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CONSTRUCTION CODE FOR PRESSURE VESSELS
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CONSTRUCTION CODE FOR PRESSURE VESSELS
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The welding of the any parts of First Class pressure vessels that are subject to pressure shall be in accordance with the provisions in this section unless such parts are free of any stress other than compressive one. Article 40. Welding Method 1. Welding shall be made in such a way that the weld zones have necessary strength for safety. 2. Welding of any parts which are liable to significant bending stress shall be avoided. Article 41. Holes in Weld zones 1. No hole may be made in any weld zone (including the adjacent areas within 6 mm from the edges of the welded metal). However, this does not apply to those weld zones that have passed radiographic examination. 2. The radiographic examination referred to in the exceptive clause of the preceding paragraph shall cover an area extending over at least 1.5 times the diameter of the hole from the center of such hole in both ways. Article 42. Efficiency of Welded Joints 1. The allowable tensile stress of weld zones shall be the value that is obtained multiplying the figures calculated using the Article 3 or the Article 4 by the efficiency of the welded joint. 2. The efficiency of any welded joint in the preceding paragraph shall be equal to the appropriate one of the values specified in the right column of the following table for different types of welded joints listed in the left column thereof:
Article 43. Post Weld Heat Treatment 1. Post weld heat treatment shall be carried out for any weld zones in carbon steels and alloy steels. However, this does not apply to weld zones that do not need post weld heat treatment such as seal welding or weld zones of austenitic stainless steels. 2. Notwithstanding the provisions in the preceding paragraph, preheating or some other available method may be used instead of post weld heat treatment to reduce the stress of weld zones in any of the large First Class pressure vessels which are to be field-welded at their installation sites and for which it is difficult to perform post weld heat treatment. 3. The post weld heat treatment shall be performed in furnace satisfying the requirements in JIS Z 3700 (Methods of Post Weld Heat Treatment Procedures) or standards that can be recognized as equivalent (hereinafter referred to as "the JIS etc." in this article). However, for such weld zones as circumferential joints in shells, tubes, etc. for which a local heating method is considered to be possible, the post weld heat treatment may be done by a local heating method. In both cases (in-furnace and local heating), the holding temperature and holding time prescribed in the JIS etc. may be reduced only if the performance of post weld heat treatment at the specified holding temperature and time is hardly feasible or otherwise unsuitable because of such factors as the need for site welding, the materials used or structural restraints. 4. In the case where use of a special material and/or a special structure or some other factors make it difficult or unsuitable to perform post weld heat treatment by either of the methods specified in the preceding paragraph, such treatment may be made by the method prescribed elsewhere by the Director-General of the Prefectural Labour Bureau. Article 44. Requirements for Weld Zones All weld zones shall have sufficient penetration and shall be free of such defects as cracks, undercuts, overlaps, craters, slag inclusion, blowholes, etc. that are harmful. Article 45. Mechanical Tests for Weld Zones Weld zones shall be found acceptable by the mechanical tests specified in the Articles 47 through 53 herein on test plates prepared in accordance with one of the followings: (1) For the welding of a longitudinal joint of a shell, one test plate shall be prepared for the whole shell and welded to the end of the shell in the same sequence of weld as for the longitudinal joint with the weld line of the former aligned with the latter. However, if longitudinal joints in different sections of a shell are not welded under the same conditions, one test plate shall be prepared for each section of the shell. (2) For the welding of a circumferential joint etc. of a shell (except when the test plate specified in the preceding item is welded under the same conditions as the circumferential joints etc. of the shell and is subjected to the mechanical tests prescribed in Articles 47 through 53 herein), one test plate shall be prepared for the whole shell separately from the shell and the likes and be welded under the same conditions as the circumferential joint etc. immediately after the latter is welded. Article 46. Test Plates 1. Test plates shall be made of a material coming under the same classification in the same JIS standards or any standards recognized as equivalent and in the same thickness as the base metal of the weld assembly, and care shall be taken to preclude any warping of the test plates due to the effects of welding. 2. Any test plate, if warped by welding, shall be straightened before it is given post weld heat treatment. 3. Test plates shall receive the same post weld heat treatment as the weld zones of the pressure vessel proper. Article 47. Mechanical Tests and Test Pieces The type of mechanical tests applicable to test plates and the number of test pieces needed for each of such tests shall be as specified in the following table, depending on the thickness range of the test plates:
