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the boiler.

M-404.2.2 Where boiler return pumps or combination return and vac-
uum pumps are used to return condensate to the boiler, they may be
connected through a Hartford Tee and Loop connection or directly to
boiler return piping. Pipe from pump to boiler shall be run up in a
vertical position from pump to height not less than three (3) feet above
the water line of the boiler, or to ceiling if ceiling is less than three (3)
feet, carried across to the boiler at that height, then dropped to below
water line of the boiler and connected to a Hartford Tee or direct to
boiler return piping with necessary check valves installed.

SECTION M-405.0 SAFETY OR RELIEF VALVES AND REDUCING VALVES

M-405.1 General: All steam boilers, hot water boilers and generators,
or any type of pressure vessel used for steam generation, for processing
or for building heating systems and tanks, and other equipment used for
the purpose of generating or storing hot water under pressure, shall be
equipped with a side outlet type and approved ASME-NB pressure-safety
or relief valve(s), approved for the type of equipment on which it is
installed, and for the temperatures, pressures and fluids with which it is to
operate (for the purposes of this article ASME-NB shall mean American
Society of Mechanical Engineers-National Board). Such valves shall be
rated as maximum unit capacity or not less than the burner output
capacity. The requirements for temperatture-relief valves shall be the
same as those required for pressure-relief valves, except that temperature-
relief valves shall be of an approved type and need not bear the seal of
the ASME-NB. Approved combination-type pressure and temperature

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STEAM AND HOT WATER HEATING SYSTEMS AND PROCESS PIPING

relief valves may be permitted on tanks up to one hundred (100) gallon
storage capacity; however, tanks in excess of one hundred (100) gallon
storage capacity shall be equipped with separated valves for relief of
temperatture and pressure.

M-405.1.1 When the horsepower of a steam boiler or generator is in
excess of five hundred (500) horsepower, a second approved relief valve
of adequate size to handle the boiler output shall be installed. Such
valve shall be permanently marked showing pressure and capacity rating.

M-405.1.2 Valves on hot water boilers and generators and hot water
pressure vessels or building heating systems shall be of the type designed
for hot water use and bear the ASME-NB permanent rating label incUcat-
ing the capacity of the valve in Btus and the pressure at which it is
to operate. When the equipment has a heat input rating in excess of
fifteen million (15,000,000) Btus, a second relief valve of adequate size
to handle the boiler output shall be installed. Temperature-relief valves
shall be permanently marked indicating temperature relief rating. Pres-
sure-relief rating is not to be in excess of thirty (30) psig for cast iron
boilers regardless of weight of water in the system, and a pressure-relief
rating is not to be in excess of forty-five (45) psig for steel boilers, regard-
less of weight of water in the system.

M-405.1.3 Required side outlet type relief valves shall be installed on
top of boilers and at the heat exchanger. Stops, valves or other obstruc-
tions that will prevent the full pressure of the heating system from being
applied to the relief valves at all times are prohibited.

M-405.2 Location: All relief valves shall be installed in openings by
the manufacturer of the equipment. If such openings are not provided,
the valves shall be installed in the piping of the equipment as close to the
equipment as possible. Pressure-relief valves shall be installed in the cold
water supply piping as close to the heater or tank as practicable, so the
valve will be under the same constant water pressure as the equipment.
Valves or stop cocks shall not be permitted between boiler or pressure
vessel and pressure valves, except on boilers in excess of one thousand
(1,000) horsepower and having two (2) or more relief valves. Reduction in
the size of the relief valve connections shall not be permitted.

M-405.3 Test lever: All relief valves shall be provided with a suitable
type hand test lever.

M-405.4 Valve setting: All valves shall be tested after installation to
indicate that they relieve at the pressure or temperatture set and desig-
nated on the valve. Any valve failing to open within ten (10) per cent
of the setting marked shall be considered defective and shall be replaced.

M-405.5 Valve seals

M-405^.1 The seal provided by the manufacturer of the relief valve
to seal valves at designated pressure or temperature shall not be broken

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without special permission of the building official. If permission is given
to change or reset the valve, such valve shall be reseated in the presence
of an authorized representative of the department and permanently
tagged and marked to indicate the new setting permitted.

