Installation process and complete construction operation process of natural gas pipeline
- 1 Installation process and complete construction operation process of natural gas pipeline
- 2 Survey site
- 3 Preparation before construction
- 4 Surveying and setting out
- 5 Steel pipe derusting, anti-corrosion and painting
- 6 Pipe welding
- 7 Pipeline excavation
- 8 Electrofusion connection
- 9 Pipe laying
- 10 Pipe backfilling
- 11 Pipe installation
- 12 Install the retaining bracket
- 13 Installation of valves and accessories
- 14 Indoor pipeline installation
- 15 Gas meter installation
- 16 Installation of surge tank
- 17 Overhead pipeline installation
- 18 Construction of supporting facilities
- 19 Pipeline purging
- 20 Strength test
- 21 Air tightness test
- 22 Handover acceptance
Preparation before construction
- 1. Organize all construction personnel to conduct detailed investigation on other pipelines within the site and draw detailed construction sketches to ensure construction safety.
- 2. Check the performance indexes of the pipes used.
- 3. Cooperate with the on-site construction team, including pipe welding, pressurization and air tightness test.
- 4. The placement of equipment shall be considered from many aspects, that is, to facilitate construction and minimize the impact on the surrounding environment.
Surveying and setting out
Steel pipe derusting, anti-corrosion and painting
- 1. Before steel pipe welding, the oxide layer and dirt on the inner and outer pipe walls shall be removed. The derusting shall be carried out by electric polishing machine. The derusted pipes shall be painted with primer in time to prevent secondary oxidation.
- 2. The steel pipe adopts ordinary anti-corrosion, primer → finish coat → finish coat. Before anti-corrosion and painting of the steel pipe, the dirt such as rust, welding slag, burr, oil and water on the coated surface shall be removed. The coating shall be complete and uniform, the color shall be consistent, and there shall be no damage and flow; The coating film shall be firmly attached and the color shall be consistent.
Steel pipe welding process requirements
(7) Welding parameters:
|Pipe wall thickness(mm)||Number of welding layers||Diameter of electrode||Welding current (A)|
|Name of the connector||Pipe wall thickness (mm)||Blunt edge||Groove angle||Hi-Lo|
- 1. Cut off the pipe with special tools, keep the end face of the pipe perpendicular to the pipe axis, scrape off its skin, scrape off half the length of the electric melting sleeve, and wipe the dirt on the connecting surface of the pipe and pipe fittings with clean cotton cloth
- 2. Draw a positioning line according to the insertion depth of the pipe, so as to ensure that the pipe can be equally inserted into the electric melting sleeve during assembly
- 3. Insert the pipe into the socket at one end of the electric melting sleeve to the positioning line, and check whether the inlet and outlet parts meet the requirements.
- 4. Install the sleeved pipe and electrofusion sleeve on the interface fixture and fix it with the fixture;
- 5. Fix the pipe at the other end on the fixture, push the fixture along the sliding shaft to insert it into the socket at the other end of the electric melting sleeve, and keep the two connecting pipes on the same axis.
- 6. Connect the wire plug of the controller with the electric fusion sleeve socket, correctly set the welding voltage, current, welding time and other parameters, open the electric fusion button of the controller, conduct electric fusion, and the welding time enters the countdown.
- 7. After the dissolution is completed, cool it to the ambient temperature according to the specified cooling time, and remove the fixture and electrofusion wire.
- 1. Before the pipeline is laid into the trench, the trench bottom shall be measured to remove sundries, large soil blocks and ponding in the trench.
- 2. Special slings must be used for lowering the pipeline into the trench. It is strictly prohibited to damage the external anti-corrosion coating of the pipeline. It is strictly prohibited to lift the pipeline sharply or tighten the pipeline, resulting in bending or permanent bending. The spacing between lifting pipes is less than 20m.
- 3. After the pipeline is lowered to the groove bottom, it shall be close to the groove bottom and properly placed without external force. If there is any suspended part, it must be filled up.
- 1. After the installation inspection of the main body of the pipeline is qualified, the trench shall be backfilled in time, but the installation interface that has not been inspected shall be reserved. Before backfilling, the sundries left at the bottom of the trench must be removed.
- 2. Garbage, wood and soft materials shall not be used for backfilling. The backfill on both sides of the pipeline and within 0.5m above the pipe top shall not contain debris such as gravel and bricks, and shall not be backfilled with lime soil. The stones in the backfill soil above 0.5m from the pipe top shall not be more than 10%, the diameter shall not be more than 0.1M, and shall be evenly distributed.
- 3. During trench backfilling, the partially suspended part of the pipe bottom shall be backfilled first, and then both sides of the pipe shall be backfilled.
