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CONSTRUCTION CODE FOR BOILERS
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CONSTRUCTION CODE FOR BOILERS
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1. Steam boilers shall be equipped with at least two safety valves to ensure that its internal pressure will never exceed the maximum allowable working pressure. For those steam boilers which have a heating surface area not larger than 50 m2, however, the number of safety valves to be installed may be reduced to one. 2. Safety valves shall be attached directly to proper parts of the boiler itself which are easily accessible for inspections and care shall be taken to ensure that their spindles will be upright. 3. All safety valves, when used for steam boilers generating flammable vapours, shall be either hermetically sealed or so configured as to send exhausts from them into a safe place outside the boiler room. Article 63. Safety Valve for Superheater 1. The superheater shall be equipped with a safety valve at or near the steam outlet so as to keep the temperature of the superheater at the design temperature or lower. 2. In the case of a once-through boiler, notwithstanding the prescription in the paragraph 2 of the preceding Article, safety valves with a combined discharge capacity at least equivalent to the maximum evaporation of the boiler may be installed at or near the outlet of the superheater. Article 64. Name Plates 1. The materials and construction of lift-type safety valve having a lift not less than 1/15 of the seat bore diameter or any full-bore safety valve (referred to as "lift-type safety valve, etc." in the following paragraph) for steam boilers exceeding 0.1 MPa in maximum allowable working pressure shall be in compliance with JIS B8210 (Steam Boilers and Pressure Vessels -- Spring Loaded Safety Valves) or have equivalent or superior mechanical properties. 2. Any lift-type safety valve, etc. shall have a name plate on its conspicuous part showing the following items: (1) Name or trademark of the manufacturer; (2) Nominal diameter; (3) Set pressure (MPa ); and (4) Discharge capacity (kg/h). Article 65. Relief Valve or Safety Valve for Hot Water Boilers 1. Any hot water boiler not exceeding 120  in working water temperature shall be equipped with a relief valve that is immediately actuated whenever the pressure in the boiler reaches the maximum allowable working pressure and keeps the internal pressure not exceeding the maximum allowable working pressure. However, this provision does not apply where a water relief pipe that keeps the internal pressure not exceeding the maximum allowable working pressure is installed at the part of such boiler which is easily accessible for inspections. 2. Hot water boilers exceeding 120 in working water temperature shall be equipped with a safety valve.
Article 66. Pressure Gauges A pressure gauge shall be attached to the steam space or water column or to a steam-side connection leading to such water column of any steam boiler in accordance with the followings: (1) The direct influx of steam into the pressure gauge shall be precluded. (2) Any valve or cock shall be so designed as to clearly show whether it is open or closed. (3) The steam connection for the pressure gauge shall have such construction that is not easily clogged. (4) The highest degree of the scale on any pressure gauge shall be in a range not lower than 1.5 times but not higher than 3 times the maximum allowable working pressure of the boiler (5) The diameter of the face of a pressure gauge shall be such that ensures easy reading. Article 67. Hydraulic Pressure Gauges for Hot Water Boilers 1. Any hot water boiler shall be equipped with a hydraulic pressure gauge installed in its main part or near its hot water outlet in accordance with the followings. However, a pressure gauge may be substituted for the hydraulic pressure gauge. (1) Any valves or cocks shall be so designed that it may be easily known whether they are open or closed. (2) The highest degree of the scale on any hydraulic pressure gauge shall be able to show a water pressure not lower than 1.5 times but not higher than 3 times the maximum allowable working pressure of the boiler. Article 68. Thermometers 1. Any steam boiler shall be provided with a thermometer to indicate the steam temperature near the outlet of the superheater. 2. Any hot water boiler shall be provided with a thermometer to indicate the water temperature near its outlet.
