This specification is formulated to improve the construction level of oil and gas pipeline projects, ensure the quality of pipeline projects, and reduce project costs. This specification is applicable to the construction and acceptance of new, modified, or expanded land-based pipeline projects for transporting crude oil and natural gas. This specification does not apply to process pipelines within oil and gas stations, oil and gas field gathering pipelines, urban gas transmission and distribution pipelines, and oil and gas pipelines within industrial enterprises, as well as oil and gas pipeline reconstruction and overhaul projects that have been put into operation. SY 0401-1998 Oil and Gas Pipeline Project Construction and Acceptance Specification SY0401-1998 Standard download decompression password: www.bzxz.net

1 General Principles
Petroleum and Natural Gas Industry Standard of the People's Republic of China Construction and Acceptance Specifications for Oil and Gas Pipeline Engineering
Approval Department: State Administration of Petroleum and Chemical Industry Date of Approval: 1999-03-03
Effective Date: 1999-10-01
SY 0401-1998
Replaces SYJ4001-1990
1.0.1 This specification is formulated to improve the construction level of oil and gas pipeline engineering, ensure the quality of pipeline engineering, and reduce engineering costs. 1.0.2 This specification is applicable to the construction and acceptance of new, modified, and expanded pipeline engineering for the transportation of crude oil and natural gas on land. This specification does not apply to process pipelines inside oil and gas transmission stations, oil and gas field gathering pipelines, urban gas transmission and distribution pipeline networks, oil and gas pipelines inside industrial enterprises, and oil and gas pipeline reconstruction and overhaul projects that have been put into operation. 1.0.3 The construction of pipeline projects is mainly divided into: surveying and laying out, cleaning of construction work belts and building of construction access roads, trench excavation, material and equipment inspection, material storage and steel pipe transportation, pipeline anti-corrosion insulation, assembly welding, pipeline trenching, backfilling, pressure testing, cleaning and gas pipeline drying, line shut-off valve installation, pipeline crossing engineering lines and ancillary projects. 1.0.4 Before construction, construction drawings review, design disclosure and on-site pile handover should be carried out, and records should be kept. A construction organization design should be prepared, and construction should be arranged reasonably according to the project quantity, construction period, natural conditions along the line, etc. 1.0.5 The construction unit should establish a quality assurance system, prepare reasonable quality plans and inspection plans, and ensure the quality of the project. 1.0.6 Enterprises that undertake the construction of oil and gas pipeline projects must obtain a petroleum construction enterprise qualification certificate issued by the state or industry competent authorities, and undertake projects within the construction scope specified in the qualification certificate. 1.0.7 The requirements for occupational safety and health, environmental protection, and cultural relics protection in the construction of oil and gas pipeline projects shall comply with national and local laws and regulations.
1.0.8 In addition to complying with the provisions of this specification, the construction and acceptance of oil and gas pipeline projects shall also comply with the provisions of the current national mandatory standards (specifications).
2 Handing over piles, moving piles, cleaning the construction work zone, measuring and setting out lines, and building construction access roads 2.1 General provisions
2.1.1 After the design unit and the construction unit hand over the control (corner) piles on site, the construction unit shall measure and set out lines, move the piles to the edge of the construction work zone, and then clean the construction work zone and build construction access roads. 2.1.2 After the trench is backfilled, the designed control (corner) piles shall be restored to their original positions. 2.2 Handing over and moving piles
2.2.1 When the design representative hands over the design control (corner) piles to the construction unit on site, the pile number, mileage, elevation and corner angle should be checked. After handing over the piles, the construction unit should take measures to protect the control (corner) piles, and the lost piles should be re-measured and replaced. 2.2.2 In plain areas, the method of moving piles equidistantly and parallel to the pipeline axis should be adopted (Figure 2.2.2). The position of the pile should be 1m inside the construction zone boundary line on the pipeline assembly welding side. The corner pile should be moved in the direction of the angle bisector of the corner. The pile after translation is called the auxiliary pile of the original pile. When it is difficult to move piles in mountainous areas, the guidance method can be used for positioning, that is, 4 guide piles are planted around the control (corner) pile, and the intersection of the four-sided diagonal lines formed by the 4 guide piles is the position of the original control (corner) pile. 343
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Centerline of pipeline ·
Pile position after translation
1\Auxiliary pile
2.3 Cleaning of construction operation zone
2#Auxiliary pile
√3Auxiliary pile
Angle bisector
Note: α is the equal distance during translation
＆4Auxiliary pile
5#Auxiliary pile
Angle bisector
Figure 2.2.2 Pile relocation method in plain area
2.3.1 The width of the construction operation zone is generally 20m if there is no stipulation in the design. When crossing or crossing rivers, ditches, roads, railways, areas with abundant groundwater and trenches with a depth of more than 5m, and where the pipe-pulling vehicle turns around, the width of the zone can be appropriately increased according to actual needs. In mountainous areas where non-mechanized construction and artificial rock drilling are carried out, the width of the land occupation can be reduced as appropriate according to the terrain and landform conditions. 2.3.2 Within the scope of the construction zone, stones, weeds and trees that affect the passage of construction machinery or construction operations should be cleared, ditches and ridges should be leveled, and low-lying areas with accumulated water should be drained. When cleaning the construction zone, attention should be paid to the protection of the land to reduce or prevent soil erosion.