- 4. The backfill soil shall be compacted in layers. The virtual paving thickness of each layer is 0.2-0.3m. The backfill soil on both sides of the pipeline and within 0.5m above the pipe top must be compacted manually. The backfill soil above 0.5m above the pipe top can be compacted by small machinery. The virtual paving thickness of each layer should be 0.25-0.4m.
- 5. After backfilling and compaction on both sides of the pipe and 0.5m above the pipe top, the support of the trench shall be removed under the condition of ensuring safety, and the gap shall be filled with fine sand.
- 6. After the backfill is compacted, the compactness shall be checked in layers, and the backfill records shall be made.
- 1. Before the installation of pipes, pipe fittings and valves, the model, specification and material shall be checked in detail to see whether they meet the design requirements, and the manufacturer’s product factory certificate and other quality assurance data shall be provided.
- 2. Before the installation of valves, the shell strength and tightness test shall be carried out one by one. The strength test pressure shall be the nominal pressure of the valve [1.5 times of the nominal pressure of the valve, the test medium shall be water, the pressure shall be maintained for 5 minutes, the test J shall be water, the pressure shall be maintained for 10 minutes, and the valve disc sealing surface shall be qualified if there is no leakage.
- 3. During pipe alignment, the flatness shall be checked and measured 200mm away from the interface center, and the allowable deviation shall not be greater than 1mm. Pay attention to the radian in the overall layout of the pipe group.
- 4. The pipe assembly clearance shall not be greater than 2mm, and the misalignment of the outer wall shall not be greater than 3mm, otherwise it shall be thinned and corrected.
- 5. During pipe connection, it is not allowed to use strong butt joint, or heat the pipe, add offset pad and other methods to eliminate the defects such as gap, deviation, staggered joint or non concentricity at the end face of the interface.
- 6. The flange connection shall be coaxial, the center deviation of the bolt hole shall not exceed 5% of the outer diameter of the hole, and the bolt shall penetrate freely, and the flange end face shall be parallel, the deviation shall not be greater than 1.5 ‰ of the outer diameter of the flange, and shall not be greater than 2mm, and the skew shall not be eliminated by tightening the bolt. All bolts shall be grade 8.8 strength bolts.
- 7. During installation, the safety distance between the gas pipeline and other adjacent pipelines and structures shall be strictly controlled, and the operation shall be carried out according to relevant operating procedures. The buried slope and depth must meet the design requirements.
- 8. For construction every other day, cast iron pipe shall be used to block the pipe orifice temporarily to prevent sewage, sundries and animals from entering the pipe.
- 9. The pipeline installation shall be inspected every 6-10m according to the inspection contents, and the next process can be carried out only after it is qualified.
Install the retaining bracket
- 1. During pipeline installation, the support shall be fixed and adjusted in time, the position of the support shall be accurate, the installation shall be flat and firm, and the contact with the pipeline shall be close.
- 2. The specification, type and installation position of the adopted support shall meet the design requirements, and the deviation of elevation and coordinate shall not exceed 10mm (there shall be no positive deviation of elevation).
- 3. The sliding surface of the guide support or sliding support shall be smooth and flat without jamming. The guide plate shall not affect the sliding of the pipe support. The fixed support shall be fixed firmly. The height of the vertical plate of the pipe support shall meet the requirements of the insulation thickness.
- 4. The support weld shall be fully welded. When welding with the pipe, the pipe wall shall be free of defects such as biting and burning through, and the welding shall be completed before the pipe system test.
- 5. After the installation of pipe support, check whether the specification, type, installation position, weld and bolt fastening meet the requirements of drawing design and construction specifications one by one, whether there is missing installation and whether they are in close contact with the pipe.
- 6. The overhead of low-pressure gas pipeline can be laid along the outer wall of buildings with fire resistance rating not lower than grade II.
- 7. The clear distance between the gas pipeline along the outer wall of the building and the door and window openings of the building: the low-pressure pipeline shall not be less than 0.3m.
Installation of valves and accessories
- 1. Check the packing before valve installation, and the gland bolt must have sufficient adjustment allowance.
- 2. Valves with flange or threaded connection shall be installed in the closed state.
- 3. Before installing the valve, the model shall be checked according to the design, and the installation direction shall be determined according to the gas flow direction.
- 4. The valve stem of the valve on the horizontal pipeline shall generally be installed within the upper half circumference.
- 5. When installing cast iron valves, avoid damage caused by strong connection or uneven stress.
