1. SCOPE………………………………………………1.1 Piping Codes
1.2
Exclusions
1.3
Pressure Testing ……………………………
2. REFERENCES
3. DEFINITIONS
4. GENERAL REQUIREMENTS ………………4.1
Construction Plan
4.2 Vertical Profile
4.3
Right of Way Preparation ……………….
4.4
Drainage
4.5 Elastic Bends
4.6 Preformed Bends …………………………..4.7 Preformed Bends for Aboveground
Pipelines
4.8 Preformed Bends for Buried Pipelines4.9 Vents and Drains …………………………..5. STORAGE AND HANDLING
5.1
Pipe Stacking ………………………………..
5.2 End Protectors
5.3 Slings for Lifting
5.4 Pipe Handling………………………………..5.5
Handling of Internally Coated pipe
5.6
Transfer of Marks ……………………………
6.
INSTALLATION OF ABOVEGROUND
PIPELINES
6.1 Pipe Examination
6.2 Stringing
……………………………………….
6.3 Lay-up
6.4 Buckling Prevention
6.5 Support Spacing and Type ……………..
6.6
Ring Girders
6.7 Piles
6.8
Concrete Supports …………………………
7.
INSTALLATION OF BURIED PIPELINES
7.1 Previous information
7.2 Cathodic Protection
……………………….
7.3
Buried
Crossings
7.4 Spot Backfilling
7.5
Cover for Flammables …………………..
7.6 Extra cover
7.7
Installation in Sand Areas
7.8
Installation in Rock Areas ………………
7.9 River Bottom
8. TIE-IN TEMPERATURES
8.1
Tie In Weld …………………………………..
8.2 Maximum
Temperature
8.3 Average
Temperature
8.4 Records ……………………………………….
9. TIE IN METHODS AND ANCHORING 9.1 Method of Tie-in for Buried Pipelines 9.2
Method of Tie-in for Aboveground
Restrained Lines ………………………….9.3 Method of Tie-in for Aboveground
Non-restrained Pipelines
10. HYDROSTATIC TESTING
10.1 Safety ………………………………………….10.2 Pneumatic Testing
11. CLEAN-UP
12. RECORDS………………………………………..
TABLE
I Maximum Localized Bend
II Maximum Allowable Bend Per Support
APPENDIX
A A.1 CALCULATIONS FOR REQUIRED
COVER…………………………………………….
1. Scope
1.1 Piping Codes
This standard supplements ASME B31.4 and ASME B31.8 transportation piping codes and defines
additional construction requirements governing onshore cross-country pipelines.
1.2 Exclusions
1.2.1 This standard does not apply to offshore pipelines and non-metallic pipelines.
1.2.2 This standard does not apply to wellhead piping, as defined in ASME B31.4, and ASME B31.8,
except for the burial of flowlines.
1.2.3 This standard does not apply to piping for utility service, or plant piping known as “on plot” except for
the burial of such.
1.3 Pressure Testing
Pressure testing is covered elsewhere.
2. References
The selection of material and equipment, and the design, construction, maintenance, and repair of
equipment and facilities covered by this standard shall comply with the latest edition of the references
listed below, unless otherwise noted.
SABIC Engineering Standards (SES)
P01-E15 Pressure Testing, and Lay- up Procedures
P01-E16 Safety Instruction Sheet
P01-E02 Design of Piping Systems for Stress and Pressure criteria
Industry Codes and Standards
American Society of Mechanical Engineers
B31.4 Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum Gas, Anhydrous Ammonia, and
Alcohols
B31.8 Gas Transmission and Distribution Piping Systems
3. Definitions
Hydrostatic Test. A pressure test conducted using water or other approved liquid as the test medium.
Leak Test. A pressure test to ensure tightness at the test pressure.
Pneumatic Test. A pressure test conducted using air or other approved gas as the test medium or in
conjunction with liquid.
Pressure Test. A test conducted to piping or equipment by subjecting it to an internal pressure using liquid
or gas to ensure strength or tightness of the system at the test pressure.
Sand Pad. An annulus of sand 300 mm thick, to protect pipe coatings
Service Test. A leak test conducted at operating pressure using the service fluid.
