Preface
This is the fifteenth edition of CSA Standard B51, Boiler, Pressure Vessel, and Pressure Piping Code. This edition incorporates a number of approved but unpublished revisions since the publication of the fourteenth edition. It supersedes all previous editions, published in 1939, 1945, 1951, 1955, 1957, 1960, 1965, 1969, 1972, 1975, 1981, 1986, 1991, and 1995.
This edition retains the content of the previous edition but has been extensively revised and reformatted all administrative requirements have been moved to Section 4 and the remaining sections contain technical requirements. Some new material has been added.
The CSA B51 Committee works closely with the ASME Boiler and Pressure Vessel Code Committees and with the National Board of Boiler and Pressure Vessel Inspectors.
It should be understood that this Code is a recommended Standard only and does not have the force of law unless adopted officially by the various jurisdictions. In keeping with CSA standard practice, the Appendices are usually considered to be nonmandatory parts of the Standard. However, the reader is advised to consult the jurisdiction as to the extent of its adoption, as the Code may have been adopted with exemptions, or additions, and may include some Appendices.
The Code is intended mainly to fulfil two purposes: first, to provide for the safe design, construction, installation, operation, inspection, testing, and repair of boilers, pressure vessels, and related equipment; and second, to promote uniform requirements among the jurisdictions.
It is also intended that the Committee shall meet periodically to review the Code, as may be found necessary, to revise it in order to meet changing conditions and to maintain uniformity throughout Canada.
This Code was prepared by the Technical Committee on Boilers and Pressure Vessels under the jurisdiction of the Standards Steering Committee on Public Safety and was formally approved by these Committees.
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B51-97, Part 1 - Boiler, Pressure Vessel, and Pressure Piping Code
Scope
1.1
Except as provided for in Clause 1.2, this Standard applies to all boilers, pressure vessels, fittings, and piping, as provided for by the Act and defined in this Standard.
Notes:
(1) In certain provinces there may be variations in size limitations quoted in this Standard. consultation with the regulatory authority is recommended.
(2) Cylinders, spheres, tubes, and drums used in transportation are subject to the Transportation of Dangerous Goods Act and Regulations under that Act; it is not intended that the provisions of this Standard conflict with or supersede the requirements of that Act or Regulations in regard to the control of these containers when used for transportation by any mode.
(3) Corresponding imperial values to the SI (metric) units are shown in parentheses for information only. Where nominal pipe sizes are shown they have been retained in nondimensional terms.
(4) All pressures shown in the text are gauge pressures, ie, above atmospheric pressure.
1.2
Requirements for compressed natural gas refuelling station pressure piping systems and containers are covered in CSA Standard B51-95, Parts 2 and 3.
1.3
This Standard does not apply to pressure-retaining components as used in hydraulic elevators.
1.4
Where any Clause of this Standard is at variance with the referenced Codes and Standards, the requirements of this Standard govern.
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B51-97, Part 2 High-Pressure Cylinders for the Onboard Storage of Natural Gas as a Fuel for Automotive Vehicles
Preface
CSA Standard B51-M1991, Appendix G, provided requirements for CNG fuel containers on vehicles. This allowed the manufacture of satisfactory, safe vessels for NGV service. However, some requirements of Appendix G were considered too prescriptive, and in some cases, design requirements were inadequately specified.
CSA Standard B51, Part 2, which replacesB51-M1991, Appendix G, is harmonized with the June 1994 edition of the ISO draft Standard TC58/SC3/WG17, High Pressure Cylinders for the On-board Storage of Natural Gas as a Fuel for Automotive Vehicles .
The emerging market for natural gas vehicles is creating a demand for large numbers of high-pressure, light-weight cylinders for the onboard storage of fuel. Weights approximating 50% of those of TC-3AA cylinders are essential for NGV service, and at the same time the level of safety currently existing for other pressure vessels must be achieved or improved upon. These needs are achieved by requiring
(a) service conditions to be specified precisely and comprehensively, as a firm basis for both cylinder design and use;
(b) a finite element/fracture mechanics analysis or the equivalent to assess cyclic pressure fatigue life and establish allowable defect sizes in metal cylinders or liners;
(c) design qualification tests;
(d) nondestructive testing and inspection of all production cylinders;
(e) destructive tests on cylinders and cylinder material taken from each batch of cylinders produced;
(f) manufacturers to have a comprehensive quality control programme, documented and implemented;
(g) periodic reinspection and, if necessary, retesting, in accordance with the manufacturer's specification; and
(h) manufacturers to specify as part of their design the safe service life of their cylinders.
The ISO draft Standard includes these requirements. Designs meeting the Standard, CSA Standard B51,
(i) will have a fatigue life that exceeds the service life specified;
(ii) when pressure-cycled to failure, will leak but not rupture; and
(iii) when subject to hydrostatic burst tests, will have factors of ``stress at burst pressure” over ``stress at working pressure” that exceed the values specified for the type of design and the materials used. The CSA B51 subcommittee responsible for the development of this Standard has consulted with the American Gas Association committee responsible for the ANSI/AGA NGV2 Standard, Basic Requirements for Compressed Natural Gas Vehicle (NGV) Fuel Containers. The two groups are committed to the development of the Standards with requirements harmonized to the greatest extent possible.