2.3.3 When cleaning and leveling the construction zone, attention should be paid to protecting the construction sign piles, and if damaged, they should be restored immediately. 2.4 Surveying and setting out
2.4.1 Surveying and setting out should be carried out according to the design control (corner) piles or their auxiliary piles, and the line position should not be changed without authorization. When the line position needs to be changed, it must be changed with the written consent of the design representative. 2.4.2 The line axis (or trench excavation edge line) and the boundary line of the construction zone should be laid out when measuring and setting out the pipeline. Add 100-meter piles on the line axis (or trench excavation edge) and the boundary line of the construction zone, and draw wires or spread white lime lines between the piles. The cross-sectional layout of the construction zone in general areas is shown in Figure 2.4.2.
Work
Pipe laying and welding
Construction access road
Figure 2.4.2 Cross-sectional layout of the construction zone
Boundary line of the construction zone
SY 0401--1998
2.4.3 When the horizontal turning angle of the pipeline is large, additional piles should be added. For elastically laid pipe sections or cold-bent pipe sections, the horizontal turning angle should be laid out on the ground according to parameters such as tangent length and external vector moment. For pipe sections using prefabricated elbows and bends, the curve should be laid out according to the radius of curvature and angle.
2.4.4 For pipelines in mountainous areas and areas with large terrain fluctuations, the longitudinal turning angle slope change points should be laid out according to the slope change point position, angle, curvature radius and other parameters indicated in the construction drawings or pipeline construction measurement results table. 2.4.5 At both ends of the crossing sections of rivers, ditches, roads and railways, at both ends of the crossing sections of underground pipelines, cables and optical cables, at both ends of the line valve room and at the boundary where the pipeline diameter, wall thickness, material and anti-corrosion layer change, the marking piles should be set up. The setting position should be on the side of the pipeline assembly welding, 1m within the boundary line of the construction work zone.
2.5 Construction of construction access roads
2.5.1 The construction access road should be flat and have sufficient bearing capacity to ensure the driving safety of construction vehicles and equipment. The width of the construction access road should be greater than 4m and smoothly connected to the road. A meeting place should be set up every 2km. The road surface width of the curve and the meeting place should be greater than 10m, and the turning radius of the curve should be greater than 18m. 2.5.2 When the construction access road passes through a small river or ditch, it should be decided whether to build a temporary bridge or reinforce the original bridge according to the on-site conditions. The bearing capacity of the bridge should be above 10t.
2.5.3 When building a construction access road in swamps, paddy fields, deserts and other areas, measures should be taken to strengthen the roadbed. 2.5.4 When the construction access road passes through shallow underground pipelines, cables, ditches and other underground structures or facilities, protective measures should be taken as appropriate. 3 Excavation of pipe trenches
3.1 Geometric dimensions of pipe trenches
3.1.1 The excavation depth of the pipe trench should meet the design requirements. The excavation depth of the pipe trench in the stone section should be 0.2m deeper than that of the pipe trench in the earth section. The depth of the pipe trench in the lateral slope section should be calculated according to the low side depth of the pipe trench cross section. 3.1.2 The slope of the pipe trench side slope should be determined according to the soil type, mechanical properties and excavation depth of the pipe trench. The slope of the steepest side slope of a trench with a depth of less than 5m (without support) can be determined according to Table 3.1.2. Table 3.1.2 Steepest slope of trench with depth less than 5 m Soil type
Medium-dense sand
Medium-dense gravel soil (filled with sand) Hard plastic light sub-clay
Medium-dense gravel soil (filled with clay) Hard plastic sub-clay, clay
Old loess
Soft soil (dewatered by well points)
Hard rock
No shear load on top of slope
Steepest slope gradient
Static load on top of slope
1 + 1.00
Dynamic load on top of slope
For trench slopes with depth exceeding 5 m, appropriate slope slowing down, additional support or stepped excavation measures can be adopted according to actual conditions. 3.1.3

3.1.4 The bottom width of the trench shall be determined according to the outer diameter of the pipeline, excavation method, assembly welding process and type of work geology. The bottom width of the trench within the depth of 5m345
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shall be determined according to formula (3.1.4). In the formula: B trench bottom width (m) see Table 3.1.4; B=Dm+K
Dm—structural outer diameter of the steel pipe (including the thickness of the anti-corrosion and insulation layer) (m); K——trench bottom widening margin (m), according to Table 3.1.4. Table 3.1.4
Ditch bottom widening margin K value
Ditch welding
Conditions and factors
Ditch depth within 3m㎡
Ditch depth 3~5 m
Earth pipe trench
Edges, cold-bent pipes
Ditch trench
Manual arc welding under the trench
Earth pipe trench
Semi-automatic welding under the trench
Note: ①When mechanical trench excavation is used, if the calculated trench bottom width is less than the bucket width, the trench bottom width is calculated according to the bucket width. ②The trench widening range of the trench at the elbow, bend, joint, and semi-automatic welding under the trench is 1m on both sides of the working point. 3.1.5 For trenches with a depth of more than 5m, the trench bottom width should be handled as appropriate according to the engineering geological conditions. 3.2 Excavation of pipe trenches
(3.1. 4)
Under-trench welding
Edges, elbows
and joints
3.2.1 Before excavating the pipe trench, the distribution of underground facilities should be explained to the construction personnel. Within 3m on both sides of the underground facilities, manual excavation should be adopted, and necessary protection should be given to the excavated underground facilities. For important underground facilities, the consent of the management unit should be obtained before excavation, and the excavation should be carried out under its supervision when necessary.
