DL 5031-1994 Technical Specification for Construction and Acceptance of Electric Power Construction (Pipeline)
Some standard content:
Ministry of Electric Power Industry of the People's Republic of China
Technical Specifications for Construction and Acceptance of Electric Power Construction
(Pipeline Section)
DL5031-94
Ministry of Electric Power Industry of the People's Republic of China
Notice on Issuing the Electric Power Industry Standard "Technical Specifications for Construction and Acceptance of Electric Power Construction (Pipeline Section)" Electric Power Technology [1994] No. 208
In order to adapt to the development of electric power industry technology and ensure the installation quality of pipelines in thermal power plants, our ministry has revised the Technical Specifications for Construction and Acceptance of Electric Power Construction (Pipeline Section) DJ56-79 issued in 1979. The new specification is the electric power industry standard, with the standard number DL5031-94. It is now approved and issued and will be implemented from October 1, 1994. The original specification will be abolished at the same time. If any units have any problems in implementation, please inform the Construction Coordination Department of our ministry. April 9, 1994
1 General
1.0.1 This specification applies to the preparation, construction and acceptance of the following pipelines in thermal power plants and heat networks:
(1) Main steam pipelines and corresponding reheat steam pipelines and main feed water pipelines of subcritical thermal power generating units of 600MW and below;
(2) General steam and water pipelines, heat network pipelines and compressed air pipelines within the scope of thermal power plants;
(3) Temporary pipelines for construction.
1.0.2 This specification does not apply to:
(1) Cast iron pipelines;
(2) Reinforced concrete pipelines;
(3) Non-ferrous metal pipelines (titanium, copper, etc.); (4) Non-metallic pipelines (plastics, etc.);
(5) Non-metallic lining pipelines;
(6) Composite metal pipelines.
1.0.3 In addition to complying with the technical requirements of this Code, the special construction and acceptance of the following types of pipelines shall also be carried out in accordance with the provisions of the relevant professional sections of the Technical Code for Construction and Acceptance of Power Construction: (1) All types of pipelines within the scope of the turbine and generator body; (2) All types of pipelines within the scope of the boiler body, as well as pipelines for smoke, wind, coal, oil, gas and ash removal systems; (3) All types of pipelines for oil pipelines and water treatment; (4) All types of pipelines for hydrogen production and hydrogen supply systems; (5) Thermal instrument pipelines; (6) Oxygen and acetylene pipelines.
1.0.4 The construction and acceptance of pipelines for imported thermal power generating units shall be carried out in accordance with the provisions of this Code, except for those otherwise specifically stipulated in the construction contract.
1.0.5 The pipeline installation project of a power plant shall be undertaken by a professional team with the necessary technical strength, testing means and management level.
1.0.6 The construction of power plant pipelines shall be carried out in accordance with the basic construction procedures, and the following conditions shall be met before construction can be carried out:
(1) The design and other technical data are complete, and the construction drawings have been reviewed;
(2) The construction organization design and construction plan of the power plant pipeline project have been prepared and approved;
(3) Technical disclosure and necessary technical training and assessment have been completed;
(4) The labor, materials, machinery and testing methods are basically complete;
(5) The construction environment meets the requirements;
(6) The water, electricity, gas, etc. used in construction can meet the construction needs. 1.0.7 The manufacturing quality and selection of pipes, pipe fittings and pipeline accessories shall comply with the current national or industry (or professional) technical standards. 1.0.8 The storage of various pipes, pipe fittings and pipeline accessories shall be carried out in accordance with the current SDJ68 "Regulations on Maintenance and Storage of Thermal Power Equipment in Power Basic Construction" and corresponding supplementary regulations. 1.0.9 All types of pipelines shall be constructed in accordance with the design drawings. If the design needs to be modified or substitute materials are used, the design unit must be requested to handle it in accordance with the relevant system.
1.0.10 In addition to the relevant provisions of this specification, the cutting and welding work in pipeline construction shall also comply with the relevant provisions of the current DL5007 "Technical Specifications for Construction and Acceptance of Power Construction (Welding Part of Thermal Power Plant)".
1.0.11 The insulation and painting of pipelines shall be carried out in accordance with the provisions of SDJ245 "Technical Specifications for Construction and Acceptance of Power Construction (Boiler Unit Part)". The coloring of pipelines shall be carried out in accordance with the provisions of DL5011 "Technical Specifications for Construction and Acceptance of Power Construction (Turbine Unit Part)".
