1. GENERAL
This specification defines
minimum quality and technical standards governing manufacturing, inspection,
testing and supply of induction bends used in offshore pipelines. This specification is to be used in
conjunction with the following documents:
· Basis of Design
84506-60-00-2L-060
· General Specification
84506-60-00-2L-000 - Definitions & Specification Directory
· General Specification
84506-60-00-2L-010 - Quality Assurance / Quality Control
· General Specification
84506-60-30-2L-210 - Seamless Linepipe
· General Specification
84506-60-30-2L-270 - Handling, Storage and Transportation of Linepipe
·
DNV Offshore Standard
OS-F101 : Submarine Pipeline Systems (2000)
2. GENERAL BENDING REQUIREMENTS
The quantity of line pipe to be
formed into bends and any additional COMPANY requirements shall be specified on
the Purchase Order.
3. MATERIALS
Induction bends manufactured
from pre-formed pipe joints shall conform to Specification Seamless
84506-60-30-2L-210.
4. MECHANICAL PROPERTIES
Mechanical properties of
induction bends formed from pipe joints, including fracture toughness, shall in
their final heat-treated condition conform to the requirements of the
applicable specification from Section 3 above.
5. INDUCTION BENDING PROCESS
Induction bends shall be
produced in accordance with manufacturing procedure specifications (MPS) that
are written in accordance with Section 7 of this specification and qualified in
accordance with Section 11 of this specification.
Induction bends shall only be
manufactured from pipe joints produced in accordance with Project
Specifications 84506-60-30-2L-210. Bends shall be formed using the incremental
induction hot bending technique over the entire bend. CONTRACTOR shall submit the following items
for COMPANY approval, prior to commencement of works.
·
Forming Procedure,
including width of heated band, bending temperature range and temperature
control methods.
·
Post-forming Heat Treatment
Procedure.
·
Quality Control Procedures
(including nondestructive testing).
5.1 CONTRACTOR submitted heat treatment procedures shall
specifically describe attachment of braces or other restraints used to prevent
bend warping. Welding such attachments
to the bend body is strictly prohibited.
Welds may be made to expendable extensions of the bend that are to be
cut off prior to finishing.
5.2 No stoppage shall be allowed during the bending process.
6. HEAT TREATMENT
Post bend heat treating shall
be applied as necessary to meet specifications.
Consideration shall be given to the manufacturing process of the pipe
(e.g., TMCP, Q&T, normalized). When
practical the pipe manufacturer should be involved in the selection of specific
pipes to be bent and in advising of post bend heat treatment conditions if
applicable.
If post bend heat treatment is
used, temperature ranges specified in approved heat treating procedure(s) shall
be measured during all heat treatment.
Thermocouples attached to representative bend sections shall confirm
actual metal temperature.
7. MANUFACTURING PROCEDURE SPECIFICATION
·
Sequence of operations and
process flow description/diagram
·
Project specific Quality
Plan
·
Equipment to be used
·
The MPS for the mother pipe
for bends. The mother pipe for bends shall be made in accordance with project
Specification 84506-60-30-2L-210
·
The pipe bender’s
nomenclature and description of the induction coil/cooling ring
·
The bending temperature
plus tolerances. Allowable variation of
temperature around pipe during bending
·
Water pressure, flow rate
(if available), and water temperature
·
Method of measuring
temperature. Locations around pipe that
temperature is measured. Method of
controlling temperature.
·
Speed of bending plus tolerance
·
If internal cooling ring is
used in addition to the external one, the nomenclature and description of that
ring
·
Procedures for starting,
controlling and stopping the bending process.
Providing details of how the speed is accelerated to the bending speed
and how it is decelerated. The point at
which the current to the coil turned on and off shall be stated. The point at which the water to the cooling
coil turned on and off shall also be stated.
The procedure shall clearly define which steps are done automatically
and which ones manually
·
Post bending heat treatment
procedure including bracing, temperature plus tolerances, time at temperature,
method of cooling from temperature and method of temperature control within the
furnace
·
Hydrostatic testing procedure
·
Non-destructive testing
procedures
·
Dimensional control
procedures
·
Marking, coating and
protection procedures
·
Material control and
tracability procedures
·
Handling, loading and
shipping procedures
8. NON-DESTRUCTIVE TESTING AND VISUAL INSPECTION
All techniques and procedures
for Visual Inspection (VI), Magnetic Particle Inspection (MPI), Dye-Penetrant
Inspection (DPI) and Ultrasonic Testing (UT) to be used by CONTRACTOR shall be
submitted in writing to COMPANY for approval prior to starting production and
will comply with the requirements of DNV OS-F101, Appendix D. All NDT and
dimensional checks shall be performed on bends in the final heat-treated
condition and after hydrostatic testing and shall be in compliance with one of
the appropriate standards listed in DNV OS-F101 Appendix D, B100.
