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Guideline

CONSTRUCTION CODE FOR PRESSURE VESSELS

Notification No.196 of the Ministry of Health, Labour and Welfare
April 30, 2003

In Japanese


Part 1. Construction Code for First Class Pressure Vessels

Chapter 2. Construction

Section 1. General


Article 9. Allowable Range of Thickness
1. The thickness of piping shall be not less than the required minimum value.
2. The thickness of any part, other than piping, of the pressure vessel shall be not less than the result of deducting 0.25 mm or 6% of the nominal thickness, whichever smaller, from the required minimum thickness.


Section 2. Shells


Article 10. Thickness of Plates
The thickness of plates used for the shell and other pressure parts of the pressure vessel shall be as specified below for each type of the plates:
(1) Not less than 2.5 mm for carbon and low alloy steel plates
(2) Not less than 1.5 mm for high alloy steel and nonferrous metal plates if they are not expected to corrode, and not less than 2.5 mm if corrosion is expected to occur

Article 11. Corrosion Allowances
The corrosion allowance for plates used for the shell and other pressure parts of the pressure vessel shall be not less than 1 mm unless such plates are made of the material which is not expected to corrode (not including carbon steel or low alloy steel).

Article 12. Minimum Thickness of Plates for Cylindrical Shells or Spherical Shells Subject to Internal Pressure
The minimum thickness of plates for the cylindrical shells or spherical shells which are subject to exposure to internal pressure shall be the summation of the followings:
(a) the thickness in which the stress generated in the said plate when it is subject to exposure to the maximum allowable working pressure becomes equal to the allowable tensile stress of the plate;
(b) the corrosion allowance.

Article 13. Minimum Thickness of Plates for Cylindrical Shells or Spherical Shells Subject to External Pressure
1. The minimum thickness of plates for the cylindrical shells which are subject to exposure to external pressure shall be the summation of the followings:
(a) the thickness in which the stress generated in the said plate when it is subject to exposure to three times as high pressure as maximum allowable working pressure becomes equal to the stress that causes buckling to the plate;
(b) the corrosion allowance.
2. The preceding paragraph shall apply to the minimum thickness of plates for the spherical shells which are subject to exposure to external pressure. In that case the phrase "three times" in the paragraph shall be replaced with the phrase "four times".

Article 14. Minimum Thickness of Plates for Conical Shells Subject to Internal Pressure
1. The Article 12 applies to the minimum thickness of plates for conical shells which are subject to exposure to internal pressure.
2. When connecting conical and cylindrical shells, such measures shall be used that ensure that the joints have necessary strength for safety.

Article 15. Minimum Thickness of Plates for Conical Shells Subject to External Pressure
The paragraph 1 of the Article 13 applies to the minimum thickness of plates for conical shells subject to exposure to external pressure.

Article 16. Strength of Tubes
1. The Article 12 applies to the minimum thickness of those tubes which are subject to exposure to internal pressure.
2. The paragraph 1 of the Article 13 applies to the minimum thickness of those tubes which are subject to exposure to external pressure.
3. The bent radius of U-tubes measured at their center line shall be such value that does not cause any excessive stress concentration.
4. Notwithstanding the provisions in the paragraph 1, the minimum thickness of threaded ends, if any, of tubes subject to exposure to internal pressure shall be the sum of the minimum thickness determined under the said paragraph plus the height of threads. For those tubes which are subject to exposure to external pressure, the minimum thickness of threaded ends, if any, of tubes, notwithstanding the provisions in the paragraph 2,shall be the sum of the minimum thickness determined under the said paragraph plus the height of threads.


Section 3. Head Plates, Cover Plates, Flat Plates and Tube Plates


Article 17. Limitation in Thickness of Head Plates
The thickness of head plates (other than those in full hemispherical shape) shall be not less than the minimum thickness of shell plates.

Article 18. Requirements for Shapes of Head Plate
The head plates shall be of the shape that does not cause any excessive stress concentration.