M-40S.5.2 Where the seal on any type of relief valve is found broken
without permission of the building official, the equipment on which the
valve is installed shall be ordered out of service until a new valve of
proper size and type has been installed on the equipment, and such new
valve is tagged and sealed in an approved manner.

Exception: If, however, the equipment cannot be ordered out of
service, the relief valve shall be inunediately checked. If found to be
operating properly, the valve shall be resealed and tagged in an ap-
proved manner.

M-40S.6 Discharge: Safety or reUef valve discharge openings shall be
piped the full size of the relief opening to a location where the discharge
cannot be injurious to the plant, the building or to personnel. If the
discharge pipe from the relief valve is piped to me outside of the building,
provisions shall be made to secure proper drainage and prevent freeze-up.
Discharge pipe from the relief valve, piped to the inside of the building,
shall be piped to within six (6) inches of the boiler room floor or to an
approved plumbing receptacle. The boiler room floor shall be provided
with a drain or an approved plumbing receptacle connected to the sewer,
and the drain pipe from such device snail not be less than one (1) nominal
iron pipe size larger than the drain outlet of the relief valve. The dis-
charge end of the pipe from any relief valve shall be open to the atmos-
phere so as to provide a minimum air gap between the overflow rim to
the receptacle of the sewer opening or floor drain of twice the inside
pipe diameter of the relief valve discharge pipe.

M-405.7 Pressure valves

M-40S.7.1 On all closed building heating systems, in addition to the
compression tank, an approved type of pressure-reducing valve and pres-
sure-relief valve shall be installed. The reducing valve shall be capable
of reducing the water supply pressure to the safe operating requirements
of the heating system. This valve shall be of not less than one-half QS)
inch nominal iron pipe size and shall be installed in the makeup water
supply line. Combination pressure-reducing and relief valves are pro-
hibited.

M-405.7.2 An approved pressure-relief valve shall be installed on all
closed heating systems. The capacity and size of the relief valve shall be
in accord with the Btu-generating capacity of the heat exchanger or
boiler. Relief valves less than one-half (X) inch pipe size shall not be
installed in any closed hot water system. On large systems, where the
Btu capacity of the system is greater than the capacity of any one (1)



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STEAM AND HOT WATER HEATING SYSTEMS ^W PIOCESS JNFINC

relief valve to provide adequate protection, two (2) or more valyes sh^
be provided to meet the Btu-generating capacity.

SECTION M-406,0 WATEK LEVEL AND STEAM PRESSURE GAU6ES
AND TRY-COCKS

M-406.1 General: Each low pressure steam l;K>iler shall be equipped
with the following:

1. a water level gauge glass mounted so that .the mid-point of the
glass is at the normal water level of the boiler;

2. at least two (2) hand operated try-cocks mounted one and one-half
(1%) inches above and one and one-half (1%) inches below the noniial
water level of the boiler; and

3. a steam pressure gauge mounted on or at the top of the boiler.

M-406.2 Gauge glass and try-cocks: The gauge glass and try-cQcks
may be mounted directly on the boiler, independent of all other con-
nections. If the boiler is equipped with a separate water column on
which the gauge ^ass and try-cocks are install^, and ^is water colump
is connected to the boiler by means of pipe and fittii^, the bottom
of the water column shall be provided with a blow down valve of Ae
gate valve type and at least the size of the piping connection of the water
column. Wherever separate water columns are to be connected to ^ilers^
the water columns shall be piped to the boiler using p)ugg^ crosses tor
all ninety (90) degree bends in such piping.

M-406.3 Steam gauge: The steam gauge shall be clearly visible ftQV^
the operating floor or normal access area at all times. It shall be the iow
pressure type with easily read numerals, at least four and one-half {43(j
inches in diameter and with a maximum rating of one and one-half (liS}
times the maximum operating pressure of the boiler. Such gauge may be
mounted directly on the boiler or at the top of the water column and
shall have a syphon loop between the gauge and the boiler connection.

