SECTION 65.607. Power Boilers, Excluding Unfired Steam Boilers and Process Steam Generators

(a) Safety valves and pressure relief valves.

(1) The use of weighted-lever safety valves, or safety valves having either the seat or disk of cast iron, is prohibited.

(2) Each boiler shall have at least one safety valve and, if it has more than 500 square feet (47 square meters) of bare tube water heating surface or has electric power input more than 1,100 kilowatts, it shall have two or more safety valves. These valves shall be "V" stamped per ASME Code.

(3) Safety valves or pressure relief valves shall be connected so as to stand in the upright position, with spindle vertical. The opening or connection between the boiler and the safety valve or pressure relief valve shall have at least the area of the valve inlet.

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

(5) Except for changeover valves as defined in §65.2(14), other valve(s) shall not be placed:

(A) between the required safety valve or pressure relief valve or valves and the boiler; or

(B) in the discharge pipe between the safety valve or pressure relief valve or valves and the atmosphere.

(6) When a discharge pipe is used, it shall be:

(A) at least full size of the safety valve discharge; and

(B) fitted with an open drain to prevent water lodging in the upper part of the safety valve or discharge pipe.

(7) When an elbow is placed on a safety valve discharge pipe:

(A) it shall be located close to the safety valve outlet; and

(B) the discharge pipe shall be securely anchored and supported.

(8) In the event multiple safety valves discharge into a common pipe, the discharge pipe shall be sized in accordance with ASME Code, Section I, PG-71.

(9) All safety valve or pressure relief valve discharges shall be located or piped to a safe point of discharge, clear from walkways or platforms.

(10) If a muffler is used on a pressure relief valve, it shall have sufficient area to prevent back pressure from interfering with the proper operation and discharge capacity of the valve. Mufflers shall not be used on High-Temperature Water Boilers.

(11) The safety valve capacity of each boiler must allow the safety valve or valves to discharge all the steam that can be generated by the boiler without allowing the pressure to rise more than 6.0% above the highest pressure to which any valve is set, and to no more than 6.0% above the MAWP. For forced-flow steam generators with no fixed steam and waterline, power-actuated relieving valves may be used in accordance with ASME Code, Section I, PG-67.

(12) One or more safety valves on every drum type boiler shall be set at or below the MAWP. The remaining valve(s) may be set within a range of 3.0% above the MAWP, but the range of setting of all the drum mounted pressure relief valves on a boiler shall not exceed 10% of the highest pressure to which any valve is set.

(13) When two 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 overpressure, considering the maximum generating capacity of all boilers.

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

(b) Feedwater supply.

(1) Each boiler shall have a feedwater supply, which will permit it to be fed at any time while under pressure, except for automatically fired miniature boilers that meet all of the following criteria:

(A) the boiler is "M" stamped per ASME Code, Section I;

(B) the boiler is designed to be fed manually;

(C) the boiler is provided with a means to prevent cold water from entering into a hot boiler; and

(D) the boiler is equipped with a warning sign visible to the operator not to introduce cold feedwater into a hot boiler.

(2) A boiler having more than 500 square feet (47 square meters) of water heating surface, shall have at least two means of feeding, one of which should be a pump, injector, or inspirator. A source of feed directly from water mains at a pressure of at least 6.0% greater than the set pressure of the safety valve with the highest setting may be considered as one of the means of feeding. Boilers fired by gaseous, liquid, or solid fuel in suspension may be equipped with a single means of feeding water, provided means are furnished for the immediate shutoff of heat input if the feedwater is interrupted.

(3) Feedwater shall not be discharged close to riveted joints of shell or furnace sheets or directly against surfaces exposed to products of combustion or to direct radiation from the fire.

(4) Feedwater piping to the boiler shall be provided with a check valve near the boiler and a stop valve or cock between the check valve and the boiler. When two or more boilers are fed from a common source, there shall also be a stop valve on the branch to each boiler between the check valve and the source of supply. Whenever a globe valve is used on the feedwater piping, the inlet shall be under the disk of the valve.

