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Requirements for Offshore Welded Pipe


Offshore welded pipes should meet the requirements of the main body of the specification "Steel Line Pipe for Gas and Liquid Pipelines for Offshore Applications" in addition to this additional requirements for Offshore Welded Pipe.

1.0 Manufacturing Process Requirements

General

  • The Supplier should submit a documented procedure to demonstrate that centerline segregation is not present.
  • Metallographic tests should be performed on cross sections of the weld line to demonstrate that the weld seam has been normalized. These cross sections should be taken from the beginning of the production and then at least once per operating shift, or whenever there is a change in grade, wall thickness, diameter, an interruption in production or the normalizing temperature drops below the set point as stated in the manufacturing procedure specification.

Requirements for Submerged Arc Welded (SAW) Pipe

  • A manufacturing procedure qualification is required either at the start of production or on a trial run made prior to the start of production. A minimum of four joints, consisting of at least one from each welding line, should be subjected to all of the mechanical tests, chemistry requirements, and nondestructive examinations in this Specification. Results of the qualification tests should meet all of the requirements of this Specification.

Requirements for Electric Welded (EW) Pipe

  • For electric welded pipe, the full thickness of the weld seam should be normalized at the upper critical temperature of the steel. This temperature should be listed in the manufacturing plan.
  • Center slit coil is not permitted unless the Supplier can demonstrate with specifications to their coil vendor and qualification data that there are controls in place to prevent centerline segregation. These documents should have specific, auditable inspection requirements.
  • A qualification test is required on one joint from each of the first four coils (this may require testing more than four joints if more than one weld line is used).  Each joint should be subjected to all of the mechanical tests, chemistry requirements, and nondestructive examinations in this Specification. Results of the qualification tests should meet all of the requirements of this Specification.
  • The edges of the coil should be milled or planed. Shearing is not permissible.
  • An automatically controlled welding process should be used. Welding temperature, current or heat input should be continuously monitored and recorded. A record of this information should be available for review during production and until the order is shipped. The record should be available for Buyer inspection.
  • A device should be used to assure that the weld seam heat treating and NDE systems are constantly tracking the weld seam both at the welding stations following the weld and in the final UT inspection. This system should be approved by Buyer. The heat treatment temperature should be continuously monitored and recorded. The record should be available for review by the Buyer inspector during production and until the order is shipped.
  • Alternate ways of assuring adequate heat treatment (full body normalizing) and seam inspection may be proposed but must be approved in writing by Buyer.

2.0 Chemical Properties and Tests 

The product chemical composition should meet the following requirements:

ELEMENT

SAW

EW

Carbon (C)

0.05-0.10%

0.05-0.10%

Manganese (Mn)

Per API 5L 3.1 *

Per API 5L 3.1 *

Silicon (Si)

0.35% max.

0.35% max.

Sulfur (S)

0.003% max.

0.003% max.

Phosphorus (P)

0.012% max.

0.012% max.

Nickel (Ni)

0.20% max.

0.20% max.

Chromium (Cr)

0.20% max.

0.20% max.

Molybdenum (Mo)

0.20% max.

0.20% max.

Copper (Cu)

0.35% max.

0.35% max.

Aluminum (Al)

0.05% max.

0.05% max.

Calcium (Ca)

2X Sulfur min. / 0.006% max.

2X Sulfur min. / 0.006% max.

Nitrogen (N)

0.012 max.

0.012 max.

Niobium (Nb)

0.08% max.

0.08% max.

Titanium (Ti)

0.025% max.

0.025% max.

Vanadium (V)

0.08% max.

0.08% max.

Nb + Ti + V

0.12% max.

0.12% max.

Carbon Equivalent (IIW)

0.38% max.

0.38% max.

* The maximum allowable Manganese content is that listed in Table 3.1 of API 5L Table 2B.  Manganese content increases based on carbon content are not permitted.

If the purchase order Data Sheet states that the pipe will be induction bent, the Supplier should ensure the appropriate base metal and welding consumable compositions are chosen to achieve the specified mechanical properties after bending.

3.0 Mechanical Properties and Tests

The mechanical properties should meet the requirements of API 5L, PSL 2.

For submerged arc welded pipe, Charpy impact tests should be performed on the weld metal and the heat affected zone. The Supplier should submit a procedure as part of the information requested in paragraph 4.1.1 for removing and notching the specimens.

For electric welded pipe, Charpy impact tests should be performed on the weld fusion line. The Supplier should submit a procedure as part of the information requested in paragraph 4.1.1 for removing and notching the specimens.

4.0 Nondestructive Inspection

General

A lamination check should be made over the whole circumference on each end of each pipe for a distance of one-inch (25 mm) from the end using a calibrated compression wave ultrasonic procedure approved by Buyer. The calibration should be done at the same frequency as the body inspection NDE units.

Additional Requirements for Submerged Arc Welded Pipe

  • Nondestructive testing for final acceptance should be performed on the SAW weld seam after hydrotest and cold expansion per the requirements of API 5L, paragraphs 9.7.2 and 9.7.2.1, except as noted herein.
  • A radiological inspection using the X-ray method for a minimum distance of eight inches from each pipe end is required in accordance with API 5L, paragraph 9.7.3.1 through 9.7.3.12.
  • A full length ultrasonic inspection of each pipe is also required per API 5L, paragraph 9.7.4.1 through 9.7.4.4.
  • The NDT reference standard for ultrasonic testing should be per API 5L, paragraph 9.7.4.2, except that it should contain OD and ID longitudinal and transverse notches and a 1/8-inch drilled hole. Unless otherwise specified, N10 notches are required for the reference standard.

Additional Requirements for Electric Welded Pipe

  • Nondestructive inspection for final acceptance should be performed on the EW weld line after hydrotest per the requirements of API 5L, SR 17, except as noted herein.
  • For pipe wall thickness less than or equal to 0.188 inches, either the ultrasonic NDT method or the electromagnetic NDT method (utilizing the diverted flux) should be used. For pipe wall thickness greater than 0.188 inches, the only acceptable method is the ultrasonic method.
  • The NDT reference standard should contain both OD and ID longitudinal notches and a drilled hole. Unless otherwise specified, N10 notches and a 1/8-inch diameter hole are required for the reference standard.

5.0 Workmanship, Visual Examination, and Repair of Defects

Repairs to welded pipe should be in strict accordance with API Specification 5L with the following additional requirements:

  • Repair welding is not permitted outside the weld zone.
  • Multiple repairs of the same location are not permitted.
  • Repaired areas should be nondestructively inspected by radiography onto suitable film or by manual ultrasonic inspection.
  • Repair welding procedures should be qualified according to Appendix B of API Specification 5L.
  • Repair welding procedure qualifications should include hardness traverses on a metallographic cross section of the weld at 2-3 mm below the cap pass and at 1-2 mm above the root.  Each traverse should include readings at a maximum of 1 mm intervals in the base metal, HAZ, and weld metal (at least three readings in each zone) on both sides of the weld.  No values should exceed 250 HV10.  The composition of the deposited weld metal should not exceed 1% Ni for all repair welds.

6.0 Pipe Marking

Pipe number should be traceable back to coil or plate.



Tags: Offshore Pipelines Welded