1. GENERAL
This specification defines minimum
quality and technical standards governing cleaning, gauging and hydrostatic
testing of piping on the subsea structures.
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 and Specification Directory
•
General Specification
84506-60-00-2L-010 - Quality Assurance / Quality Control
•
General Specification 84506-60-00-2L-020
- General Offshore Specification
•
General Specification
84506-60-31-2L-520 - Specification Piping Fabrication
Welding
•
DNV-OS-F101 Submarine Pipeline Systems
2000
2. TESTING REQUIREMENTS
CONTRACTOR shall furnish all equipment and materials
including, but not limited to temporary pig launchers/receivers, cleaning and
gauging pigs, flanges, blind flanges, gaskets, nuts and bolts, water strainers
and filters, fill and pressure pumps, meters, fittings, piping and hoses
incidental to filling, cleaning, gauging and hydrotesting the piping. Sufficient spare parts and supplies for major
equipment shall be provided at job site to ensure continuous and reliable
execution of all operations.
CONTRACTOR shall submit a detailed testing plan to COMPANY
for approval, 3 weeks prior to start of the Work. The testing plan shall contain a step-by-step
description of the flooding, cleaning, gauging and hydrotesting procedures,
equipment, manpower and sub-contractors proposed for the test, including, as a
minimum:
a)
Schematic diagram of the test equipment
set-up, with line sizes, pump capacities, volumes, elevations, valves and
fittings (including rating).
b)
Types and number of pigs to be used in
cleaning and gauging operations.
c)
Make up of test crew.
d)
Calibration of all deadweight tester,
pressure, and temperature recorder.
e)
Leak detection and repair procedures,
including a list of equipment available to make repairs.
f)
Methods and equipment proposed to
retrieve pigs that become stuck in the piping.
g)
Test procedure.
h)
Monitoring and recording of test
pressure and temperature.
i) Depressuring,
dewatering and draining.
3. MATERIALS AND EQUIPMENT
3.1 All
test equipment shall be calibrated and certified 30 days prior to
hydrotesting. Copies of test
certificates shall be submitted to COMPANY for approval prior to start of
filling of the piping.
3.2 All
equipment, especially pumps, air compressors, and test instruments shall be
designed and rated for the duty intended and certified for operation in
classified zones if required and shall be subject to COMPANY approval prior to
use.
4. FILL MEDIUM
4.1 The
fill medium shall be fresh potable water, free of suspended matter. Water analysis to be provided by CONTRACTOR
and approved by COMPANY, 24 hours prior to fill. Water containing silt, suspended material or
harmful corrosive components shall not be used unless it can be treated to
COMPANY’s satisfaction by use of filters or chemical additives.
4.2 Test
heads, valves and appurtenances shall be checked prior to filling the pipeline
to ensure they are in proper working order, and valves are in the correct
position. Fittings shall be checked for
tightness before filling, and only new gaskets shall be used.
4.3
In cases where permits are required to
withdraw and discharge water, no water shall be taken from said source unless
the appropriate permits have been acquired.
5. CLEANING AND GAUGING
5.1 On
completion of piping fabrication, cleaning and gauging shall be completed using
two (2) different types of pipeline pigs. One shall be used for cleaning, and the other
for checking the minimum internal diameter of the piping.
1.
Cleaning: poly brush pig
2.
Gauging: gauging pig with aluminum plates
5.2 COMPANY
shall witness insertion of the pigs into the piping section. CONTRACTOR shall not commence the pigging run
until notified by COMPANY.
5.3 CONTRACTOR
shall remove the pigs from piping in COMPANY’s presence, and carefully examine
for wear or deformation to the gauging plate.
5.4 Cleaning
pigs shall consist of a shaft mounted assembly of urethane cups and wire
brushes, or a foam filled pig with externally attached wire brushes, such that
cleaning pigs will force harmful material adhering to the pipe walls, or
objects left in the piping, ahead of the pigs.
