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D.C. Municipal Regulations (Last Updated: September 13, 2017) |
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Title 12. CONSTRUCTION CODES SUPPLEMENT OF 2013 |
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SubTilte 12-E. MECHANICAL CODE SUPPLEMENT OF 2013 |
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Chapter 12-E10. BOILERS, WATER HEATERS AND PRESSURE VESSELS |
Section 12-E1010. SAFETY VALVES
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Strike Section 1010 of the International Mechanical Code in its entirety and insert new Section 1010 in the Mechanical Code in its place to read as follows:
1010.1 General. Each steam boiler shall be provided with one or more safety valves of the spring-pop type, having side outlet discharge, adjusted and sealed to discharge at a pressure not to exceed 15 pounds per square inch (psi) (103 kPa). Seals shall be attached so as to prevent the valve from being taken apart or re-set to relieve at a higher pressure without breaking the seal.
1010.2 Lever-lifting device. Each valve shall have a substantial lever-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. Where the lever is more than 78 inches (1981 mm) above the floor, a flexible chain or cable operating over a pulley shall be provided so that the valve can be tested.
1010.3 Safety valve marking. Each steam safety valve shall bear the ASME symbol to indicate that it complies with the requirements of the ASME Code in regard to construction, testing and rating, and shall be plainly and permanently marked by the manufacturer in such a way that the marking will be readable when the valve is installed and will not be obliterated in service.
1010.3.1 Marking data. The marking shall include the following information:
1. The manufacturer’s name;
2. The type and catalog number;
3. The pressure at which it is set to open; and
4. The capacity in pounds of steam per hour as certified by the National Board.
1010.4 Valve capacity. The steam safety valve capacity for each steam boiler shall be such that with the fuel burning equipment installed and operating at maximum capacity, the pressure cannot rise more than 5 psi (34 kPa) above the maximum allowable working pressure of the boiler.
1010.5 Non-compliant valves. When a safety valve no longer meets the provisions of Sections 1010.1 through 1010.4, such as when there is no stamping on a valve or it is not legible, or when a safety valve does not function properly, a new safety valve or valves as required in Section 1010 shall be installed.
1010.6 Installation. It shall be the responsibility of the contractor making the installation or changes to a system to provide and install the necessary safety valves, as required by this Chapter and/or recommended by the manufacturer.
1010.7 Accumulation test. In case of dispute over the safety valve capacity or when, in the judgment of the code official or insurance company inspector, it is considered necessary to test the capacity of the safety valves, an accumulation test shall be conducted by the contractor, owner or operator in the presence of the code official or insurance company inspector.
1010.7.1 Test procedure. The accumulation test shall be conducted by closing off all other discharge outlets from the boiler and operating the fuel burning equipment at maximum capacity. The safety valves shall be sufficient to prevent the pressure from rising more than 5 psi (34 kPa) above the maximum allowable working pressure of the boiler. Provision shall be made for piping the steam discharge from the boiler room during the test.
1010.8 Minimum capacity. The minimum required capacity of the safety valve or valves, in pounds of steam per hour, shall be determined as follows:
1. For steel or cast iron boilers, multiply the area of heating surface in square feet, if available, by 5 or use the maximum rating output of the boiler as specified by the manufacturer, whichever is greater.
2. If the fuel burning equipment installed will produce a greater output than the minimum obtained in Item 1 of Section 1010.8, the minimum capacity of the safety valve or valves shall be based on the maximum output obtainable. In any event the requirements of Section 1010.4 shall be met.
1010.9 Safety valves connection. Safety valves shall be connected to boilers, with the spindle in a vertical position, in any one of the following ways:
1. Directly to a tapped or flanged opening in the boiler;
2. To a fitting connected to the boiler by a close nipple;
3. To a Y-base;
4. To a valveless steam pipe between the adjacent boilers; or
5. To a valveless header connecting steam outlets on the same boiler.
1010.9.1 Y-base connection. When a Y-base is used pursuant to Item 3 of Section 1010.9 above, the inlet area shall not be less than the combined outlet areas.
1010.9.2 Clearance. There shall be sufficient clearance above and around safety valves so that they can be removed and replaced without dismantling. The identification plate shall be located so as to be readable.
1010.10 Shut-off prohibition. No shut-off or connection of any description shall be placed between a safety valve and the boiler, nor on the valve discharge pipe between such valve and the atmosphere. A safety valve shall not be connected to an internal pipe in the boiler. Tubing or galvanized pipe shall not be used between the valve and boiler.
1010.11 Discharge pipe. A discharge pipe shall not be used on safety valves on low pressure equipment, except where a boiler is located in a restricted space or where the discharge from the valve might constitute a hazard to persons or to equipment. A discharge pipe shall be designed to accommodate the opening of a single valve or the aggregate area of all valves, based on the nominal diameter of the discharge openings of the valves with which it connects. The cross section of the discharge pipe shall be equal to the area of all of the safety valves discharging into it.
1010.11.1 Discharge pipe installation. The discharge pipe shall be fitted with an open 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 discharge pipe, it shall be located close to the valve outlet and 45° turns shall be used. The discharge pipe shall be braced and supported so that no weight or strain is placed on the valve body. The discharge shall be arranged so there will be no danger of scalding attendants. A safety valve shall not be installed so as to discharge inside the casing of a self-contained boiler.
1010.11.2 Discharge pipe location. The safety valve or valves of each high-pressure boiler shall be provided with a full size discharge pipe leading to a safe point of discharge, which shall be above the roof of the building where it is located, or of any adjoining building to which it could constitute a hazard or nuisance. Visible, non-valved drains shall be provided to receive the discharge from the valve discharge piping.
1010.11.3 Discharge pipes not required. Boilers of 25 horsepower (18.6 kW) or less shall not be required to have safety valve discharge pipes if the discharge from the safety valve will not constitute a hazard.
1010.12 Connection of two or more boilers. When two or more boilers with different allowable working pressures are connected to a common steam main, safety valves shall be allowed to be set at a pressure exceeding the lowest allowable pressure, provided that the boilers with allowable working pressures below the safety valves’ set pressure shall be protected by a safety valve or valves placed on the connecting pipe to the steam main.
1010.12.1 Connecting pipe. The area or combined area of the safety valve or valves placed on the connecting pipe to the steam main, as provided for in Section 1010.12, shall not be less than the area of the connecting pipe or the area of the steam main, whichever is smaller. Each safety valve placed on the connecting pipe shall be set at the lowest allowable pressure of any of the connected boilers.