Detailed explanation of PE gas pipeline welding construction process

Detailed explanation of PE gas pipeline welding construction process

Welding of polyethylene gas pipeline

Section 1 Material Quality and Storage

1. Materials

(1) General provisions

1. The pipes, fittings, valves and pipeline ancillary equipment in the polyethylene pipeline and steel skeleton polyethylene composite pipeline system shall comply with the relevant national product regulations.

2. The user's acceptance of pipes and fittings should check the following items according to relevant standards:

(1), inspection certificate

(2) Test report
The thickness of the scraped scale should be 0.1-0.2mm when entering the epidermis;

3. When the steel skeleton polyethylene composite pipe and the polyethylene pipe with a nominal outer diameter of less than 90mm, and the pipe roundness affects the installation, a round tool should be used to round the input end;

4. Insert the end of the pipe or fitting into the socket of the electrofusion pipe fitting to the position of the length mark, and check the matching size;

5. Before energizing, straighten the two corresponding parts to be connected so that they are on the same axis, and fix the pipes and fittings with special fixtures.

5. The operation of electrofusion saddle connection shall meet the following requirements:

1. A mechanical device should be used to fix the pipe section of the main pipe connection part to maintain straightness and roundness;

2. The connection part of the pipe should be wiped clean, and the surface of the connection part of the main pipe should be scraped off with a scraper;

3. Before power-on, the fused saddle-shaped connection pipe fittings should be fixed to the pipe connection parts with mechanical devices.

6. The quality inspection of the fused connection joint shall meet the following requirements:

1. Electric fusion bearing connection

1) The pipe at the port of the electrofusion pipe fitting or the socket pipe fitting should have obvious skin scratch marks and obvious entry length marks;

2) For polyethylene piping system, there should be no molten material overflow at the joint; when steel skeleton polyethylene composite pipe system is connected by steel skeleton electric fusion pipe fittings, a small amount of overflow material and overflow can be allowed at the joint ( Axial dimension) shall not exceed the requirements of Table 5.3.6;

Table 5.3.6 Allowable overflow amount (axial dimension) of steel frame electrofusion pipe fittings mm

Pipe nominal diameter DN

50≤DN≤300

300 ＜ DN≤500

Overflowing edge of electrofusion pipe

10

15

3) The resistance wire in the electric fusion pipe fittings should not be extruded (except for the special structural design of the electric fusion pipe fittings);

4). There should be a small amount of molten material overflowing in the observation hole on the electric melting pipe fittings, but the overflowing material should not be flowing.

5). Any situation that does not meet the above requirements shall be judged as unqualified.

2. Electrofusion saddle connection

1). There should be obvious scratch marks on the pipes around the fused saddle-shaped fittings;

2). The outlet of the saddle-shaped branch or saddle-shaped tee should be perpendicular to the center line of the pipe;

3) The pipe wall should not collapse;

4). The molten material should not overflow around the saddle pipe fittings;

5) A small amount of molten material should overflow in the observation hole on the saddle-shaped pipe fittings, but the overflow material should not be flowing.

6). Any situation that does not comply with the above requirements is judged as unqualified.

4. Flange connection

(1) The connection between the flange of the metal pipe end and the metal pipe shall comply with the regulations and design requirements of the flange connection of the metal pipe.

(2) The flange connection at the polyethylene pipe end or steel frame polyethylene composite pipe end shall meet the following requirements:

1. The flange should be sleeved into the end of the polyethylene flange connector to be connected;

2. The flat end of the flange connector should be connected to the polyethylene composite pipe according to the requirements of the hot melt connection or electric fusion connection specified in this regulation.

(3) The screw holes on the two flanges are parallel, the flange faces are parallel to each other, the bolt holes and the bolt diameter should be matched, the bolt specifications should be the same, the nuts should be on the same side; the bolts on the fastening flange should be symmetrical The order should be tightened evenly and should not be assembled forcefully; after tightening the bolts, it is advisable to extend the nut 1 ~ 3 screws.

(4) The flange sealing surface and seals shall not have defects such as scratches and pits that affect the sealing performance, and the material shall meet the requirements for the transportation of town gas.

(5) The flanges and fasteners should be treated with anti-corrosion treatment and meet the design pressure requirements.

5. Connection of steel-plastic adapter

(1) The connection between the polyethylene pipe end of the steel-plastic conversion joint and the polyethylene pipe or steel skeleton polyethylene composite pipe shall comply with the corresponding provisions for hot melt connection or electric fusion connection in this Regulation.

(2) The connection between the steel pipe end of the steel-plastic conversion joint and the metal pipe shall comply with the corresponding regulations on welding or flange connection of the steel pipe.

(3) When the steel pipe end of the steel-plastic conversion joint is welded to the steel pipe, cooling measures should be taken in the steel-plastic transition section.

(4) After the steel-plastic conversion joint is connected, the joint shall be subjected to anti-corrosion treatment, and the anti-corrosion level shall meet the design requirements and pass the inspection.

Section 4 Pipeline Laying

1. General Provisions

(1) The earthwork construction of polyethylene pipes and steel skeleton polyethylene composite pipes shall comply with the relevant provisions of the current national standard "Code for Construction and Acceptance of Urban Gas Transmission and Distribution Engineering" CJJ33.

(2) When laying polyethylene pipes, the allowable bending radius of the pipe should not be less than 25 times the nominal diameter; when there are socket fittings on the bent pipe section, the allowable bending radius of the pipe should not be less than 125 times the nominal diameter.

(3) When laying the steel skeleton polyethylene composite pipe, the allowable bending radius of the steel mesh skeleton polyethylene composite pipe should meet the requirements of the following table, and the allowable bending radius of the mesh steel belt polyethylene composite pipe should meet the regulations of the following table.