3.2.2 When excavating the pipe trench, the excavated earth and stone should be piled up on the side of the trench opposite to the welding construction, and the piled soil should be 0.5m away from the trench edge. 3.2.3 When excavating the pipe trench in the cultivated area, the surface cultivated soil and the lower soil should be piled up separately. 3.2.4 The blasting excavation of the pipe trench should be completed before the pipe is laid. Blasting operations should be undertaken by teams with blasting qualifications. Safety measures should be formulated for blasting operations, and blasting safety distances should be specified. The safety of nearby residents, pedestrians, and above-ground and underground facilities should not be threatened. For important facilities that may be affected, relevant units and personnel should be notified in advance, and blasting can only be carried out after safety protection measures are taken. 3.2.5 When excavating trenches, attention should be paid to protecting underground cultural relics. Once cultural relics are discovered, the site should be protected first, and then reported to the local competent authorities. 3.3 Trench Acceptance
3.3.1 The allowable deviations of the trench centerline, trench bottom elevation, trench bottom width, and slope change point displacement should comply with the provisions of Table 3.3.1. Table 3.3.1 Allowable deviation of trench
Offset of trench centerline
Elevation of trench bottom
Allowable deviation (mm)
Width of trench bottom
Displacement of slope change point
Allowable deviation (mm)
3.3.2 The trench in straight section should be straight; the trench in curved section should have smooth transition and the curvature radius required by the design should be guaranteed. 3.3.3 There should be no falling stones on the trench wall of the stone section trench and no stones on the trench bottom. 3.3.4 After the trench is excavated, it should be inspected and accepted in time. If it does not meet the requirements, it should be repaired in time. The inspection record of the trench should be kept, and the process handover procedures should be handled in time after acceptance.
4 Main materials, pipeline accessories, equipment and inspection for the project 4.1 General provisions
SY 0401--1998
4.1.1 The materials, specifications and models of the materials, pipeline accessories and equipment used in the project must meet the design requirements, and their quality should meet the requirements of the relevant national or industry standards in force. Materials, accessories and equipment should have factory certificates, quality certificates and material certificates or instructions for use. 4.1.2 Pipeline accessories shall not be made of cast iron, and pipe elbows should be seamless, straight seam or double straight seam structures, and spiral welded steel pipes should not be used. The elbow body should not have T-shaped or circular welds. Elbows should be made and inspected in accordance with relevant standards and design requirements. 4.1.3 Elbows, cold-bent pipes and elastically laid pipe sections of pipeline lines should meet the requirements of Table 4.1.3. Table 4.1.3 Regulations for elbows, cold-bent pipes, and flexible pipe sections
Cold-bent pipes
D≤323.9 mm
D>323.9 mm
Flexible pipe sections
Note: D-bzxZ.net
Outer diameter of the pipe.