5.5 Gauging
pigs shall consist of a shaft-mounted assembly of two urethane cups and a
COMPANY approved gauging plate(s).
Gauging plates shall have the leading edge chamfered 45o for
half the plate thickness.
5.6 Every
pig shall be permanently marked with a unique number that shall be clearly
visible in a photograph. Gauge plates
shall be photographed both before and after each gauging run.
5.7
If in COMPANY’s opinion, cleaning pigs
have not adequately cleaned the piping, the pig sequence shall be repeated
until results obtained are satisfactory to COMPANY.
6. PIGGING OPERATIONS
6.1 The
pigging sequence shall be repeated such that each individual piping section
will be cleaned and gauged. The pigging
sequence shall be:
a)
Run one (1) cleaning pig.
b)
Retrieve and inspect the cleaning pig
from the piping.
c)
If the piping has not been adequately
cleaned by the first cleaning pig run, in COMPANY’S opinion, CONTRACTOR shall
make a second cleaning pig run at no extra cost to COMPANY.
d)
Run the gauging pig through the piping.
e)
Inspect plate wear.
6.2 Gauging or cleaning pigs shall be driven
at a speed of 0.2 meters/second. Driving
pressure shall be recorded on a recording pressure chart with a minimum range
of 2068 kPa (300 psig), and a minimum chart size of 254 mm (10 inches). A
procedure to cover the deceleration of the pig at the receiver shall be
developed by the CONTRACTOR and submitted for COMPANY approval. Chart time
shall correspond to actual time. Charts
and other data relating to cleaning and gauging shall be turned over to COMPANY
at the completion of each run.
6.3 Pumps shall be capable of driving pigs at
the above speed and pressure range, and pumping pressure.
6.4 Should
a pig become stuck, CONTRACTOR shall cease operations and immediately inform
COMPANY. CONTRACTOR at his cost shall retrieve all stuck pigs in accordance
with COMPANY approved procedures.
7. STANDARDS OF ACCEPTABILITY FOR GAUGING
7.1 Piping sections shall not be accepted if
the gauging plate suffers deformation.
When such defects are indicated, the piping section containing the
defect shall be located, cut out and replaced, and the piping gauged again at
no additional cost to COMPANY. Repair of
damaged pipe shall be performed based on a procedure prepared by CONTRACTOR and
approved by COMPANY. All gauging plates
shall become property of COMPANY.
8. PIPELINE PRESSURIZING AND HYDROTESTING
8.1 CONTRACTOR
shall notify COMPANY at least 48 hours prior to hydrostatic pressure testing of
the piping, and shall obtain COMPANY approval to proceed. COMPANY shall be present prior to start of
the hydrotest.
8.2 All
fittings, hoses, valves and test equipment shall have pressure ratings greater
than or equal to the test pressure.
8.3 Typical
minimum instrumentation for each test section dependant on the test range shall
be as follows:
|
2
|
24 hour Pressure Recorders, 0 – 170 kPa (0 - 5,000 psi)
280 mm (11 inch) diameter chart
|
|
2
|
Deadweight Tester (range - 1.25 x specified test pressure)
accuracy to ± 0.1 bar, Sensitivity 0.05bar
|
|
4
|
24-hour Temperature Recorders –30ºC to 50ºC (-22°F to
+120°F)
|
|
2
|
Ambient Thermometers –30ºC to 50ºC (-22°F to +120°F)
|
|
2
|
Water meters / Stroke counters
|
|
|
Supply
of charts for Pressure and Temperature Recorders
|
8.4 Prior
to start of the test all fittings shall be tested for tightness, and all appertenances
shall be fitted with plugs or blind flanges, except where gauges, pumps or
recorders are fitted. Warning signs
shall be placed at all places where there is exposed pipe and appurtenances.
8.5 CONTRACTOR
shall retain on site sufficient manpower and equipment to repair any leaks that
may occur during the hydrotest.
