Power Boilers

PURPOSE: This rule is to address the design, construction, installation, and operation of power boilers. (1) As used in this rule, the term “these rules” is intended to mean 11 CSR 40-2.010 through 11 CSR 40-2.065. (2) Power Boilers Installed or Contracted for, Prior to November 12, 1986. (A) The service life of any boiler of standard construction shall be unlimited provided it meets the inspection requirements of (B) The service life of any nonstandard boiler shall be thirty (30) years. The thirty (30)-year life may be extended with the chief inspector’s approval and compliance with the following requirements: 1. The operating pressure cannot exceed the maximum allowable working pressure (MAWP). The boiler MAWP shall be calculated in accordance with American Society of Mechanical Engineers (ASME) Section I Code or the requirements of the original Code of construction. Boilers manufactured to a standard other than the ASME Code shall be evaluated in accordance with the “state special” requirements of 11 CSR 40-2.064. The allowable stress shall be no greater than twentytwo percent (22%) of the tensile strength of the material. If the tensile strength is unknown, an allowable stress of twelve thousand pounds per square inch (12,000 psi) shall be used. The joint efficiency shall be in accordance with the appropriate edition and addenda of the ASME Section I Code or the National Board Inspection Code (NBIC); 2. Biennial pressure test shall be performed at or above normal operating pressure, not to exceed the MAWP of the boiler. The pressure test shall be held for at least thirty (30) minutes and documented to the satisfaction of the inspector. The inspector need not witness the test. If the boiler exhibits any leaks, the boiler shall be repaired prior to restoring it to service; 3. All safety devices and controls required by the ASME Section I Code and these rules shall be installed and operable. (3) Power Boilers Installed or Contracted for After November 12, 1986. (A) New and second hand boilers shall be designed, fabricated, and installed in accordance with the ASME Section I Code and these rules. (B) Reinstalled boilers may be of standard or nonstandard construction and shall be installed in accordance with the requirements of the ASME Code and these rules. Approval of the chief inspector shall be obtained prior to reinstalling a nonstandard boiler. (4) Boiler external piping (BEP) shall be designed, fabricated, and installed in accordance with the ASME Section I and B31.1 Codes. The piping is considered part of the boiler unit and need not be separately tagged and inspected. (A) Installations made, or contracted for, after November 12, 1986, shall meet the requirements of ASME Section I, and B31.1 Codes and these rules for boiler external piping except as follows: 1. BEP assembled by bolting, threading, or other mechanical means need not be installed by an ASME certificate holder provided all of the following apply: A. The MAWP of the boiler does not exceed one hundred fifty (150) psi; and B. The maximum pipe size does not exceed two inches (2") nominal pipe size (NPS); and C. The maximum operating temperature does not exceed four hundred degrees Fahrenheit (400 °F); and D. The piping is schedule 80 or greater SA-53 or SA-106 material; and E. All valves, flanges, and fittings are American National Standards Institute (ANSI) class 150 or greater; and F. All welding, including attachments and seal welds are by an ASME certificate holder; and G. The completed installation is tested in accordance with the American Society of Mechanical Engineers Code Section I. (B) Installations made prior to November 12, 1986, may remain in service provided the installation is acceptable to the inspector. (5) General Requirements for Power Boilers. (A) Boilers with heat input less than 12,500,000 British thermal units per hour (Btu/hr) contracted after January 1, 2004, shall meet the requirements of ASME CSD-1. Fuel gas piping for these boilers shall comply with the requirements of National Fire Protection Association (NFPA) 54. Oil burning equipment shall comply with the requirements of NFPA 31. Single unit boilers with heat input greater than or equal to 12,500,000 Btu/hr, boilers with pulverized fuel systems, and waste heat boilers shall meet the requirements of NFPA 85. All controls required by NFPA 85 for automatically fired boilers shall be installed in accordance with the installation requirements of ASME CSD-1. Existing installations are exempt from these rules except that any modification or replacements to the controls after January 1, 2004, shall meet the requirements for new installations. Boilers installed on or after January 1, 2010, must be in accordance with the National Board Inspection Code, Part 1, and these rules. (B) A pressure-reducing valve is required in the fluid supply to a boiler when the fluid supply pressure exceeds the maximum allowable working pressure of the boiler. All devices shall operate so as to protect the lowest pressure rated object from an over pressure condition. (C) Blowoff/blowdown equipment shall meet the requirements of the National Board Rules and Recommendations for the Design and Construction of Boiler Blowoff Systems. Blowoff tanks shall be constructed to the ASME Section VIII, Division 1 Code. (D) All safety and safety relief valve outlets shall be piped to a safe discharge. There shall be no valves on the outlet piping or between the boiler and the safety or safety relief valve inlet. The end of all discharge piping shall be visible to the operator when piped into a drain. Drains on safety or safety relief valve bodies shall remain open at all times. Safety or safety relief valve inlets and outlets shall not be reduced. Weighted-lever safety valves are prohibited. Safety valves with either the seat or disk of cast iron are prohibited. The minimum valve capacity shall be in accordance with ASME Section I Code. Alternatively, the capacity shall be determined based on the burner output rating or by multiplying the heating surface in square feet by the applicable value in the following table. Minimum Pounds of Steam per Hour per Square Foot of Heating Surface Fire Tube Water Tube Boiler Boiler Boiler Hand fired 5 6 Stoker fired 7 9 Oil, gas, pulverized fuel fired 8 10 Waterwall Hand fired 8 8 Stoker fired 10 12 Oil, gas, pulverized fuel fired 14 16 When