Okla. Admin. Code § 380:25-5-25

Current through Vol. 42, No. 8, January 2, 2025

Section 380:25-5-25 - Safety valves/safety relief valves

(a)Steam boilers.

(1) Each steam boiler shall have one or more ASME/National Board stamped and certified safety valves of the spring pop-type, adjusted and sealed to discharge at a pressure not to exceed 15 psig. Seals shall be attached in a manner to prevent the valve from being taken apart without breaking the seal. The safety valves shall be arranged so that they cannot be reset to relieve at a higher pressure than the maximum allowable working pressure on the boiler. A body drain connection below seat level shall be provided by the manufacturer, and this drain shall not be plugged during or after field inspection. For valves exceeding 2 in. pipe size, the drain hole or holes shall be tapped not less than 3/8 in. pipe size. For valves less than 2 in., the drain hole shall not be less than 1/4 in. diameter. Every safety valve or safety relief valve shall be connected so as to stand in an upright position, with spindle vertical.

(2) No safety valve of a steam boiler shall be smaller than 1/2 in. No safety valve shall be larger than 4 1/2 in. The inlet opening shall have an inside diameter equal to, or greater than, the seat diameter.

(3) The minimum relieving capacity of the valve or valves shall be governed by the capacity marking on the boiler.

(4) The minimum valve capacity in pounds per hour shall be the greater of that determined by dividing the maximum BTU output at the boiler nozzle obtained by the firing of any fuel for which the unit is installed by 1000, or shall be determined on the basis of the pounds of steam generated per hour per square foot of boiler heating surface as given in the following table. In many cases a greater relieving capacity of valves than the minimum specified by these rules will have to be provided. In every case, the requirements of Section 380:25-5-25(a)(5) shall be met.


ALL BOILERSMINIMUM POUNDS OF STEAM PER HOURPER SQUARE FOOT OF HEATING SURFACE

	Firetube Boilers	Watertube Boilers
Boiler Heating Surface:
Hand fired	5	6
Stoker fired	7	8
Oil, gas or pulverized fuel fired	8	10
Waterwall Heating Surface:
Hand fired	8	8
Stoker fired	10	12
Oil, gas or pulverized fuel fired	14	16

Notes for Table:
1. When a boiler is fired only by a gas giving a heat value not in excess of 200 BTU per cubic foot, the minimum safety valve or safety relief valve relieving capacity may be based on the value given for handfired boilers above.
2. The minimum safety valve or safety relief valve relieving capacity for electric boilers shall be 3.5 pounds per hour per kilowatt input.
3. For heating surface determination see ASME Code Section IV.

(5) The 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 above the maximum allowable working pressure.

(6) When operating conditions are changed, or additional boiler heating surface is installed, the valve capacity shall be increased, if necessary, to meet the new conditions and be in accordance with Section 380:25-5-25(a)(5). When additional valves are required, they may be installed on the outlet piping provided there is no intervening valve.

(7) If there is any doubt as to the capacity of the safety valve, an accumulation test may be run (see ASME Code, Section VI, Recommended Rules for Care and Operation of Heating Boilers).

(8) No valve of any description shall be placed between the safety valve and the boiler, nor on the discharge pipe between the safety valve and the atmosphere. THE DISCHARGE PIPE SHALL BE AT LEAST FULL SIZE AND BE FITTED WITH AN OPEN DRAIN TO PREVENT WATER LODGING IN THE UPPER PART OF THE SAFETY VALVE OR IN THE DISCHARGE PIPE. WHEN AN ELBOW IS PLACED ON THE SAFETY VALVE DISCHARGE PIPE, IT SHALL BE LOCATED CLOSE TO THE SAFETY VALVE OUTLET, OR THE DISCHARGE PIPE SHALL BE SECURELY ANCHORED AND SUPPORTED. ALL SAFETY VALVE DISCHARGE SHALL BE SO LOCATED OR PIPED AS NOT TO ENDANGER PERSONS WORKING IN THE AREA.

(b)Hot water heating and/or hot water supply boilers.

(1) Each hot water heating and/or hot water supply boiler shall have at least one ASME/National Board stamped and certified safety relief valve set to relieve at or below the maximum allowable working pressure of the boiler. Each hot water supply boiler shall have at least one ASME/National Board stamped and certified safety relief valve of the automatic reseating type set to relieve at or below maximum allowable working pressure of the boiler. Safety relief valves ASME/National Board stamped and certified as to capacity shall have pop action when tested by steam. When more than one safety relief valve is used on either a hot water heating or hot water supply boiler, the additional valve or valves shall be ASME/National Board stamped and certified and may be set within a range not to exceed 6 psi above the maximum allowable working pressure of the boiler up to and including 60 psi, and 5 percent for those having a maximum allowable working pressure exceeding 60 psi. Safety relief valves shall be spring loaded. Safety relief valves shall be so arranged that they cannot be reset at a higher pressure than the maximum permitted by this paragraph. Every safety valve or safety relief valve shall be connected so as to stand in an upright position, with spindle vertical.

(2) No material liable to fail due to deterioration or vulcanization when subject to saturated steam temperatures corresponding to capacity test pressure shall be used for any part.

