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CONSTRUCTION CODE FOR BOILERS
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CONSTRUCTION CODE FOR BOILERS
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Article 7. Allowable Range of Thickness 1. The wall thickness of any piping or tubing shall be not less than the required minimum value. 2. The thickness of any part, other than piping or tubing, of the boiler shall be not less than the remainder of the minimum thickness minus 0.25 mm.
1. The thickness of plates used for the shell or dome of the boiler shall be not less than 6 mm except where such plates are used for the shells or domes described in the following items, in which case their thickness shall be: (1) Not less than 8 mm when used for those shells or domes which are fitted with a stay or stays or which are larger than 900 mm but not larger than 1,350 mm in inside diameter; (2) Not less than 10 mm when used for shells or domes exceeding 1,350 mm but not exceeding 1,850 mm in inside diameter; or (3) Not less than 12 mm when used for shells or domes exceeding 1,850 mm in inside diameter. 2. The plate thickness of the shell of any water tube boiler to which water tubes are attached by expanding shall not be less than 10 mm at the contact surface that makes a perfectly annular shape. Article 9. Minimum Plate Thickness of Shells or Domes Subject to Internal Pressure The minimum thickness of plates used for shells or domes which are subject to exposure to internal pressure shall be the summation of the followings: (a) such thickness as the stress that is generated in the plate under the maximum allowable working pressure becomes equal to its allowable tensile stress; and (b) the corrosion allowance.
Article 10. Limits to Thickness of Head Plates The thickness of any head plate (other than full-hemispherical ones) shall be equal to or thicker than the minimum thickness of the shell. Article 11. Requirements for Shapes of Head Plates The shape of head plates shall not cause excessive stress concentration. Article 12. Minimum Thickness of Unstayed Head Plates 1. The Article 9 applies to the minimum thickness of unstayed head plates that are subject to exposure to pressure on their concave side which form a part of sphere. 2. The minimum thickness of unstayed head plates which are subject to exposure to pressure on their convex side and which form a part of sphere shall be the greater value of the followings: (1) the summation of the followings: (a) the value obtained by multiplying such thickness as the stress that is generated in the head plate when its concave side is subject to exposure to the maximum allowable working pressure becomes equal to the allowable tensile stress of the head plate, by 1.67; and (b) the corrosion allowance. (2) the summation of the followings: (a) such thickness as the stress that is generated in the head plate when its convex side is subject to exposure to the quadruple of the maximum allowable working pressure becomes equal to the stress that causes buckling to the head plate; and (b) the corrosion allowance. Article 13. Unreinforced Openings in Head Plates Any opening in the head plate, if it is to be left unreinforced based on the proviso in the Article 34, such measures shall be taken that does not cause any excessive stress concentration around a manhole or the knuckle part of the head plate. Article 14. Minimum Thickness of Unstayed Flat Plates etc. The Article 9 applies to the minimum thickness of: - flat plates such as flat head plates, flat cover plates, flat bottom plates, which are not supported by stays; - flat head plates of shell boilers to which flues are to be attached; and - flat head plates or flat firebox crown plates of vertical boilers.
1. The minimum thickness of tube plates for smoke tube boilers shall be the appropriate one of the values specified in the right column of the following table according to the outside diameter of such tube plates in the left column of the same table:
2. The minimum thickness of tube plates for those smoke tube boilers of which the smoke tubes are not smaller than 38 mm but not larger than 102 mm in outside diameter shall be equal to either the appropriate one of such thicknesses specified in the table under the preceding paragraph or the one determined by the following equation, whichever greater:
Article 16. Minimum Pitch of Smoke tubes The minimum pitch for the smoke tubes of smoke tube boilers shall be determined by the following equation:
Article 17. Stays for Rear Tube Plates of Externally Fired Horizontal Tubular Boilers Stays for the rear tube plate of any externally fired horizontal tubular boiler shall be selected from among bar stays, dog stays, gusset stays and some other stays which do not cause any overheat at the bottom of the boiler shell. Article 18. Minimum Thickness of Tube Plates in Combustion Chambers The minimum thickness of the tube plates for locomotive boilers and the likes, in which load on the crown plate of the combustion chamber also affects the tube plate shall be the summation of the followings: (a) such thickness as the stress that is generated in the tube plate when it is subject to exposure to the maximum allowable working pressure becomes equal to the allowable compression stress of the said tube plate; (b) the corrosion allowance.
Article 19. Plate Thickness of Flues or Fireboxes Chambers The plate thickness of those flues or fireboxes which are to be provided with flanges shall be not less than 8 mm. Article 20. Minimum Plate Thickness of Flues or Fireboxes The minimum plate thickness of plain flues, the firebox of vertical cross-tube boilers, and corrugated flues shall be the summation of the followings: (a) such thickness as the stress that is generated in the said plate when it is subject to exposure to the pressure three times as much as the maximum allowable working pressure becomes equal to the stress that causes buckling to the said plate; (b) the corrosion allowance. Article 21. Flanges of Plain Flues The radius of a knuckle part (measured on the side exposed to flames) in the flange of any plain flue shall have such value that does not cause any excessive stress concentration in the flange. Article 22. Space between Flues and Smoke tubes For flue and smoke tube boilers, the space between the outer surfaces of the flue and the adjacent smoke tube shall have such value that does not cause any overheat to the flue or smoke tube. Article 23. Minimum Plate Thickness of Stack Tubes The Article 20 applies to the minimum plate thickness of any stack tube. Article 24. Inside Diameter of Stack Tubes The inside diameter of any stack tube attached to a vertical boiler in such a way that it passes through the firebox crown plate and head plate of the said boiler shall have the value that does not cause buckling to the stack tube.