Steel mesh skeleton polyethylene composite pipe allows bending radius mm

Pipe nominal diameter DN

Allow bending radius

50≤DN≤150

80DN

, 150 ＜ DN≤300

100DN

300 ＜ DN≤500

110DN

Perforated steel tape polyethylene composite pipe allows bending radius mm

Pipe nominal diameter DN

Allow bending radius

50≤DN≤110

150DN

140 ＜ DN≤250

250DN

DN≥315

350DN

(4) When the pipeline is constructed in areas with high groundwater level or during the rainy season, water level reduction or drainage measures should be taken to remove the accumulated water in the ditch in time. It is strictly forbidden to backfill the pipeline while it is floating.

2. Laying of buried pipelines

(1) For laying pipes for excavated trenches (not including buried laying by feeding method), the pipeline should be laid only after the elevation of the trench bottom and the quality of the pipe foundation are qualified.

(2) When the pipeline is lowered, the metal material shall not be used to directly bundle and lift the pipeline, and the pipeline shall be prevented from being scratched, twisted or subjected to excessive stretching and bending.

(3) Polyethylene pipes should be laid in a meandering shape and can be laid along with the terrain; steel skeleton polyethylene composite pipes should be laid naturally in a straight line. The bending radius of the pipeline shall comply with the provisions of this regulation, and no mechanical or heating methods shall be used to bend the pipeline.

(4) The horizontal and vertical net distance between the pipeline and the building, structure or adjacent pipeline shall comply with the provisions of this Regulation.

(5) The minimum soil thickness of the buried pipeline shall comply with the provisions of Article 4.3.3 of this Regulation.

(6) When laying pipelines, metal tracers (belts), warning tapes or other signs should be buried along the pipe.

The tracer line (band) should be laid on the tube, and should have good conductivity, effective electrical connection and set up signal source well.

The laying of warning tape shall meet the following requirements:

1. The warning tape should be laid 300-500mm above the top of the pipe, but it should not be laid on the roadbed or road surface;

2. For pipes with a diameter not greater than 400mm, a warning tape can be laid directly above the pipe; for pipes with a diameter greater than 400mm, two warning tapes with a horizontal clear distance of 100-200mm should be laid in parallel directly above the pipe;

3. The warning tape should be made of polyethylene or materials that are not easily decomposed. The color should be yellow, and the warning tape is printed with eye-catching and permanent warning words.

(VII). When polyethylene coiled pipes or polyethylene straight pipes or steel skeleton polyethylene composite pipes restricted by construction conditions are laid in the ground by towing method, during the process of pipeline towing, the bottom of the trench should not possibly damage the surface of the pipeline The length of stones and sharp protrusions should not exceed 300m.

(8) When the polyethylene coil is laid in the ground by the feeding method, the warning tape should be laid in accordance with the regulations of this regulation and fed into the trench along with the pipeline. The bending radius of the pipeline should meet the regulations of this regulation.

3. Laying into the pipe

(1) The section is applicable to the laying method of the inlet pipe whose outer diameter is not greater than 90% of the inner diameter of the old pipe.

(2) A working pit should be excavated at the start-stop section, and its length should meet the construction requirements, and the allowable bending radius of the pipeline should meet the requirements of Article 6.1.3 of this code. The working pit spacing should not exceed 300m.

(3) Before the pipeline is inserted, pipe cleaning equipment should be used to remove the deposits, sharp burrs, welds and other debris on the inner wall of the old pipe, and blow off the debris in the pipe with compressed air. When necessary, use a pipe endoscope to check the degree of clearance of the inner wall of the old pipe, or pull the polyethylene pipe section through the old pipe, and determine the degree of clearance of the inner wall of the old pipe by checking the surface scratches of the polyethylene pipe section.

(4) The pipeline inserted into the laying shall be connected by hot-melt or electric fusion according to the requirements of this regulation. If necessary, cut out the flange of the hot-melt butt connection or the terminal of the electric fusion connection.

(E) Before the pipeline is inserted, all welded joints of the connected pipeline should be inspected one by one, and after the safety protection measures are effectively guaranteed, the leak detection shall be carried out and the construction shall be carried out after passing the test. After insertion, the strength test and tightness test of the insertion tube should be carried out with the piping system.

(6) When inserting and laying, a funnel-shaped guide sliding port with a lower hardness must be added to the old pipe insertion port.

(7) When the insertion tube is laid by the drag method, the drag force shall comply with the provisions of Article 6.2.7 of this Regulation.

(8) The length of the inserted pipe extending out of the old pipe port should be able to meet the requirements of pipeline shrinkage recovery, pipe shrinkage and pipe connection.

(9) Between the two insertion sections, the cold shrinkage allowance and the uneven settlement allowance of the pipeline must be set aside and riveted or fixed at an appropriate length in each section. At each port of the pipe section, the annular space between the inserted pipe and the old pipe should be sealed with flexible material. The opening of the old pipe between the pipe sections shall be protected by casing.

(X). When the branch pipe is connected to the insertion pipe, it should be carried out after the main pipe resumes the diameter reduction and after 24 hours of relaxation.

4. Pipeline crossing

(1) The laying period, procedures and construction organization plan of pipelines crossing railways, roads and rivers, and other pipelines and ditches should be approved by the relevant management departments and comply with the relevant provisions of this regulation.

(2) During the construction of the pipeline crossing, it must be ensured that the buildings and structures around the crossing section will not be subsidenced, displaced or destroyed.

(3) When the pipeline traverses, the drag force on the pipeline shall comply with the provisions of Article 6.2.7 of this Regulation.