System Test. An in-situ pressure test applied to a group of piping and equipment tested as a system.
4. General Requirements
4.1 Construction Plan
A construction plan containing a route drawing, detailed plan drawings, piping and instrument diagrams,
hydrostatic test diagrams, and project specific items shall be issued and shall be the basis for installing the
pipeline. The end of the pipeline shall be stated in the Scope of Work, and is normally the upstream end. A metric measurement shall be used for the horizontal survey. Profile surveying shall be in meters and
decimal fractions of a meter.
4.2 Vertical Profile
The Construction Contractor shall determine the vertical profile of the pipeline, the amount of cover, the
location and degree of elastic and preformed bends, and the locations of vents and drains in accordance
with this standard and the construction drawings. The change in slope of the pipeline at normal spacing of
30 m, and at intermediate stations as required, shall be calculated.
4.3 Right of Way Preparation
4.3.1 The right-of-way shall be graded to a flat or smooth rolling surface and shall be wide enough to drive
a vehicle on at least one side of the line. Irregularities shall not obstruct access of construction equipment.
Fills and cuts shall be made to reduce the number of bends to the pipe for conformance to the site. Fills
shall be provided to support construction equipment in areas where the soil fill does not provide sufficient
support. The width of such fills and cuts shall not be less than the area to be stabilized in accordance with
paragraph 7.7.5, and the adjacent slopes shall not be steeper than four to one.
4.3.2 The final finished right-of-way shall be completed in a manner which permits routine operation and
maintenance access with standard four wheel drive vehicles.
4.4 Drainage
When the pipeline construction changes the natural drainage pattern, either by the grading of the
right-of-way or by a bermed-over cover, adequate drainage shall be provided to prevent wash-out of the
pipeline cover by rain storms.
4.5 Elastic Bends
The project specifications shall dictate the maximum change in slope, or direction, for elastic bends. Larger
changes of slope, or direction, shall be made with preformed, bent in the field, or purchased as such.
4.6 Preformed Bends
4.6.1 Fabrication
Preformed bends shall be made from a length of pipe which has been bent with a smooth stretch bending
machine. The bent section is then welded into the string. No wrinkle bends or hot bends shall be used. At
any point along a preformed bend, the pipe diameter shall not be reduced by more than 2.5 percent of the
nominal pipe diameter. Bends are not allowed closer than 600 mm from a circumferential weld unless the
weld is backwelded. The weld shall be radiographed after the bend is made.
4.6.2 Fitting
Bends with a large change of direction, may be purchased as a fitting, and must conform to all of the
physical properties of the adjoining pipe.
4.7 Preformed Bends for Aboveground Pipelines
4.7.1 Maximum Bite
The maximum permissible localized bend or “bite” at one place on the pipe and the minimum spacing of
such bites are shown in Table 1.
Table I
Maximum Localized Bend
When pipe is internally coated, the bend angle per bite may be reduced to minimize damage to the
coating. (As a minimum, the internal coatings shall withstand the bends described in paragraph 4.8.1). For
above ground pipelines at road crossings where preformed bends are required, the bend angle and bite
shall be per section 4.8 below.
When relatively thin wall spiral-welded pipe is used, the bend angle per bite may need to be reduced to
avoid wrinkling the pipe. A bend angle of 75 percent is a good starting point.
4.7.2 Vertical Preformed Bends
Vertical preformed bends shall be used when changes of slope are required and are larger than
permissible for elastic bends. The preformed bend shall be welded to the pipe string such that its center
will be on the support at which the change in slope occurs. Movements of the string due to temperature
changes after the location was established may be neglected. The maximum allowable angle of preformed
bend per support in a typical long string, in the order of 900 to 1200 m, decreases as the distance between
the bend and either free end of the string increases as shown in Table 2.
Table II
Maximum Allowable Bend Per Support
4.7.3 Restrained Pipe
When the aboveground pipeline is restrained, the angle of vertical bend per support is limited by the design
of the support, in accordance with the Project Specifications.
4.7.4 Horizontal Deflections
All horizontal deflections shall be made at deflection anchors and consist of a series of very large radius
field bends held in special supports designed for horizontal thrust, for aboveground restrained pipelines, as
shown on the Project Drawings.