SECTION M-407.0 BLOW-OFF VALVES

M-407.1 General: Each steam boiler shall be provided with a proper
size blow-oflF or drain valve or valves of the quick opening or one^foiurfli
(%) turn type. Such blow-o£F or drain valves shall be installed in the can-
ing of the boiler provided by the manufacturer or in the return head^ at
the boiler and shall be so installed that the boiler will be x^mpletely
drained. The blow-oflF or drain valve shall be at least three-fourths ^
inch size for boilers of up to one thousand (1,000) square feet of ra^-
tion capacity, one (1) inch for boilers up to three thousand (3,000)
square feet of radiation capacity, one and one-fourth (IX) indies ior
boilers up to eight thousand (8,000) square feet of radiation capacity
and one and one-half (Hi) inches for boilers in excess of eight th(Mi$ipMKl

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THE BOCA BASIC MECHANICAL COOE/1975

(8,000) square feet of radiation capacity. The blow-oflF or drain valve
shall not be connected directly to any sanitary sewer system. When
drained to a sewer, it shall drain to an open floor drain, approved receptor
or to a regular blow-off tank or sump. The temperatture of the discharge
water shall not exceed one hundred eighty (180) degrees F. when it
enters the sanitary sewer system. The blow-off or draM may discharge
into an approved leaching pit.

M-407.2 Blow-off and sump tanks

M-407.2.1 Blow-off or sump tanks shall be installed where either are
necessary to properly blow down or drain the boiler, or where the boiler
is set or pitted below the level of the boiler room or below the low point
of any floor drain connected to the sewer.

M-407.2.2 Where sump or blow-off tanks are installed below the level
of sewer piping, an automatically controlled, power-driven pump shall be
provided to raise the water for proper drainage into the sewer.

M-407.2.3 All piping between blow-off and drain valves and connecting
to sump or flush tank shall be connected directly to the tank and shall not
be less than the size piping of the blow-off or drain valve. Such pipe and
fittings shall be capable of withstanding the full pressure of the boiler.

SECTION M-406.0 LOW WATER CUT-OFF CONTROLS, WATER FEEDERS

M-408.1 General: An external low water cut-off control shall be in-
stalled on all fuel-fired steam boilers or generators in such a manner so
that the fuel-firing device will shut off when the level of the water is
within one (1) inch of the bottom of the gauge glass. The use of internal
type low water cut-off valves is prohibited.

M-408.1.1 A water feeder may be installed to operate and maintain
the water at the proper operating level in steam boilers. A water feeder
shall not be equipped with a low water cut-off control. Combination
feeders and low water cut-offs are permitted.

M-408.1.2 The quick hook-up type of low water cut-off or combination
feeder and cut-off that are attached or connected to the gauge glass con-
nections of a steam boiler are permitted on steam boilers not in excess of
two thousand (2,000) square feet of radiation capacity or the equivalent
in boiler horsepower. All boilers larger in size shall use the type of low
water cut-off or feeder combination tibat is attached directly to the boiler
by means of separate pipe connection, one above the water line of the
boiler, the other at least twelve (12) inches below the normal operating
water line of the boiler. The connecting pipe to the boiler shall be not less
than on (1) inch iron pipe size. Such pipe shall have a blow-off valve
installed at the lower connection.

M-408.1.3 Each type of low water control and combination-type feeder
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STEAM AND HOT WATER HEATIMI SYSTEMS AND PROCESS PIPING

and control shall be equipped with a flushing valve, gate valve or quick-
opening valve. This valve shall be the full size of the opening provided
at the bottom of the control. Flushing valves shall be provided with
permanently marked tags carrying instructions to the operator to flush
the low water control at least once a week.

M-408.2 Special types: Special types of low water cut-offs and water
feeders that are supplied by the manufacturers of boilers as part of the
boiler equipment or built into the boiler are acceptable when approved
by the building o£Bcial.

SECTION M-409.0 PIPING FOR STEAM AND HOT WATER HEATING SYSTEMS

M-409.1 General: All steel and wrought iron pipe shall be at least
Schedule 40 pipe, or pipe or tubing of equivalent working pressure and
tensile strength. Brass or copper pipe, and copper or steel tuoing may be
used on hot water heating installations if the system is designed to
operate within such pipe or tubing working pressure rating.

M-409.2 Reaming: All pipe or tubing shall be reamed after cutting
to not less than full internal dimensions.

M-409.3 Pipe joining: Steel or wrought iron piping may be joined by
welding or by the use of screw or flanged fittings. Copper or tinned steel
tubing may be joined by blazing, soldering or approved compression
fittings.