7 Test and inspection

7.1 General

7.1.1 After the installation of polyethylene pipelines and steel skeleton polyethylene composite pipelines, pipeline blowing, strength test and tightness test shall be carried out in sequence. In addition to the provisions of this regulation, the test and acceptance of pipelines should also comply with the relevant provisions of the current national standard "Code for Construction and Acceptance of Urban Gas Transmission and Distribution Engineering".

7.1.2 The slotted pipeline system shall be backfilled with backfill to the top of the pipe of 0.5m or more, followed by purging, strength test and tightness test.

For pipelines laid by towing method, feeding method and insertion method, the pipeline section should be leak-checked in advance; after laying, the pipeline system should be sequentially purged, strength tested and tightness tested.

7.1.3 The medium of purge, strength test and tightness test should be compressed air, and its temperature should not exceed 40 ℃; oil-water separator and filter should be installed at the outlet of the compressor.

7.1.4 During the purge, strength test and tightness test, the pipeline shall be isolated from the unrelated system and the system already in operation, and shall be provided with obvious signs, and shall not be isolated with valves.

7.1.5 The strength test and tightness test shall meet the following conditions:

1 Before the strength test and the tightness test, the test plan of the strength test and the tightness test shall be prepared;

2 After the pipeline system installation and inspection are qualified, it should be backfilled in time;

3 The supporting piers and anchoring facilities of the pipe fittings have reached the design strength; the bends and tees without supporting piers and anchoring facilities shall be strengthened

4 All openings of the test pipe section should be blocked, but the valve should not be used as a blocking plate;

5 All valves in the test section of the pipeline must be fully opened;

6 The pipeline has been purged.

7.1.6 When performing the strength test and the tightness test, the foaming agent such as detergent or soap liquid may be used for the air leak inspection. After the inspection is completed, the foaming agent such as detergent or soap liquid on the pipeline shall be washed away in time.

7.1.7 The defects found during the strength test and tightness test of polyethylene pipes and steel skeleton polyethylene composite pipes must be treated after the test pressure is reduced to atmospheric pressure, and the test should be repeated after passing the treatment.

Section 5 Pipeline Pressure Test

1. General Provisions

(1) After the pipeline installation is completed, the construction unit is responsible for organizing the purge work and preparing the purge plan before the purge.

(2) The purge port should be located in an open area, and reinforcement measures should be taken; the exhaust port should be grounded. A safe area should be set up during purge, and no one is allowed to stand at the purge exit.

(3) The pressure of the purge gas should not exceed 0.3MPa.

(4) The flow rate of the purge gas should be not less than 20m / s, and not more than 40m / s.

(5) The length of the pipeline to be purged each time should be determined according to the purge medium, pressure and gas volume, and should not exceed 500m.

(6) Pressure regulators, condensate tanks, valves and other equipment should not participate in the purge, and should be installed after passing the purge.

(7) When the exhaust is visually inspected for smoke and dust, a white cloth or white lacquered wood target board should be installed at the exhaust port for inspection. Within 5 minutes, no dust, plastic debris and other debris on the target are qualified.

(8) The purge should be repeated several times, and the record should be made until the purge is confirmed.

(9) After the purge is qualified and the equipment is reset, other operations that affect the cleaning in the pipe shall not be carried out.

2. Strength test

(1) The strength test of the pipeline system should be carried out in sections, and the length of the test pipe section should not exceed 1km.

(2) The pressure gauge for strength test shall be within the valid period of verification, its range shall be 1.5 to 2 times of the test pressure, and its accuracy shall not be lower than 1.5.

(3) The strength test pressure should be 1.5 times the design pressure, and the minimum test pressure should meet the following requirements:

1SDR11 polyethylene pipe should not be less than 0.40MPa;

2SDR17.6 polyethylene pipe should not be less than 0.20MPa;

3 Steel skeleton polyethylene composite pipeline shall not be less than 0.40MPa.

(4) During the strength test, the pressure should be gradually increased, first to 50% of the test pressure, for initial inspection, if there is no leakage or abnormal phenomenon, continue to slowly increase the pressure to the test pressure. After reaching the test pressure, it is advisable to stabilize the pressure for 1h, and observe that the pressure gauge should not be less than 30min, and no obvious pressure drop is qualified.

(5) The joints connected to each other by the pipe sections that pass the section pressure test may not undergo the strength test after passing the appearance inspection.

3. Tightness test

The tightness test of polyethylene pipes and steel skeleton polyethylene composite pipes shall be carried out in accordance with the tightness test requirements stipulated in the current national standard "Code for Construction and Acceptance of Urban Gas Transmission and Distribution Engineering" CJJ33.

4. Completion and acceptance of the project

(1) The completion acceptance of the polyethylene pipeline and steel skeleton polyethylene composite pipeline project shall be implemented in accordance with the requirements of the completion and acceptance of the project stipulated in the current national standard "Code for Construction and Acceptance of Urban Gas Transmission and Distribution Engineering" CJJ33.

(2) The project completion data should also include the following inspection qualification records:

1 Flip and excision inspection record;

2 Tracer (band) conductivity inspection record.

(3) Grade and grade of polyethylene raw materials used

(4), appearance

(5), color

(6), length

(7), out of roundness

(8), outer diameter and wall thickness

(9) Production date

(10), product logo

If there is any objection to the physical and mechanical properties, a third party should be commissioned for inspection.

3. The storage time of pipes from production to use should not exceed 1 year, and the fittings should not exceed 2 years. When the above time limit is exceeded, it is better to re-sample and perform performance inspection. Pipe inspection items: hydrostatic strength (165h / 80 ℃), thermal stability and elongation at break; pipe inspection items: hydrostatic strength (165h / 80 ℃), tensile strength of butt fusion welding or welding strength of electrofusion pipe fittings .