4.2 Inspection and repair of materials and equipment
Radius of curvature R
≥30D
≥40D
≥1000D
Appearance and main dimensions
No wrinkles, cracks, heavy skin, mechanical damage; other regulations
Ovality is less than or equal to 2.0%, R etc. "Can be cut into small angles for use, but when the short arc is longer than 5D, the wall thickness reduction rate is less than or equal to 51mm and should be greater than 9.0%
No wrinkles , cracks, mechanical damage, the elliptical end of the bend retains a 2m straight pipe section, the ellipticity is less than or equal to 2.0%
No wrinkles, cracks, mechanical damage, the ellipticity of the bend is less than or equal to 2.0%
Greater than or equal to 1%
Meet the design requirements
4.2.1 The factory certificates, quality certificates and material certificates of the materials, pipeline accessories and equipment used in the project should be checked. When there is doubt about their quality (or performance), they should be re-inspected, and those that fail to meet the standards shall not be used. 4.2.2 The outer diameter, wall thickness, ellipticity and other dimensional deviations of the steel pipe should be checked according to the pipe manufacturing standards. There should be no cracks, scars, folds or other defects on the surface of the steel pipe whose depth exceeds the deviation under the nominal wall thickness. 4.2.3 If the steel pipe has harmful defects such as bending, pits, grooves, notches, flattening, etc., it should be repaired or eliminated before use: the notches or interlayers at the ends of the steel pipe should be polished and repaired. If the notches or interlayers cannot be repaired, the pipe section where they are located should be cut off and the groove should be reprocessed.
When the deformation or flattening of the steel pipe exceeds the standard requirements, it should be discarded. 2
3 Minor pits at non-stress concentration points with a depth not exceeding 2% of the nominal pipe diameter and a length not exceeding 10mm may not be repaired, but they must not affect the butt welding. If there are pits at the pipe welding seam, the part of the pipe section where they are located should be cut off. 4 The pipe section where the bent part of the steel pipe is located should be cut off. 5 It is strictly forbidden to use patching and welding methods for repair. 4.2.4 Defects in the pipe welding seam should be repaired according to the pipe making standards. 4.2.5 The materials of elbows and bent pipes should match the physical, chemical properties and weldability of the conveying pipe. The longitudinal weld of the hot-bending elbows and bends of straight seam steel pipes shall be located at the 45° position of the inner arc of the elbows and bends. The pipe diameter deformation rate of any bending part shall not be greater than 4.9% of the nominal diameter of the pipe, and shall meet the size requirements for passing through the pipe cleaner (ball). The bending angle, outer diameter of the steel pipe, wall thickness, radius of curvature and material model and other parameters shall be marked at the end of each elbow and bend; other requirements shall comply with the provisions of Table 4.1.3 of this standard. 4.2.6 Before installing the insulating joint or insulating flange, a water pressure test shall be carried out. The test pressure shall be 1.5 times the design pressure, and the voltage stabilization time shall be 5 minutes. No leakage is qualified. After the pressure test, the residual water shall be wiped off and the insulation test shall be carried out. The test shall be measured with a 500V megohmmeter, and the insulation resistance shall be greater than 2 MQ.
4.2.7 Before installing the line cut-off valve, appearance inspection, valve opening and closing inspection and water pressure test shall be carried out. The inspection requirements shall comply with the provisions of Table 4.2.7.
Table 4.2.7
Appearance inspection
Opening and closing inspection
Shell strength test
Water pressure test
Valve tightness test
Inspection and test regulations for cut-off valves
Inspection and test contents
Auxiliary equipment
Anti-corrosion layer of buried valves
Opening and closing indicator
1.5 times the maximum working pressure, steady pressure for 5 minutes
1.1 times the maximum working pressure, steady pressure Press for 2min
Inspection standard
No sand holes
No cracks
Complete and intact
Electric spark leak detectionNo leak points
No leakage
No leakage
4.2.8 Various anti-corrosion materials, including primer, primer, patching and repair materials, shall be subjected to random inspection tests for coating or application according to relevant technical standards or design requirements before use. If the test fails, the random inspection test shall be doubled according to the number of samples. If it still fails, it shall not be put into use. 5 Storage of materials and loading, unloading, transportation and pipe laying of steel pipes 5.1 Storage of materials
5.1.1 Steel pipes, pipeline accessories, valves, coatings and other equipment materials shall be properly kept in accordance with the requirements of the product manual. During storage, they shall be inspected to prevent rust, deformation, aging or performance degradation. 5.1.2 Glass cloth, plastic cloth, polyethylene, epoxy powder, coal tar enamel inner (outer) wrapping tape, welding materials, heat shrink sleeves and other materials should be stored in the warehouse, among which epoxy powder and welding materials should be stored in a ventilated and dry warehouse, and the relative humidity of welding rods should not exceed 60% during long-term storage. Steel pipes, pipe fittings, valves, asphalt, coal tar enamel and other materials or equipment can be classified and stored in the open air. The storage site should be flat and free of stones, and there should be no water accumulation on the ground. The storage site should maintain a slope of 1% to 2% and be equipped with drainage ditches. Roads for cars and cranes to enter and exit the site should be built in the storage site, and there should be no overhead power lines above the site. The warehouse for flammable and explosive items should be equipped with fire-fighting equipment according to relevant standards. 5.1.3 Steel pipes or anti-corrosion steel pipes should be stacked in layers in the same direction, and the stacking height should not exceed 3m, and it should be ensured that the pipes do not lose stability and deformation, and the anti-corrosion layer is not damaged. Steel pipes or anti-corrosion steel pipes of different specifications and materials should be stacked separately. There should be cushions between each layer of anti-corrosion pipes. Two rows of sleepers or sandbags should be laid under the bottom layer of pipes. The distance between the pipes and the ground should be greater than 50mm. To ensure the stability of the pipe stack, the steel pipes or anti-corrosion pipes in the bottom layer should be wedged with wedges.
