. No materials likely to fail due to deterioration or vulcanization,
when subjected to saturated steam temperature corresponding to capacity test
pressure, shall be used for any part.
(F) No pressure relief valve shall be smaller
than 3/4 inch nominal pipe size (20 mm) nor larger than 4 1/2 inch nominal pipe
size (115 mm) except that boilers having a heat input not greater than 15,000
Btu/hr (4.4 kilowatts) may be equipped with a rated pressure relief valve of
1/2 inch nominal pipe size (15 mm). The inlet opening shall have an inside
diameter approximately equal to, or greater than, the seat diameter. In no case
shall the minimum opening through any part of the valve be less than 1/4 inch
(6 mm) diameter or its equivalent area.
(G) The required steam relieving capacity, in
pounds per hour, of the pressure relieving device or devices on a boiler shall
be the greater of that determined by dividing the maximum output in Btu at the
boiler nozzle obtained by the firing of any fuel for which the unit is
installed by 1,000, or shall be determined on the basis of pounds of steam
generated per hour per square foot of boiler heating surface as given in §
65.615, Exhibit 7. For cast iron boilers, the minimum valve capacity shall be
determined by the maximum output method.
(H) In every case, the pressure relief valve
capacity for each boiler with a single pressure relief valve shall be such
that, with the fuel burning equipment installed and operated at maximum
capacity, the pressure cannot rise more than 10% above the MAWP. When more than
one pressure relief valve is used, the overpressure shall be limited to 10%
above the set pressure of the highest set valve.
(I) Pressure relief valve piping. No valve
shall be placed between the pressure relief valve and the boiler nor on the
discharge pipe between the pressure relief valve and the drain. When a
discharge pipe is used, it shall be full size and fitted with an open drain to
prevent water from lodging in the upper part of the pressure relief valve or in
the discharge pipe. When an elbow is placed on the pressure relief valve
discharge pipe, it shall be located close to the valve outlet. The discharge
pipe shall be securely anchored and supported, independent of the valve.
Mufflers shall not be used on hot water supply boilers.
(J) Pressure relief valves and safety valves
shall be installed on the boiler with spindles positioned vertically. The
opening or connection between the boiler and any pressure relief valve or
safety valve shall have at least the area of the valve inlet.
(2) Makeup water connections.
(A) Makeup water or water treatment shall be
introduced into a boiler through the return piping system or through an
independent makeup water connection which does not discharge against parts of
the boiler exposed to direct radiant heat from the fire. Makeup water or water
treatment shall not be introduced through openings or connections provided for
inspection or cleaning, pressure relief valve, pressure gage, or temperature
gage.
(B) Makeup water pipe shall
be provided with a check valve near the boiler and a stop valve or cock between
the check valve and the boiler or between the check valve and the piping
system.
(3) Low-water
fuel cutoffs and water feeding devices.
(A)
All automatically fired hot water supply boilers shall have an automatic
low-water fuel cutoff that has been designed for hot water service, and it
shall be so located as to automatically cut off the fuel supply when the
surface of the water falls to a level below the normal waterline
established.
(B) The MAWP of all
low water fuel cutoff and flow sensing devices shall be set at or above the
boiler stamped MAWP.
(C) When
low-water fuel cutoff and feedwater pump controls are combined in a single
device, an additional separate low-water fuel cutoff shall be installed. The
additional control shall be wired in series electrically with the existing
low-water fuel cutoff.
(D) When a
low-water fuel cutoff is housed in either the water column or a separate
chamber it shall be provided with a blowdown pipe and valve not less than 3/4
inch nominal pipe size (20 mm). The arrangement shall be such that when the
water column is blown down, the water level in it will be lowered sufficiently
to activate the low-water fuel cutoff device.
(E) As there is no normal water line to be
maintained in a hot water supply boiler, any location of the low-water fuel
cutoff above the lowest safe water level established by the boiler manufacturer
is satisfactory.
(F) All
automatically fired hot water heating boilers, when installed in a forced
circulation system and not under continuous attendance, shall be equipped in
the manner described in this subsection. A coil-type boiler or a water-tube
boiler requiring forced circulation to prevent overheating of the coils or
tubes shall have a flow sensing device which is listed by a nationally
recognized testing agency to prevent burner operation at a flow rate inadequate
to protect the boiler unit against overheating.