8.1 All personnel performing non-destructive testing shall be
qualified to the requirements of SNT-TC-1A, Level II or equivalent.
8.2
Completed induction
bends shall be inspected as per DNV OS-F101
Section 7 G800. Bends shall be free from cracks and other injurious
defects. All beveled faces shall also
meet the above criteria when tested by MPI or Dye Penetrant Inspection (DPI)
methods.
8.3
All bends will be
subject to one hundred percent (100%) Visual Inspection as per DNV-OS-F101,
Section 7 G800.
8.4
Minor surface defect
may be removed by grinding subject to agreement provided the remaining wall
thickness is not less than the minimum specified wall thickness and a smooth
transition exists between the ground area and the original contour, i.e. no
stress risers. Defect removal shall be
confirmed by MPI. Defect removal that
results in less than specified minimum wall thickness shall result in bend
rejection.
8.5 Longitudinal surface defects, score marks, etc. shall be
investigated by UT examination, to confirm orientation and depth, and reported
to COMPANY prior to any attempted repair or removal by grinding. COMPANY may at its discretion reject the
bend.
8.6 Welding repair of the base material is not permitted.
8.7 Surface hardness measurements using an approved hardness
tester shall be performed on all finished bends as per DNV OS-F101 section 7
G800
8.8 Each bend outer radius shall be subject to UT examination for
transverse defects before shipment. This
examination shall be made with an angle probe along a 150-mm band on the outer
bend radius. Defects in excess of those
specified in 84506-60-30-2L-210 shall be rejected. Cracks, regardless of depth,
shall be rejected.
8.9 CONTRACTOR shall subject each bend to a hydrotest in
accordance with E1100 of Section 6 of the DNV OS-F101 except that the holding
time shall be two hours.
9. DIMENSIONAL TOLERANCES
Dimensional tolerances shall
meet the requirements of DNV OS-F101
Section 7 G1000 and the following.
In case of conflict, the tolerances contained in this specification
shall govern.
9.1 Minimum internal diameter of each bend shall be guaranteed by
passing a gauging plate, consisting of two rigidly fixed circular parallel
concentric plates, through the completed bend. Minimum gauging plate thickness
shall be 6mm. The gauging plate
shall be required to pass completely through the bend without obstruction. Unless stated otherwise on the Purchase
Order, the gauging plate diameters shall be:
·
Gauging plate diameter =
Ninety-six percent (96%) of minimum guaranteed nominal internal diameter
·
Minimum distance between
gauging plates = 1.5 x ID
9.2 Maximum percent ovality shall be determined by measuring the
bend outside diameter, and is defined as maximum outside diameter minus minimum
outside diameter, divided by nominal pipe diameter and multiplied by 100. Maximum percent ovality shall not exceed 3%
for body and 1.5% for ends.
9.3 Bend
radius shall be measured and shall be within 1% of that specified.
9.4 Angular bend tolerance shall be +/- zero point five degrees
(0.50o), determined by intersecting tangent centerlines, measured by
appropriate equipment.
9.5 Out-of-plane bend angle tolerance shall not exceed 10mm
deviation from a flat base.
9.6 The inside diameter of each end of each bend shall be measured
within 100 mm of the pipe end and shall meet the tolerance requirement of the
appropriate linepipe specification listed in Section 3.
9.7
Bends shall have
tangents at both ends with lengths as shown on the Purchase Order. Bend ends
shall be beveled in accordance with Project Specification 84506-60-30-2L-210.
Where required, tapered transitions shall have minimum one in four slope. The
pipe end face shall be perpendicular with the axis of the pipe within 1.5 mm as
measured with a square.
9.8
The allowable
thickness after bending shall be as defined in the Basis of Design. Contractor
shall not accept pipe for bending of less than nominal wall thickness. Thicker
walled pipe may be required for bend production to achieve a minimum wall
thickness that is compatible with that of the adjoining pipe,
as specified in DNV OS-F101.
10. MARKINGS AND COATINGS
Induction pipe bends shall be
paint-stenciled on both inside ends with CONTRACTOR name, material grade, pipe
number, size and wall thickness, bend radius, bend angle and weight in
kilograms. Additionally, the Purchase
Order number and COMPANY project name (ADGF Project) shall be clearly marked on
the bend OD.