(2) Quality requirements

1. Gas-fired polyethylene pipes, fittings and valves for underground use shall meet the following requirements:

(1) Polyethylene pipes shall comply with the provisions of the current national standard "Buried Polyethylene (PE) Pipeline System for Gas-Part 1: Pipes" GB15558.1;

(2) The wall thickness of polyethylene welded pipe fittings should not be less than 1.2 times the wall thickness of the corresponding connecting pipe, and its physical and mechanical properties should comply with the current national standard "Buried polyethylene (PE) piping system for gas: Part 2: Pipe fittings 》 GB15558.2;

(3) Polyethylene pipe fittings shall comply with the provisions of the current national standard "Buried polyethylene (PE) piping system for gas: Part 2: Pipe fittings" GB15558.2;

(4). The polyethylene ball valve shall comply with the provisions of the current national standard PE3GB15558.3 "Buried polyethylene (PE) piping system for gas: Part 3: Valves";

(5) The steel-plastic conversion joint shall meet the requirements of the corresponding standards.

2. The steel skeleton polyethylene pipes, fittings and valves for underground use shall meet the following requirements:

(1). The steel wire mesh (welded) skeleton polyethylene composite pipe of the inner diameter series should meet the requirements of the current national standard "Steel skeleton polyethylene plastic composite pipe for gas" CJ / T125, and the pipe fittings connected to it should meet the current national standard The steel skeleton polyethylene plastic composite pipe fittings "CJ / T126 provisions;

(2) The specifications of the outer diameter series of steel wire mesh (welded) skeleton polyethylene composite pipe should meet the requirements of relevant standards, and the physical and mechanical properties should comply with the current national standard "Steel skeleton polyethylene plastic composite pipe for gas" CJ / T125 Regulations.

(3) The steel mesh (winding) skeleton polyethylene composite pipe shall comply with the provisions of the current national standard "steel mesh skeleton plastic (polyethylene) composite pipe fittings" CJ / T189;

(4). The mesh steel belt polyethylene composite pipe shall comply with the provisions of the current national standard "Buried Hole Mesh Steel Belt Polyethylene Composite Pipe for Gas" CJ / T182.

(2) Transportation and storage

1. The transportation of pipes, fittings and valves should meet the following requirements:

(1) When transporting, do not throw, drop, roll, or tow; during winter transportation, it should be handled with care. When mechanical equipment is used to hoist straight pipes, they must be hoisted with non-metallic ropes (belts).

(2) When transporting the pipe, it should be placed on a flatbed car with baffles or in a flat cabin. The stacking place must not have sharp protrusions that may damage the pipe, and should be tied and fixed with non-metallic rope (band), and There should be sun protection measures; when transporting the pipe fittings, they should be neatly arranged and fixed firmly one by one according to the box, and there should be sun protection measures.

(3) When transporting pipe fittings and valves, they shall be neatly arranged and fixed firmly one by one according to the boxes, and corresponding measures against rain shall be provided.

2. The storage of pipes, fittings and valves shall meet the following requirements:

(1) Pipes, fittings and valves should be stored in well-ventilated warehouses or sheds, away from heat sources, and should be protected from sun and rain;

(2) It is strictly forbidden to store with oils or chemicals, and the storage area should have fire prevention measures.

(3) Pipes should be stacked horizontally on a flat support or ground. When the straight pipes are stacked in triangles and the rectangles are stacked with supports on both sides, the stacking height should not exceed 1.5m; when the straight pipes are stored in layers, the height of each layer should not exceed 1m, and the total height should not exceed 3m.

(4) Pipe storage should be stored in boxes on shelves or stacked on flat ground; when stacked in boxes, the stacking height should not exceed 1.5m.

(5). When storing pipes, fittings and valves, they should be stored separately according to different specifications and different types, and the principle of "first in first out" should be observed.

(6) When the pipes and fittings are temporarily stored outdoors, they should be covered by coverings.

Section 2 Piping Design

1. General Provisions

(1) The pipeline design should meet the requirements of the town gas master plan. On the basis of the feasibility study, the long-term and the short-term should be combined, with the main focus on the short-term.

(2) The selection of materials, wall thicknesses and pressure levels of pipes and fittings should be determined after technical and economic comparison based on geological conditions, surrounding environment, types of gas delivered, working pressure, construction method, etc.

(3) When polyethylene pipes are used to transport natural gas, liquefied petroleum gas and artificial coal gas, the design pressure should not exceed the maximum allowable working pressure of the pipeline, and the maximum allowable working pressure should comply with the following table. Maximum allowable working pressure of polyethylene pipeline (MPa)

Types of town gas

PE80

PE100

SDR11

SDR17.6

SDR11

SDR17.6

natural gas

0.50

0.30

0.70

0.40

liquefied petroleum gas

Mixed air

0.40

0.20

0.50

0.30

Gaseous

0.20

0.10

0.30

0.20

Artificial gas

Dry gas

0.40

0.20

0.50

0.30

other

0.20

0.1

0.30

0.20

(3) When natural steel, liquefied petroleum gas and artificial gas are transported by steel skeleton polyethylene composite pipelines, the design pressure should not exceed the maximum allowable working pressure of the pipeline, and the maximum allowable working pressure should comply with the following table.