(G) If a water feed device is utilized, it
shall be constructed to prevent feedwater from entering the boiler through the
water column or separate chamber of the low-water fuel cutoff.
(4) Pressure and temperature
gages.
(A) Each hot water supply boiler shall
have a pressure or altitude gage connected to it or to its flow connection
which cannot be shut off from the boiler except by a cock with tee or lever
handle placed in a pipe near the gage. The handle of the cock shall be parallel
to the pipe in which it is located when the cock is open.
(B) The scale on the dial of the pressure or
altitude gage shall be graduated to not less than 1 1/2 nor more than 3 1/2
times the pressure at which the pressure relief valve is set. The gage shall be
provided with effective stops for the indicating pointer at the zero point and
at the maximum pressure point.
(C)
Piping and tubing for pressure or altitude gage connections shall be of
nonferrous metal when smaller than 1 inch nominal pipe size (25 mm).
(D) Each hot water supply boiler shall have a
thermometer or temperature gage located and connected so that it shall be
readable, and shall be located so that it shall at all times indicate the
temperature of the water in the boiler at or near the outlet. If placed on the
outlet piping, it must be located between the stop valve and the
boiler.
(5) Stop valves.
(A) Stop valves shall be located at an
accessible point in the supply and return pipe connections near the boiler
nozzle of a single hot water supply boiler installation to permit draining the
boiler without emptying the system.
(B) When the boiler is located above the
system and can be drained without draining the system, stop valves may be
eliminated.
(C) Type of stop valve.
When stop valves over two inches in size are used, they shall be of the outside
screw-and-yoke rising stem type or of such other type as to indicate at a
distance whether it is closed or open by the position of its stem or other
operating mechanism. The wheel may be carried either on the yoke or attached to
the stem. If the valve is of the plug cock type, it shall be fitted with a slow
opening mechanism and an indicating device and the plug shall be held in place
by a guard or gland.
(6)
Drain valve.
(A) Each hot water supply boiler
shall have one or more drain connections, fitted with valves or cocks
connecting to the lowest water containing spaces. The minimum size of the drain
piping, valves, and cocks shall be 3/4 inch nominal pipe size (20 mm). The
discharge piping shall be full size to the point of discharge. When the blowoff
connection is located at the lowest water containing space, a separate drain
connection is not required.
(B)
Minimum pressure rating. The minimum pressure rating of valves and cocks used
for blowoff or drain purposes shall be at least equal to the pressure stamped
on the boiler, but in no case less than 30 psig (207 kilopascals). The
temperature rating of such valves and cocks shall not be less than 250 degrees
Fahrenheit (121 degrees Celsius).
(7) Provisions for thermal expansion.
(A) If a system is equipped with a check
valve or pressure reducing valve in the cold water inlet line, consideration
should be given to the installation of an airtight expansion tank or other
suitable air cushion. Otherwise, due to the thermal expansion of the water, the
pressure relief valve may lift periodically.
(B) If an expansion tank is provided, it
shall be constructed in accordance with the ASME Code, Section VIII, Division 1
or Section X, and the pressure and temperature ratings of the tank shall be
equal to or greater than the pressure and temperature ratings of the system
pressure. Except for pre-pressurized tanks, which should be installed on the
cold water side, provisions shall be made for draining the tank without
emptying the system.
(C) If the
expansion tank was originally equipped with a sight glass, the sight glass and
sight glass valves shall be in working condition at all times, and the water
level shall be maintained as per the manufacturer's recommendations.
(8) Piping, fittings, and valves.
(A) All piping, fittings and valves on the
boiler supply and return lines shall have a pressure rating equal to or greater
than the MAWP of the boiler and a temperature rating of no less than 250
degrees Fahrenheit (121 degrees Celsius).
(B) All piping, fittings and valves other
than the boiler supply and return lines shall have a minimum pressure and
temperature rating equal to or greater than the maximum expected pressure and
temperature that may be reached.
(d) Potable Water Heaters (ASME Code HLW).
(1) Pressure relief valves.
(A) Potable water heaters (tank type) must
have at least one officially rated temperature and pressure relief valve, or
one officially rated pressure relief valve, set to relieve at or below the
maximum allowable pressure of the heater. No pressure relief valve may be
smaller than 3/4 inch nominal pipe size (20 mm). The valve (s) must be marked
with the Code Symbol "V" or "HV." At no time may the temperature probe of the
temperature and pressure relief valve be removed or modified.
