Iowa Code r. 875-94.6 - Hot water supply boilers installed before July 1, 1960
(1)
Scope. This rule establishes minimum requirements for
installation, operation, and inspection of hot water supply boilers installed
before July 1, 1960, when any of the following limitations are exceeded:
a. Heat input of 200,000 Btu's per
hour.
b. Water temperature of
210°F.
c. A water containing
capacity of 120 gallons.
(2)
Safety relief valves.
Each hot water supply boiler must have at least one pressure and temperature
relief valve bearing the National Board "HV" stamp installed on the hot water
outlet line.
(3)
Safety
valves and safety relief valves for tanks and heat exchangers.
a. When a hot water supply vessel is heated
indirectly by steam in a coil or pipe, the pressure of the steam used shall not
exceed the safe working pressure of the tank. A safety relief valve at least 1
inch in diameter shall be installed on the tank and shall be set to relieve at
or below the maximum allowable working pressure of the tank.
b. When water over 160° F is circulated
through the coils or tubes of a heat exchanger to warm the water for space
heating or hot water supply, the heat exchanger shall be equipped with one or
more safety relief valves bearing the National Board "HV" stamp of sufficient
rated capacity to prevent the heat exchanger pressure from rising more than 10
percent above the maximum allowable working pressure of the vessel. The valves
shall be set to relieve at or below the maximum allowable working pressure of
the heat exchanger.
c. When water
over 160° F is circulated through the coils or tubes of a heat exchanger to
generate low-pressure steam, the heat exchanger shall be equipped with one or
more safety valves bearing the National Board "HV" stamp of sufficient rated
capacity to prevent the heat exchanger pressure from rising more than 5 psig
above the maximum allowable working pressure of the vessel. The valves shall be
set to relieve at a pressure not to exceed 15 psig.
(4)
Gages. Temperature and
pressure gages shall be installed in accordance with 94.5(2).
(5)
Temperature controls.
Temperature controls shall be installed in accordance with 94.5(3).
(6)
Stop valves.
a. Stop valves shall be placed in the supply
and return pipe connections of a single hot water supply boiler installation to
permit draining the boiler without emptying the system.
b. Where two or more boilers are connected in
a common system, a stop valve shall be used in each boiler's supply and return
pipe connection.
(7)
Thermal expansion. If a system is equipped with a check valve
or pressure-reducing valve in the cold water inlet line, an airtight expansion
tank or other suitable air cushion shall be installed. When an expansion tank
is provided, it shall be constructed in accordance with the ASME Code, Section
VIII, Division 1, in effect when installed, for a maximum allowable working
pressure equal to or greater than the water heater. Except for prepressurized
tanks, provisions shall be made for draining the tank without emptying the
system.
Notes
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No prior version found.