Article 69. Glass Water Gauges 1. Any steam boiler other than the once-through boiler shall have at least two glass water gauges attached to its main part or water column. However, for the following steam boilers, one of such water gauges may be replaced by some other type of water level indicator. (1) those steam boilers with the shell not exceeding 750 mm in inside diameter (2) those steam boilers with two or more remote water level indicators. 2. Glass water gauges shall be installed in such a place that their glass tube bottoms will indicate the minimum water level to be maintained during the operation of the steam boiler (hereinafter called the "safety low water level"). 3. The glass of water gauges for steam boilers shall meet the requirements in JIS B 8211 (Boilers -- Gauge Glasses) or have equivalent or superior mechanical properties. 4. Glass water gauges shall be so constructed that they can be cleaned and inspected from time to time as necessary. Article 70. Water Columns 1. No cast iron water column may be used for any boiler exceeding 1.6 MPa maximum allowable working pressure. 2. Water columns shall have such construction that is not easily clogged. Article 71. Connections with Water Columns 1. The connection pipes linking the water column and the boiler shall have such construction that is not easily clogged, and the water-side connection and the water column shall be so constructed that their insides can be cleaned easily. 2. The water-side connection shall be free of any convex or concave bend between the two ends, and neither of its joints with the boiler and the water column may be above the lowest water level that can be known with the water gauges. 3. The steam-side connection shall be free of any part where drain may gather, and neither of its joints with the water column and the boiler may be located below the highest water level that can be known with the water gauges. 4. The provisions in the preceding three paragraphs apply correspondingly to attaching measures of the connections to the water gauges. Article 72. Gauge Cocks 1. If gauge cocks are used as a water level indicator other than the glass water gauge, at least three of such instruments shall be installed at those places which cover the same range of height as specified for the installation of the glass tube of glass water gauge. However, for those steam boilers which are not larger than 750 mm in inside diameter of the shell and are smaller than 10 m2 in area of the heating surface, the required number of gauge cocks may be reduced to two. 2. The lowest of such set of gauge cocks shall be located at the same level as the safety low water level. 3. The pipes connecting the gauge cocks and the steam boiler shall have such construction that is not easily clogged.
Article 73. Feedwater Units 1. Any steam boiler shall be provided with a feedwater unit that has a water supply capacity at least equivalent to the maximum evaporation of the boiler. 2. Notwithstanding the provisions in the preceding paragraph, any of those steam boilers in which a heat supply continues even after fuel is shut-off or which do not have the fuel shut-off at low water system specified in the paragraph 2 of the Article 84 shall be equipped with two feedwater units each of which can, independently of the other, supply water at least sufficient for the maximum evaporation rate of the boiler whenever necessary. However, if one of the feedwater units consists of a combination of two or more feedwater pumps, the water supply capacity of the other unit may be set at a level not lower than 25% of the maximum evaporation rate of the steam boiler and not lower than that of the largest pump in the said multi-pump feedwater unit. 3. The two feedwater units for any of the steam boilers in which a heat supply continues even after fuel is shut-off shall be capable of being operated by separate power systems. Article 74. Special Provisions for Two or More Steam Boilers Installed Close Together Two or more adjacent boilers connected and operated together shall be deemed a single steam boiler, and accordingly, the provisions in the preceding article apply to the said group of boilers. Article 75. Feedwater Valves and Check Valves The feed pipe from each feedwater unit shall be provided with a feedwater valve and a check valve near the steam boiler. However, for once-through boilers and those steam boilers whose maximum allowable working pressure is lower than 0.1 MPa the installation of only feedwater valves may be deemed sufficient. Article 76. Internal Feedwater Pipes The internal feedwater pipes, if used, shall be so constructed as to permit its dismantlement.
