Pipeline installation construction scheme
I. General situation of the project:
1.1 Project name: Pipeline installation project of coke oven body area A of Shougang Jingtang Iron and Steel Plant Phase I coking project.
1.2 project site: Shougang Jingtang iron and steel plant, Caofeidian industrial zone, Tangshan city.
1.3 the main construction contents of the pipeline are: a. the heating gas pipeline of the coke oven body, the condensate drainage pipeline, the decarburization air pipeline and the gas pipeline arranged along the top gas collector. The maximum wall thickness of the pipeline is 11mm and the maximum diameter is 1821 mm. Among them, the main coke oven gas pipeline is DN911×11 with a total length of 121.81m, and the main blast furnace gas pipeline is DN1811×11 with a total length of 122.41m.:
II. Compilation basis
2.1 Construction Drawings
2.2 Current national and industrial standards and specifications:
2.2.1 GB51235-97 Code for Construction and Acceptance of Industrial Metal Pipeline Engineering
2.2.2 GB51236-98 Field Equipment, Code for construction and acceptance of industrial pipeline welding engineering
2.2.3 Technical Specification for Painting of Pipeline Equipment and Platform Escalator JNBJ-12-14-95
2.2.4 Code for Gas Safety in Industrial Enterprises GB6222-86
2.2.5 Code for Construction and Acceptance of Thermal Insulation Engineering of Industrial Equipment and Pipeline.
3.1.2 prepare the joint diagram according to the pipeline single line diagram. Determine the number of live joints and prefabricated pipe sections installed on site.
3.1.3 make technical disclosure according to the pipeline single-line diagram, floor plan and flow chart, and prepare the construction plan.
3.2 according to the prepared joint diagram and related documents, the pipeline technicians will list the pipe fittings (such as bent pipes, pressed tees, etc.) to be processed in the diagram in detail and submit them to professional processing manufacturers to start processing the pipe fittings.
3.3 set up a 21×11m steel platform at the site to facilitate the assembly and connection of pipelines.
3.4 preparation of construction materials: divide their respective scope of supply with party a, and apply to party a for the materials provided by party a and transport them to the construction site; Provided by the construction unit (including consumable materials), put forward the material application plan and purchase in place in time.
3.5 construction personnel preparation: reasonably organize pipeline installation personnel according to the site construction conditions (see the attached table for the manpower plan).
3.6 preparation of construction machines and tools: according to the site construction conditions, reasonably organize the construction machines and tools for pipeline installation (see the attached table for construction machines and tools).
IV. Construction measures
4.1 Pipeline construction and installation procedures are as follows
4.2 Material in and out of the warehouse and inspection:
4.2.1 All materials must be inspected and checked for appearance, quantity, specification, size and model according to the design requirements. If there is any problem, they cannot be used, and the supplier shall be notified to return them in time.
4.2.2 all construction materials must be submitted to the supervision engineer for inspection, and can only be used for construction after passing the inspection.
4.2.3 after all pipes and pipe components pass the inspection, color codes of various materials shall be prepared along the direction of the pipe axis according to the identification regulations of the project department on pipe components, and the specifications, models, materials and standard numbers of the pipe components shall be listed (such as GB9948 and GB/T8163).
4.2.4 For small pipe fittings, they shall be placed on the shelves according to the standards, materials, specifications and models of the pipe fittings, and listed and identified.
4.2.5 the construction teams are subject to quota acquisition, and the supply is issued in strict accordance with the single-line diagram (combined with the pipeline number).
4.3 Valve inspection:
4.3.1 The appearance, size and model of the valve shall conform to the specifications and design requirements, the working pressure and performance shall conform to the design requirements, and the shell appearance shall be smooth, clean and free from defects such as sand holes and cracks; The valve switch is flexible, the indication is correct, and it has the certificate (including the valve test certificate).
4.3.2 after the valve enters the site, a pressure test shall be conducted, and the unqualified valve shall not be used.
4.3.3 the safety valves must be debugged according to the opening pressure specified in the design documents, and the pressure should be stable when adjusting the pressure, and the opening and closing tests of each safety valve shall not be less than 3 times.
