There is a commentary available for this Clause.
Except as allowed by Clause 126.96.36.199, the materials and design for closures shall be as specified in the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. Components fitted with a closure shall be designed to ensure that pressure cannot be trapped in any area of the component, when the closure is opened, due to the presence of internal devices or equipment. Components fitted with a quick-opening closure, such as a pig or scraper sending or receiving device, shall be equipped with suitable isolation and venting equipment. Where practical the component shall be equipped with a pressure indicating interlocking device.
1) Any pig or scraper sending or receiving device should also be equipped with a pressure-indicating device separate from the trap pressure venting connection.
2) Closures should be designed in consideration of the requirements of ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, Non-Mandatory Appendix FF.
3) For sour service, see Clause 16.4.2.
The hub material may be dual certified as an ASME/ASTM material. The grade of the ASTM material may be used when calculating the required thickness at the bevel of the weld that will join the hub to the matching pipe (see Figure 7.2).
Note: An example of the dual-certified material is ASME SA350 LF2 Class 1/ASTM A694 F48.
Orange-peel bull plugs and swages, fish tails, and flat closures shall not be allowed.
4.3.14 Pressure design for components — Elbows
Wrought steel welding elbows, factory-made bends, and transverse segments cut therefrom may be used, provided that the arc length measured along the crotch is at least 25 mm for sizes NPS 2 to NPS 3.5, and at least 50 mm for sizes NPS 4 and larger. Where applicable, allowances shall be made for the installation of liners and the passage of internal inspection tools and pipeline scrapers.
4.3.15 Pressure design for components — Tees and crosses
Steel buttwelding tees and crosses shall be acceptable for all ratios of branch pipe diameter to run pipe diameter.
4.3.16 Pressure design for components — Branch connections
Branch connections shall be made using tees and crosses, integrally reinforced extruded outlet headers, or welded connections, subject to the requirements of Clauses 4.3.17 to 4.3.20, except that mechanical fittings may be used for making hot taps on pipelines, provided that they are designed to withstand the operating pressures of the pipeline and are suitable for the purpose.
Consideration shall be given to the design of branch connections to withstand all forces and moments to which they can be subjected.
Note: The design requirements in Clauses 4.3.17 to 4.3.20 are minimum requirements for branch connections subjected to pressure; in addition, however, forces and moments are usually applied to the branch by such factors as thermal expansion and contraction, vibration, mass of pipe, components, cover, contents, and earth settlement.
CSA Z662-15 (Oil and gas pipeline systems)
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