Article 25. Horizontal and Vertical Spaces between Center Lines of Stays Article 25. Horizontal and Vertical Spaces between Center Lines of Stays The horizontal and vertical spaces between center lines of stays, if stays are screwed through the plate and caulked at one or both ends, shall be such that do not cause any excessive stress concentration in the adjacent stay, when a stay is broken. Article 26. Stay Bolts etc. 1. The sectional area of stay bolts, bar stays, stay tubes, and gusset stays (referred to "stay bolts, etc." in the following paragraph) shall be not less than such an area where the stress generated in the said cross section when it is subject to exposure to the maximum allowable working pressure becomes equal to the value obtained by dividing the allowable tensile stress of the said stay bolts, etc by 1.1. 2. When stay bolts etc. are attached to the plate, the attached parts of stay bolts etc. shall be made by suitable measures to ensure necessary strength for safety. Article 27. Telltale Holes in Stay Bolts For any stay bolt not larger than 200 mm in length, a telltale hole shall be made which can warn of the damage of the stay caused by blowout of steam. However, this does not apply where there is no appreciable difference in temperature between the two plates connected each other by such stay bolt. Article 28. Construction of Girder Stays 1.The girder stay shall be constructed in such a way that scale or other sediment does not accumulate between the girder and the crown plate. 2.The girder stays shall be constructed in such a way that does not cause buckling to the crown palate. 3.The compressive force transmitted from an end of a girder stay to the crown plate shall not exert any excessive load to that crown plate. Article 29. Minimum Plate Thickness of Girder Stays The Article 9 applies to the minimum plate thickness of girder stays. Article 30. Thickness of Stayed Plate The minimum thickness of any plate supported by a stay or a set of stays shall be not less than 8 mm. Article 31. Minimum Thickness of Stayed Flat Plate etc. The Article 9 applies to the minimum thickness of stayed flat plate, and tube nest of tube plate of smoke tube boilers, or any part adjacent to the said tube nest of a flat tube plate of smoke tube boilers. Article 32. Reinforcement of Flat Plate Parts of Smoke tube Boilers When the flat plate part above the tube nest of any smoke tube boiler not exceeding 0.7MPa in maximum allowable working pressure and not larger than 900 mm in the inside diameter is reinforced with angle steels, the reinforcing measures shall ensure the necessary strength for safety.
Boilers shall be equipped in their shells or head plates with manholes which allows entry inside them, cleaning holes with the size enabling removal of scale or other sediment, and inspection holes with the size enabling inspection. However, this provision does not apply to the boilers that are deemed to have other openings which serve as a substitute for such holes by their structure. Article 34. Reinforcement of Openings in Shells, Headers, etc. Any openings in the shell, the header, dished head plate, full hemispherical head plate, semi-ellipsoidal head plate, and flat plate specifically flat head plate, flat cover plate, and flat bottom plate shall be strengthened with reinforcing members. However this provision does not apply to holes that are in no danger of causing stress concentration in their surrounding.
1. The Article 20 applies to the minimum thickness of smoke tubes. 2. The Article 9 applies to the minimum thickness of tubes that are subject to exposure to internal pressure such as water tubes, superheater tubes, and economizer tubes. 3. The Article 9 applies to the minimum thickness of feedwater pipes and blowoff pipes. In this case, "the maximum allowable working pressure" shall be replaced by "the smaller one of either the pressure obtained multiplying the maximum allowable working pressure by 1.25 or the pressure obtained adding 1.5 MPa to the maximum allowable working pressure". Article 36. Minimum Thickness Value of Smoke tubes etc. The minimum thickness value of such tubes as smoke tubes, water tubes, superheater tubes and economizer tubes, which are subject to exposure to internal pressure shall be at least equal to the appropriate one of the values specified in the right column of the following table according to the outside diameter of tubes shown in the left column thereof:
Article 37. Strength of Cylindrical Headers The Article 9 applies to the strength of cylindrical headers. Article 38. Rectangular Headers All headers rectangular in cross section shall meet the following requirements: (1) Any groove-like flaw on the inside surface of the header shall not affect safety. (2) The inside radius of each knuckle part of the rectangular cross section of the header (for a corrugated header, the radius measured before the corrugation is made) shall be such that does not cause any excessive stress concentration in the said corner part. (3) The minimum thickness of a box header shall be the summation of the followings: (a) such thickness as the stress that is generated in the box header when it is subject to exposure to the maximum allowable working pressure becomes equal to its allowable tensile stress; and (b) the corrosion allowance. Article 39. Minimum Thickness of Nozzle Stubs The Article 9 applies to the minimum thickness of nozzle stubs. However, the thickness of cast steel nozzle stubs shall not be less than 8 mm and that of cast iron nozzle stubs shall not be less than 11 mm. Article 40. Flanges 1. All flanges shall, depending on their types, meet JIS B2220 (Welded Steel Flanges), JIS B2238 (General Rules for Steel Pipe Flanges), or JIS B2239 (General Rules for Cast Iron Pipe Flanges), or have equivalent or superior mechanical properties. 2. When a flange or some other component subject to exposure to pressure is to be attached to the shell or the head plate with studs, care shall be taken to ensure that the screwed-in length will be sufficient to have necessary strength for safety. Article 41. Attaching of Tubes or Nozzle Stubs When tubes other than stay tubes or nozzle stubs are attached to the shell, head plate, tube plate, header or some other boiler component, the attaching shall be made by suitable measures to ensure that the attached parts have necessary strength for safety. |
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