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 TB 55-1900-201-45/1
j. Safety valves used on low pressure steam boilers shall be set to pop at a pressure not to exceed the pres-
sure recommended by the boiler manufacturer. Hot water heating boiler pressure relief valves should relieve at or below
the maximum allowable working pressure of the boiler. When more than one relief valve is used on hot-water heating
boilers, the additional valve shall be rated and may be set within a range not to exceed 20 percent of the lowest pressure
to which any valve is set. Relief valve capacity shall be such that with the fuel burning equipment installed, pressure
cannot rise more than 20 percent above the highest maximum allowable working pressure for pressure up to and includ-
ing 30 PSI and 10 percent for pressure over 30 PSI (206.7 kPa).
k. All hot water heating or hot water supply boilers marked for working pressure not exceeding 30 PSI and
steam-heating boilers not exceeding 15 PSI shall be subject to a hydrostatic test of the maximum allowable working
pressure (in accordance with current USCG standards).
l.
Hydrostatic test shall be applied to least biannually and/or when major repairs are completed.
2-51. Control System for Heating Boilers. An operating test shall be conducted to insure that all the control compo-
nents and safety devices are in satisfactory condition and meet the manufacturers operating instructions.
a. Flame safeguard. The operation of the flame safeguard system shall be verified by simulating flame and
ignition failures. Operation of the audible alarm and visible indicator should be verified.
b. Limit and miscellaneous controls. Boiler shutdown due to the operation of boiler limit controls and miscella-
neous control devices shall be verified.
c. Water level controls. Water level controls should be tested by slowly lowering the water level in the boiler.
The operating water level controls and low-water cutoffs shall be tested individually. The operation of the visible indica-
tor associated with the low-water cutoff shall be verified.
d. Combustion controls. The combustion controls should provide smooth light off and stable operation.
e. Fuel supply controls. The satisfactory operation of the fuel control valves for conditions of operation and
shutdown shall be verified.
2-52.
Unfired Pressure Vessels.
a. All unfired pressure vessels shall be given a visual external inspection at least biannually to determine con-
dition of supports, insulation and the general condition of the pressure vessels. If practicable, the usual internal inspec-
tion should also be made.
2-28
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