- 6. The installation position of the valve shall not hinder the disassembly and maintenance of the equipment, pipeline and valve itself. The installation height of the valve shall be convenient for operation and maintenance. Generally, it is appropriate to be 1.2m away from the ground. When the valve is more than 1.8m away from the floor, it shall be centrally arranged and a fixed platform shall be set.
- 7. For valves on side-by-side pipelines, the clear distance between hand wheels shall not be less than 100mm. In order to reduce the pipeline spacing, valves arranged side-by-side shall be staggered.
- 8. The operating mechanism and transmission device of the valve shall be adjusted as necessary to make the action flexible and accurate.
Indoor pipeline installation
- 1. First install the pipe support according to the drawing and the actual situation, then install the processed pipe, and fix it after appropriate adjustment. If the floor has reserved the casing, install it according to the reserved position. If not reserved, the casing shall be added.
- 2. In order to ensure the installation quality, the riser installation shall be measured and installed with pendant and level.
- 3. The installation of buried pipeline at the entrance shall be constructed according to the slope requirements of the drawing of 0.02%, and polyethylene shall be strengthened for anti-corrosion treatment according to the requirements of the drawing.
- 4. There shall be no welded junction in the pipe passing through the floor casing.
- 5. The finished pipe orifice shall be bound with plastic cloth to prevent foreign matters from entering.
- 6. The straightness of horizontal pipeline for pipeline installation shall be 2L / 1000 and 3L / 1000 of riser.
- 7. The horizontal clear distance from indoor water supply, drainage and heating pipes shall not be less than 100mm, and the cross clear distance shall not be less than 10mm.
Gas meter installation
- 1. The gas meter must meet the following conditions before installation.
- 2. The gas meter has factory certificate, the manufacturer has production license, and the meter has been tested by legal testing unit;
- 3. It shall not exceed 4 months from the date of delivery. If it exceeds, it shall be tested by the legal testing unit;
- 4. No obvious damage. During the installation of gas meter, collision, inversion and knocking are not allowed, and rust, sundries and oil stain are not allowed to fall into the instrument.
- 5. The diaphragm meter must be installed flatly, and the lower part shall be supported. The horizontal clear distance between the gas meter and the surrounding facilities is listed in the following table.
Installation of surge tank
- 1. It shall be stated on the certificate of the pressure regulating box that it meets the requirements of the quality standard through the air pressure test, strength and tightness, as well as the adjustment of inlet and outlet pressure. Do not install without the above instructions.
- 2. When installing the surge tank, it shall meet the following requirements:
- 3. Before installation, check that the outer surface of the surge tank is free of defects such as sand sticking, sand holes and cracks;
- 4. The installation of the surge tank shall be flat and stable, and the inlet and outlet directions shall not be wrong;
- 5. The connecting pipe of the membrane of the surge tank and the connecting pipe of the commander shall be connected above the outlet pipe of the surge tank, and the length of the connecting pipe shall meet the actual requirements.
Overhead pipeline installation
- 1. The construction personnel shall be skilled and have high-altitude operation experience.
- 2. The lifting machinery used by the personnel shall be an electric basket (the disassembly and assembly of the basket must be operated by licensed professionals), and the lifting of pipes shall be a 2-ton electric crane. Walkie talkies shall be equipped on site to ensure clear signals and close cooperation among the commanders, overhead construction personnel, lifting machinery operators and ground assistance personnel.
- 3. Safety rope shall be set along the overhead construction pipeline. The safety rope shall be bound firmly and independently, and shall not be bound on the lifting machinery and basket support. A falling self-locking device is set on the safety rope. Overhead construction personnel shall wear safety helmets and safety belts. The connection between the safety belt and the self-locking device shall be reliable and firm.
- 4. Before the installation of the pipe support, the measurement shall be carried out to ensure the correct position of the support. The support installation must be flat and firm and in good contact with the pipe.
- 5. The overhead pipeline shall be prefabricated and derusted on the ground, and the first layer of yellow marking ready mixed paint shall be painted.
- 6. The prefabricated pipeline shall be hoisted to the installation position with hoisting machinery, fixed by personnel in a basket, and painted with the second layer of yellow marking ready mixed paint.
Construction of supporting facilities
Air tightness test
- 1. After the completion of all construction of the project, the handover acceptance shall be carried out, and the owner, the supervision unit and other relevant departments shall be notified to attend the handover.
- 2. The acceptance items mainly include strength, air tightness test, valve well and other aboveground facilities, which can be passed only after confirmation and signature.
- 3. The project acceptance shall be formally completed after the owner’s acceptance team and other departments issue the acceptance certificate.
- 4. For the delivery of completion data, the completion data shall include all contents in the completion data specified by the owner, and the owner shall issue the handover certificate of completion data.