8.6 Pressure,
time, ambient temperature and test water temperature shall be recorded during
pressuring and testing operations, using a pressure recorder and temperature
recorder equipped with twenty-four (24) hour charts. Pressure recorder accuracy and repeatability
shall be ± zero point one percent (0.1%).
Temperature recorder accuracy and repeatability shall be ± 1oC
(1.8oF). Possible temperature
effects on the pressure shall be evaluated by a qualified person, and be taken
into account to determine correct pressure.
8.7 Pressure
recorder, dial pressure gauge and deadweight tester shall be installed in
parallel on a manifold, with adequate valves and venting for each device;
preferably with a pressure snubber.
Pressure recorders shall be calibrated and tested by a deadweight tester
capable of measuring increments of 10.343 kPa (1.5 psi), prior to start of the
test.
8.8 Pressurizing
pumps shall be installed with the suction port flooded at all times, and with a
minimum suction head of 1.5 m (5 feet).
Discharge pipes shall be connected to the system through a check valve
and leak-proof injection block valve, and shall be easily separable from the system
to be tested after the test pressure is achieved.
8.9 When
test pressure is reached, the pump shall be shut down, the inlet block valve
closed and the injection line vented between the two injection block
valves. An observation period shall be
made to verify that test pressure is being maintained and that test water
temperature has stabilized to COMPANY satisfaction. Prior to start of test, the
inlet block valve will be locked off.
8.10 Continuous
pressure chart records shall be maintained during the 24-hour test period,
confirmed by deadweight tester at the beginning, at half hour intervals, and at
the end of the test period. Each time a
deadweight tester reading is made, the pressure shall be ink marked on the
recorder chart. Time, test water
temperature and deadweight tester readings made during the test period shall be
entered in the table provided on the certification form. A time-pressure plot shall be made using
deadweight tester measurements during the test, to determine if the test is
satisfactory.
8.11 The
cause of any pressure-temperature changes occurring in the 24-hour test period
shall be noted. Pressure increase due to
temperature increase during the test period may be limited by a slow
bleed-off. The time and amount of
pressure bled off, as measured by deadweight tester, and the volume and
temperature of the liquid bled off shall be measured and recorded. If there is a pressure loss, CONTRACTOR shall
evaluate how much pressure loss can be attributed to change in temperature and
to free air dissolving into the water
8.12 Hydrotests
shall not be accepted until the full test period is recorded without
inexplicable and/or undocumented pressure loss verified by COMPANY to its
complete satisfaction.
8.13 If
CONTRACTOR cannot explain any pressure drop during the test period to COMPANY
satisfaction, CONTRACTOR shall extend the test period, on COMPANY request,
until satisfactory results are obtained.
8.14 Should
a failure occur, the system shall be depressurized prior to inspection and
necessary repairs carried out. The test
shall be repeated until a continuous test has been maintained for 24 hours
without unacceptable deviations in the specified test pressure. All recorded pressure readings shall be
deadweight tester readings.
8.15 Should
it be determined that a leak or break occurred as the result of CONTRACTOR
furnished material, workmanship or negligence, the system shall be repaired and
retested by CONTRACTOR. A detailed
repair program shall be developed, and approved by COMPANY, including
procedures for depressurizing, removing and disposing test media, making
repairs, refilling with test media, venting and depressurizing.
8.16 Repairable
weld defects shall be cut out and repaired in strict accordance with Piping
Fabrication and Welding Specification 84506-60-31-2L-520. Pipe containing non-repairable weld defects,
splits, ruptures, cracks or other defects shall be removed as a cylinder and
replaced by a length of sound pipe from parent pipe of the same grade and wall
thickness. Replacement pipe sections
shall be welded in the line in accordance with approved welding procedures.
8.17 Complete
test failure records shall be maintained, including exact locations, type and
cause of failure, method of repair, etc.