Maximum allowable working pressure of steel skeleton polyethylene composite pipeline (MPa)

Types of town gas

DN≤200mm

DN ＞ 200mm

natural gas

0.7

0.5

liquefied petroleum gas

Mixed air

0.5

0.4

Gaseous

0.2

0.1

Artificial gas

Dry gas

0.5

0.4

other

0.2

0.1

Note: Thin-walled series of steel skeleton polyethylene composite pipelines should not be used to transport town gas.

(4) When the working temperature of polyethylene pipes and steel skeleton polyethylene composite pipes is above 20 ℃, the maximum allowable working pressure shall be reduced according to the working temperature to the reduction factor of the working pressure. .

Reduction factor of working temperature to working pressure of pipeline

Operating temperature

-20 ℃ ≤t ≤20 ℃

20 ℃ ＜ t ≤30 ℃

30 ℃ ＜ t ≤40 ℃

Reduction factor

1.0

0.9

0.76

Note: The working temperature in the table refers to the highest monthly average temperature of the pipeline working environment

(V) When using polyethylene pipe in the polyethylene piping system, the welding pressure of the system should not exceed 0.2MPa; the welding pipe should be prefabricated in the factory, and the nominal pressure level of the pipe selected for welding pipe It should not be less than 1.2 times the pressure rating of the pipe in the pipeline system, and protective measures such as reinforcement should be applied to the polyethylene welded pipe during the construction process.

(6) The pipelines of various pressure levels should be connected by pressure regulating devices. When it is possible to exceed the maximum allowable working pressure, safety protection equipment to prevent pipeline overpressure should be installed.

(7) Tracer lines (belts) and warning tapes should be designed along the pipeline.

2. Pipeline layout

(1). Polyethylene pipes and steel skeleton polyethylene composite pipes shall not pass under buildings and large structures (excluding large structures such as overhead buildings and overpasses), and shall not accumulate flammable and explosive materials and have corrosion. Sexual liquids cross under the site; they must not be laid in the same trench as non-gas pipelines or cables.

(2) The horizontal net distance and vertical net distance between polyethylene pipes and steel skeleton polyethylene composite pipes and thermal pipes shall not be less than those specified in the table below, and shall ensure that the temperature of the soil around the gas pipes is not greater than 40 ℃; The horizontal net distance and vertical net distance between buildings, structures or other adjacent pipes shall comply with the provisions of the current national standard "Code for Design of Town Gas Design" GB50028. When the temperature of the outer wall of the insulation layer of the directly buried steam force pipeline is not greater than 60 ℃, the horizontal clear distance can be halved.

Horizontal horizontal distance between polyethylene pipes and steel skeleton polyethylene composite pipes and thermal pipes (m)

Item

Gas pipeline

Low pressure

Medium pressure

Sub-high pressure

B

A

B

heat

force

tube

Buried directly

Hot water

1.0

1.0

1.0

1.5

Steam

2.0

2.0

2.0

3.0

In the trench

(To the outer wall)

1.0

1.5

1.5

2.0

Vertical clear distance between polyethylene pipes and steel skeleton polyethylene composite pipes and thermal pipes (m)

Item

Gas pipeline (when there is a bushing, count as bushing)

Heat pipe

Gas pipe above the directly buried (hot water) pipe

0.5 plus casing

The gas pipe is directly below the buried (hot water) pipe

1.0 plus casing

Gas pipe above the trench

0.2 plus casing or 0.4

The gas pipe is under the pipe trench

0.3 plus casing

(3) The minimum soil thickness (from the ground to the top of the pipe) of polyethylene pipes and steel skeleton polyethylene composite pipes shall meet the following requirements:

1 Buried under the carriageway, not less than 0.9m;

2 Buried under non-vehicle walkways (including sidewalks), not less than 0.6m;

3 When buried in a place where it is impossible for the motor vehicle to reach, it shall not be less than 0.5m;

4 When buried under the paddy field, it shall not be less than 0.8m.

(4) The foundation of polyethylene pipeline and steel skeleton polyethylene composite pipeline should be the original soil layer without sharp hard soil and stone. When the original soil layer has sharp hard soil and stone, it should be paved with fine sand or fine soil. For the section that may cause uneven settlement of the pipeline, the foundation shall be treated or other anti-settlement measures shall be taken.

(V) When polyethylene pipes and steel skeleton polyethylene composite pipes are used to transport fuel gas containing condensate, they should be buried below the soil freezing line and a condensate tank should be installed. The slope of the pipeline to the condensate tank should not be less than 0.003.

(6) When polyethylene pipes and steel skeleton polyethylene composite pipes pass through drainage pipe trenches, combined trenches, tunnels and other various use trenches (excluding thermal pipe trenches), polyethylene pipes and steel skeleton polyethylene The composite pipeline is laid in a rigid casing, the casing extending beyond the outer wall of the structure should not be less than the horizontal horizontal distance corresponding to Article 4.3.2 of this Regulation, and flexible anti-corrosion and waterproof materials should be used at both ends of the casing and between the casing and the building seal.

(7) Polyethylene pipes and steel skeleton polyethylene composite pipes should be crossed vertically when crossing railways, highways, tram tracks and main urban trunk roads, and should comply with the provisions of the current national standard "Urban Gas Design Code" GB50028.

(8). When polyethylene pipes and steel skeleton polyethylene composite pipes pass through rivers, they can be traversed by the bottom of the river and comply with the following regulations:

1 The thickness of the overlying soil from the polyethylene pipeline and the steel skeleton polyethylene composite pipeline to the planned river bottom should be determined according to the erosion conditions of the water flow. Dredging and anchoring depth;

2 Stabilization measures should be determined based on calculations;

3 Signs shall be set up and down the river banks where polyethylene pipes and steel skeleton polyethylene composite pipes are buried.