4.4 derusting and anticorrosion of pipelines
5.4.1 After the heating gas pipeline is installed, the primer Y53-1 red lead oily antirust paint shall be applied twice, and then the topcoat C14-42 alkyd enamel paint shall be applied twice, among which the gas pipeline shall be painted yellow-brown, and the ladder platform, various supports, hangers and bases shall be painted camel gray with the color code Y11；; The railings are painted brown and the color code is Y17.
5.4.2 The connecting branch pipes and horizontal pipes of the coke oven gas pipeline in the basement shall be painted in green and red alternately;
the paint of each connecting branch pipe of blast furnace gas is painted alternately in red and green;
4.5 pipeline fabrication
4.5.1 Before cutting, actual measurement should be made on the equipment and foundation in place, and fabrication should be made based on the measured data.
4.5.2 the choice of free pipe section and closed pipe section should be reasonable, and the closed pipe section should be processed according to the installation length after field measurement.
4.5.3 after blanking, the pipes shall be transplanted with marks in time to ensure the traceability of materials; The pipe should be cut from the end without steel grade and standard number.
4.5.4 the cutting surface of the cutting pipe should be polished clean and smooth with a grinding wheel to ensure the welding quality. The foreign matter left in the tube during cutting must be removed.
4.5.5 If the carbon steel pipe is cut with a grinding wheel cutter and an oxyacetylene flame, the inclination deviation △ of the end face of the cut should not be greater than 1% of the outer diameter of the pipe, and should not exceed 3mm, as shown in the following figure:
4.5.6 Grinding wheels for cutting and polishing stainless steel pipes and steel pipes with special regulations cannot be used for carbon steel pipe construction, and vice versa.
4.5.7 preparation of groove: the pipe connection is mainly by welding, and the groove is the first condition of welding, which must be carried out according to the documents specified in the specification. The groove types of medium and low pressure pipes are I-type and V-type, as shown in the figure below, and the groove and its vicinity are polished to metallic luster with an angular grinder.
4.5.8 before the pipeline assembly, clean the dirt, oil stain and rust within 25mm of the inner and outer surfaces of the joint, and clean the sundries in the pipe with a wire brush or mop. Temporary blind plates should be added to the pipe sections that are not closed during prefabrication and installation to prevent sundries from entering the pipeline.
4.5.9 pipe segment assembly. When the pipes are aligned, the straightness shall be measured 211mm away from the center of the interface (as shown in the figure below).
when the nominal diameter of the pipe is less than 111mm, the allowable deviation value α is 1 mm; When the nominal diameter of the pipe is greater than or equal to 111mm, the allowable deviation α is 2 mm; But the deviation value of the whole length shall not exceed 11 mm. When connecting pipes, it is not allowed to use methods such as strong butt joint, offset pad or extra pad to eliminate the defects such as gap, deviation, staggered mouth or misalignment at the end face of the interface. When the pipeline installation is discontinuous, the nozzle must be closed in time.
4.5.11 Look at the picture carefully, carefully consider and arrange the positions of pipeline prefabrication port and site installation port, and the distance between girth weld and hanger
should not be less than 51mm；; The distance between the weld to be heat-treated and the support and hanger shall not be less than 5 times of the width of the weld and not less than 111 mm..
4.5.11 the pipeline shall be numbered according to the specified requirements (pipeline number, joint number and welder number) to facilitate quality control and search during installation.
4.5.12 the inside of the finished pipe section shall be cleaned, and the nozzle shall be closed in time to ensure the cleanliness of the pipe. In particular, it is pointed out that all nozzles of this project must be completely closed before installation to ensure that the sealing rate of the pipeline entering the installation site is 111%.
4.6 pipeline processing
4.6.1 pipe cutting
a medium and low pressure carbon steel pipes with nominal diameter DN≤51 are cut by mechanical method (such as profile cutter), and steel pipes with dn > 51 are cut by oxygen-acetylene flame.
b cast iron pipe is cut with hacksaw and crescent extrusion knife.
the cut surface of c pipe should be smooth, free of cracks, double skin, burrs, bumps, necking, slag, iron oxide pins, etc. The inclination deviation of the cut plane is 1% of the pipe diameter, but shall not exceed 3mm.