5.1.4 Valves should be stored in their original packaging, and waterproof measures should be taken during storage. 5.1.5 Asphalt should be stored on a site with a cement mortar floor. A fence (railway) should be set up around the site. A canopy should be set up when the weather is hot. 5.2 Loading and unloading of steel pipes
5.2.1 Special lifting equipment should be used for loading and unloading of pipes. They should be lifted and placed gently during operation. It is strictly forbidden to drop, bump, knock or bump. Attention should be paid to protecting the pipe mouth and the anti-corrosion layer. When directly hooking the pipe mouth, no gaps or scars should be caused on the pipe mouth. 5.2.2 A shoulder pole lifting equipment should be used for lifting double-jointed pipes. 348
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5.2.3 Pipe grabbers are only allowed to grab light pipes shorter than 12m. During operation, they should be grabbed and put down gently, and steel pipes should not be damaged or pinched, or hung or hit other objects.
5.2.4 When loading and unloading vehicles on electrified railway platforms, the railway industry operating procedures should be followed, and the consent of the railway station management department should be obtained. 5.2.5 During the driving, lifting, loading and unloading process of all construction machinery and equipment, the safe distance between any part and the overhead power line should comply with the provisions of Table 5.2.5.
Safety distance between construction machinery and equipment and overhead power lines Power line voltage (kV)
Safety distance (m)
5.3 Transportation of steel pipes by automobile
1～35
>0, 01(n—50)+5
5.3.1 The transportation of steel pipes by automobile shall comply with the relevant regulations of the transportation department. When transporting pipes on plain roads, the height of the pipes should not exceed 2.4m. When transporting pipes on mountainous roads, the height of the pipes should not exceed 2m, and the length of the pipes extending behind the vehicle should not exceed 4m. 5.3.2 Before loading the anti-corrosion pipes, the anti-corrosion grade and wall thickness of the pipes should be checked, and pipes of different anti-corrosion grades and wall thicknesses should not be mixed. 5.3.3 When transporting anti-corrosion pipes, protective measures should be taken for the anti-corrosion layer. Rubber sheets or other soft material pads should be properly set between the anti-corrosion pipes and the frame or column, between the anti-corrosion pipes, and between the anti-corrosion pipes and the binding ropes. The outside of the binding rope should be covered with a rubber tube or other soft tube sleeve. 5.3.4 The anti-corrosion pipes transported to the site should be inspected and accepted by the construction unit one by one, and the handover procedures should be handled. 5.4 Pipe laying
5.4.1 Pipes should be laid according to the position specified in the design drawings, the steel pipe specifications used and the anti-corrosion layer grade. Before laying pipes, the circumference and diameter of the pipe mouth should be measured to match the counterparts.
5.4.2 The pipe stacking site should be flat, without stones, stagnant water, hard roots and other objects that damage the anti-corrosion layer. If necessary, two-row soil burial, sandbags or straw bags should be placed under the anti-corrosion pipes.
5.4.3 The location of the pipe stacking should be away from overhead power lines and as close to the pipelines as possible. The distance between pipe stacks should not exceed 500m. 5.4.4 Pipe piers should be laid (built) before laying pipes on the trench, and one pipe pier should be set under each pipe. The height of the pipe pier in plain areas should be 0.4~0.5m, and in mountainous areas, it should be set according to the terrain changes. The pipe pier can be built with soil and compacted. When it is inconvenient to take soil, soft materials can be filled in sacks as pipe piers.
5.4.5 When laying pipes on the trench, the density of steel pipes should be appropriate, and the ends of the pipes should be staggered to facilitate cleaning inside the pipe, cleaning the slope and lifting. When the pipe crane is used for laying and lifting, it is advisable to lift a single pipe. When lifting two or more pipes, effective protective measures should be taken to prevent damage to the anti-corrosion layer.
5.4.6 When laying pipes on the trench and assembling and welding, a certain safety distance should be maintained from the edge of the pipeline to the edge of the trench, and its value should comply with the provisions of Table 5.4.6.