M-409.4 Pipe support: Pipe and piping shall be properly hung and
supported to permit expansion and contraction. "U" bends, swing joints
or expansion joints shall be installed so as to permit free expansion and
contraction of the piping. Swing joints or "U" bends shall be fabricated
of equivalent pipe material and shall be suitable for the pressures and
temperatures at which the installation is designed to operate. Expansion
joints of either the slip sleeve or corrugated copper type may be used
where such joints meet the temperature and pressure requirements of the
installation.

M-409.4.1 All piping shall be securely supported on substantial non-
combustible supports or hangers. The hangers or supports shall be
securely fastened to an adequate support or structural member, and the
hangers or supports shall be so spaced that there shall not be undue stress
or strain on the pipe, joints, fittings or valves so that sagging will not
occur in the pipe between points of suspension under normal operating
conditions.

M-409.4.2 The piping shall be securely fastened to proper type anchor
foimdations where necessary to prevent undue stress or strain on boilers
or equipment due to weight of the pipe or expansion and contraction.

M-409.5 Piping through walls, floors, etc.: Piping passing through

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walls, ceilings, floors, beams, or any portion of the building structure shall
be free to expand and contract and shall not be embedded in plaster,
concrete or masonry. Such piping shall be provided with metal sleeves
or thimbles when passing through concrete or masonry walls, ceilings,
floors or beams, and such sleeves or thimbles shall be at least three-eigh^
{%) inch larger than the outside diameter of the pipe plus the insulation.
Openings throueh wooden floors, ceilings, walls and beams shall be at
least three-eighms (X) inch larger than me outside diameter of the pipe
or the pipe plus insulation. When copper tubing is installed in a concrete
slab or in the earth below a slab, it shall be installed in a sleeve with a
diameter not less than three-fotuths (X) inch greater than the outside
diameter of the tubing; the tubing shall be arranged to permit expansion
and contraction without damage to the tubing or to the building structure,
and all joints shall be made with solders or copper brazing rods having a
minimum melting point of one thousand (1,000) degrees F. Where steel
pipe is installed in a concrete slab or in the earth below a slab, it shall be
installed in a casing or conduit, and such steel pipe shall be protected
against corrosion. The casing or conduit shall be laid in a straight line
and shall extend into accessible portions of the building to permit the
removal or insertion of the pipe when the casing or conduit is in place.
Corrosion protection shall consist of a thick coating of bituminous ma-
terial, applied in molten condition, with a wrapping of asbestos fabric
saturated with bitumens. Mill-wrapped pipe shall be acceptable if all
joints are protected in substantially the same manner as the original pipe.
The building o£Scial shall approve the type of sleeve and insulation to be
used on piping carrying steam, water, or other fluids at temperatures in
excess of three hundred (300) degrees F (see Section M-417.0 for radiant
heatings systems).

M-409^ Vertical piping secured: Vertical piping shall be secured
at sufficiently close intervals to keep the pipe in alignment and carry the
weight of the pipe and contents but not less than at every other story



M-400.7 Branch main stress: Where the main stream supply or hot
water supply piping or the main return piping of a system is divided
into two (2) or more branch mains or returns, such branches from the
main piping shall be taken off with tees and elbows or "Y" branch fittings,
so installed and connected that undue stresses or strains from pipe ex-
pansion or other causes shall not be placed on the pipe fittings or threads
at the point or points of junction of the piping.

M-409.8 BuU-heading tec: The use of bull-heading tee connections is
^xihibited where the side opening of a tee is connected to the main
piping and where two (2) branch connections are taken off of the run of
the tee, Aereby forming a rigid connection.

M-409«9 Welding: Where welding is used as a means of connecting

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STEAM AND HOT WATER HEATING SYSTEMS AND PROCESS PIPING

or joining branch mains to the main steam piping, provisions shall be
made for the expansion of the pipe at this point so that undue stresses or
strains shall not be placed on the welds or piping. The bull-heading or
rigid tee is prohibited on this type of connection.

M-409.10 Ck>nnections from mains, branch mains or return piping:

All connections from the mains, branch mains or return piping of a steam
system to radiators or to supply risers running to upper floors of a build-
ing shall be taken off at the top of the supply or return piping by use of
a forty-five (45) degree or ninety (90) degree elbow, where fittings are
used or welded into the top of the piping, where the welded method of
connection is used.