4.8 Preformed Bends for Buried Pipelines
4.8.1 Bends for Buried Pipelines
The bends for buried pipelines shall be long radius with maximum bend or “bite” at one place on the pipe of
0.50° and minimum spacing of such bites of 0.9 m. In order to use a more severe angle for a preformed
bend, calculations, which consider expected temperature rise, weight of pipe, fluid and cover, shall show
that such a bend will be adequately restrained. unless there are space limitations. Cover shall be in
accordance with paragraph 7.6.
4.8.2 Horizontal Bends
Preformed horizontal bends shall normally consist of pipe joints with a maximum of 3° bend per joint
corresponding to an overall bend radius of approximately 210 m. In order to use a smaller radius,
calculations similar to those discussed in paragraph 3.8.1 shall show that such a bend will be adequately
restrained.
4.8.3 Composite Bends
When there are composite bends having both vertical and horizontal components, the overall bend radius
shall be limited to requirements in paragraph 4.8.2.
4.8.4 Cover
Appendix A of this specification contains sample calculations for required covers over bends.
4.9 Vents and Drains
Permanent vents and drains with plugged or blinded valves, and provision for blow-down of pipeline
sections at selected locations shall be installed only as required by the Project Drawings. Temporary vent
valves, if required during the initial filling, and draining of the pipeline for hydrostatic test, shall be removed
and the connection plugged and seal welded after the test. The weld shall be mag particle, or dye
penetrant tested.
5. Storage and Handling
5.1 Pipe Stacking
Pipe stacking shall be made in a manner which will not damage the pipe or coating.
5.2 End Protectors
End Protectors shall remain on pipes and fittings while in storage.
5.3 Slings for Lifting
Slings for Lifting pipe shall be nylon or similar material to prevent damage to the pipe surface. Wire rope
slings shall not be used.
5.4 Pipe Handling
Pipe shall not be rolled or dropped off trucks. The pipe handling procedure and equipment shall be
approved by the Construction Engineer.
5.5 Handling of Internally Coated pipe
Internally coated pipe shall be handled from the outside diameter (O.D.) only.
5.6 Transfer of Marks
When a length of pipe is cut from a longer joint of pipe, all vendor markings and other identifying
information shall be transferred to each length of pipe.
6. Installation of Aboveground Pipelines
6.1 Pipe Examination
Each length of pipe shall be examined to make sure it is free from internal obstructions. Any obstructions
shall be removed before the pipe is welded into a string.
6.2 Stringing
Pipe joints shall be welded to form strings of 900 to 1200 m. Pipe strings or portions thereof shall not be
moved until all joints have been fully welded and inspected.
6.3 Lay-up
When open ends of pipeline strings are not attended, they shall be capped to prevent entry of debris. Each
string of the pipeline shall be cleaned to remove all debris. Except for internally coated pipe, each string
shall be gauged by passing an internal gauging plate of not less than 90 percent of the inside diameter for
pipe sizes smaller than NPS 20 and 93 percent for pipe sizes NPS 20 and larger. Cleaning shall be done
before pipeline valves are installed or the soft seats of valves shall be protected against damage from
debris.
6.4 Buckling Prevention
In hilly terrain the strings shall be laid out to avoid buckling due to temperature changes before the line is
held down by ring girder supports.
6.5 Support Spacing and Type
The Project Drawings indicate the support spacing and type. Support elevations shall be maintained within
+/- 6 mm. If support elevations are established during construction, the slope shall be calculated from the
actual support elevations and distances.
6.6 Ring Girders
Ring girders shall be installed within +/- 6 mm horizontal and vertical tolerances.
6.7 Piles
Driven piles shall be coated to prevent corrosion and shall be driven in accordance with Project
Specifications.
6.8 Concrete Supports
The supports shall be installed on a stable base material to prevent future settling. The base of each
support shall be at least 1.8 m in diameter. The support base shall be stabilized using marl or weathered
crude oil. Determination of the type of stabilization should generally be based on the economics of the two
stabilization options.
7. Installation of Buried Pipelines
7.1 Previous information
Paragraphs 5.1, 5.2, and 5.3 also apply to buried pipelines.