a boiler is fired only by a gas having a heat value not in excess of two hundred British thermal units per cubic foot (200 Btu/cu. ft.), the minimum safety or safety relief valve capacity may be based on the value given for hand fired boilers. The minimum safety or safety relief valve capacity for electric boilers shall be 3.5 pounds per hour per kilowatt input. (E) Each boiler shall be safely supported. There shall be no excessive vibration in either the boiler or the connecting piping. (F) All existing boilers shall have adequate clearance on all sides and top to facilitate repair, maintenance, and inspection. Boilers installed or reinstalled on or after January 1, 2010, shall meet the following requirements: 1. There shall be at least thirty-six inches (36") of clearance on each side of the boiler. Boilers in battery shall not be installed any closer than forty-eight inches (48"). The front and rear of the boiler shall not be located nearer than thirty-six inches (36") from any wall or structure; 2. Boilers shall be installed to allow for removal and installation of tubes; 3. Boilers with top-opening manholes shall have at least eighty-four inches (84") of unobstructed clearance above the manhole to the ceiling of the boiler room; 4. Boilers without top-opening manholes shall have at least thirty-six inches (36") clearance from the top of the boiler; and 5. Boilers with bottom openings used for inspection or maintenance shall have at least twelve inches (12") of unobstructed clearance. 6. Note: Alternatively, clearances in accordance with the manufacturer’s recommendations are subject to the approval of the chief inspector. (G) All rooms containing boilers and/or water heaters with a combined capacity over one (1) million Btu/hr and over five hundred (500) square feet floor area shall have at least two (2) exits remotely located from each other. (H) Ladders and runways shall be provided between or over the top of boilers installed or reinstalled on or after January 1, 2010, that are more than eight feet (8') above the operating floor to afford accessibility for normal operation, maintenance, and inspection. These ladders and runways must be built and installed in accordance with the National Board Inspection Code, Part 1. (I) Combustion air—The boiler room shall have an adequate air supply to permit clean, safe combustion, minimize soot formation, and maintain a minimum of nineteen and onehalf percent (19.5%) oxygen in the air of the boiler room. The combustion and ventilation air shall be supplied by an unobstructed opening or by power ventilation or fans. 1. Unobstructed air openings shall be sized on the basis of one (1) sq. in. (6.50 sq. mm) free area per two thousand British thermal units per hour (2,000 Btu/hr) (five hundred eightysix watts per hour (586 W/hr)) maximum fuel input of the combined burners located in the boiler room or as specified in the National Fire Protection Association (NFPA) standards for oil and gas burning installations for the particular job conditions. The boiler room air supply openings shall be kept clear at all times. 2. Power ventilators or fans shall be sized on the basis of 0.2 cfm (.0057 cubic meters per minute) for each one thousand British thermal units per hour (1,000 Btu/hr) (two hundred ninety-three watts per hour (293 W/hr)) of maximum fuel input for the combination burners of all boilers located in the boiler room. Additional capacity shall be required for any other fuel burning equipment in the boiler room. 3. When power ventilators or fans are used to supply combustion air, they shall be installed with interlock devices so that the burners will not operate without an adequate number of ventilators/fans in operation. 4. When combustion air is supplied to the boiler by an independent duct, with or without the employment of power ventilators or fans, the duct shall be sized and installed in accordance with the manufacturer’s recommendations. However, ventilation of the boiler room must still be considered. 5. Care should be taken to ensure that steam and water lines are not routed across combustion air openings, where freezing may occur. 6. Opening boiler room door(s) and/or window(s) is unacceptable for supplying combustion air. (J) Controls— 1. Oil-fired, gas-fired, and electrically heated boilers shall be equipped with suitable primary (flame safeguard) safety controls, limit switches, and burners or electric elements that are labeled and listed by a nationally or internationally recognized standard. 2. All controls and devices shall be installed in accordance with the manufacturer’s recommendations, and/or industry standards, as applicable. 3. All automatically fired boilers shall have a disconnecting means capable of being locked in the open position and shall be installed at an accessible location in the same room as the object. This disconnect means shall disconnect all sources of potential from the object. 4. A manually operated remote shutdown switch or circuit breaker shall be located just outside the entrance door of the room the object is located in and be marked for easy identification. Consideration should be given to the type and location of the switch to safeguard against tampering. If the entrance door is on the building exterior, the switch should be located just inside the door. If there is more than one (1) door to the room, there should be a switch located at each door. The emergency switch must be installed in accordance with the manufacturer’s instructions or a nationally recognized standard and must cause a safety shutdown and lockout. (K) Code nameplates shall remain readily accessible at all times. Loose or missing nameplates shall be replaced or reattached as provided for in the NBIC. (L) Rental boilers used for temporary service shall meet all of the requirements of these rules. AUTHORITY: section 650.215, RSMo 2000.* Original rule filed May 12, 1986, effective Oct. 27, 1986. Amended: Filed Dec. 1, 1987, effective Feb. 11, 1988. Amended: Filed Sept. 27, 1990, effective Feb. 14, 1991. Amended: Filed Oct. 3, 1995, effective April 30, 1996. Rescinded: Filed March 10, 2003, effective Aug. 30, 2003. Readopted: Filed Sept. 25, 2002, effective May 30, 2003. Amended: Filed Jan. 12, 2006, effective June 30, 2006. Amended: Filed June 30, 2009, effective Feb. 28, 2010. *Original authority: 650.215, RSMo 1984, amended 1990, 1993, 1995.