Rules & Regulations of the State of Tennessee, Chapter 0800-03-03, Section 0800-03-03-.11 - EXISTING HEATING BOILERS | Rules & Regulations of the State of Tennessee

(1) Standard Boilers. The maximum allowable working pressure of standard boilers shall in no case exceed the pressure indicated by the manufacturer's identification stamped or cast on the boiler or on a plate secured on it.

(2) Nonstandard Riveted Boilers. The maximum allowable working pressure on the shell of a nonstandard riveted heating boiler shall be determined in accordance with Rule 0800-03-03-.10(3) except that in no case shall the maximum allowable working pressure of a steam heating boiler exceed 15 psig, or a hot water boiler exceed 160 psig or 250°F.

(3) Nonstandard Welded Boiler. The maximum allowable working pressure of a nonstandard steel or wrought iron heating boiler of welded construction shall not exceed 15 psig for steam. For other than steam service, the maximum allowable working pressure shall be calculated in accordance with ASME Code, Section IV but in no case shall it exceed 30 psig.

(4) Nonstandard Cast Iron Boilers.

(a) A maximum allowable working pressure of a nonstandard boiler composed principally of cast iron shall not exceed 15 psig for steam service or 30 psig for hot water service.

(b) The maximum allowable working pressure of a nonstandard boiler having cast iron shell or heads and steel or wrought iron tubes shall not exceed 15 psig for steam service or 30 psig for hot water service.

(5) Safety Valves.

(a) Each steam boiler shall have one (1) or more ASME/NB stamped 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 valves 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 of 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 installation. For valves exceeding two and one half (21/2) inches pipe size, the drain holes or holes shall be tapped not less than three eighths (3/8) inch pipe size. For valves less than two and one half (21/2) inches, the drain hole shall not be less than one fourth (1/4) inch in diameter.

(b) No safety valve for a steam heating boiler shall be smaller than one half (1/2) inch unless the boiler and radiating surface consist of a self-contained unit. No safety valve shall be larger than four and one half (41/2) inches. The inlet opening shall have an inside diameter equal to, or greater than, the seat diameter.

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

(d) 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 one thousand (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 Table 2. 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 subparagraph (e) of this rule shall be met.

Table 2

Minimum Pounds of Steam Per Hour

Per 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

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 hand-fired boilers above.

2. The minimum safety valve or safety relief valve relieving capacity for electric boilers shall be three and one half (31/2) pounds per hour per kilowatt input.

3. For heating surface determination, see ASME Code, Section IV, Paragraph HG-403.

(e) 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 psig above the maximum allowable working pressure.

(f) When operating conditions are changed, or when additional boiler heating surface is installed, the valve capacity shall be increased (if necessary) to meet the new conditions and comply with this paragraph. When additional valves are required, they may be installed on the outlet piping, provided there is no intervening valve.

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

(h) No valve of any description shall be placed between the safety valve and the boiler , and on the discharge pipe between the safety valve and the atmosphere. The discharge pipe shall be at least full-size, and shall be fitted with an open drain to prevent water lodging in the upper part of the safety valve and 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; and the discharge pipe shall be securely anchored and supported. All safety valve discharges shall be so located and piped as not to endanger persons in the area.

(6) Safety Relief Valve Requirements for Hot Water Boilers.

(a) Each hot water heating boiler shall have at least one (1) ASME/NB stamped 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 (1) ASME/NB stamped 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/NB stamped as to capacity, shall have pop action when tested by steam. When more than one (1) safety relief valve is used on either hot water heating or hot water supply boilers, the additional valve or valves shall be ASME/NB rated, and may be set within a range not to exceed 6 psig above the maximum allowable working pressure of the boiler up to and including 60 psig, and five percent (5%) for those having a maximum allowable working pressure exceeding 60 psig. 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 subparagraph.

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

(c) No safety relief valve shall be smaller than three fourths (3/4) inch nor larger than four and one half (41/2) inches 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 one half (1/2) inch standard pipe. 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 one fourth (1/4) inch in diameter or its equivalent area.

(d) 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 one thousand (1,000) or shall be determined on the basis of pounds of steam generated per hour per square foot of boiler heating surface as given in Table 2. 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 subparagraph (f) of this rule shall be met.

(e) When operating conditions are changed, or when 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 Table 2 and subparagraph (f) of this rule. The additional valves required, on account of changed conditions, may be installed on the outlet piping provided there is no intervening valve.

(f) The safety relief valve capacity for each boiler shall be such that, with the fuel burning equipment installed and operating at maximum capacity, the pressure cannot rise more than 5 psig above the maximum allowable working pressure for steam heating boilers, and ten percent (10%) above maximum allowable working pressures for hot water boilers.