(B) The pressure relief valve shall have a
capacity equal to or exceeding the rated burner input of the heater. The
relieving capacity for electric water heaters shall be 3,500 Btu/hr (1.0
kilowatts) per kilowatt of input.
(C) The ASME Btu rating on the valve shall be
used to determine the relieving capacity.
(D) Pressure relief valves shall be connected
directly to the heater within the top 6 inches of the tank.
(E) Pressure relief valves may be installed
vertically or horizontally. The center line of the horizontal connection shall
be no lower than 4 inches from the top of the shell.
(F) Pressure relief valves shall not be
connected to an internal pipe in the heater, or to a cold water feed line
connected to the heater.
(G)
Pressure relief valve piping. No valve shall be placed between the pressure
relief valve and the boiler nor on the discharge pipe between the pressure
relief valve and the drain. When a discharge pipe is used, it shall be full
size and fitted with an open drain to prevent water from lodging in the upper
part of the pressure relief valve or in the discharge pipe. When an elbow is
placed on the pressure relief valve discharge pipe, it shall be located close
to the valve outlet. The discharge pipe shall be securely anchored and
supported, independent of the valve. Mufflers shall not be used on potable
water heaters.
(2) Water
supply.
(A) Water supply shall be introduced
into a water heater through an independent water supply connection. Water shall
not be introduced through openings or connections provided for cleaning,
pressure relief valves, drains, pressure gage or temperature gage.
(B) If the water supply pressure to a hot
water heater exceeds 75% of the set pressure of the pressure relief valve, a
pressure reducing valve is required.
(3) Flow sensing device.
(A) All automatically fired potable water
heaters, when installed in a forced circulation system and not under continuous
attendance, shall be equipped in the manner described in this subsection. A
coil-type boiler or a water-tube boiler requiring forced circulation to prevent
overheating of the coils or tubes shall have a flow sensing device which is
listed by a nationally recognized testing agency to prevent burner operation at
a flow rate inadequate to protect the boiler unit against
overheating.
(B) The MAWP of all
flow sensing devices shall be set at or above the boiler stamped
MAWP.
(4) Gages.
(A) Temperature gages. Each hot water heater
shall have a thermometer located and connected at or near the outlet that is
readable. The thermometer shall at all times indicate the temperatures of the
water in the hot water heater. If placed on the outlet piping, it must be
located between the stop valve and the boiler.
(B) Pressure gages. Each hot water heater
that is of the coil type or water tube shall have a pressure gage located as
close to the boiler as possible that is graduated to not less than 1 1/2 or
more than 3 1/2 times the pressure at which the pressure relief valve is
set.
(5) Stop valves.
Stop valves should be placed in the supply and discharge pipe connections of
the hot water heater installation to permit draining the heater without
emptying the system.
(6) Drain
valves. Each hot water heater shall have a bottom drain pipe connection fitted
with a valve or cock connected to the lowest water space practical. The minimum
size bottom drain shall be 3/4 inch nominal pipe size (20 mm).
(7) Provisions for thermal expansion.
(A) If a system is equipped with a check
valve or pressure reducing valve in the cold water inlet line, consideration
should be given to the installation of an airtight expansion tank or other
suitable air cushion. Otherwise, due to the thermal expansion of the water, the
pressure relief valve may lift periodically.
(B) If an expansion tank is provided, it
shall be constructed in accordance with the ASME Code, Section VIII, Division 1
or Section X, and the pressure and temperature ratings of the tank shall be
equal to or greater than the pressure and temperature ratings of the system
pressure.
(C) Except for
pre-pressurized tanks, which should be installed on the cold water side,
provisions shall be made for draining the tank without emptying the
system.
(D) If the expansion tank
was originally equipped with a sight glass, the sight glass and sight glass
valves shall be in working condition at all times, and the water level shall be
maintained as per the manufacturer's recommendations.
(8) Piping, fittings, and valves.
(A) All piping, fittings and valves on the
boiler supply and return lines shall have a pressure rating equal to or greater
than the MAWP of the boiler and a temperature rating of no less than 210
degrees Fahrenheit (99 degrees Celsius).
(B) All piping, fittings and valves other
than the boiler supply and return lines shall have a minimum pressure and
temperature rating equal to or greater than the maximum expected pressure and
temperature that may be reached.
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.
No prior version found.