(IX). On sub-high pressure, medium-pressure polyethylene pipes and steel skeleton polyethylene composite pipes, and low-pressure steel skeleton polyethylene composite pipes, segmented valves should be installed, and it is advisable to set loose pipes on both sides of the valve; Valves should be installed at the starting point of polyethylene pipe branches.

(10) The detection pipes on the polyethylene pipes and the steel skeleton polyethylene composite pipe system, the drain pipes of the condensate tank, the water seal valves and valves should all be equipped with shields or wells.

(11). When the polyethylene pipes and steel skeleton polyethylene composite pipes are connected to the pressure regulating box installed on the external wall of the building, they shall be taken out of the ground to take protection and sealing measures, and shall not be exposed; Directly into the building. When polyethylene pipes and steel skeleton polyethylene composite pipes must pass through building (structure) structure foundations, external walls or be laid in walls, they must be protected by hard bushings and comply with the current national standard "Urban Gas Design Code" GB50028 Provisions.

The second section pipeline connection

1. General Provisions

(1) Before the pipeline connection, the pipe, pipe fittings and pipeline auxiliary equipment should be checked according to the design requirements, and the appearance inspection should be carried out at the construction site. The depth of the pipe surface scratches should not exceed 10% of the pipe wall thickness, and it should be used after meeting the requirements.

(2) For the connection of polyethylene pipes and fittings and the connection of steel skeleton polyethylene composite pipes and fittings, special connection equipment must be selected according to different connection forms, and thread connection and bonding are not allowed. When connecting, open flame heating is strictly prohibited.

(3) The connection of polyethylene piping system should also meet the following requirements:

1 The connection of polyethylene pipes and fittings should use hot-melt butt connection or electric fusion connection (electric fusion bearing connection, electric fusion saddle connection); polyethylene pipes should be connected with metal pipes or metal accessories by flange connection or steel-plastic For connection of conversion joints, inspection wells should be installed with flange connections;

2 Pipes, fittings and pipe accessories made of polyethylene materials of different grades with a difference in melt mass flow rate of not less than 0.5g / 10min (190 ° C, 5kg), and polyethylene with different standard dimension ratios (SDR) of welded ends When connecting gas pipelines, electric fusion connection must be used;

3 Polyethylene pipes with a nominal diameter of less than 90mm should be connected by electrofusion.

(4) For the connection of steel skeleton polyethylene composite pipes and fittings, electric fusion socket connection or flange connection shall be adopted; for the connection of steel skeleton polyethylene composite pipe to metal pipes or pipeline accessories (metal), flange connection shall be adopted, and Inspection wells should be set up;

(5) The ambient temperature of the pipeline hot melt or electric fusion connection should be in the range of -5 ~ 45 ℃, when the temperature is lower than -5 or the wind is greater than 5 conditions for hot melt and electric fusion connection operation, should be taken Insulation and windproof measures, and the connection process should be adjusted; when hot melt and electric fusion connection operations are carried out in hot summer, shading measures should be taken.

(6) When the temperature difference between the storage place of the pipe and pipe fittings and the construction site is large, the pipe and pipe fittings should be placed on the construction site for a certain period of time to make the temperature close to the temperature of the construction site.If you want to know more about it please do not hesitate to contact me. WhatsApp:+86-15966835076(7) When the pipes are connected, polyethylene pipes should be cut with a special cutter or pipe cutting tool. The cutting end face should be smooth, smooth and free of burrs, and the end face should be perpendicular to the pipe axis; the steel skeleton polyethylene composite pipe cutting should be special Pipe cutting tool, after cutting, the end face should be flat and perpendicular to the pipe axis, and the end face should be sealed with polyethylene material. It is strictly forbidden to use the pipe without the end face welded.

(8) When the pipeline is connected, the pipe mouth shall be temporarily blocked every time the work is closed.

(9) After the pipeline is connected, the joint quality shall be inspected in accordance with the relevant provisions of this regulation. Unqualified persons must be reworked, and re-check the joint quality after rework. When there is a dispute about the welding quality inspection, the qualification inspection should be carried out according to the following table.

Hot melt butt welding process qualification inspection and test requirements

Serial number

Inspection and test items

Inspection and test parameters

Inspection and test requirements

Inspection and test methods

1

Tensile properties

23 ± 2 ℃

Test until destruction:

Resilience, through

Brittle, failed

"Determination of Tensile Strength and Failure Form of Hot Melt Butt Joints of Polyethylene (PE) Pipes and Fittings" GB / T19810

2

Withstand voltage

(Hydrostatic)

Strength test

Sealed joint, type a;

Direction, arbitrary;

Adjustment time, 12h;

During the test, 165h;

Ring stress

PE80, 4.5MPa

PE100, 5.4MPa

Test temperature, 80 ℃

No damage or leakage at the welding place

"Test method for internal pressure resistance of thermoplastic pipes for fluid transportation" GB / T6111

Qualification inspection and test requirements of electrofusion socket welding process

Serial number

Inspection and test items

Inspection and test parameters

Inspection and test requirements

Inspection and test methods

1

Sectional inspection of electrofusion pipe fittings

The resistance wire in the electrofusion pipe fittings should be neatly arranged, and there should be no bulging, bare, staggered lines, no free after welding, no visible boundaries on the welding surface of the pipe fittings and the pipe, no defects such as virtual welding, overwelding bubbles, etc.