Article 77. Stop Valves 1. Steam stop valves shall be strong enough to withstand the maximum allowable working pressure and maximum steam temperature of the steam boiler to which they are attached. 2. If any of such valves is installed in a place where drain may collect, a drainage shall be provided. 3. Superheaters shall be provided with drainages. Article 78. Size and Number of Blowoff Pipes and Blowoff Valves 1. Steam boilers other than the once-through boiler shall be equipped with a blowoff pipe that can discharge scale or other sediment and that is fitted with a blowoff valve or a blowoff cock. 2. The blowoff pipe for steam boilers other than mobile boilers not lower than 1 MPa in maximum allowable working pressure shall be fitted with at least two blowoff valves or at least one each of blowoff valve and blowoff cock arranged in series. 3. Blowoff pipes for two or more steam boilers shall be installed separately for each of them. Article 79. Construction of Blowoff Valves and Blowoff Cocks 1. Blowoff valves or blowoff cocks shall be installed in a conspicuous, readily accessible place so that they can be handled easily. 2. Blowoff valves shall be so constructed as to preclude the deposit of scales or other sediments on their inside surfaces and shall have the necessary strength for safety.
Article 80. Hand-Operated Dampers The controls of hand operated dampers shall be installed in a place where they can be worked easily. Article 81. Explosion Doors 1. If the explosion door of any boiler is located within 2 m of the job site of boiler operators, the boiler shall be equipped with a device to disperse explosive gases in a safe direction. 2. An explosion door shall be provided for each pulverized coal firing equipment. Article 82. Openings Equipped to Combustion Chambers The combustion chamber of any boiler shall have a manhole large enough to provide an access to its inside for cleaning and inspections. However, this does not apply to those flue boilers of which the flues do not exceed 500 mm in diameter and which have cleaning holes both in the front and back or those boilers which are so constructed as to provide an access to the inside of their combustion chambers. Article 83. Stacks of Boilers The stacks of boilers shall be so constructed as to preclude any damage to the boilers from rain that may otherwise get in through them. However, this provision does not apply those stacks which are installed in a place where such damage could not occur.
Article 84. Automatic Feedwater Regulators etc 1. An automatic feedwater regulator shall be provided for each steam boiler. 2. Steam boilers not including once-through boilers which have automatic feedwater regulators shall be equipped with a device to automatically shut-off the fuel supply if the water level is below the specified safety low water at the start-up of the boiler or if the water level falls below such low during boiler operation (referred to as the "low water level fuel shut-off device" in the paragraph 4 of this Article and the paragraph 1 of the Article 97 herein). 3. Once-through boilers shall be provided with a device that automatically cuts off the fuel supply if the boiler is short of water at start-up or if boiler water runs short during operation, or with some other safety device which services as a substitute. 4. Notwithstanding the provision in the paragraph 2, in one of the following cases, a low water level alarm (a device that gives an alarm when the water level falls below the safety low water level) may be substituted for the low water level fuel shut-off device. (1) Emergency fuel shut-off is precluded by the properties of the fuel or the structure of the firing equipment; (2) Emergency shutdown of the boiler is inadvisable due to such factors as the specified operating conditions. Article 85. Flame Safeguard System 1. The firing equipment of any boiler shall be equipped with a device that can automatically find any combustion failure or inadvertent cut-off of air supply and can immediately shut-off the fuel supply whenever such trouble is detected (referred to as the "flame safeguard system" in the subsequent paragraphs of this Article). However, this provision does not apply to either of the instances given in one of the items in the paragraph 4 of the preceding Article. 2. The flame safeguard system shall be designed: (1) To Shut-off fuel immediately if the power supply for its actuation is cut-off; and (2) To avoid resuming fuel supply automatically during and after the stoppage of such power supply. 3. The flame safeguard system for any boiler with automatic ignition capability shall be designed to automatically shut-off the fuel supply if the boiler fails to start burning because of trouble or some other causes or if no flames are detected after ignition, and also such device shall be given the function to hold up the restart of the boiler until the restarting procedure is taken by hand. 4. The flame safeguard system shall have the function to preclude the ignition of the firing equipment if it makes false detection of flames due to the malfunction of its flame detecting mechanism or some other causes before the beginning of combustion. |
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