2. Test pieces for the mechanical tests shall be prepared in accordance with the prescription in the Appendix 11 of JIS B 8265 (Construction of pressure vessel -- General principles) or any standards recognized as equivalent. Article 48. Tensile Test 1. The method of tensile tests and the shape and dimensions of test pieces for such tests shall be in accordance with JIS Z3121 (Method of Tensile Test for Butt Welded Joints) or any standards recognized as equivalent. 2. Notwithstanding the provision in the preceding paragraph, any test piece which is too thick to be subjected to a tensile test may be cut by a thin saw into slices of proper thickness for the test purposes, and then a tensile test may be conducted on each of such slices. In this instance, all slices of the test piece shall meet the requirement of the said test. Article 49. Acceptance Criteria for Tensile Test Results 1. In a tensile test, the test piece shall be deemed acceptable if its tensile strength is found to be not less than the appropriate one of the values given below, depending on the type of base metal: (1) For 9% nickel steels, aluminum and aluminum alloys, copper and copper alloys, and titanium and titanium alloys, not including those which may be used under conditions beyond their allowable tensile stress - 4 times the allowable tensile stress of the base metal; (2) For base metals other than those mentioned in the preceding item - specified minimum tensile strength of the base metal. 2. Those test pieces which break at any part of their base metals during the tensile test referred to in the preceding paragraph may be considered acceptable if their tensile strength is found to be not less than 95% of the appropriate one of the values specified in the two items of the preceding paragraph and if their weld zones are found to be free of any defect. 3. In the case where a test piece is rejected in the tensile test mentioned in the paragraph 1 of this Article because of any defect in the base metal of the test piece, such test may be deemed not valid. Article 50. Bend Test 1. The shape and dimensions of test pieces for a face bend, root bend, side bend and longitudinal bend test, and the methods and jigs thereof, shall be in accordance with the prescription in JIS Z 3122 (Methods of Bend Test for Butt Welded Joint) or any standards recognized as equivalent. 2. The paragraph 2 of the Article 48 applies to the bend test Article 51. Acceptance Criteria for Bend Test Results In any of the bend tests, the test piece shall be deemed acceptable if no crack exceeding 3 mm in length (not including minute cracks at corners of the test piece edges) appears on the outside of its weld. Article 52. Impact Test 1. Impact tests shall be conducted separately on the heat-affected zone and weld of the test plate in accordance with the specifications in JIS Z 2242 (Method of Impact Test for Metallic Materials) or any standards recognized as equivalent. The applicable test temperature shall be not higher than the minimum working temperature for the First Class pressure vessel covered by the test. 2. The shape and dimensions of impact test pieces shall be the V-notch test specimen prescribed in JIS Z 2202 (Test Pieces for Impact Test for Metallic Materials) or any specimen that is prescribed in standards recognized as equivalent to the said JIS standard, and such test pieces shall be prepared in accordance with the Appendix 11 of JIS B 8265 (Construction of pressure vessel -- General principles) or any standards recognized as equivalent. Article 53. Acceptance Criteria for Impact Test As for the acceptance criteria for the impact test, the prescription in JIS B 8265 (Construction of pressure vessel -- General principles) or in standards recognized as equivalent shall apply. Article 54. Eligibility Requirements for Retests As for the conditions of conducting retests for test pieces rejected in mechanical tests specified in the Article 49 or the article 51, or by the provision in the preceding Article, the prescription in JIS B 8265 (Construction of pressure vessel -- General principles) or in standards recognized as equivalent shall apply. Article 55. Test Pieces and Acceptance Criteria for Retests 1.Any retest for a tensile test or a bend test shall be conducted on two new test pieces prepared for each of the test pieces rejected in either of these tests, from the test plate which had been the base metal of the rejected test pieces or from another which was made at the same time as the said test plate, and the new test pieces shall be deemed acceptable if both of them are found by the tensile or bend retest to come up to the acceptance criteria in Article 49 or 51, whichever applicable. 2. As for the acceptance criteria for the retest of an impact test, the prescription in JIS B 8265 (Construction of pressure vessel -- General principles) or in standards recognized as equivalent shall apply. 3. If the test plate is not large enough to make the additional test pieces under any of the preceding two paragraphs, a new test plate may be prepared by the same welder who made the older test plate from which the rejected test pieces were taken, and under the same conditions as those under which such older test plate was prepared. Article 56. Radiographic Examination 1. Any of the welded joints specified in the following items shall be subject to radiographic examination over its full length, and the results of such examination shall meet the requirements set forth in the applicable items of Article 58 (referred to simply as the "applicable requirements" in the following paragraph and in the paragraph 2 of the Article 62). However, this does not apply to those parts of any welded joint on which it is difficult to conduct radiographic examination. (1) Welded joints in shells, head plates or other similar pressure vessel components which are made of carbon steel plates exceeding 38 mm in thickness (2) Welded joints in shells, head plates or other similar pressure vessel components which are made of low alloy steel or austenitic stainless steel plates exceeding 25 mm in thickness (3) Welded joints in shells, head plates or other similar pressure vessel components which are made of high alloy steel plates (not including austenitic stainless steel plates) and which are designated by the Director-General of the Prefectural Labour Bureau (4) Welded joints in those First