Article 19. Minimum Thickness of Unstayed Head Plates Subject to Pressure on Concave Side
The Article 12 applies to the minimum thickness of those unstayed spherical head plates which are subject to exposure to pressure on their concave side.

Article 20. 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 33, 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 21. Minimum Thickness of Conical Head Plates etc. Subject to Internal Pressure
1. The Article 12 applies to the minimum thickness of those conical head plates which are subject to exposure to internal pressure and to the minimum thickness of the head portion of those dished cover plates with bolted flanges which are subject to exposure to pressure on their concave side.
2. When the conical head plates are attached to the shell, the attaching shall be made by suitable measures to ensure that the attached parts have necessary strength for safety.

Article 22. Minimum Thickness of Unstayed Head Plates Subject to Pressure on Convex Side
The minimum thickness of unstayed spherical head plates (excluding those made of cast iron) which are subject to exposure to pressure on their convex side shall be the greater of:
(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;
(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;
(b) the corrosion allowance.

Article 23. Minimum Thickness of Cast Iron Head Plates Subject to Pressure on Convex Side
The minimum thickness of those unstayed spherical cast iron head plates which are subject to exposure to pressure on their convex side shall be equal to their respective minimum thicknesses calculated on the assumption that their concave side is subject to exposure to pressure, or to 1/100 of the inside diameter of their flange, whichever greater.

Article 24. Minimum Thickness of Conical Head Plates Subject to External Pressure
The paragraph 1 of the Article 13 applies to the minimum thickness of those conical head plates which are subject to exposure to external pressure.

Article 25. Minimum Thickness of Unstayed Flat Plates etc.
1. The Article 12 applies to the minimum thickness of unstayed flat plates, such as flat head plates, flat cover plates and flat bottom plates, and of a jacket closure that is welded to the shell (referred to as "jacket closure" in the following paragraph).
2. The shape of the jacket closure shall be such that does not cause any excessive stress concentration in the jacket closure.

Article 26. Minimum Thickness of Flat Tube Plates etc. without Tube-Stays
1. The minimum thickness of the flat tube plates of heat exchangers and other similar equipment which are not supported by stay-tubes, and of those flat tube plates which function as a flat cover plate shall be the greater of the following values:
(1) the summation of the followings:
(a) such thickness as the stress that is generated in the flat tube plate when it is subject to exposure to the maximum allowable working pressure becomes equal to the allowable bending stress of the flat tube plate; and
(b) the corrosion allowance.
(2) the summation of the followings:
(a) such thickness as the stress that is generated in the flat tube plate when it is subject to exposure to the maximum allowable working pressure becomes equal to the allowable shearing stress of the flat tube plate; and
(b) the corrosion allowance.

Article 27. Expansion Joints
1. If the stresses generated in the shell and tubing of a heat exchanger with both fixed tube plates, depending on their relative elongations, are greater than their respective allowable stresses, the shell shall be fitted with an expansion joint.
2. The expansion joint shall be verified that it has necessary fatigue strength for safety.


Section 4. Stays and Stayed Plates


Article 28. Minimum Sectional Area etc. of Stays
1. The sectional area of stays 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 cross section by 1.1.
2. Notwithstanding the stipulation in the preceding paragraph, the sectional area of welded stays shall be not less than the value that is calculated by dividing by 0.6 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 cross section by 1.1.
3. When stays are attached, suitable measures shall be taken to ensure that the attaching parts have necessary strength for safety.

Article 29. Thickness of Stayed Plates and Pitch of Stays
1. The thickness of a stayed plate shall be not less than 8 mm except when it is supported by bar stays welded to it.
2. The pitch of the bar stays referred to in the proviso of the preceding paragraph shall be such that does not cause any excessive stress concentration in the attached part.

Article 30. Minimum Thickness of Stayed Flat Plates etc.
The Article 12 applies to the minimum thickness of stayed flat plates and of those stayed flat tube plates for heat exchangers or other similar equipment.