Table 5.4.6 Safe distance between the pipe pier edge and the edge of the trench A Soil category
Dry hard soil
Moist soft soil
The distance from the center of the pier (the center of the assembled pipeline) to the center of the trench (the center of the line) shall be calculated according to formula (5.4.6). S≥Dm
(5.4.6)
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Where: S—--the distance from the center of the pier (assembly pipeline) to the center of the trench (line) (m); the structural outer diameter of the steel pipe, (m);
K——the widening margin of the trench bottom (m) (values ​​are taken according to Table 3.1.4); α---the horizontal projection distance of the trench slope (m); h--the trench depth (m);
i--the slope gradient (values ​​are taken according to 3.1.2); A—safety distance (m) (values ​​are taken according to Table 5.4.6). 5.4.7 When laying pipes under the trench, a distance of about 100 mm should be left between the ends of the pipes, and the pipes should be placed staggered. 6 Pipeline anti-corrosion insulation and thermal insulation engineering
6.0.1 For the anti-corrosion and thermal insulation of steel pipes, elbows, and cold-bent pipes, on-site anti-corrosion patching and repairing construction should comply with the design requirements and the provisions of the current relevant standards.
6.0.2 The outer surface of the anti-corrosion layer should be flat, without defects such as missing coating, wrinkles, streams, bubbles and pinholes; the anti-corrosion layer should be able to effectively adhere to the metal surface; anti-corrosion patching and repairing should use anti-corrosion materials that match the performance of the pipeline anti-corrosion layer; polyethylene heat shrink sleeves (tapes), polyethylene cold-wrapped adhesive tapes, and two-component epoxy powder repairing liquids, repairing hot melt rods and other patching and repairing materials should be constructed according to the requirements of the manufacturer's instructions. 6.0.3 The anti-corrosion of pipeline anchor piers, crossing section pipelines, and cathode protection test line welding points should be inspected and qualified by quality inspection personnel before proceeding to the next process. The anti-corrosion material at the welding point of the cathodic protection test line should match the pipeline anti-corrosion layer and have good adhesion to the outer skin of the test line. 6.0.4 The anti-corrosion layer of the pipeline outlet and the ground should be more than 100mm above the ground, and a heat shrink sleeve or other protective measures should be taken outside the pipe at the junction with the ground. The overlap of the heat shrink sleeve should be smooth, without damage and leakage. 7 Pipeline welding and acceptance
7.1 General provisions
7.1.1 The applicable methods for pipeline welding include manual welding, semi-automatic welding, automatic welding or any combination of the above methods. 7.1.2 The performance of pipeline welding equipment should meet the welding process requirements, and have good working condition and safety performance, suitable for field working conditions.
7.1.3 Before welding construction, a detailed welding process instruction book should be formulated according to the design requirements, and the welding process assessment should be carried out accordingly. Then, a welding process specification should be compiled based on the qualified welding process. The welding process assessment should comply with the relevant provisions of "Steel Pipeline Welding and Acceptance" SY/T4103.
7.1.4 The welder shall have the corresponding qualification certificate. The welder qualification examination shall comply with the relevant provisions of SY/T4103. 7.1.5 Welding shall not be carried out in any of the following environments without taking effective protective measures: 1 Rainy or snowy days;
2 The relative humidity of the atmosphere exceeds 90%;
3 When welding with coated electrodes manually, the wind speed exceeds 8m/s; when welding with gas shielded welding, the wind speed exceeds 2.2m/s; when welding with flux-cored wire self-shielded welding, the wind speed exceeds 11m/s;
4 The ambient temperature is lower than the temperature specified in the welding procedure. 7.2 Pipeline assembly and welding
7.2.1 The design of butt weld grooves shall comply with the provisions of Figure 7.2.1. 7.2.2 The design of equal wall thickness butt weld joints shall comply with the provisions of Figure 7.2.2. 7.2.3 The design of butt welded joints with unequal wall thickness shall comply with the provisions of Figure 7.2.3-1 and Figure 7.2.3-3. 7.2.4 The corresponding pipe group shall comply with the provisions of Table 7.2.4. 350