10.1 Induction bends shall be abrasive blasted to remove loose scale
and other foreign material after all required heat treatment has been
performed.
10.2 All induction bends shall be externally coated with a COMPANY
approved; high build, two-pack epoxy or COMPANY approved equivalent.
10.3 All beveled ends shall be stamped with the pipe number using a
round soft nosed punch and suitably protected against damage during
transit. Ends shall be coated with a
weldable primer such as Deoxaluminite, or COMPANY approved equal, that can be
easily removed with solvent and that will prevent weld preparation rusting for
a period of at least twelve (12) months under exposed field conditions.
11. MANUFACTURING PROCEDURE QUALIFICATION TESTS
At least one qualification test
bend shall be made for each pipe diameter, wall thickness, strength grade, and
bending procedure to be used. The radius
for the test bend shall be that of the smallest radius bend on the order and it
shall contain the same length tangents as required on production bends. The bend shall be made using the
manufacturing procedure specification.
COMPANY acceptance of proposed manufacturing procedure specification
shall be contingent on test results. The
following tests shall be performed on each test bend. The mechanical properties shall meet the
requirements specified in Section 4 of this specification.
11.1 All non-destructive examinations, dimensional measurements, and
surface hardness tests are required for production bends.
11.2 Additional surface hardness reading shall be taken at four
equally spaced locations around the bend using approved hardness measuring
equipment at the following locations:
·
Each tangent
·
Each transition area
·
Center of the bend
·
At least two other
locations in the bend area.
11.3 Additional UT surveys shall be made on the finished bend to determine
wall thickness. These surveys shall be
made along three lines.
·
Center of bend axis
·
Inside radius and outside
radius of the bend
·
Neutral axis or weld in
case of seam welded bends
Readings shall be spaced no more than 150 mm apart and 50 mm or
more from the ends. Minimum wall
thickness at any point shall be at least ninety-five percent (95%) of nominal
wall thickness of connecting pipe joints.
11.4 Mechanical
testing shall be made in accordance with DNV OS F101 Section 7 G600.
11.5 The bend is to be subject to one hundred percent (100%) ultrasonic
testing of the bend body. Acceptance criteria in accordance with
84506-60-30-2L-210
12. PRODUCTION TESTING
Production testing of bends shall be carried out as per DNV
section 7 G900.
13. INSPECTION
CONTRACTOR shall furnish
COMPANY inspectors reasonable facilities and space, without charge, for
inspection, testing and information gathering regarding work progress and
quality for induction bending of pipejoints. COMPANY inspectors shall have free
access to all parts of the plant concerned with the work.
13.1 CONTRACTOR shall notify COMPANY at least three weeks prior to
commencement of production, to allow time for final approval by COMPANY of both
manufacturing and inspection procedures.
13.2 After production has started on the order, CONTRACTOR shall
notify COMPANY inspectors at least twenty-four (24) hours in advance of any
changes in production schedules.
13.3
COMPANY inspectors
shall operate independently of CONTRACTOR inspectors.
13.4
Contractor shall
notify Company at least three weeks prior to any bending procedure
qualifications, production testing and final testing.
14. SHIPMENT
CONTRACTOR shall submit for
COMPANY approval, when quoting, drawings of proposed induction bend stacking
and shipping methods. CONTRACTOR shall
ensure induction bends are located so as to reduce the possibility of critical
stresses and fatigue cracks due to cold working in transit. Stresses shall be limited so that no
additional bend out-of-roundness can occur during shipment.
Timber blanks or metal end
bevel protectors shall be used to protect end bevels. Bends shall be lifted and stacked in strict
accordance with Project Specification for Handling, Storage and Transportation (84506-60-30-2L-270).
15. CONTRACTOR DOCUMENT SUBMITTALS
CONTRACTOR shall submit to
COMPANY for approval the following documents prior to commencement of work.
·
Work Procedures
·
Manufacturing Procedure
Specifications
·
Manufacturing Procedure
Qualification
·
Shop Drawings
·
Handling and Packing
Procedures
CONTRACTOR shall submit to
COMPANY for approval a data book containing all relevant documents including:
·
Results of Manufacturing
Procedure Qualification
·
Certified NDT Reports and
Inspectors qualifications
·
Certified Mechanical Test
Reports
·
Mill Certificates
·
Results of any special
tests required by this specification
·
Certified Drawings
·
Storage Procedures
·
Calibration Certificates
All certificates shall be in
the English language and use metric units of measure. CONTRACTOR and COMPANY Representative shall
visibly sign certificates.
All data shall be submitted to COMPANY in both hard copy
and electronic format.