4.5.1 Buttwelded joints
Buttwelded joints shall be as specified in Clauses 7.2 to 7.15.
Consideration shall be given to avoiding welding stresses that can result in damage to any cement- mortar lining.
Where piping containing partial-penetration welds required by design is to be installed, the stress and strain effects in the weld zone shall be considered for design, construction, and operating conditions, and appropriate measures shall be taken.
4.5.2 Threaded joints
Threaded pipe-to-pipe and pipe-to-component joints shall not be used for
a) permanently buried installations, except for auxiliary joints (such as drains, valve body bleeds, and instrument taps) directly into components;
b) pipe larger than 114.3 mm OD;
c) pipe larger than 60.3 mm OD with a maximum operating pressure greater than 3.5 MPa; or
d) piping in HVP or CO2 service, except for joints in instrument piping.
1) Threaded joints should be avoided where crevice corrosion, severe erosion, cyclic loading, bending, or unusual loading conditions can occur.
2) For limitation for sour service pipelines, see Clause 16.3.5.
4.5.3 Sleeve, coupled, mechanical interference fit, and other patented joints
Sleeve, coupled, mechanical interference fit, and other patented joints shall not be used in HVP and CO2 pipeline systems.
Sleeve, coupled, mechanical interference fit, and other patented joints may be used in LVP pipeline systems, provided that, where applicable
a) the materials are qualified as specified in Clause 5.1;
b) a sample of the type of joint to be used has been proof tested under simulated service conditions incorporating anticipated vibration, cyclic operation, low temperature, thermal expansion, and other such conditions; and
c) adequate provision is made to prevent separation of the joint as a result of longitudinal or lateral movement that would exceed the capability of the joining members.
Mechanical interference fit joints may be used in gas pipeline systems, provided that such joints are installed in a Class 1 location.
4.5.4 Additional requirements for mechanical interference fit joints
Note: For limitations for sour service pipelines, refer to Clause 16.10.2.
Mechanical interference fit joining methods shall be as specified in Clause 7.16.
Piping containing mechanical interference fit joints shall not be installed above grade.
Mechanical interference fit joining methods shall be used only on electric-welded or seamless pipe.
Note: When ordering plain-end pipe that will subsequently be subjected to plastic deformation in preparation for mechanical interference fit joining, designers should consider supplementing the pipe purchase specification with additional requirements, such as the following:
a) tighter dimensional tolerances;
b) ductility tests or increased minimum elongation requirements for tensile tests;
c) limits on the inside and outside height of the weld flash of electric-welded pipe; and
d) an upper limit on yield strength.
Designers shall take into consideration the tensile, torsional, and compressive strengths of the mechanical interference fit joint and the effect of torsional and bending loads on the joint.
Piping containing mechanical interference fit joints shall not be subjected to service conditions that can adversely affect the performance of the joint.
Mechanical interference fit joints shall not be used to join dissimilar pipe materials.
CSA Z662-15 (Oil and gas pipeline systems)
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