Fittings, pipe or valves that fail and are replaced due to inherent metallurgical
or mechanical deficiencies shall be reported as to the location and pressure at
which they failed.
8.18 Hydrotest
results shall be witnessed and certified by COMPANY and CONTRACTOR as a
condition of test acceptance, and immediately after COMPANY acceptance of a
successful test, CONTRACTOR shall relieve the test pressure on the completed
section.
8.19 Originals
of all records, data, and charts shall be clearly marked with the following
information and shall be furnished to COMPANY:
•
COMPANY and CONTRACTOR’s Representative
names.
•
Description of facilities tested.
•
Test date and times (start and
completion).
•
Test pressure and duration.
•
Description of test medium used.
•
Total volume of any chemical additives
and water injected.
•
Full explanation of any pressure
discontinuity appearing on a chart.
•
Full explanation of any failures during
the test operation.
•
COMPANY and CONTRACTOR’s
Representatives signatures.
•
All submitted documents shall be signed
and dated by the COMPANY and CONTRACTOR representative.
9. TEST PROCEDURE
CONTRACTOR shall provide an enclosed weatherproof and
properly lighted facility to house deadweight testers and recorders during
pressure testing.
9.1 At
all times starting from pigging through pressure testing, CONTRACTOR shall
record the following:
•
Ambient temperature (with recorder)
•
Pipe temperature (with recorder)
•
Pressure (with recorder)
•
Pressure with deadweight testing
9.2 The
following steps shall be taken and considered part of the test procedure.
•
Build up pressure to test pressure, (as
per the relevant design code for infield or export systems) and maintain
pressure for 30 minutes
•
Check for leaks in hoses, fittings,
etc.
•
Increase pressure to 50% of test
pressure (check for air) stabilise for 1 hour
•
Increase to test pressure and stabilize
for 2 hours
•
Start test after stabilization occurs
9.3 After
reaching test pressure, the pump shall be stopped, during which time all
fittings, instruments and valves shall be checked for visible leaks. All valves shall be closed and no water shall
be added. Deadweight pressure readings
shall be recorded at 15-minute intervals. If stabilization does not occur
pressure shall be increased to test pressure and test to be re-initiated.
9.4 After
stabilization occurs test pressure shall be maintained for a minimum of
twenty-four (24) hours during which no water is added. In the event that a
change in pressure occurs COMPANY will accept the test provided that CONTRACTOR
can prove to COMPANY’S complete satisfaction that the change was due to a
temperature change.
9.5 CONTRACTOR
shall ensure at least two qualified personnel are present at all times during
the hydrotest to take deadweight readings, and periodically check the test head
and fittings for visible leakage.
9.6 Upon
completing the twenty-four (24) hour test period approval shall be obtained
from COMPANY representative.
10. WELD REPAIR
For a leak in a circumferential weld, CONTRACTOR shall
retain the suspect weld for further mechanical inspection to evaluate the cause
of failure. CONTRACTOR shall remove the damaged section and install a new pup
piece at least 3D long, where possible or at the COMPANY’s discretion
11. DEPRESSURIZING AND DEWATERING
Following the hydrotest to COMPANY’S complete satisfaction,
the pressure shall be released at an approved rate (1 bar/min). The rate of
depressurisation will be recorded on a chart to be submitted to the COMPANY.
CONTRACTOR shall drain piping to COMPANY’s satisfaction.
12. DOCUMENTATION
Official original records, including signed, stamped and
dated charts and forms, shall be bound in a report (separate report for each
subsea structure), by CONTRACTOR and delivered to COMPANY no later than one
week after the piping has been cleaned, gauged and tested. The report shall contain the following
information as a minimum:
a)
Description of equipment and set-up
locations with layouts
b)
Deadweight tester records.
c)
Temperature and pressure recording
charts used during cleaning, gauging and testing.
d)
All gauging plates run through the
piping sections including plate deformations.
All data shall be submitted to COMPANY in both hard copy and
electronic format.