(5) In all cases where returns are fed back to the boiler by gravity, there shall be a check valve and stop valve in each return line, the stop valve to be placed between boiler and the check valve, and both shall be located as close to the boiler as is practicable. Best practice is that no stop valve be placed in the supply and return pipe connections of a single boiler installation.

(6) Where deaerating heaters are not used, best practice is that the temperature of the feedwater be not less than 120 degrees Fahrenheit (49 degrees Celsius), to avoid the possibility of setting up localized stress. Where deaerating heaters are used, best practice is for the minimum feedwater temperature be not less than 215 degrees Fahrenheit (102 degrees Celsius), so that dissolved gases may be thoroughly released.

(c) Water level indicators.

(1) Each boiler, except forced-flow steam generators with no fixed steam and waterline, and high-temperature water boilers of the forced circulation type that have no steam and waterline shall have at least one water gage glass.

(2) Except for electric boilers of the electrode type, boilers with a MAWP over 400 psig (three (3) megapascals) shall be provided with two water gage glasses, which may be connected to a single water column or connected directly to the drum.

(3) Two independent remote level indicators may be provided instead of one of the two required gage glasses for boiler drum water level indication, when the MAWP is above 400 psig (three (3) megapascals). When both remote level indicators are in reliable operation, the remaining gage glass may be shut off, but shall be maintained in serviceable condition.

(4) In all installations where direct visual observations of the water gage glass(es) cannot be made, two remote level indicators shall be provided at operational level.

(5) The gage glass cock connections shall not be less than 1/2 inch nominal pipe size (15 mm).

(6) No outlet connections, except for damper regulator, feedwater regulator, drains, steam gages, or apparatus of such form as does not permit the escape of an appreciable amount of steam or water there from, shall be placed in the pipes connecting a water column or gage glass to a boiler.

(7) The water column shall be fitted with a drain cock or drain valve of at least 3/4 inch nominal pipe size (20 mm). The water column blowdown pipe shall not be less than 3/4 inch nominal pipe size (20 mm), and shall be piped to a safe point of discharge.

(8) Connections from the boiler to remote level indicators shall be at least 3/4 inch nominal pipe size (20 mm), to and including the isolation valve, and at least 1/2 inch (13 mm) OD tubing from the isolation valve to the remote level indicator. These connections shall be completely independent of other connections for any function other than water level indication.

(d) Low-water fuel cutoff and water feeding devices.

(1) All automatically fired steam boilers, except boilers having a constant attendant, who has no other duties while the boiler is in operation, shall be equipped with approved low-water fuel cutoffs.

(A) These devices shall be installed in such a manner that they cannot be rendered inoperative by the manipulation of any manual control or regulating apparatus.

(B) In boilers with a fixed water line, the low-water fuel cutoff devices shall be tested regularly by lowering the water level sufficiently to shut off the fuel supply to the burner when the water level reaches the lowest safe level for operation. Boilers that do not have a fixed water line shall be equipped with a flow sensing device, thermal couple or expansion ring that is listed by a nationally recognized testing agency to prevent burner operation at a flow rate inadequate to protect the boiler unit against overheating.

(C) The low-water cutoff shall be rated for a pressure and temperature equal to or greater than the MAWP and temperature of the boiler.

(D) For High-Temperature Water Boilers requiring forced flow circulation, an approved flow sensing device shall be installed on the outlet, as close to the boiler as possible.

(2) When a low-water fuel cutoff and feedwater pump control is combined in a single device, an additional separate low-water fuel cutoff shall be installed. The additional control shall be wired in series electrically with the existing low-water fuel cutoff.

(3) When a low-water fuel cutoff is housed in either the water column or a separate chamber it shall be provided with a blowdown pipe and valve not less than 3/4 inch nominal pipe size (20 mm). The arrangement shall be such that when the water column is blown down, the water level in it will be lowered sufficiently to activate the lower-water fuel cutoff device.

(4) If a water feed device is utilized, it shall be constructed to prevent feedwater from entering the boiler through the water column or separate chamber of the low-water fuel cutoff.

(e) Pressure gages.

(1) Each boiler shall have a pressure gage that is readable.

(A) The dial of the pressure gage shall be graduated to approximately double the pressure at which the safety valve is set, but in no case, less than one and one-half times this pressure.