7.2 Cathodic Protection
If the pipeline crosses or comes within 50 m of buried pipelines or is within 50 m of other buried steel
installations, Cathodic Protection may be required in accordance with the Project Specifications. All
bonding stations shall be completed and the line backfilled. The as-built drawings shall indicate any buried
installations and bonding stations.
7.3 Buried Crossings
Buried installations crossing the pipeline route shall be located in advance of grading and trenching. The
trench bottom shall be surveyed to establish the elastic bends and required preformed bends in rolling
terrain or when passing through dunes. When the pipe is lowered into the trench, the pipe shall conform to
the trench bottom and shall be supported at all points. The maximum allowable unsupported length before
backfilling is 3 m. Any such voids shall be carefully backfilled. The minimum clearance between pipelines
or between a pipeline and an obstruction shall be as specified in the Project Specifications, unless
additional clearance is specified on the pipeline drawings.
7.4 Spot Backfilling
Spot backfilling shall be used to restrain the pipe after it has been lowered into the trench. Spot backfill
shall have full specified cover and shall cover all preformed bends a distance of 6 m to each side of the
centers of the bends. The maximum clear distance between spot backfills shall be as specified by the
project design. Spot backfills shall cover the pipe for at least 4.5 m along the pipe.
7.5 Cover for Flammables
LPG lines, gas lines, and oil well flowlines shall have a minimum cover of 900 mm. Other lines shall have a
minimum cover of 600 mm. Original grade shall be restored over the pipeline unless otherwise specified
below. Additional cover required at road or rail crossings shall be as noted on the drawings.
7.6 Extra cover
Project specifications shall specify where extra cover is required at vertical, horizontal, and composite
preformed bends based on bend radius and tie-in temperature, to adequately restrain the buried pipeline.
Such extra cover shall extend a minimum of 6 m beyond a bent portion of pipe.
7.7 Installation in Sand Areas
7.7.1 Trench width
The trench shall be wide enough to allow lowering the pipe without damaging the pipe or the coating and
shall be excavated to the depth required to provide the specified depth of cover below finished grade or as
required by the Project Specifications.
7.7.2 Trench Bottom
The bottom of the trench shall be free of rock or other material that could damage the pipe coating.
7.7.3 Sand Pad
The pipe shall be embedded in an annulus of clean sand not less than 300 mm thick in a manner which
shall not damage the coating. The sand shall not contain stones larger than 6 mm.
7.7.4 Backfill remainder
The remainder of the backfill shall be placed in a manner which shall not disturb the annulus of clean sand
around the pipe (sand pad). Backfill shall not contain rock larger than 50 mm size.
7.7.5 Active Sand
The retention of the sand cover in active sand areas must be ensured. The backfill shall be stabilized with
marl of 150 mm minimum depth, other stable material, or weathered crude oil with a minimum of 13 mm
penetration, to ensure the retention. If the line passes through a sand dune, the width of leveled, stabilized
right-of-way shall be 3 m on each side of the pipeline plus 1 m for every 1 m for every of dune height (or fill
height) in both the “cut” and the “fill” areas.
7.8 Installation in Rock Areas
Normally, aboveground construction shall be used in rock areas where blasting would be required for
trenching. When there is economic justification, a “half trenching” alternative may be used as follows:
a. The minimum trench depth shall be such that the top of the pipe is below the original ground
surface or the pipe centerline is 150 mm below the top of the rock.
b. The minimum width of the bottom of the trench in rock areas shall be 600 mm wider than the
pipe. The pipe shall be centered in the trench.
c. Selected bedding material shall be placed in the bottom of the trench and made level. The
bedding material shall be clean sand or soil and shall not cause damage to the coating. The bedding
material shall not contain stones larger than 6 mm. In addition, sand pads shall be placed at
approximately every 9 m to support the pipe 200 mm off the prepared bottom. The bottom of the
trench shall be inspected to insure that no rocks will protrude anywhere to within 100 mm of the pipe.
d. After lowering the pipe into the trench, the Contractor shall use surveying sticks to establish
dimensional controls to satisfy the inspector that the final cover will be sufficient and centered over
the pipeline.
e. A pad of selected bedding material shall be placed under and around the pipe to provide a
minimum cover of 200 mm around the entire circumference of the pipe. The sand pile remaining
above the 200 mm cover shall be shaped to its natural angle of repose, approximately 35° from the
horizontal.
f. The remaining backfill and berm shall be placed in a manner to avoid disturbing the sand pad.