1.0.12 The safety, environment and fire prevention of power plant pipeline construction shall be carried out in accordance with the relevant provisions of the current DL5009.1 "Safety Work Regulations for Power Construction (Part of Thermal Power Plant)". 2 Terminology
2.0.1 Pipe fittings - a general term for the parts that together with pipes constitute the pipeline system itself, including elbows, bends, tees, reducers, pipe sockets, flanges, plugs, caps, etc. 2.0.2 Pipe accessories - refers to the external supporting parts used in the pipeline system, including supports, hangers, gaskets, seals, fasteners, etc. 2.0.3 Bends - refers to pipes with bent axes. 2.0.4 Elbows refer to bends with a bending radius less than or equal to 2D and a straight pipe section less than 1D.
5 Miter elbows
An elbow (also called a welded elbow or shrimp bend) made by welding two or more straight pipe
sections together in a plane that divides the bend angle equally.
2.0.6 Calculation of wall thickness of straight pipes
Negative deviation value of straight pipe wall thickness.
refers to the minimum wall thickness of the straight pipe plus
2.0.7 Monitoring section - a pipe section installed on the horizontal section of the main steam pipeline and high-temperature reheat steam pipeline with a design temperature greater than 450°C for creep monitoring.
2.0.8 Swelling measurement point - a device or mark set on the monitoring section or steam pipeline to measure the creep deformation of the pipeline. 2.0.9 Pipeline classification - Power plant pipelines can be classified according to the design pressure P as the main parameter, see Table 2.0.9.
Pipeline level
High-pressure pipeline
Medium-pressure pipeline
Low-pressure pipeline
Pipeline classification
Main parameters
p>8MPa
8MPa=≥p>1.6MPa
p≤1.6MPa
Note: Reheat cold section and hot section pipelines are regarded as high-pressure pipelines. 3 Inspection of pipes, pipe fittings, pipeline accessories
and valves
General provisions
3.1.1 Pipes, pipe fittings, pipeline accessories and valves must have a certificate of conformity from the manufacturer, and the relevant indicators should comply with the current national or industry technical standards.
3.1.2 Before using pipes, pipe fittings, pipeline accessories and valves, their specifications, materials and technical parameters should be checked according to the design requirements. 3.1.3 Before using pipes, pipe fittings, pipeline accessories and valves, they should be inspected for appearance. The surface requirements are as follows: (1) No defects such as cracks, shrinkage holes, slag inclusions, sand adhesion, folding, welding leakage, heavy skin, etc.
(2) The surface should be smooth and no sharp scratches are allowed; (3) The depth of the dent should not exceed 1.5mm, and the maximum size of the dent should not be greater than 5% of the circumference of the pipe and not greater than 40mm. 3.1.4 Before using medium and low alloy steel pipes, pipe fittings, pipeline accessories and valves, they should be spectrally reviewed piece by piece and marked with materials.
3.2 Pipe Inspection
3.2.1 Before the construction of pipelines with a design pressure greater than or equal to 1.6MPa, the following items of the pipes used should also be confirmed to comply with the current national or industry technical standards:wwW.bzxz.Net
(1) Chemical composition analysis results:
(2) Mechanical properties test results (tensile strength, yield strength, elongation);
(3) Impact toughness test results of high-pressure alloy steel pipes with a wall thickness greater than or equal to 12mm:
(4) Heat treatment status description or metallographic analysis results of alloy steel pipes;
3.2.2 Before using seamed pipes with a design pressure greater than 0.1MPa, their weld inspection reports should be checked.
3.2.3 Local defects such as scratches, pits, corrosion, etc. on the pipe surface should be inspected and identified. The wall thickness of the treated pipe should not be less than the calculated wall thickness of the straight pipe, and records should be made and inspection reports submitted. 3.2.4 Medium and low alloy steel pipes used in high-pressure pipelines should be subjected to thickness measurement inspections on no less than three sections and records should be kept. 3.2.5 Steel pipes that pass the inspection should be placed separately according to material and specifications and properly stored to prevent rust.