(3) No safety relief valve shall be smaller than 3/4 in. or larger than 4 1/2 in. standard pipe size, except that boilers having a heat input not greater than 15,000 BTU per hour may be equipped with a safety relief valve of 1/2 in. standard pipe size. The inlet opening shall have an inside diameter approximately equal to, or greater than, the seat diameter. In no case shall the minimum opening through any part of the valve be less than 1/4 in. diameter or its equivalent area.

(4) The required steam relieving capacity, in pounds per hour, of the pressure relieving device or devices on a boiler shall be the greater of that determined by dividing the maximum output in BTU at the boiler nozzle, obtained by the firing of any fuel for which the unit is installed by 1,000, or shall be determined on a basis of pounds of steam generated per hour per square foot of heating surface as given in 380:25-5-25. In many cases, a greater relieving capacity of valves will have to be provided than the minimum specified by these rules. In every case the requirements of Section 380:25-5-25(b)(6) shall be met.

(5) When operating conditions are changed, or additional boiler heating surface is installed, the valve capacity shall be increased, if necessary, to meet the new conditions and shall be in accordance with Section 380:25-5-25(b)(6). The additional valves required, on account of changed conditions, may be installed on the outlet piping provided there is no intervening valve.

(6) Safety relief valve capacity for each boiler shall be such that, with the fuel burning equipment installed and operated at maximum capacity, the pressure cannot rise more than 10 percent above the maximum allowable working pressure. When more than one safety relief valve is used, the over pressure shall be limited to 10 percent above the set pressure of the highest set valve allowed by Section 380:25-5-25(a)(1).

(7) If there is any doubt as to the capacity of the safety relief valve, an accumulation test may be run (See ASME Code, Section VI, Recommended Rules for Care and Operation of Heating Boilers).

(c)ASME code stamped water heaters.

(1) Each ASME Code stamped water heater which provides corrosion resistance for supplying potable water for commercial purposes at pressures not exceeding 160 psi and temperatures not in excess of 210°F shall have at least one officially rated safety relief valve or one officially rated pressure temperature relief valve.

(A)Permissible Mountings. Safety relief valves shall be connected to the top of water heaters or directly to a tapped or flanged opening in the water heater, to a fitting connected to the water heater by a short nipple, to a Y-base, or to a valveless water heater connecting water outlets on the same heater. Safety relief valves shall be installed with their spindles upright and vertical with no horizontal connecting pipe, except that, when the safety relief valve is mounted directly on the water heater vessel with no more than 4 in. maximum interconnecting piping, the valve may be installed in the horizontal position with the outlet pointed down. The center line of the safety relief valve connection shall be no lower that 4 in. from the top of the shell.

(B)Requirements for Common Connection for Two or More Valves.

(i) When a water heater if fitted with two or more safety relief valves on one connection, this connection shall have a cross-sectional area not less than the combined areas of inlet connections of all the safety relief valves with which it connects.

(ii) When a Y-base is used, the inlet area shall be not less than the combined outlet areas. When the size of the water heater requires a safety relief valve larger that 4 1/2 in. diameter, two or more valves having the required combined capacity shall be used. When two or more valves are used on a water heater, they may be single, directly attached, or mounted on a Y-base.

(C)Threaded connections. A threaded connection may be used for attaching a valve.

(D)Prohibited mountings. Safety relief valves shall not be connected to an internal pipe in the water heater or a cold water feed line connected to the water heater.

(E)Use of shutoff valves prohibited. No shutoff of any description shall be placed between the safety relief valve and the water heater, or on discharge pipes between such valves and the atmosphere.

(F)Safety relief valve discharge piping.

(i) A discharge pipe shall be installed on the outlet of a safety relief valve, and when a discharge pipe is used, its internal cross-sectional area shall be not less than the full area of the valve outlet or of the total of the valve outlets discharging thereunto, and shall be as short and straight as possible and so arranged as to avoid undue stress on the valve or valves. When an elbow is placed on a safety relief discharge pipe, it shall be located close to the valve outlet.

(ii) The discharge from safety relief valves shall be so arranged that there will be no danger of scalding attendants. When the safety relief valve discharge is piped away from the water heater to the point of discharge, there shall be provisions for properly draining the piping and valve body. The size and arrangement of discharge piping shall be such that any pressure that may exist or develop will not reduce the relieving capacity of the relieving devices below that required to protect the water heater.

(2)Water supply.

(A)Connections. Water supply shall be introduced into a water heater through an independent water supply connection. Feedwater shall not be introduced through openings or connections provided for cleaning, safety relief valves, drain, pressure gage, or temperature gage.

(B)Pressure. If the water supply pressure to a water heater exceeds 75% of the set pressure of the safety relief valve, a pressure reducing valve is required.

(C)Stop valves. A stop valve shall be placed in the water supply pipe connection of an ASME code stamped water heater installation and should be placed in the discharge connection.

(D)Bottom drain valve.

(i) Each water heater shall have a bottom drain pipe connection fitted with a valve or cock connected with the lowest water space practicable. The minimum size bottom drain valve shall be 3/4 in.

(ii) Any discharge piping connected to the bottom drain connection shall be full size to the point of discharge.

(E)Thermometer. Each installed water heater shall have a thermometer so located and connected that it shall be easily readable. The thermometer shall be so located that it shall at all times indicate the temperature in degrees Fahrenheit of the water in the hot water heater at or near the outlet.

Okla. Admin. Code § 380:25-5-25

Amended at 16 Ok Reg 3017, eff 7-12-99