M-409.11 Cold water supply to hot water tank: The cold water sup-
ply to a hot water tank used for processing shall be discharged within
three (3) inches of the bottom of the tank either by direct connection
at this point or by means of a pipe or tube inside of the tank. There
shall be installed, on the cold water line close to the tank, a hand shut-off
valve and a check valve. The check valve shall be installed to prevent
hot water flow back from the tank into the cold water supply piping.

M-409.12 Approved materials

M-409.12.1 All threads on pipe, valves, flanges, and similar fittings shall
conform to American Standard Taper Pipe Threads.

M-409.12.2 Required gaskets shall be made of material approved for
the pressure and temperature to which they are to be subjected. Rubber
shall not be used where pressures exceed fifteen (15) psig steam and
forty-five (45) psig water or where temperatures are greater than two
hundred fifty (250) degrees F.

M-409.12.3 Threaded joints shall be made up with an approved thread
compound or lubricant.

M-409.12.4 Screw-type flanges of cast iron, steel or forged integral type
may be used up to their working pressure and temperature ratings. AH
companion flanges shall have matching facing and drilling.

M-409.12.5 All pipe fittings and valves used on high pressure installa-
tion shall be of the type designed for the pressures and temperatures of
the installation.

M-409.12.6 All pipe and piping used on high pressure-high temperature
installations shall be of the required weight and strength suitable for the
type service and pressure intended. Stress relieving may be required by
the department for high pressure-high temperature welded installations.

SECTION M-410.0 PITCH OF PIPING

M-410.1 General: All piping shall be properly pitched or graded for
proper venting. Wherever practical, the water pipe shall be so pitched

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TNE BOCA BASIC MECHANICAL CODE/1975

that the air or gases flowing to a high point or vent point will flow in the
same direction as the water.

M-410.2 Steam mains: All steam mains shall be pitched or graded
in the direction of the flow of steam from the boiler. The grade or pitch
shall be at least one (1) inch per each twenty (20) feet of horizontal pipe
nm. The high point shall be established at or near the boiler. The pitch
or grades shall be carried to the end or ends of the steam mains. The ends
of the steam mains shall be properly dripped and connected into the
return piping of the system so that the condensate will be carried back
to the boiler directly or to a boiler return pump or return trap.

M-410.3 Branches

M-410.3.1 All branches to radiators or to supply risers on steam heating
systems shall pitch up from the point of connection to a main or return
piping at least one (1) inch per each four (4) feet of horizontal run.
If the horizontal run from the main to the radiator or riser on the steam
system is over eight (8) feet in length, such run shall be increased one
(1) pipe size.

M-410.3.2 If the building or structtural conditions are such that the
branches cannot be pitched up from the connection point and must be
pitched down to the point where they rise to connect into the radiator
or riser, the branch shall be dripped to a steam trap at the low point and
trap connected to the return piping.

M^IO.4 Grading

M-410.4.1 Where structural conditions make it necessary to regrade or
elevate the steam main or mains, or where the difference in the floor or
ceiling heights or levels requires that the pipe be regraded, and where
the change in grade or level causes the formation of pockets in which
condensate can collect and cut down the capacity of the piping, a drip
pocket and steam trap shall be installed at the low point and connected
to the return piping. The size of the drip connection trap and trap con-
nection shall be adequate to drain the amount of condensate anticipated,
but the drip connection shall not be less than three-fourths (JK) inch
iron pipe size.

M-410.4.2 Where structural conditions of the building are such that
the steam main cannot be pitched so that the steam and condensate will
flow in the same direction, and it becomes necessary to pitch the main
piping up so that it is necessary for the condensate to flow back against
the flow of steam, the size of the pipe main shall be increased and
properly dripped.

M-410.4.3 Runouts: Steam lines having runouts shall be sized so that
the pressure drop does not exceed twenty-five hundredths (0.25) psig per
one hundred (lOO) feet of length in order that the critical steam velocity
will not be exceeded.

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SECTION M-411.0 EXPANSION TANKS

M-411.1 General: An expansion- or compression-type tank shall be
installed and used on all hot water heating systems. The size of such


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