3.3 Inspection of pipe fittings
3.3.1 Before the construction of medium and high-pressure pipelines, the following items of the pipe fittings used should be confirmed to comply with the current national or industry technical standards: (1) Chemical composition analysis results;
(2) Heat treatment status description or metallographic analysis results of alloy steel pipe fittings;
(3) Non-destructive testing results of high-pressure pipe fittings. 3.3.2 The flange sealing surface should be smooth and free of radial grooves, pores, cracks, burrs or other defects that reduce strength and connection reliability.
3.3.3 Flanges with concave and convex surfaces or concave and convex rings should fit naturally, and the height of the convex surface should not be less than the depth of the groove. 3.3.4 The supporting part of the connecting bolt on the flange end face should be parallel to the flange joint surface to ensure that the end face is evenly stressed when the flange is connected.
5 Before using the flange, the dimensions of each part should be checked according to the design drawings and checked with the flange on the equipment to be connected to ensure correct connection.
3.4 Inspection of pipe accessories
3.4.1 The threads of bolts and nuts should be complete, without defects such as scratches and burrs. The bolts and nuts should fit well without looseness or jamming.
3.4.2 Alloy steel bolts used for design temperatures greater than 430℃ and diameters greater than or equal to M30 should be numbered one by one and hardness checked one by one. Those that fail to meet the requirements shall not be used.
3.4.3 The gasket material of the flange should meet the design requirements. If there are no specific requirements, it can be selected according to the provisions of Table A5 in Appendix A. 3.4.4 Asbestos rubber gaskets should be flexible, free of aging, deterioration or delamination, and the surface should not have defects such as folds and wrinkles. 3.4.5 The surface of the metal gasket should be visually inspected with a flat ruler. It should have good contact, no cracks, burrs, rust and rough processing defects, and its hardness should be lower than the flange hardness.
3.4.6 Metal-clad and wound gaskets should not have radial scratches, looseness and other defects.
3.4.7 The assembly dimensions and welding methods of the steel structure of the pipeline support and hanger shall comply with the provisions of 4.4 of this specification.
3.4.8 The working surface of the sliding bracket shall be smooth and flexible without sticking.
3.4.9 The inspection of the pipeline support and hanger spring shall comply with the provisions of Articles 4.4.4 and 4.4.5 of this specification.
3.5 Valve Inspection
3.5.1 Before installing various valves, the following inspections should be carried out: (1) Whether the packing material meets the design requirements and whether the filling method is correct. If there is no design requirement for the sealing packing material, it can be selected according to Table A6 in Appendix A:
(2) Whether the valve stem at the packing seal is corroded; (3) Whether the switch is flexible and the indication is correct; (4) There are no obvious manufacturing defects on the appearance of the cast valve. 3.5.2 Valves used as closed-circuit components (for isolation) must be inspected for tightness before installation to check the tightness of the joints between the valve seat and the valve core, the valve cover and the packing chamber. The tightness test of the valve should be carried out at a water pressure of 1.25 times the nameplate pressure. 3.5.3 Low-pressure valves should be sampled from each batch (same manufacturer, same specification and same model) at a ratio of no less than 10% (at least one) for tightness test. If there are unqualified ones, another 20% should be sampled. If there are still unqualified ones, they should be checked one by one; valves used for high-pressure pipelines should be tested for tightness one by one.
3.5.4 For safety gates or valves with a nominal pressure less than or equal to 0.6MPa and a nominal diameter greater than or equal to 800mm, color printing can be used to check the tightness of the valve core sealing surface; for large-diameter welded valves with a nominal diameter greater than or equal to 600mm, oil or water seepage methods can be used instead of water pressure tightness test. 3.5.5 Before the valve is tested for tightness, it is strictly forbidden to have grease or other coatings on the joint surface.
3.5.6 The method of conducting tightness hydraulic test on valves shall comply with the provisions of the manufacturer. For the test of stop valves, water shall be introduced from the top of the valve body; for the test of gate valves, the valve shall be closed and each sealing surface shall be inspected.
3.5.7 After the valve passes the tightness test, the accumulated water in the body cavity shall be drained and stored in a classified manner.