Section 5. Openings and Reinforcement Thereof


Article 31. Openings of First Class Pressure Vessels
First Class pressure vessels shall have, in their shells or head plates, for cleaning and inspection, a manhole large enough to provide an access to the inside, a cleaning hole large enough to remove scale or other sediment, and a inspection hole large enough to carry out inspection. However, this provision does not apply to any of the First Class pressure vessels having an alternative hole due to their structures.

Article 32. Peep Holes
1. Glazed peep holes may be provided in the shells or head plates of those First Class pressure vessels of which interior conditions have to be watched during operation.
2. The glass plate used for such peep holes is required to come up to the standards in JIS R3206 (Tempered Glass) or to have mechanical properties at least equal to such standards.
3. The minimum thickness of the glass plate specified in the preceding paragraph shall be determined by:

Where
t = minimum thickness of the glass plate (mm);
P = maximum allowable working pressure (MPa) of the shell, head plate, etc. in which a peep hole is provided;
A = area of the part of the glass plate (cm2) subject to exposure to pressure; and
σb = allowable bending stress (N/mm2) of the glass plate, i.e. 15 (N/mm2) for tempered glass and 1/10 of the bending strength for other types of glass.

Article 33. Reinforcement of Openings
All openings in shells, head plates, etc. shall be reinforced with stiffeners having sufficient strength. However, this provision does not apply to openings that are in no danger of causing excessive stress concentration around them.


Section 6. Tubes, Nozzle Stubs and Flanges


Article 34. Screwing-in of Tubes, Nozzle Stubs, etc.
1. Tubes or nozzle stubs exceeding 90 mm in outside diameter shall not be screwed into shells or head plates with a maximum allowable working pressure of more than 1MPa. However, this does not apply to threaded plug closures for inspection access holes or any other similar fittings.
2. Tubes exceeding 115 mm in outside diameter shall not be screwed into any of the First Class pressure vessels in which flammable vapours may be generated.

Article 35. Requirements for Attaching of Tubes, Nozzle Stubs, etc.
1.When tubes, nozzle stubs, etc. are to be attached to shell, head plates, tube plates, etc., the attaching shall be made by suitable measures to ensure that the attached parts have necessary strength for safety.
2. If tubes or other similar components are attached to the shells, tube plates, etc. of those First Class pressure vessels in which flammable or toxic vapours may be generated, seal welding shall be provided.

Article 36. Flanges
1. Flanges for pressure vessel shells shall meet the standards in JIS B2220 (Steel Pipe Flanges), JIS B2238(General rules for steel pipe flanges ), JIS B2239(General Rules for Cast Iron Pipe Flanges)or JIS B2240 (General Rules for Copper Alloy Pipe Flanges), or shall have the equivalent or superior mechanical properties, depending on their types. However, these flanges shall not be used under pressure higher than the nominal pressure level specified in JIS B2238, JIS B2239, and JIS B2240.
2. If the product of the outside diameter (mm) of the shell to be fitted with a flange multiplied by its maximum allowable working pressure (MPa) is greater than 500, the shell flange shall be provided with a hub.
3. Flanges, other than those for shells, shall meet the standards in JIS B2220 (Steel Pipe Flanges), JIS B2238(General rules for steel pipe flanges), JIS B2239(General Rules for Cast Iron Pipe Flanges)or JIS B2240 (General Rules for Copper Alloy Pipe Flanges), or shall have the equivalent or superior mechanical properties.

Article 37. Minimum Thickness of Flanges for Dished Cover Plates
The Article 12 applies to the minimum thickness of flanges to be attached with bolts to those dished cover plates which are subject to exposure to pressure on their concave side.

Article 38. Bolts for Cover Plates
1. Bolts for those cover plates which may be removed frequently for operating purposes shall have necessary strength for safety.
INDEX
1-1 / 1-2 / 1-3 / 1-4 / 1-5 / 2
Supplementary Provisions


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