"Technical Rules for Welding of Polyethylene Pipes for Gas" TSGD2002

2

DN ＜ 90 extrusion peel test

23 ± 2 ℃

Peeling brittle failure percentage≤33.3%

"Extrusion Peeling Test of Polyethylene Electrofusion Components for Plastic Pipes and Fittings" GB / T19806

3

DN≥90 Tensile peel test

23 ± 2 ℃

Peeling brittle failure percentage≤33.3%

"Tensile Peeling Test of Polyethylene Fused Assemblies with Nominal Diameter of Plastic Pipes and Fittings of 90mm or More" GB / T19808

4

Withstand voltage

(Hydrostatic)

Strength test

Sealed joint, type a;

Direction, arbitrary;

Adjustment time, 12h;

Test time, 165h;

Ring stress

PE80, 4.5MPa

PE100,5.4MPa

Test temperature, 80 ℃

No damage or leakage at the welding place

"Test method for internal pressure resistance of thermoplastic pipes for fluid transportation" GB / T6111

Qualification inspection and test requirements of electrofusion saddle welding process

Serial number

Inspection and test

project

Inspection and

Test parameters

Inspection and test requirements

Inspection and test methods

1

DN≤225 extrusion peel test

23 ± 2 ℃

Peeling brittle failure percentage≤33.3%

"Extrusion Peeling Test of Polyethylene Electrofusion Components for Plastic Pipes and Fittings" GB / T19806

2

DN ＞ 225 tear peel test

23 ± 2 ℃

Peeling brittle failure percentage≤33.3%

"Technical Rules for Welding Ethylene Pipes for Gas" TSGD2002

Second, hot melt connection

(1) The hot-melt butt joint equipment shall meet the following requirements:

1 The frame should be firm and stable, and can ensure the easy switching of the heating plate and the milling tool and the convenient movement and correction of the pipe or pipe fitting;

2 Fixtures should be able to fix pipes or fittings, and can quickly position or remove pipes or fittings;

3 The milling cutter should be a double-sided milling cutter, and the end face of the pipe or pipe fitting to be connected should be milled into a clean, flat, and parallel matching surface perpendicular to the central axis of the pipe;

4 The surface structure of the heating plate should be complete and kept clean, the temperature distribution should be uniform, and the allowable deviation is ± 5 ℃ of the set temperature;

5 The pressure display index value of the pressure system should not be greater than 0.1MPa;

6 The voltage fluctuation range of the power supply used by the welding equipment should not exceed ± 15% of the rated voltage;

7 The hot-melt butt-connected equipment should be regularly calibrated and verified, and the period should not exceed 1 year.



(2) The welding process of the hot-melt butt connection shall comply with the provisions of the above figure, and the welding parameters shall comply with the provisions of the following table.

P2—Welding specified pressure (gauge pressure, MPa)

P dragging-dragging pressure (gauge pressure, MPa)

t1—the time for the curling to reach the specified height;

t2—The heat absorption time required for welding,

t3—the time (s) specified for switching;

t4—Adjust the pressure to the time (s) specified by P1;

t5—cooling time (min).

SDR11 pipe hot-melt butt welding parameters

Nominal diameter DN

(Mm)

Pipe wall thickness e

(mm)

P2

(MPa)

Pressure = P1 protrusion height h

(mm)

Pressure ≈P drag heat time

t2 (s)

Switching time t3

(s)

Boost time t4

(s)

Pressure = P1 cooling time t5

(s)

75

6.8

219 / S2

1.0

68

≤5

＜ 6

≥10

90

8.2

315 / S2

1.5

82

≤6

＜ 7

≥11

110

10.0

471 / S2

1.5

100

≤6

＜ 7

≥14

125

11.4

608 / S2

1.5

114

≤6

＜ 8

≥15

140

12.7

763 / S2

2.0

127

≤8

＜ 8

≥17

160

14.5

996 / S2

2.0

145

≤8

＜ 9

≥19

180

16.4

1261 / S2

2.0

164

≤8

＜ 10

≥21

200

18.2

1557 / S2

2.0

182

≤8

＜ 11

≥23

225

20.5

1971 / S2

2.5

205

≤10

＜ 12

≥26

250

22.7

2433 / S2

2.5

227

≤10

＜ 13

≥28

280

25.5

3052 / S2

2.5

255

≤12

＜ 14

≥31

315

28.6

3862 / S2

3.0

286

≤12

＜ 15

≥35

355

32.3

4903 / S2

3.0

323

≤12

＜ 17

≥39

400

36.4

6228 / S2

3.0

364

≤12

＜ 19

≥44

450

40.9

7882 / S2

3.5

409

≤12

＜ 21

≥50

500

45.5

9731 / S2

3.5

455

≤12

＜ 23

≥55

560

50.9

12207 / S2

4.0

509

≤12

＜ 25

≥61

630

57.3

15450 / S2

4.0

573

≤12

＜ 29

≥67

Note: 1. The above parameters are based on an ambient temperature of 20 ℃;

2. Surface temperature of hot plate: PE80 is 210 ± 10 ℃, PE100 is 225 ± 10 ℃;

3. S2 is the total effective area (mm2) of the piston in the hydraulic cylinder of the welding machine, provided by the welding machine manufacturer.