3.5.8 The following valves must be disassembled and inspected before installation: (1) Valves for design temperatures greater than or equal to 450°C; (2) Safety valves and throttle valves;
(3) Valves that fail the tightness test. Before disassembling the valve, the dirt shall be cleaned up, otherwise 3.5.9
Opening and closing operations and disassembly shall not be carried out. When disassembling and inspecting valves with special structures, the disassembly and assembly sequence specified by the manufacturer shall be followed to prevent damage to components or affect personal safety.
3.5.10 The following inspections should be carried out on the dismantled valves: (1) The internal parts of alloy steel valves should be subjected to spectral review (no marking is required on the parts, but the inspection results should be recorded); (2) Whether the joint between the valve seat and the valve housing is firm and whether there is any looseness; (3) Whether the joint surface between the valve core and the valve seat is consistent and whether there are any defects on the joint surface:
(4) Whether the connection between the valve stem and the valve core is flexible and reliable; (5) Whether the valve stem is bent or corroded, whether the valve stem and the packing gland fit each other properly, and whether there are any defects such as broken threads on the valve stem;
(6) The joint condition of the valve cover flange surface;
(7) The opening and closing stroke and terminal position of the throttle valve should also be checked and marked as much as possible.
3.5.11 After the valve is disassembled for inspection and defects are eliminated, it shall meet the following quality requirements:
(1) The material of alloy steel parts meets the design requirements; (2) The assembly is correct, the movement is flexible, and the opening indicator indicates correctly;
(3) The specifications and quality of the gaskets and packings used meet the technical requirements; (4) The packing is filled correctly, the interface must be cut into an oblique mouth, and the interface of each layer should be staggered. After the packing is compressed, the sealing should be guaranteed and it should not hinder the opening and closing of the valve stem.
3.5.12 The flow-through parts of valves used in oil systems should be cleaned, and the molding sand and paint should be removed, and oil-resistant packing and gaskets should be replaced. 3.5.13 When the gate valve and stop valve are reassembled after disassembly inspection, the valve disc must be in the open position before the valve cover screws can be tightened. 3.5.14 The valve should be tested for tightness after disassembly and reassembly. 3.5.15 For all kinds of valves, when the manufacturer ensures product quality and provides product quality and use guarantee, disassembly and tightness inspection are not required; otherwise, they shall comply with the provisions of this section. 3.5.16 The operating mechanism and transmission device of the valve shall be inspected and adjusted as necessary according to the design requirements to achieve flexible action and correct indication.
4 Preparation of pipes, pipe fittings and pipeline accessories
4.1 General provisions
4.1.1 The preparation of pipes and the production of supports and hangers shall comply with the provisions of the design drawings and relevant standards.
4.1.2 The materials and specifications of steel pipes, steel plates, round steel and other steel sections shall comply with the design requirements.
4.1.3 The cutting of pipes shall comply with the relevant provisions of the current DL5007 "Technical Specifications for Construction and Acceptance of Electric Power Construction (Welding of Thermal Power Plants)".
After high-pressure steel pipes and alloy steel pipes are cut, they shall be promptly transplanted to the original 4.1.47
marked.
4.2 Bending
4.2.1 If thickened pipes are not used for bending, pipes with positive tolerances on the wall thickness should be selected.
4.2.2 The bending radius of the bending pipe should meet the design requirements. If there is no design requirement, the minimum bending radius of the bending pipe should meet the relevant provisions of the industry standard DL/T515 "Power Station Bending Pipes". 4.2.3 When medium frequency heating is used for bending pipes, the following provisions should be met: (1) The heating temperature for bending low carbon steel pipes is 850-1000℃. When the pipe wall thickness is not more than 25mm, water spray cooling is adopted. Otherwise, forced air cooling is suitable, and heat treatment is not required after bending.
(2) When bending alloy steel pipes, the heating temperature at the back of the pipe shall not exceed 900℃, and strong air cooling is adopted for cooling. Normalizing and tempering treatment should be carried out after bending.
(3) When bending a new steel grade steel pipe, the maximum deformation of the back arc of the steel grade bend must be tested. Only after confirming that there are no defects such as intergranular cracks can the process be determined and the steel grade steel pipe be bent. 4.2.4 When a new steel grade is used for the first time, or when the heat treatment specification of a commonly used steel grade is changed, a random inspection test should be carried out after heat treatment (samples are cut from the bending part) to obtain the data specified in items (2), (3) and (4) of Article 3.2.1 of this specification. 4.2.5 After the bend is made, the inner and outer surfaces should be cleaned. 4.2.6 After the bend is made, the data such as the out-of-roundness, waviness, angle deviation and wall thickness reduction should meet the following requirements: (1) The out-of-roundness of the bending part shall not be greater than: High-pressure pipeline
Medium- and low-pressure pipelines
(2) The allowable value of the waviness of the bending part is shown in Table 4.2.6.