Owners or users of cylinders designed to this Standard should note that the cylinders are designed to operate safely if used in accordance with specified service conditions for a specified finite service life only. The expiry date is marked on each cylinder, and it is the responsibility of owners and users to ensure cylinders are not used after that date.
Scope
1.1
This Standard sets out minimum requirements for serially produced light-weight refillable gas cylinders, original equipment and conversions, having a water capacity exceeding 20 L (1220 in3) but not exceeding 1000 L (35.3 ft3). The cylinders are intended only for the onboard storage of high-pressure compressed natural gas as a fuel for automotive vehicles to which the cylinders are to be fixed. Cylinders may be of any steel, aluminum, or nonmetallic material, design, or method of manufacture suitable for the specified service conditions.
1.2
Cylinders covered by this Standard are designated as follows:
(a) CNG-1 — Metal;
(b) CNG-2 — Metal liner reinforced with resin-impregnated continuous filament (hoop-wrapped);
(c) CNG-3 — Metal liner reinforced with resin-impregnated continuous filament (fully wrapped); and
(d) CNG-4 — Nonmetallic liner with resin-impregnated continuous filament (all-composite).
1.3
Service conditions to which the cylinders will be subjected are detailed in Clause 4. This Standard is based upon a working pressure for natural gas as a fuel of 200 bar (2900 psi) settled at 15°C (59°F), with a maximum filling pressure of 260 bar (3770 psi). Other working pressures can be accommodated by adjusting the pressure by the appropriate factor (ratio). For example, a 250 bar working pressure system will require pressures to be multiplied by 1.25.
The service life of the cylinder is to be defined by the manufacturer and may vary with applications. Definition of service life is based upon filling the cylinders 1000 times a year. The maximum service life of types CNG-2, CNG-3, and CNG-4 cylinders shall be 20 years. For all cylinders a ``safe life” design principle is used.
For metal and metal-lined cylinders, the cylinder life is based upon the rate of fatigue crack growth. The ultrasonic inspection, or equivalent, of each cylinder or liner is required to ensure the absence of flaws that exceed the maximum allowable size determined by fracture mechanics. This approach permits the optimized design and manufacture of light-weight cylinders for natural gas vehicle service.
For all-composite cylinders with nonmetallic non-load-bearing liners, the ``safe life” is ensured by appropriate design methods, design qualification testing, and manufacturing controls.
1.4
This Standard does not cover the use of stainless steel or welded metallic cylinders or liners.
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B51-97, Part 3 Requirements for CNG Refuelling Station Pressure Piping Systems and Ground Storage Vessels
Preface
CSA Standard B51, Part 3, is a mandatory part of this Standard. The requirements included herein have been incorporated as a separate Part to provide a clear distinction between these CNG refuelling station requirements and those for general boiler, pressure vessel, and pressure piping systems, and thus facilitate their application.
Requirements for vehicle fuel tanks are in CSA Standard B51, Part 2.
Filling limits specified by Clause 4.2 of CSA Standard B51, Part 2, High-Pressure Cylinders for the Onboard Storage of Natural Gas as a Fuel for Automotive Vehicles, are the basis of the design pressures specified in this Part for refuelling stations. Thus, the compatibility of new stations and new vehicle cylinders is assured. Use of the filling limits specified is consistent with CSA's objective to harmonize CSA Standards to the greatest extent possible with standards in other countries.
CGA Standard CAN/CGA-B149.1 specifies the maximum filling pressure for natural gas vehicles in Canada as follows:
(a) up to the temperature-compensated equivalent of 200 bar (2900 psi) at 15°C (59°F); and
(b) temperature-compensated pressure shall not exceed 248.2 bar (3600 psig).
Data are available that the vehicle cylinders designed and registered in compliance with earlier editions of CSA Standard B51, Appendix G, are suitable for the filling limits now specified.
Scope
1.1
CSA Standard B51-97, Part 3, contains mandatory requirements for compressed natural gas (CNG) refuelling station pressure piping systems and ground storage vessels.
1.2
Pressure piping systems covered in this Part are those systems
(a) between the termination of the utility's piping, usually at the meter, and the inlet to the compressor assembly at a CNG refuelling station, if the design pressure exceeds 414 kPa (60 psi); and
(b) from the inlet to the compressor assembly through to the dispenser nozzle, except for the mechanical parts of the compressor and any subsystems designed for 414 kPa (60 psi) or less.
1.3
Ground storage vessels covered in this Part are pressure vessels installed at CNG refuelling stations and intended to store CNG at pressure for delivery to vehicle fuel tanks.