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

(h) No valve of any description shall be placed between the safety relief valve and the boiler, and on the discharge pipe between the safety relief valve and the atmosphere. The discharge pipe shall be at least full-size, and shall be fitted with an open drain to prevent water lodging in the upper part of the safety relief valve or in the discharge pipe. When an elbow is placed on the safety relief valve discharge pipe, it shall be located close to the safety relief valve outlet; and the discharge pipe shall be properly supported. All safety relief valve discharges shall be so located and piped as not to endanger persons in the area.

(7) Steam Gauges.

(a) Each steam boiler shall have a steam gauge connected to its steam space, its water column, or its steam connection, by means of a siphon or equivalent device exterior to the boiler. The siphon (or equivalent device) shall be a sufficient capacity to keep the gauge tube filled with water and shall be so arranged that the gauge cannot be shut off from the boiler except by a cock with tee or lever handle placed in the pipe near the gauge. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.

(b) The scale on the dial of a steam gauge shall be graduated to not less than 30 psig - nor more than 60 psig. The gauge shall be provided with effective stops for the indicating pointer at the zero (0) point and at the maximum pressure point. The travel of the pointer from zero (0) to 30 psig pressure shall be at least three (3) inches.

(8) Pressure or Altitude Gauge and Thermometers.

(a) Each hot water heating or hot water supply boiler shall have a pressure or altitude gauge connected to it or to its flow connection in such a manner that it cannot be shut off from the boiler except by a cock with tee or lever handle, placed on the pipe near the gauge. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.

(b) The scale on the dial of the pressure or altitude gauge shall be graduated approximately to not less than one and one half (11/2) nor more than three and one half (31/2) times the pressure at which the safety relief valve is set. See NBIC Part 1, Section 3.8.2.1.

(c) Piping or tubing for pressure or altitude gauge connections shall be of nonferrous metal when smaller than one (1) inch pipe size.

(d) Each hot water boiler shall have a thermometer so located and connected that it will be easily readable when observing the water pressure or altitude gauge. The thermometer shall be so located that it will at all times indicate the temperature in degrees Fahrenheit of the water in the boiler at or near the outlet.

(9) Water Gauge Glasses.

(a) Each steam boiler shall have one (1) or more water gauge glasses attached to the water column or boiler by means of valved fittings. The lower fitting shall be provided with a drain valve of the straightaway type, with opening not less than one fourth (1/4) inch diameter to facilitate cleaning. Gauge glass replacement shall be possible while the boiler is under pressure.

(b) Transparent material, other than glass, may be used for the water gauge, provided that the material has proven suitable for the pressure temperature and corrosive conditions encountered in service.

(10) Stop Valves and Check Valves.

(a) If a boiler may be closed off from the heating system by closing a steam stop valve, there shall be a check valve in the condensate return line between the boiler and the system.

(b) If any part of a heating system may be closed off from the remainder of the system by closing a steam stop valve, there shall be a check valve in the condensate return pipe from the part of the system.

(11) Feedwater Connections.

(a) Feedwater, make-up water, or water treatment shall be introduced into a boiler through the return piping system or through an independent feedwater connection which does not discharge against parts of the boiler exposed to direct radiant heat from the fire. Feedwater, make-up water, or water treatment shall not be introduced through openings or connections provided for inspection or cleaning, safety valve, safety relief valve, surface blowoff, water column water gauge glass, pressure gauge or temperature gauge.

(b) The feedwater pipe shall be provided with a check valve near the boiler and a stop valve or cock between the check valve and the boiler or return pipe system.

(12) Return Pump. Each boiler equipped with a condensate return pump shall be provided with a water level control arranged to automatically maintain the water level in the boiler within the range of the gauge glass.

(13) Repairs and Renewals of Fittings and Appliances. Whenever fittings or appliances are repaired or replaced, the work shall comply with the rules governing new installations.

Rules & Regulations of the State of TennesseeTitle 0800 - Labor and Workforce DevelopmentSubtitle 0800-03 - Boilers, Elevators, Amusement Devices, and other Related RulesChapter 0800-03-03 - Boiler InspectionsSection 0800-03-03-.11 - EXISTING HEATING BOILERS

Rules & Regulations of the State of Tennessee
Title 0800 - Labor and Workforce Development
Subtitle 0800-03 - Boilers, Elevators, Amusement Devices, and other Related Rules
Chapter 0800-03-03 - Boiler Inspections
Section 0800-03-03-.11 - EXISTING HEATING BOILERS