（3）After bending, the allowable angle deviation is ±0.5°; (4) The measured wall thickness of the outer arc part of the bent pipe shall not be less than the minimum wall thickness of the straight pipe;
（5）The out-of-roundness of the straight pipe section of the bent pipe shall comply with the technical requirements of the steel pipe.
Allowable value of waviness 8 (mm) Table 4.2.6 Method
≥426
Medium frequency bending
Do/tDa/t
Waviness diagram
t≥4g
-outer diameter
4.2.7After the pipe is bent, there should be no defects such as cracks, delamination, overburning, etc. on the pipe wall surface. If in doubt, non-destructive testing should be carried out.
4.2.8After high-pressure steel pipes are bent, non-destructive testing should be carried out, and those that require heat treatment should be carried out after heat treatment. If defects are allowed to be repaired, the wall thickness after repair should not be less than the minimum wall thickness of the straight pipe. 4.2.9 Alloy steel pipes shall be subjected to metallographic structure and hardness inspection after bending and heat treatment, and shall comply with the provisions of DL438 "Technical Supervision Regulations for Metals in Thermal Power Plants".
4.2.10 After the high-pressure bending pipe is qualified, a product quality inspection certificate shall be provided.
4.3 Processing of rolled pipes, pipe fittings and pipe accessories
4.3.1 The preparation and processing of various pipe fittings shall be in accordance with the provisions of the design drawings. The materials used shall meet the design requirements. 4.3.2 Forgings shall comply with the relevant technical regulations of the current state or industry.
4.3.3 The surface transition zone of forged pipe fittings and pipeline accessories shall be smooth. After mechanical processing, there shall be no defects such as cracks on the surface that affect strength and tightness.
4.3.4 Steel pipes, pipe fittings and pipeline accessories rolled with steel plates shall not have defects such as leaking welding and incomplete penetration. The weld shall pass the kerosene penetration test. For pressure pipelines, non-destructive testing shall also be carried out in accordance with relevant regulations. 4.3.5 Steel pipes rolled from steel plates shall meet the following requirements: (1) When the pipe sections are butt-jointed, the longitudinal welds shall be staggered and shall not be less than 100 mm;
(2) When holes are drilled in the main pipe, the holes shall not be drilled on the welds.
4.3.6 The welds of the rolled pipes shall be of guaranteed quality. When the nominal diameter of the rolled pipes is greater than or equal to 1000 mm, the bottom welding shall be performed inside the pipes. 4.3.7 Coiled pipes with a diameter less than 2000mm may have no more than two longitudinal welds, and the spacing between the two longitudinal welds should be greater than 300mm. 4.3.8 The geometric dimensions of the rolled steel pipe shall meet the following requirements: (1) The outer diameter shall be converted into circumference for inspection, and the length adjustment deviation shall not exceed ±4mm;
Figure 4.3.8 Schematic diagram of verticality deviation of pipe end face
(2) For out-of-roundness deviation, check with a rounding template with an inner diameter of 1/6 to 1/4 of the circumference. There should be no gap greater than 1mm; 1155
(3) The verticality deviation A of the pipe end face (see Figure 4.3.8) shall not be greater than the provisions of Table 4.3.10.
4.3.9 During the coiling process, the plate surface should be free from mechanical damage. The seriously scratched parts should be ground and made to transition smoothly. The grinding depth of the pressure pipe shall not exceed 10% of the plate thickness, and the wall thickness after grinding shall not be less than the minimum wall thickness of the straight pipe. 4.3.10 The plane deviation P and end angle deviation Q of various elbows shall not be greater than the provisions of Table 4.3.10 (see Figure 4.3.10). The out-of-roundness of pushed and pressed elbows shall meet the following requirements when there are no design regulations:
Figure 4.3.10 Elbow geometry
Deviation diagram
Plane deviation and angle deviation
Pipe outer diameter Do
Do≤133
133
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