Class pressure vessels which are required to have an airtight construction to contain harmful substances, specifically radioactive or lethal materials (5) Welded joints in those First Class pressure vessels which are made of any of the steels whose allowable tensile stress is determined under the item 2 of the paragraph 1 of the Article 3. (6) Welded joints in those First Class pressure vessels which are subject to a pneumatic pressure test 2. Any longitudinal joint, circumferential joint, etc., other than the welded joints specified in each item of the preceding paragraph, shall be subject to radiographic examination for its portion corresponding to 20% of its total length (including an intersection, if any, of a longitudinal and circumferential joint; in case that the length corresponding to 20% of its total length is less than 300 mm, the length to be examined shall be 300 mm), and the results of such examination shall meet the applicable requirements. However, this does not apply to those welded joints which are recognized by the Director-General of the Prefectural Labour Bureau to require no radiographic examination or which are subject to exposure only to external pressure. 3. Notwithstanding the provisions in the preceding two paragraphs, radiographic examination may be omitted for any circumferential joint in a shell whose longitudinal joints have been found by radiographic examination to meet the applicable requirements, provided that such circumferential joint has been welded by the same boiler welder and by the same method that were employed in welding the longitudinal joints. Article 57. Height of Reinforcement of Weld 1. The reinforcement of weld for any of those joints which are subject to radiographic examination shall be such that does not interfere with the said examination. 2. Radiographic examination of single-butt-welded joints using a backing may be conducted with the backing retained in place unless it interferes with such examination. Article 58. Methods and Acceptance Criteria for Radiographic Examination The method and results of radiographic examination shall meet one of the requirements in the followings, depending on the type of base metal: (1) Steel (excluding stainless steel) -The examination shall be conducted in accordance with JIS Z3104 (Methods of Radiographic Examination for Welded Joints in Steel), and the defects of the Grade 1 through the Grade 4 shall be the Class 1 or the Class 2 of the classification by the image on radiograph specified in the said JIS standard, or the examination shall be conducted in accordance with other method that is recognized as equivalent to the said standard and the equivalent results shall be obtained. (2) Stainless steel - The examination shall be conducted in accordance with JIS Z3106 (Methods of Radiographic Examination for Welded Joints in Stainless Steel), and the defects of the Grade 1 through the Grade 4 shall be the Class 1 or the Class 2 of the classification by the image on radiograph specified in the said standard, or the examination shall be conducted in accordance with other method that is recognized as equivalent to the said standard and the equivalent results shall be obtained. (3) Aluminum and aluminum alloys -The examination shall be conducted in accordance with JIS Z3105 (Methods of Radiographic Examination for Welded Joints in Aluminum), and the number and length of the defects shall be the Class 1 or the Class 2 of the classification by the image on radiograph specified in the said standard and there shall be no crack, copper inclusion, or the examination shall be conducted in accordance with other method that is recognized as equivalent to the said standard and the equivalent results shall be obtained. (4) Titanium and titanium alloys -The examination shall be conducted in accordance with JIS Z3107 (Methods of Radiographic Examination for Titanium Welds by X-ray), and the level of the defects shall be the Class 1 or the Class 2 of the classification by the image on radiograph specified in the said standard and there shall be no crack, copper inclusion, inadequate penetration or inadequate fusion, or the examination shall be conducted in accordance with other method that is recognized as equivalent to the said standard and the equivalent results shall be obtained. Article 59. Ultrasonic Examination 1. An ultrasonic flaw detection test shall be conducted on those of the welded joints (other than weld zones not exceeding 10 mm in thickness or those in austenitic stainless steel or in 9% nickel steel) specified in each item of the paragraph 1 of the Article 56 on which it is difficult to conduct radiographic examination, and the results of such test shall satisfy the requirements set forth in the following paragraph. 2. An ultrasonic flaw detection test on any of such welded joints shall be conducted in accordance with JIS Z 3060 (Method of Ultrasonic Examination for Welds of Ferritic Steel), and the defect classification of the welded joint based on the ranges of flaw echo height and indicated flaw length shall be the Class1 or the Class 2 of the classification specified in the said JIS standard, or the examination shall be conducted in accordance with other method that is recognized as equivalent to the said standard and the equivalent results shall be obtained. Article 60. Magnetic Particle Examination 1. The welded joints specified in the item 5 of the paragraph 1 of the Article 56 and the weld zones for openings in, and for attaching reinforcements or some other fittings to, those First Class pressure vessels which are required to have an airtight construction to contain harmful substances, specifically radioactive or lethal materials, (referred to simply as the "welded joints" in the rest of this paragraph and in the paragraph 1 of the Article 61 below) shall be subject to magnetic particle examination over their whole length, and the results of such examination shall meet the requirements set forth in the following paragraph. However, this does not apply where the welded joints are nonmagnetic or where it is otherwise difficult to perform magnetic particle examination on the said joints. 