30°±2.5
(1.5±0.75) mm
（a）Standard groove of steel pipe for downward welding
32.5°±2.5°
(1.5±0.75)m
（c）When t≤22mm, standard groove of steel pipe and pipe fittings 1
SY 0401--1998
32.5°±2.5°
(1. 5±0.75) mm
（b）Standard groove of steel pipe for upward welding
10°±1
37.5°±2.5°
(1. 5±0.75)mm
（d）When t>22mm, standard groove of steel pipe and pipe fitting Figure 7.2.1 Groove design
55～65°
（a）Butt welding of steel pipe downward
32. 5°± 2. 5~ 37. 5 ±2. 5°2～3.5
（c）Butt welding of steel pipe and pipe fitting
60°～70°
2 ~ 3. 5
（b）Butt welding of steel pipe upward
32.5±2.5°~37.5°±2.5°
（d）Butt welding of steel pipe and pipe fitting
Figure 7.2.2 Design of butt welding joint with equal wall thickness
SY 0401—1998
14~30°
(a) Pipe outside welding
Maximum 2.5m
(c) Pipe inside welding
Figure 7.2. 3-1
Maximum 30°
Figure 7. 2. 3-2
Maximum 30″
1430°
(b) External pipe welding
14°～30°
(d) Internal pipe welding
Design of butt weld joints with same outer diameter and unequal wall thicknessMaximum 30°
Design of butt weld joints with same inner diameter and unequal wall thickness14～30
14°～30*
Figure 7.2.3-3 Design of butt weld joints with different inner and outer diameters and unequal wall thicknessTable 7.2. 4 Pipeline assembly regulations
Inspection items
Pipe cleaning
Pipe opening cleaning (within 10mm) and repairing Spiral weld or straight seam residual height grinding of pipe ends
Spacing between spiral welds or straight seams at two pipe openings
Misalignment and misalignment correction requirements
Regulations
No debris
Pipe opening is intact, without rust, oil stains, paint end 10 mm The excess height within the range is ground off and the transition is smooth. The spacing is greater than or equal to 100mm
The staggered mouth is less than or equal to 1.6mm, the circumference is evenly distributed, and some are hammered
Inspection items
Length of short section of steel pipe
The length of the middle straight pipe section of two adjacent and opposite elastic laying pipes The length of the middle straight pipe section of two adjacent and opposite elbows After segmentation, the short arc length of the small angle elbow Pipe docking deviation
Double pipe rotary welding platform
Manual welding working space
Semi-automatic welding working space
7.2.5 Welding materials shall meet the following requirements: SY 0401-1998
Requirements
Greater than the pipe diameter, and not less than 0.5m
Greater than or equal to 0.5m
Not less than the outer diameter of the pipe, and not less than 0.5 m
is greater than 51mm
is less than or equal to 3, and the oblique cut is not allowed (shrimp waist is prohibited). The joint pipe is straight and there is no jumping when rotating.
is greater than D.4m (from the pipe wall)
is greater than 0.5m (from the pipe wall), and the two sides of the groove welding are greater than 0.8m. The welding rod should not be damaged, moldy, oily, or rusted; the welding wire should not be rusted or bent; the flux should not be deteriorated; the purity and 1
dryness of the shielding gas should meet the requirements of the welding process regulations. 2 Low-hydrogen welding rods should be dried before welding, the drying temperature is 350~~400℃, the constant temperature time is 1~2h, and they should be stored at 100~~150℃ after drying. When welding, they should be taken out as needed and placed in the welding rod insulation box, but the time should not exceed 4h. The welding rods that are not used up on the same day should be recycled and stored, and used first after re-drying. The number of re-drying shall not exceed twice. 3. The drying temperature of cellulose electrodes should be 80~～100℃, and the drying time should be 0.5～1h. Cellulose electrodes do not need to be dried if they are well packaged and not damp.
During the welding process, if the electrode coating turns red, burns, or the arc is seriously deflected, the electrode should be replaced immediately. 4
7.2. During the welding process, the protection of pipes and anti-magic layers should meet the following requirements: 1. During welding, the arc should not be struck on the pipe wall outside the groove; 2. The ground wire of the welding machine should be firmly connected to the pipe to prevent the ground wire and the pipe wall from generating an arc and burning the pipe; 3. For epoxy powder anti-corrosion pipes, a protective layer with a width of 0.8m should be wrapped around the pipe mouths at both ends of the weld before welding to prevent welding spatter and burns.