(B) The pressure gage shall be connected to the steam space, to the water column, or its steam connection.

(C) A valve or cock shall be placed in the gage connection adjacent to the gage.

(D) An additional valve or cock may be located near the boiler providing it is locked or sealed in the open position.

(E) No other shutoff valves shall be located between the gage and the boiler.

(F) The pipe connection shall be of ample size and arranged so that it may be cleared by blowing down.

(G) For a steam boiler, the gage or connection shall contain a siphon or equivalent device which will develop and maintain a water seal that will prevent steam from entering the gage tube.

(2) Each boiler shall have a valved connection at least 1/4 inch nominal pipe size (6 mm) connected to the steam space for the exclusive purpose of attaching a test gage when the boiler is in service to test the accuracy of the pressure gage.

(f) Stop valves.

(1) Each steam outlet from a boiler (except safety valve connections) shall be fitted with a stop valve located as close as practicable to the boiler.

(2) When a stop valve is located that allows water to accumulate, ample drains shall be provided. The drain shall be piped to a safe location and shall not be discharged on the boiler or its setting.

(3) When boilers provided with manholes or other similar opening that permits access for human occupancy and that are connected to a common steam main, the steam connection from each boiler shall be fitted with two stop valves, with an ample drain between them. The discharge of the drain shall be visible to the operator while manipulating the valves and shall be piped clear of the boiler setting. Best practice is for the first valve to be an automatic nonreturn valve (set next to the boiler), and a second valve of the outside-screw-and-yoke type.

(g) Blowdown connection.

(1) The construction of the setting around each blowdown pipe shall permit free expansion and contraction. These setting openings must be sealed without restricting the movement of the blowdown piping.

(2) All blowdown piping, when exposed to furnace heat, shall be protected by firebrick or other heat-resisting material, and constructed to allow the piping to be inspected.

(3) Each boiler shall have a blowdown pipe, fitted with a valve or cock, in direct connection with the lowest water space. The piping shall be run full size without the use of a reducer or bushings and shall not be galvanized. Cocks shall be of gland or guard type and suitable for the pressure allowed. The use of globe valves shall be in accordance with ASME code.

(4) When the MAWP exceeds 100 psig (700 kilopascals), the piping shall be at least schedule 80 steel and shall not be galvanized. Each blowdown pipe shall be provided with two valves or a valve and cock, such valves and cocks shall be adequate for design conditions of the boiler.

(5) All fittings between the boiler and blowdown valve shall be of steel or extra-heavy malleable iron. In case of renewal of blowdown pipe or fittings, they shall be installed in accordance with the requirements of the applicable section of the ASME code.

(6) It is recommended that blowdown tanks be designed, constructed, and installed in accordance with National Board recommended rules for boiler blowoff equipment.

(h) Boiler external piping. All boiler external piping, as referenced in the ASME code, shall be examined for compliance to the boiler's code of construction and shall be documented in the appropriate block on the inspection report.

(i) Provisions for thermal expansion for High-Temperature Water Boilers.

(1) An airtight tank or other suitable air cushion that is consistent with the volume and capacity of the system shall be installed. Expansion tanks shall be constructed in accordance with the ASME Code, Section VIII, Division 1, and the pressure and temperature ratings of the tank shall be equal to or greater than the pressure and temperature ratings of the system pressure. A pressure relief valve shall be installed with a set pressure at or below the MAWP of the expansion tank. Alternately the boiler pressure relief valve may be used provided the expansion tank's MAWP is equal to or greater than the set pressure of the pressure relief valve.

(2) Provisions shall be made for draining the tank without emptying the system, except for pre-pressurized tanks.

(3) If the expansion tank was originally equipped with a sight glass, the sight glass and sight glass valves shall be in working condition at all times, and the water level shall be maintained as per the manufacturer's recommendations.

Source Note: The provisions of this §65.607 adopted to be effective June 15, 2015, 40 TexReg 3121; amended to be effective January 15, 2018, 43 TexReg 75; amended to be effective September 1, 2018, 43 TexReg 5361; amended to be effective July 1, 2020, 45 TexReg 4330