2. Magnetic particle examination of any of such welded joints shall be conducted in accordance with JIS G 0565 (Methods for Magnetic Particle Testing of Ferromagnetic Materials and Classification of Magnetic Particle Indication), or standards recognized as equivalent. 3. The acceptance criteria for magnetic particle examination shall be in accordance with JIS B 8270 (Pressure vessels--General standard) or standards recognized as equivalent. Article 61. Liquid Penetrant Examination 1. Welded joints covered by the proviso in the paragraph 1 of the Article 60 shall be subject to liquid penetrant examination over its whole length, and the results of such examination shall meet the requirements set forth in the paragraph 3 of this Article. 2. Liquid penetrant examination of such welded joints shall be conducted in accordance with JIS Z 2343 (Non-destructive Testing -- Penetrant Testing -- Part 1: General Principles -- Method for Liquid Penetrant Testing and Classification of the Penetrant Indication), or standards recognized as equivalent. 3. The acceptance criteria for liquid penetrant examination shall be in accordance with JIS B 8270 (Pressure vessels--General standard) or standards recognized as equivalent. Article 62. Retests for Nondestructive Tests If the results of any radiographic examination fail to meet the applicable requirements, the welded joint examined shall be subject to repairs and a retest in accordance with the appropriate one of the following items, depending on the type of such joint: (1) In the case of any of the welded joints specified in each item of the paragraph 1 of the Article 56, its defective part or parts that are the cause of its failure to meet the applicable requirements shall, after being completely removed and rewelded, be subjected to another radiographic examination, the results of which shall satisfy the requirements. The provision in the paragraph 3 of the Article 58 does not apply to the said reexamination. (2) In the case of any of the welded joints specified in the paragraph 2 of the Article 56, any two parts thereof (referred to simply as the "two parts" in the rest of this paragraph) shall be subject to radiographic reexamination as prescribed in (a) or (b) below. However, such reexamination may be replaced by the radiographic examination under the paragraph 1 of the Article 56. (a) If the two parts are found by reexamination to meet the applicable requirements, the defective portion of the welded joint that was the cause of its failure to satisfy the requirements in the first radiographic examination shall, after being completely removed and rewelded, be subjected to another radiographic examination, the results of which shall meet the said requirements. (b) In any instance other than the one set forth in the (a) above, radiographic examination covering the whole length of the welded joint shall be conducted. After completely removing the defective portion of the welded joint that was the cause of its failure to meet the requirements, rewelding shall be performed. Another radiographic examination shall be conducted for the rewelded portion, and the results shall satisfy the said requirements. 2. If the results of ultrasonic, magnetic particle or liquid penetrant examination fail to meet the requirements specified in the paragraph 2 of the Article 59, the paragraph 3 of the Article 60 or the paragraph 3 of the Article 61 respectively, the defective part of the welded joint causing such failure shall, after being completely removed and rewelded, be subjected to appropriate reexamination, the results of which shall satisfy the applicable requirements. Section 2. Hydraulic Test 1. First Class pressure vessels shall be examined by a hydraulic test at the appropriate one of the pressure levels specified in the following items for their types to prove that there is nothing abnormal with them: (1) For First Class pressure vessels made of steel or a nonferrous metal - 1.5 times the maximum allowable working pressure as temperature-corrected under the paragraph 5 of this Article; (2) For cast iron First Class pressure vessels with the maximum allowable working pressure not exceeding 0.1 MPa - 0.2 MPa (3) For cast iron First Class pressure vessels with the maximum allowable working pressure exceeding 0.1 MPa - two times the maximum allowable working pressure; or (4) Enameled or glass-lined First Class pressure vessels - appropriate one of the pressure levels specified in the item 1 through the item 3 of this paragraph when these vessels are tested before they are enameled or glass-lined, or the maximum allowable working pressure if they are tested after going through such coating process. 2. For those First Class pressure vessels which are to be plated, a hydraulic test may be conducted on them after their plating is finished. 3. Large First Class pressure vessels and some others which are structurally unfit to fill up with water shall be examined by a pneumatic test, as a replacement for a hydraulic test, to prove that there is nothing abnormal with them. The pressure level applicable to such test shall be 1.25 times the maximum allowable working pressure as temperature-corrected under Paragraph 5 of this Article. 4. The pneumatic test referred to in the preceding paragraph shall be performed with the pressure level first raised to 50% of the maximum allowable working pressure, then increased to the specified test pressure gradually by 10% of the maximum allowable working pressure at a time and finally lowered to the maximum allowable working pressure, at which the pressure vessel shall be checked to see if there is anything wrong with it. 5. The temperature correction of pressure for a hydraulic or pneumatic test shall be made by the following equation:
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