7.2.7 The use of the butt jointer shall meet the following requirements: When using the internal butt jointer, it shall be disassembled and moved after the root welding is completed. When moving the butt jointer, the pipe shall remain stable; 1
When using the external butt jointer, it shall be disassembled after 50% of the root welding is completed. The completed root welding shall be divided into multiple sections and evenly distributed. 2
Preheating before welding shall meet the following requirements:
Preheating before welding shall be carried out according to the temperature specified in the welding process specification, and the interlayer temperature during welding shall not be lower than its preheating temperature; 2
When welding two materials with different preheating requirements, the material with higher preheating temperature requirement shall prevail; 3
The preheating width shall be 50mm on both sides of the weld. The temperature shall be measured using an infrared thermometer or other measuring tools. The temperature at the end of preheating should be higher than the specified temperature but should not exceed 50°C. 7. 2. 9
Pipeline welding shall comply with the following provisions:
Downward welding shall comply with the provisions of "Pipeline Downward Welding Process Specification" SY/T4071; the root weld must be fully melted and the back side must be well formed. After the root welding is completed, the welder should carefully check whether there are cracks. If there are cracks, they should be eliminated and then re-welded;
The electrode joints should be slightly polished. The electrode joints of two adjacent layers should not overlap and should be staggered by more than 20mm; 3
During the welding process, attention should be paid to controlling the interlayer temperature. When the interlayer temperature is lower than the specified requirements, it should be reheated; 4
5 After each welding, the slag should be carefully cleaned to remove surface pores, slag inclusions and other defects. The grinding wheel powder should also be removed. 353
SY 0401—1998
6 The electrode diameter, welding polarity, current, voltage, welding speed, and rod transport method used should comply with the requirements of the welding procedure specification. 7.2.10 After the weld is welded, the surface slag and spatter should be cleaned. 7.2.11 For welds that require post-heating or heat treatment, post-heating or heat treatment should be carried out in accordance with the provisions of the welding procedure specification. 7.2.12 Before leaving get off work every day, the pipe ends of the pipelines should be temporarily sealed to prevent foreign objects from entering. Pipelines under trenches should also be waterproofed. 7.2.13 The weld mark should consist of the code of the welder or the assembly line welder group and the number of welds they have completed. The mark can be written with a marker on the surface of the anti-corrosion layer 1m downstream of the weld (oil and gas flow direction), and welding records should be made at the same time. 7.3 Inspection and acceptance of welds
7.3.1 The weld should be visually inspected first, and non-destructive testing can be carried out only after the appearance inspection is qualified. The appearance inspection of welds should comply with the provisions of Article 6.4 of SY/T4103-1995, and the weld cover size should comply with the following provisions. 1 Width: upper width of groove + (2~4) mm; 2 Residual height: 0~1.6 mm. The local width shall not exceed 3 mm, and the length shall not exceed 50 mm. 7.3.2 When performing radiographic and ultrasonic testing, the weld acceptance standards shall be the SY4056 "Radiographic and Quality Grading of Butt Welds of Petroleum and Natural Gas Steel Pipelines" and the SY4065 "Ultrasonic Testing and Quality Grading of Butt Welds of Petroleum and Natural Gas Steel Pipelines". The qualified level shall comply with the following provisions:
1 When the design pressure of the oil pipeline is less than or equal to 6.4MPa, the qualified level is Level III; when the design pressure is greater than 6.4MPa, the qualified level is Level II.
2 When the design pressure of the gas pipeline is less than or equal to 4MPa, the qualified level of the pipeline in the first and second level areas is Level III, and the qualified level of the pipeline in the third and fourth level areas is Level IⅡ; when the design pressure is greater than 4MPa, the qualified level is Level I. 7.3.3 According to needs, the weld non-destructive testing acceptance standards may also be selected from the provisions of Chapter 9 of SY/T4103-1995. 7.3.4 The flaw detection ratio of oil pipelines can be selected from the following: 1. After 100% ultrasonic flaw detection, 5% of the welds completed by each welder or assembly line welder group every day shall be re-inspected by radiographic flaw detection; 2. No ultrasonic flaw detection shall be performed, and only radiographic flaw detection spot check shall be performed. The spot check ratio is 15% of the welds completed by each welder or assembly line welder group every day.
7.3.5 The flaw detection ratio of gas pipelines can be selected from the following: 1100% ultrasonic flaw detection, and then the welds completed by each welder or assembly line welder group every day shall be re-inspected by radiographic flaw detection in proportion. The re-inspection ratio shall comply with the following provisions: 5% in the first-level area; 10% in the second-level area; 15% in the third-level area; 20% in the fourth-level area. 2 No ultrasonic flaw detection is performed, only radiographic flaw detection spot check is performed. The spot check ratio of the number of welds completed by each welder or assembly line welder group every day shall comply with the following provisions: 10% in the first-level area; 15% in the second-level area; 40% in the third-level area; 75% in the fourth-level area.
7.3.6 During the re-inspection or spot check of radiographic flaw detection, if the number of welds per day does not meet the required proportion, each dry meter can be used as an inspection section, and the inspection can be carried out as the welds are welded according to the specified proportion, and the inspection and spot check can be carried out evenly. 7.3.7 During the re-inspection or spot check of radiographic flaw detection, if one weld is unqualified, the welds welded by the welder or the assembly line welding group on that day or in the inspection section shall be double-checked. If there are more unqualified welds, the remaining welds shall be radiographically inspected one by one. 7.3.8 For pipeline welds that cross rivers, reservoirs, roads, railways, and pass through underground pipelines, cables, and optical cables, and for welds connecting steel pipes and elbows, the joints of joints after pressure testing shall be 100% radiographically inspected. 7.3.9 The removal and repair of welding defects shall comply with the provisions of Chapter 10 of SY/T4103-1995. For pipes of grade X60 and above, 354
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