Other material shall be pushed up from the sides, or new material shall be placed adjacent to the
sand pad. Coarse material shall not be placed on top of the sand pad and be allowed to roll down.
Backfill shall not contain rock larger than 150 mm size.
g. The width of the flat top (berm) of the dike shall be at least twice the pipe diameter along the
overall minimum cover above the top of the pipe. For every 300 mm of additional cover required at
vertical or horizontal bends, the berm width shall be increased 600 mm. The ramped sides of the dike
shall not be steeper than 35°.
h. The entire dike shall be stabilized with marl of 150 mm minimum depth or by spraying with
weathered crude oil to saturate the outer surface. The crude shall penetrate a minimum of 12 mm.
Typically, this requires approximately 4.5 L/ m2
of berm surface.
i. Diversion ditches and/or culverts for flood water shall be provided to keep the pipeline cover
from acting as a dam or a channel bank.
7.9 River Bottom
When a buried pipeline is installed through a river bottom, wadi, or other places where water run-off occurs,
concrete coated pipe shall be used to provide the required stability in case of floods. The use of concrete
blocks placed over the pipeline is prohibited.
8. Tie-in Temperatures
8.1 Tie In Weld
A tie-in weld is a weld that connects a pipeline string to another string, or to the pipeline under construction,
or to an anchor. The segment of the pipeline between tie-in points remains fully restrained at the tie-in
temperature if shrinkage of the segment is prevented by adequate anchorage at both ends. For normal
daily temperature variations during construction, one of the following will provide adequate anchorage:
a. Full thrust anchor
b.
Intermediate anchor with a full string of pipe welded to each side of the anchor
c. Friction forces along the “tail”: At least 450 m of buried pipeline; a 900 to 1200 m string on
wooden skids or sand; or 1800 to 2400 m of pipe, a double string, resting on steel supports.
8.2 Maximum Temperature
The Construction Engineer shall determine the highest practical tie-in temperature for each tie-in weld of a
buried pipeline and for each above-ground pipeline segment from one anchorage point to another,
including any intervening road crossings. The tie-in temperature shall be within the range stated in the
Project Specification.
8.3 Average Temperature
The actual tie-in temperature shall be the average of two readings, one at the top and one at the bottom of
the pipe. The temperature measuring device shall contact the pipe and shall be shielded from direct
sunlight.
8.4 Records
The Contractor shall record all tie-in temperatures and the pipeline stations of the tie-ins.
9. Tie in Methods and Anchoring
9.1 Method of Tie-in for Buried Pipelines
9.1.1 When a sufficient number of strings have been completed, the first string of a buried pipeline shall be
placed in the trench and spot backfilled (or tied into an anchor) during the hottest part of the day. The
subsequent strings shall be connected to the starting end by tie-in welds. Each new string must be kept
free of movement to prevent cracks in the tie-in weld.
9.1.2 The portion of the pipeline between the trench and the bank shall be supported by sidebooms holding
the line in a gentle S-curve. During the night and the cool periods of the day, there should be at least 900 to
1200 m of pipe on the bank to keep the S-curve in sufficient tension to restrain the pipe in the trench.
9.1.3 If the S-curve cannot fully restrain the line during the cool periods, the curve will develop slack as the
line becomes warm. This will require the lifting of the tail to move the slack towards the free end of the line
when the temperature is high.
9.1.4 Alternatively, the tie-in weld may be made in the trench (at tie-in temperature) and the tail may be
resting in the trench.
9.1.5 The spot-backfilling to tie down the line up to a point 1200 m from the free end of the tail may be done
at any temperature of the pipe. Backfilling closer to the free end may be placed only during the hottest part
of the day.
9.2 Method of Tie-in for Aboveground Restrained Lines
9.2.1 When a sufficient number of strings have been completed, the starting end of the pipeline shall be
tied in to a full thrust anchor or to a minimum of 600 m length of buried pipeline by a tie-in weld. The strings
which have been tied-in while resting on the skids or on the sand shall be placed onto the supports by
sidebooms, holding the line in a gentle S-curve between supports and skids.