SDR17.6 pipe hot-melt butt welding parameters

Nominal diameter DN

(Mm)

Pipe wall thickness e

(mm)

P2

(MPa)

Pressure = P1 protrusion height h

(mm)

Pressure ≈P drag heat time

t2 (s)

Switching time t3

(s)

Boost time t4

(s)

Pressure = P1 cooling time t5

(s)

110

6.3

305 / S2

1.0

63

≤5

＜ 6

9

125

7.1

394 / S2

1.5

71

≤6

＜ 6

10

140

8.0

495 / S2

1.5

80

≤6

＜ 6

11

160

9.1

646 / S2

1.5

91

≤6

＜ 7

13

180

10.2

818 / S2

1.5

102

≤6

＜ 7

14

200

11.4

1010 / S2

1.5

114

≤6

＜ 8

15

225

12.8

1278 / S2

2.0

128

≤8

＜ 8

17

250

14.2

1578 / S2

2.0

142

≤8

＜ 9

19

280

15.9

1979 / S2

2.0

159

≤8

＜ 10

20

315

17.9

2505 / S2

2.0

179

≤8

＜ 11

twenty three

355

20.2

3181 / S2

2.5

202

≤10

＜ 12

25

400

22.7

4039 / S2

2.5

227

≤10

＜ 13

28

450

25.6

5111 / S2

2.5

256

≤10

＜ 14

32

500

28.4

6310 / S2

3.0

284

≤12

＜ 15

35

560

31.8

7916 / S2

3.0

318

≤12

＜ 17

39

630

35.8

10018 / S2

3.0

358

≤12

＜ 18

44

Note: 1. The above parameters are based on an ambient temperature of 20 ℃;

2. Surface temperature of hot plate: 210 ± 10 ℃ for PE80, 225 ± 10 ℃ for PE100;

3. S2 is the total effective area (mm2) of the piston in the hydraulic cylinder of the welding machine, provided by the welding machine manufacturer.

(3) The operation of hot-melt butt connection shall meet the following requirements:

1. According to the specifications of the pipe or pipe fittings, select the corresponding fixture, and the connection end of the connection piece should extend out of the fixture, and the free length should not be less than 10% of the nominal diameter. Connect the parts so that they are on the same axis. The wrong edge should not be greater than 10% of the wall thickness;

2. Wipe clean the connecting parts of polyethylene pipes or fittings, and mill the end faces of the parts to be perpendicular to the axis. The average thickness of chips should not exceed 0.2mm, and the welding surface after cutting should be prevented from contamination;

3. The end face of the connecting piece should be heated by hot-melt butt connecting equipment;

4. After the heat absorption time reaches the process requirements, the heating plate should be quickly withdrawn, and the uniformity of the melting of the heating surface of the to-be-connected parts should be checked, and there should be no damage. Use uniform external force to make the connection surface fully contact within the specified time, and flanging to form a uniform double flange;

5. During the cooling period, the connection piece shall not be moved or any external force shall be applied to the connection piece.

(4) The quality inspection of the hot-melt butt joint shall meet the following requirements:

1. After the connection is completed, 100% flanging symmetry, joint alignment test and no less than 10% flanging cut test should be performed on the joint;

2. Flange symmetry test. The joint shall have smooth and symmetrical flanges along the entire circumference of the pipe, and the depth (A) of the lowest part of the flange shall not be lower than the surface of the pipe as shown in Figure 1;



Figure 1 Flange symmetry



Figure 2 Connector alignment

3. Alignment inspection of joints. The amount of misalignment (V) at any point on the outer circumference of the welded seam adjacent to the flanging should not exceed 10% of the pipe wall thickness, as shown in Figure 2;

4. Flip and cut inspection. Use a special tool to remove the external welded flange without damaging the pipes and joints (Figure 5.2.4-3). Flanging and cutting inspection should meet the following requirements:

1) The flanging should be solid and smooth, and the root is wider (Figure 5.2.4-4);

2) There should be no impurities, small holes, distortion or damage on the underside of the flanging;

3) Carry out a 180 ° back bend test (Figure 5.2.4-5) every 50 mm. There should be no cracks or cracks, and no fusion lines should be exposed at the joints.



Figure 5.2.4-3 Sketch of flanging and cutting



Figure 5.2.4-4 Qualified solid flanging



Figure 5.2.4-5 Flanging back bending test

5 When all the welds of the sampling inspection are qualified, the batch of welds represented by this sampling shall be deemed to be all qualified; if there is a situation that does not meet the requirements of the above clauses, the weld is judged to be unqualified, and the Provision for double sampling inspection:

(1) For every unqualified weld, the same batch of welds welded by the welder shall be double-checked and inspected in accordance with this regulation;

(2) If unqualified welds still appear in the second sampling inspection, all welds of the same batch welded by the welder shall be inspected.

3. Electrofusion connection

1. The electrofusion connection equipment shall meet the following requirements:

1 The type of electrofusion connection equipment should meet the requirements of electrofusion pipe fittings;

2 The electrofusion connection tool should work normally when it is powered by the national grid or generator;

3 The protection level of the shell should not be lower than IP54, all printed circuit boards should be waterproof, dustproof, shockproof, and the switches and buttons should be waterproof;

4 The input and output cables should be able to maintain toughness in the working range exceeding -10 ℃ ～ 40 ℃;

5 The accuracy of the temperature sensor should not be less than ± 1 ℃, and should be protected against mechanical damage;

6 The allowable deviation of the output voltage should be controlled within ± 1.5% of the set voltage; the allowable deviation of the output current should be controlled within ± 1.5% of the rated current; the allowable deviation of the welding time should be controlled within ± 1% of the theoretical time.

7Electrofusion connection equipment should be regularly calibrated and verified, and the period should not exceed 1 year.

2. The electrofusion connection tool and the electrofusion tube should be correctly connected. When connected, the voltage and heating time of the electric heating should meet the regulations of the electrofusion connection device and the electrofusion tube manufacturer.

3. During the cooling of the electrofusion connection, it is not allowed to move the connection piece or exert any external force on the connection piece.

4. The connection operation of electric fusion bearing shall meet the following requirements:

1. Wipe clean the connecting parts of pipes and fittings;

2. Measure the length of the socket of the pipe, and mark the length of the inlet and outlet of the pipe or the inlet of the pipe and the length of the scraping plus 10mm