Indiana Administrative Code
Title 675 - FIRE PREVENTION AND BUILDING SAFETY COMMISSION
Article 30 - INDIANA BOILER AND PRESSURE VESSEL RULES
Rule 8 - Existing Installations of Power Boilers (prior to July 1, 1953)
Section 8-14 - Safety valves; prohibited types; installation; standards; relieving capacity

(a) The use of weighted-lever safety valves is prohibited and these valves shall be replaced by direct spring loaded pop type valves that conform to the requirements in Section I of the ASME B&PVC.

(b) Safety valves having either the seat or disc of cast iron shall not be used.

(c) Each boiler shall have at least one (1) safety valve. Each boiler having more than five hundred (500) square feet of water heating surface shall have two (2) or more safety valves.

(d) The valve or valves shall be connected to the boiler, independent of any other steam connection, and attached as close as possible to the boiler, without unnecessary intervening pipe or fittings.

(e) No valve of any description shall be placed between the safety valve and the boiler nor on the escape pipe (if used) between the safety valve and the atmosphere. When an escape pipe is used, its area shall not be less than the cross-sectional area of the valve or drain to prevent water from lodging in the upper part of the valve or in the pipe. When an elbow is placed on a safety valve escape pipe, it shall be located close to the safety valve outlet, and the escape pipe shall be securely supported. All safety valve discharges shall be so located or piped as to be carried clear from walkways or platforms used to control the main stop valves of boilers or steam headers and discharged to a safe location.

(f) The safety valve capacity of each boiler shall be such that the safety valve or valves will discharge all the steam that can be generated by the boiler without allowing the pressure to rise more than six percent (6%) above the highest pressure to which any valve is set, and in no case to more than six percent (6%) above the maximum allowable working pressure.

(g) One (1) or more safety valves on every boiler shall be set at or below the maximum allowable working pressure. The remaining valves may be set not to exceed three percent (3%) above the maximum allowable working pressure, but the range of setting of all the safety valves on a boiler shall not exceed ten percent (10%) of the highest pressure to which any valve is set.

(h) When two (2) or more boilers operating at different pressures and safety valve settings are interconnected, the lower pressure boilers or interconnected piping shall be equipped with safety valves of sufficient capacity to prevent over pressure considering the generating capacity of all the boilers.

(i) In those cases where the boiler is supplied with feed water directly from pressure mains without the use of feeding apparatus (not to include return traps), no safety valve shall be set at a pressure greater than ninety-four percent (94%) of the lowest pressure obtained in the supply main feeding the boiler.

(j) When the required relief capacity is unknown, the relieving capacity of the safety valves shall be checked by one (1) of the following methods and, if found to be insufficient, additional valves shall be provided: