1. GENERAL
This specification defines minimum
quality and technical standards governing materials, inspection and testing of
concrete coating applied to pipes used in offshore pipelines. This specification is to be used in
conjunction with the following documents:
·
Basis of Design 84506-60-30-2L-060
·
General Specification 84506-60-00-2L-000
- Definitions and Specification Directory
·
General Specification
84506-60-00-2L-010 - Quality Assurance / Quality Control
·
DNV OS - F101 – Submarine Pipeline
Systems (2000)
·
ASTM C-150 - Specification for Portland
Cement
·
ASTM C-33 - Specification for Concrete
Aggregates
·
ASTM D-75 - Standard Practice for
Sampling Aggregates
·
ASTM C-29 - Test Method for Unit Weight
and Voids in Aggregate
·
ASTM A-82 - Steel Wire, Plain for
concrete Reinforcement
·
ASTM A185 - Steel Welded Wire for
Concrete Reinforcement
·
ASTM A-390 - Zinc – Coated Steel Wire
·
ASTM C-642 - Test Method for Specific
Gravity, absorption, and Voids in Hardened Concrete
·
ASTM C-171 - Specification for Sheet
Material for Curing Concrete
·
ASTM C-172 - Standard Practice for
Sampling Freshly Mixed Concrete
·
ASTM C-31 - Standard Practice for
Making and Curing Concrete Test Specimens in the Field
·
ASTM C-39 - Standard Test Method for
Compressive Strength of Cylindrical Concrete Specimens
2. COATING APPLICATION REQUIREMENTS
2.1 CONTRACTOR
shall perform a procedure qualification trial (PQT) prior to production to
demonstrate that safety, quality and environmental standards are being
achieved. This trial shall comprise 5
joints of each pipe size, all of which shall be subject to all QC tests.
2.2 CONTRACTOR
shall apply the concrete using either the impingement or compression methods.
2.3 CONTRACTOR
furnished equipment, tools and consumables shall be of good quality and
adequate design, maintained in good condition, and subject to COMPANY approval.
2.4 CONTRACTOR
shall tally all pipes throughout the concrete coating process. CONTRACTOR shall ensure no pipes are concrete
coated until COMPANY acceptance of the external anti-corrosion coating.
2.5 CONTRACTOR
shall attach sacrificial aluminum bracelet anodes to selected anti-corrosion
coated pipes in strict accordance with Aluminum Bracelet Anode Installation,
Specification 84506-60-30-2L-240, and before concrete weight coating
application.
2.6 COMPANY
shall have full access to concrete weight coating plant and inspection
activities.
3. MATERIALS
3.2 Portland
cement shall conform to ASTM C-150 Specifications for Portland Cement, or
COMPANY approved equal. Cement shall be
suitable for marine use and shall have a tricalcium aluminate content less than
nine percent (9%) and a maximum alkali content of zero point six percent
(0.6%). Cement shall be stored to protect it from the environment. Cement that has become lumpy, hardened, or
contaminated, or otherwise partially cured shall not be used.
3.3 Silica
sand and aggregate mixes shall conform in all respects to ASTM C-33, and shall
be clean, graded from fine to coarse and free from salt, alkali, harmful
substances and organic impurities.
Aggregate sampling and testing shall be in accordance with ASTM
D-75. Aggregate mix grading and
cleanliness shall be checked at least once a week. COMPANY reserves the right to reject any
aggregate considered to be unacceptable by virtue of source, grading, quality
or cleanliness.
3.4 Silica
sand and aggregate and iron ore may be stored outside but must be separated
from each other and from earth, and other materials to COMPANY satisfaction.
3.5 Iron
ore shall be free of clay and harmful amounts of alkali, deleterious substances
and organic impurities that may affect concrete strength and shall conform to
ASTM C-29. COMPANY reserves the right to
reject any iron ore considered to be unacceptable by virtue of source, grading,
quality or cleanliness.
3.6 Water
shall be potable and free from acids, alcohol, alkali, oil, salt, any organic
material, and shall be suitable for use in concrete. Salt or brackish water shall not be used
under any circumstances. CONTRACTOR
shall identify the water source. Water
quality and cleanliness shall be checked at least once a week. Admixtures and curing membranes shall not be
used. Note for the first month of production samples will be taken once per
week and then with COMPANY approval may be reduced. A copy of all tests will be
submitted to the COMPANY.
3.7 Reinforcing
steel shall be either spirally wound mesh or cage. If wire mesh is used it shall be Bekaert
"Armapipe" or COMPANY approved equivalent conforming to ASTM
A-82. If cage is used, steel bars shall
conform to ASTM A-185 or ASTM A-390 with a minimum bar diameter of 5.0 mm.
3.7.1 Circumferential
steel wire reinforcement shall be at least zero point five percent (0.5%) of
concrete cross-sectional area.
Longitudinal wire reinforcement shall be at least zero point one percent
(0.1%) of concrete cross-sectional area.
Cages shall end 15 mm – 30 mm from each cut back concrete end and 25 mm
to 50 mm clear of anodes. Longitudinal and circumferential wire reinforcement
shall be spot welded to form rigid cages and positioned in the center 30% of
the concrete coating by non-metallic, electrically insulating spacers. These spacers shall have sufficient base area
to prevent damage to the anti-corrosion coating.
3.7.2 Steel
wire mesh reinforcement shall be equally spaced throughout the concrete
coating, as close to center as possible for a single wrap. Except at lead end of pipe steel wire shall
have a minimum separation of 15.0 mm from anti-corrosion coating and the
concrete surface and a minimum separation of 50 mm from anodes. The number of
wire reinforcement wraps shall be determined by the required concrete coating
thickness:
|
Concrete Thickness
|
Number of Wraps
|
|
25
to 50 mm
|
1
|
|
50
to 100 mm
|
2
|
|
over
100 mm
|
3
|
Space
between wraps: S = T/(W+1) +/- 0.1 T
Where, T = Concrete coating thickness
W = Number of wire wraps
Each spiral of wire mesh reinforcement
shall overlap the previous spiral by nominal 25 mm.
4. CONCRETE MIX DESIGN
4.1 CONTRACTOR shall select the proportions
of cement, sand, aggregate and iron ore to produce the specified concrete
density, compressive strength and seawater saturated submerged pipe
weight. CONTRACTOR shall provide the
proposed mix proportions, water-cement ratio and aggregate particle size
distribution curves to COMPANY for approval before material procurement.
4.2 CONTRACTOR shall demonstrate to COMPANY
satisfaction that coated pipe lengths meet the specified seawater saturated
submerged weight, either with a full size concrete weight coated pipe submerged
in seawater, or by calculations based on test seawater-saturated samples of
hardened concrete.
4.3 Weight batching equipment and water
gauges shall be accurate to within 2% of agreed values, and shall be
recalibrated at least once per week.
4.4 CONTRACTOR shall conduct specific gravity
tests, in strict accordance with ASTM C-642, on oven-dried and
seawater-saturated samples of hardened concrete to ensure the concrete mix will
meet the requirements of ASTM C-642. If potable water is used for these tests
then calculations to be submitted and approved to ensure compliance.
5. CONCRETE APPLICATION
5.1 Unless
continuously fed direct from the enamel or FBE plant to the coating plant
without being stockpiled. Immediately prior to concrete coating or fitting of
steel reinforcement cages, CONTRACTOR shall ensure there are no holidays in the
anti-corrosion coating by using a holiday detector in accordance with the
relevant Project Specification for anti-corrosion coating (Asphalt Enamel
Coating Export Pipeline 84506-60-30-2L-260 or Fusion Bonded Epoxy Coating
Infield System 84506-60-30-2L-620).
5.2 CONTRCTOR
shall demonstrate through testing that the bond/shear resistance between the
anti-corrosion coating and the concrete weight coating is satisfactory all
anticipated lay stresses such that no slippage between the anti-corrosion
coating and concrete weight coating occurs.
5.3 If
normal ambient air temperature does not exceed 30°C. Concrete weight coating shall take
place only if the pipe temperature and ambient air temperatures are within the
range of 5oC to 30oC, unless coating takes place in areas
shaded from direct sunlight.
5.4 CONTRACTOR
shall apply consistently proportioned concrete weight coating to anti-corrosion
coated steel pipe as specified herein.
CONTRACTOR shall calibrate the equipment regularly.
5.5 Cement
and aggregate shall be introduced in the proper proportion, either by
"continuous-metering system" or "batch-mix system", to a
pug mill for thorough mixing. Water
shall be added as required during the mixing process to ensure a consistent
material ready for application, based on a daily check of the aggregate mix
water content.
5.6 Equipment
that tends to separate concrete ingredients shall not be used, and concrete
shall be applied within 30 minutes after water is first added to the mix, and
then only if no additional water has been added to the mix to return concrete
to its original slump angle.
5.7 Reclaimed
concrete may be thoroughly mixed into fresh concrete at the pug mill, provided
that it does not exceed seven percent (7%) of total volume.
5.8 Pipes
shall be rotated to form an even and continuous concrete jacket, with spirally
applied reinforcing wire simultaneously added to the concrete. Concrete coating shall finish between 75 to
100 mm from each end of the anti-corrosion coating on pipe sizes < 20
inches and 172 to 200 mm on pipe sizes 20 inches and larger.
5.9 Each
pipe shall be coated in a continuous operation.
When more than one application is required to produce the specified
coating thickness, time between the first and last coat shall not exceed 30
minutes. If a time lapse greater than 30
minutes does occur, the concrete coating shall be removed and the entire pipe
shall be recoated.
5.10 Pipe
ends shall be washed and examined immediately after transfer from the coating
station, to ensure proper cutback distances and that all concrete has been
removed from the pipe interior, bevel, steel cutback and exposed anti-corrosion
coating.
5.11 Steel
reinforcing wires shall not be in physical or electrical contact with the pipe
or anode. CONTRACTOR shall verify that
no electrical path exists between the steel reinforcing wires and the steel
pipe or the anode.
5.12 Following
concrete application on pipes with bracelet anodes, concrete shall be carefully
hand applied up to anode material, feathering as necessary to provide a smooth
transition should the anode have a different overall diameter to the concrete
weight coating. Any concrete extending
or sprayed onto anode surfaces shall be removed before curing.
6. CONCRETE CURING
6.1 Concrete
coatings may be cured by any of the three methods detailed below but whichever
is used, the concrete shall never be allowed to dehydrate. The method shall be proposed by the
CONTRACTOR and approved by the COMPANY.
6.2 The
use of admixtures to accelerate curing is not permitted. The temperature of the concrete coat shall
not be allowed to fall below 2ºC during the initial 24 hours of curing.
6.3 Pipes
may be handled other than by the uncoated ends once the compressive strength of
the coating exceeds 16,000 kPa.
6.4 Where
applicable water curing shall commence not later than two hours after coating
and shall comprise keeping the coating continuously moist for a period of not
less than four days. Water curing using
a water spray shall not be allowed when the ambient temperature falls below 5C.
6.5 Any
sheet or film used for concrete curing shall comply with ASTM C171. Samples of the material shall be taken and
tested to ensure conformance with ASTM C171 for every batch of material, unless
manufacturer's test results demonstrating conformance are available.
6.6 If
steam or fog curing is to be used as part of the process then the CONTRACTOR
shall demonstrate that the process will have no detrimental effects upon the
concrete. On no account shall the pipe wall temperature be allowed to reach a
level which could cause damage to the anti-corrosion coating or internal
coating. Steam or fog curing shall begin
within two hours after concrete application and shall continue until the
concrete has achieved a compressive strength of 10,000 kPa or greater.
7. COATING TOLERANCES
7.1 CONTRACTOR
shall measure concrete coating overall diameter, immediately following concrete
coating, at five (5) locations along each pipe.
Average overall diameter tolerance range shall be - ±
10 mm. The concrete coating shall be
concentric on the pipe.
7.2 CONTRACTOR
shall weigh each pipe immediately after concrete coating, which shall be
between ninety-five percent (95%) and one hundred seven percent (107%) of
calculated total pipe weight (steel pipe, corrosion coating, and concrete
jacket). Average weight for each day’s
production shall be between one hundred percent (100%) and one hundred five
percent (105%) of calculated pipe weight.
CONTRACTOR shall not add additional weight to underweight pipes to
increase the average daily weight.
8. COATING REPAIRS
8.1 Concrete
coating in which defects appear, or that do not conform to this specification,
shall be promptly repaired to COMPANY satisfaction. Certain repairs are permitted for concrete
coatings due to damage in handling and storage, as detailed below.
8.2 Damaged
areas of 300 cm2 and less than twenty-five percent (25%) of total
concrete coating thickness in depth, may be accepted without repair, should
remaining concrete be sound and wire reinforcement is not exposed. If wire reinforcement is exposed, area exceeds
300 cm2 or depth exceeds twenty-five percent (25%), damage shall be
repaired. If the total damaged area of
an individual pipe exceeds 20% of the concrete surface area on that pipe, the
pipe shall be stripped and re-coated.
8.3 Damaged
areas in excess of 300 cm2, but less than 1,000 cm2, shall
be repaired in the following manner, should remaining concrete be sound:
·
Remove damaged or loose concrete
·
Restore the reinforcement steel.
·
When necessary prepare by undercutting
and exposing the reinforcement steel wires by chiseling out the damaged concrete
and undercutting the sides to form a key
·
Wet the fresh surface of the remaining
concrete coating at the point of coating damage.
·
Place the concrete repair mixture into
and through the reinforcement steel until the surface is level with the coating
around the repair.
·
Cure the repair
8.4 Damaged
areas in excess of 1,000 cm2 shall be repaired as follows:
·
Remove concrete around the entire pipe
circumference throughout the length of the damaged area, whilst concrete is in
a green condition.
·
Replace concrete by impingement.
8.5 Circumferencial
cracks less than 1.5 mm in width, need not be repaired unless they extend more
than one hundred eighty degrees (180o) around the pipe or more than
300mm.
Circumferential cracks in excess of 300 mm in length shall
be repaired irrespective of width.
Longitudinal cracks shall be repaired irrespective of length
or width.
Annular cracks less than 30 mm in depth will be accepted
without repair. Annular cracks deeper
than 30 mm are not permitted and shall necessitate stripping and recoating the
pipe.
Crack repairs shall be made by widening the crack to 25 mm
for the necessary depth and length and packing the prepared crack with repair
material level with the existing coating.
8.6 Should
gaps be visible at pipe ends, between the concrete and anti-corrosion coatings,
the pipe shall be repaired to the satisfaction of the Company.
8.7 Voids
and core holes shall be repaired in accordance with Section 8.3.
8.8 All
repairs shall be properly cured for a minimum of four (4) days before further
handling. Note if fog cured method is used then pipes must be stored for 12
hours before moving.
9. INSPECTION AND TESTING
9.1 COMPANY
shall have full access to all parts of CONTRACTOR coating plants, laboratories
and pipe storage facilities to inspect materials, equipment and CONTRACTOR’s
work. CONTRACTOR shall provide
reasonable assistance to COMPANY at all times to enable COMPANY monitoring and
inspection.
9.2 CONTRACTOR
shall furnish all material, equipment and qualified personnel to perform
examinations and testing specified herein.
COMPANY inspection shall not relieve CONTRACTOR of its responsibility to
ensure quality control.
9.3 Daily
concrete mix samples, as applied during coating, shall be taken to determine
the concrete coating compressive strength and density. CONTRACTOR shall submit full details for
COMPANY approval, including calibration data for measuring dimensions and
weights of concrete coated pipes, and methods for calculating “as applied”
concrete density and deviations from specified pipe weights.
9.4 Compressive
strength shall be determined from samples prepared in cylindrical
"Proctor" molds at the job site, obtained in accordance with ASTM
C-31 and ASTM C-172. Eight (8) test
cylinders shall be taken four in first half of shift and four in second half of
shift.. These cylinders shall be
prepared and tested as outlined in ASTM C-39 to determine seven (7) day and
twenty-eight (28) day concrete compressive strengths. When a core is taken from a pipe still being
cured, the core shall continue to be cured in the same way as the pipe.
Compressive strength shall be:
·
Seven day 15,000 kPa
·
Twenty-eight day 40,000 kPa
In the event of a single core specimen failing to meet the
minimum strength requirements, the spare shall be tested. Should the spare also fail, then the COMPANY
shall have the right to order additional testing of the suspect pipe coatings
represented by the cores or to reject the pipe joints coated with concrete
represented by the cores.
All core samples shall be marked with the pipe number from
which they were taken. In the event of a
core failure, CONTRACTOR shall retest one time.
If the retest fails, the pipe shall be stripped and recoated. Pipes coated previously and subsequently to
the failed joint shall be tested in the same manner until an acceptable joint
is found. Additional cores shall be
taken and tested as necessary to satisfy COMPANY that the specified
requirements are being achieved.
9.5 CONTRACTOR
shall perform seawater absorption tests on a concrete weight coated pipe of
each pipe size and concrete thickness/density combination and calculations
based on test seawater-saturated samples of hardened concrete, after a minimum
of 28 days curing. Water absorption
shall not exceed eight percent (8%). If potable water is used for these tests
then calculations to be submitted and approved to ensure compliance.
9.6 CONTRACTOR
shall demonstrate on one pipe per day that there is no electrical continuity
between the steel re-enforcement and the steel pipe or the anode.
10. CONCRETE DENSITY AND WEIGHT CALCULATIONS
Concrete density “as-applied” can be checked using average
diameter measurements and pipe weights.
10.1 CONTRACTOR
shall weigh each concrete coated pipe immediately after coating, and measure
outside concrete diameter at five evenly spaced points along the pipe
length. The average measurement shall be
used to calculate coating thickness and concrete density. Measurements may be made either on the scale
or as soon as the pipe is placed on the curing rack. Weight report entries and density
calculations for each concrete coated pipe shall be made within 30 minutes
after coating, using the following calculations:
Density (kg/m3)
= W - (L x w)
0.785(D2 - d2)(L -
2l)
Weight (calculated) in kg = 0.785 x 3044(D2 - d2)(L
- 2l) + (L x w)
Where,
W = weight
of concrete coated pipe measured by CONTRACTOR (kg)
w = weight
/ m (nominal) of anti-corrosion coated pipe (kg/m)
L = pipe
length (m)
L = length
(average of both ends) of concrete coating cutback (m)
D = diameter
(average) of concrete coated pipe joint (m)
d = diameter
(nominal) of corrosion resistant coated pipe (m)
Notes:
1.
Weights
shall be obtained to the nearest 10 kilogram (0.01 tonnes)
2.
Lengths
shall be obtained to the nearest 0.01 meter (10 mm)
3.
Density
calculations shall also account for anodes, if fitted.
10.2 Concrete
coating density shall not vary more than plus seven percent (+7%), minus five
percent (-5%), with a daily production average between one hundred percent
(100%) and one hundred and five percent (105%) of the calculated concrete
density. If density varies by more than
stated tolerances, CONTRACTOR shall immediately inform COMPANY of the
deviation.
10.3 Specific
weight shall be based on seawater-saturated surface-dry conditions and shall
equal specification requirements. Test
data developed in accordance with ASTM C-642, including water absorption
calculations, shall be recorded and furnished to COMPANY.
10.4 Scales
used for obtaining weights shall be certified accurate to plus or minus one
half percent (+/- 0.5%), and current calibration certificates shall be provided
to COMPANY prior to start of work.
CONTRACTOR to calibrate scales at start of production.
10.5 Where
applicable CONTRACTOR shall check concrete density with a slurry densitometer
at least once every four (4) hours of operation. Impinged concrete or repairs
do not qualify for this test.
11. IDENTIFICATION AND MARKING
11.1 Each
pipe shall be paint stenciled on the internal pipe surface with the nominal concrete
coating thickness and concrete coated pipe weight. The concrete coated pipe
shall be color coded externally, to signify a pipe size, wall thickness,
concrete coating thickness, concrete density or other pipe differences. Color
coding shall be approved by COMPANY.
11.2 The
original pipe identification shall be provided by color coding and internal
marking of the pipe.
11.3 For
seam welded pipes, CONTRACTOR shall paint a 100 mm long white stripe on the
concrete at each pipe end to define the position of the weld seam.
12. QUALITY CONTROL
CONTRACTOR shall implement a documented quality control
program that shall be used to provide verifiable evidence that materials,
inspection and testing conform to the specifications.
13. INSPECTION AND REJECTION
13.1 CONTRACTOR
facilities, materials and work shall be subject to COMPANY inspection, however
this does not relieve CONTRACTOR of its obligation for performing code
inspections.
13.2 Completed
weight coating containing defects originating with CONTRACTOR materials, or
workmanship, or that are not in complete compliance with the specifications or
the Purchase Order shall be rejected.
14. PRODUCTION RECORDS
CONTRACTOR shall provide to COMPANY, on a daily basis, the
following information for each concrete weight coated pipe:
·
Concrete weight coating application
date
·
Pipe Serial Number
·
Pipe diameter (mm) / wall thickness
(mm) / length (m)
·
Anode joint (where appropriate)
·
Concrete mix proportions as applied
·
Pipe weight (steel and corrosion
coating) (kg)
·
Pipe weight after concrete weight
coating (kg)
·
Average concrete coating overall
diameter and thickness (mm)
·
Calculated concrete coating unit weight
(kg/m)
·
Deviation from specified unit weight
(%)
·
Average specified unit weight deviation
of all pipe (%)
·
Total length of all pipe coated today
(m) / to date (m)
·
Total pipe joints sent for repair today
/ to date
·
Nature of concrete coating defects
·
Results of seven (7) day and
twenty-eight (28) compressive strength tests (kPa)
·
All records indicated herein shall be
fully identified with the pipe or materials they represent. These records shall be kept for one year
after weight coating application. All records indicated herein shall be fully
identified with the specific materials they represent. Records shall be available for COMPANY
examination at the time and place of inspection, whether at the point of
manufacture or other CONTRACTOR locations.
15. DOCUMENT SUBMITTALS
CONTRACTOR shall submit the following documents to COMPANY
for approval 30 days prior to commencing work:
a.
Description of Coating Equipment and
Scale Certificates
b.
Application Procedures
c.
Testing Procedures
d.
Handling, Transport and Storage
Procedures
e.
Production Schedule
CONTRACTOR shall submit to COMPANY for approval a databook
containing the following documents as a minimum:
a.
Material Test Certificates
b.
Production Reports
c.
Certified Inspection Reports
d.
Calibration Certificates
e.
Certified Physical Test Reports
f.
Tally Record of Pipe Coated / Loaded
Out
g.
Pipe Reconciliation
All certificates shall be in the English language and use
metric units of measure. CONTRACTOR and
COMPANY shall visibly sign certificates.
All data shall be supplied to COMPANY in hard copy and
electronic format.