Design pressure strength shall be according to ASME B31.3 paragraph 304.7.2. Flexibility and stress intensification factor shall be documented with maximum allowed thinning of the outside wall for the actual bending radius.

A specification detailing all requirements shall be prepared. The following criteria are applicable:

- All bending shall be performed in accordance with a qualified procedure.

The bend radius may be freely chosen if all other criteria are fulfilled.

The equipment and process shall be qualified and maintained to ensure that the material properties fulfil the requirements for piping fabrication.

The limitations and/or additional testing for the different material types related to cold forming are given in table 1 below.

When solution annealing heat treatment is required, the heat treatment manufacturer shall be qualified according to Norsok M-650.

The longitudinal weld of welded pipes shall not be located in a zone ± 40° from the bend tensile axis.

Flaring may only be performed for pressure rating up to Class 150 (PN 20) when shown on the piping class data sheet.

The design code requirement to minimum wall thickness shall be fulfilled. The strength increase of cold bent pipe shall not be included in the pipe wall thickness calculations.

No welding shall be performed in the plastically deformed zone nor closer than 2 times WT, minimum 30 mm, to this zone unless properly qualified on cold formed material.

All cold forming shall be performed in accordance with a written procedure detailing:

Material

Diameter

Wall thickness

Type of forming equipment

Relevant forming parameters

Inspection and NDT of bends and flares, including acceptance criteria

Any post bending heat treatment

The following essential variables shall apply for bend qualification:

The qualification bend shall be 90°. Specimens for destructive testing shall be sampled from the area exposed to the most severe deformation. For welded pipe both the weld and base material shall be tested.

The material properties of the qualification bend shall be verified by testing after bending. All tests specified in the applicable MDS for pipe and table 1 shall be performed, except cross weld tensile testing.

Acceptance criteria shall be according to the applicable MDS with the following exception:

Elongation shall comply with ASME B31.3 paragraph 332.

Impact toughness shall satisfy Norsok M-601 table 1.

Hardness values shall comply with table 1.

The qualification bend shall be subjected to 100 % visual examination and 100 % MT or PT as applicable. For welded pipe the weld area shall be 100 % RT after bending. NDT methods and acceptance criteria shall be as for the pipe MDS.

The out-of-roundness, wall thickness and other dimensional requirement of the qualification bend shall be checked before and after bending. The requirements of the design code shall be met.

Documentation of the qualification shall be:

Record of bending method and parameters

Record of bending radius and angle

Report with results of all tests performed.

Material certificate

Qualification shall be performed for each combination of the following essential variables:

The rest ductility shall be checked as close to the outer edge as possible and shall be minimum 5 %.

The qualification flare shall be subjected to 100 % visual examination and 100% MT or PT as applicable. The acceptance criteria is no cracking.

The NDT requirements for cold forming shall be as stated below. The same NDT groups as for M-601 are used. For MT and PT the acceptance criteria shall be in accordance with ASME VIII, Div.1, Appendix 6 and 8 respectively.

*Notes:

Spot means 2 % and shall be representative.

10 % examination shall apply for the weld. Formed area in the base material shall examined to the same extent as for seamless pipe within the same NDT group. If no defects are found in the weld area in 20 bends per material, dimension, and wall thickness, the extent of examination may be reduced to 5 %.

10% shall be uniformly distributed and shall be representative for the production.

If defect indications are revealed, the NDT extent shall be increased to 100 % until the reasons for the defect indications are concluded and necessary corrections in the forming process are made.

Production testing shall be performed to demonstrate that the requirements listed above are fulfilled. The testing frequency shall be agreed with each Project and/or Company.

For welded 22 and 25 % Cr duplex SS pipes material certificates shall be checked; if the lowest reported Charpy V single value is below 100 Joule (standard specimen) impact testing shall be performed for this position after bending to verify compliance with NORSOK M-601.

Induction bending shall be performed in accordance with a written procedure detailing:

Material

Diameter

Bend radius

Wall thickness

Bending equipment

Bending speed

Bending temperature

Cooling technique

Inspection and NDT of bends, including acceptance criteria

Any post bending heat treatment

Qualification shall be performed for each combination of the following essential variables:

Specimens for destructive testing shall be sampled from the area exposed to the most severe deformation and the transition zone.

The material properties of the qualification bend shall be verified by testing after bending. The extent of testing and acceptance criteria shall be as for the applicable MDS. For bends intended for sour service the hardness requirements of NACE MR0175 shall be fulfilled.

The qualification bend shall be subjected to 100 % visual examination and 100 % MT or PT as applicable. For welded pipe the weld area shall be 100 % radiographed after bending.

The out-of-roundness and wall thickness of the qualification bend shall be checked before and after bending. The requirements of the design code shall be met.

The following NDT shall be performed on all induction bent pipe:

The NDT methods and acceptance criteria shall be in accordance with the applicable MDS.

Cold formed pipes which have undergone a new heat treatment e.g. normalising, quenched and tempering, or solution annealing shall be subject to re-certification. The new testing including lot definition, extent of testing, test location, acceptance criteria, etc. shall be in accordance with the MDS for wrought fittings.

All induction bent pipes shall be re-certified. The new testing including lot definition, extent of testing, test location, acceptance criteria, etc. shall be in accordance with the MDS for wrought fittings.

All components shall be subject to 100% dimensional check. The dimensions shall comply with Norsok Standard L-004, section 6.5.

EN 10 204 Type 3.1 B.