9.2.2 There shall always be at least 900 to 1200 m of pipe attached to the line on skids or on the ground to
restrain it. The line shall be on the supports during the night and cool periods of the day.
9.2.3 Any canted supports on which the pipe lies shall be straightened. The top halves of ring girders or
straps shall be bolted onto the tied-in portion of the pipeline.
9.2.4 As an alternative, strings may be welded while resting on permanent supports. Two strings may be
tied together with a tie-in weld and the 1800 to 2400 m double string may be tied to the pipeline at tie-in
temperature. Double strings shall not be added until the end of the line can be tied to an end anchor or
buried pipeline in order to obtain the highest possible effective tie-in temperature.
9.3 Method of Tie-in for Aboveground Non-restrained Pipelines
Tie-in welds shall be made in a manner to avoid overloading intermediate anchors that are not designed to
take the pipe support friction force developed by a pipe string. A string shall always be connected to each
side of the anchor stub when the work is stopped at the end of the day. During the day, the time during
which only one string is connected shall be kept to a minimum.
10. Hydrostatic Testing
10.1 Safety
Pressure testing safety shall be followed during pressure testing.
10.2 Pneumatic Testing
Hydrostatic testing of piping shall be in accordance with P10E15.
11. Clean-Up
Construction waste materials shall be removed from the right-of-way as the construction progresses.
12. Records
12.1 Record books, shall be sent to the Contractor Design Office. Documentation shall describe and
locate all repairs and tie-in temperatures.
12.2 All survey data and as-built drawings shall be sent to the Contractor Design Office. The following
information shall be included:
a. Bottom-of-line elevations and ground elevations at all 30 m stations and at all preformed bends;
b. The location and degree of all horizontal bends;
c. The location and degree of all preformed sagbends and overbends;
d. The location of all vents and drains;
e. The identification, station, elevation, and size of all pipes which cross the pipeline and of any
other buried steel installations within 30 m;
f. The stations of all markers, appurtenances and cathodic protection facilities;
g. All other data which should be included on a maintenance record profile, including the stations of
block valves, anchors, road crossing, and changes in the grade of the pipe, wall thickness, and
diameter;
h. Safety Instruction Sheets per SES P01-E16.
Appendix A
A.1 Calculations For Required Cover
A.2.1 Overbends
a. Overbends must be held down by the weight of pipe and soil to counteract the uplift component
of the axial restraining force in the hot operating condition. The length of pipe including the bent
portion which is contributing to resisting the uplift is the critical length for an axially loaded column. The
axial force in the pipe tends to increase the arch height of this length of pipe, lifting it off the bottom of
the ditch. The weight of pipe overburden should cause a sag in the same length of pipe which exceeds
the increase in arch height to keep the pipe on the bottom of the ditch.
b. The desired safety factor is to be given. It appears that small diameter pipe (e.g. NPS 8 and
smaller) needs relatively more cover than large diameter pipe for small angle bends. However, it is
reasonable to accept a lower safety factor for small pipe than for large pipe. On this basis, the normal
minimum cover of 600 mm for oil and water lines and 900 mm for gas and NGL lines would be
sufficient for bends up to 2°. Only a small percentage of bends need to be larger than 2°.
A.2.2 Sagbends
a. Sagbends are subject to uplift when the line is below the tie-in temperature and (usually) also
depressurized. The uplift force is a function of the axial tension and the bend radius.
b. For small angles, it is assumed that the length of pipe which is effective, is the same as for
overbends. The maximum temperature drop will normally not exceed 25 °C. Higher temperature drops
must be expected in NGL pipelines which can cool due to blow-down. The minimum cover will usually
be adequate for all sagbends except when a large temperature drop can occur or when smaller than
standard bend radius is used. In the hot operating condition, the sagbends feel a downward load
which could double the soil pressure under the pipe. This does not create an unsafe condition.
A.2.3 Lateral Bends
The net passive soil resistance against the lateral load exerted by the pipeline must be conservatively
estimated because frequently, the cover of the line is a mounded fill with a width of only two pipe diameters.