4.6.2 elbow fabrication
a elbow fabrication should be made according to the requirements of design drawings. If there is no clear requirement in design, the following table can be used:
Minimum bending radius table of elbow
Minimum bending radius of elbow fabrication method
Hot bending of medium and low pressure steel pipes is 3.5DW
Cold bending is 4.1DW
Press bending is 1.1 DW < p.
when b pipe is heated, the temperature rise will be slow and uniform, so as to ensure the heat penetration of the pipe and prevent overheating and carburization.
4.6.3 thread processing (medium and low pressure pipes)
a is processed by a set of silk machines or a stranded plate.
b thread processing times: dn < 32mm is 1 ~ 2 times, dn = 32 ~ 51 is 2 ~ 3 times, and dn > 51mm is 3 times.
c oil is often added in the process of threading. From the last 1/3 length, the die should be gradually relaxed to form a cone.
d thread should be straight, clear, complete and smooth, and there should be no burrs and disordered threads. The total length of broken and missing threads should not exceed 11% of the total thread length.
e during machining, the force shall be even, and it is not allowed to use the method of adding casing to extend the handle for threading.
4.6.4 pipe fitting processing
if the design requires it, it shall be processed according to the design drawing, and if the design does not require it, it shall be processed according to the following requirements.
a number of joints of welded elbow
elbow degree
content 91 degrees 61 degrees 45 degrees 31 degrees
end joint 2 2 2 2
middle joint 2 1 1 /
Note: when DN > 411 mm, the number of middle joints can be increased, but the minimum width of the inner side should not be less than 51 mm.
main dimension deviation table of welded elbow
circumference deviation dn > 1111 ≤ 6mm
dn ≤ 1111 ≤ 4mm
vertical deviation between end face and center line ≤1%DW and not more than 3mm
b ovality of welded special-shaped pipe ≤1%DW and ≤5mm.
the vertical deviation of branch pipe of c welded tee is not more than 1% of its height and not more than 3mm.
4.7 pipeline welding
4.7.1 spot welding and welding of fixed fixture welds, the selected materials and technological measures are the same as the formal welding requirements.
4.7.2 Requirements for pipe wall misalignment:
For pipes with the same wall thickness, the misalignment of the inner wall shall be ≤ 2mm; When pipes with different wall thicknesses exceed 2mm, it shall be implemented according to Article 4.2.4 of GB51235-97.
4.7.3 the distance between the center faces of two butt welds on the straight section dn ≥ 1.51 mm, dn < 1.51, 1≥DW (pipe diameter).
4.7.4 the distance between the weld and the bending point of the elbow is L≥111mm and L≥DW.
4.7.5 the longitudinal weld of the coiled tube should be placed in an easy-to-repair position and not at the bottom.
4.7.6 For process pipelines and pipelines with high cleaning requirements and difficult cleaning after welding, argon arc welding shall be used for the bottom weld.
when welding pipes and fittings with p>4.7.7 DN≥411, back sealing welding shall be carried out on the inner weld root.
4.8 pipe flange connection
4.8.1 When the flange is welded to the pipe, the flange end face should be perpendicular to the center line of the pipe, and the allowable deviation is 1mm when DN≤311mm, and 2mm when DN > 311.
4.8.2 the distance between the pipe inserted into the flange and the sealing surface is L=(1/2~2/3δ), where δ is the flange thickness.
4.8.3 bolts used for flange connection shall be of the same specification, with the same installation direction, symmetrical and even fastening, and the flange connection shall be kept parallel, with the deviation not more than 1.5% of the flange external diameter. And not more than 2mm, shall not use the method of tightening bolts to eliminate deflection, flange connection should be kept on the same axis, and its screw hole can ensure the free penetration of bolts.
4.8.4 flange gaskets, bolts and nuts shall be coated with graphite powder, molybdenum disulfide grease, graphite engine oil, etc. according to the needs of the site.
4.9 threaded connection
before connection, select appropriate fillers according to the pipelines with different media, and use thick white paint and hemp for the connection of the lower nozzle.
Key points of threaded connection:
4.9.1 Select qualified pipe tongs, apply packing on the thread outside the pipe end before connection, and then tighten it once, and do not reverse it. After tightening, a screw tail shall be left. Pay attention to that the packing shall not squeeze into the pipe cavity, and the packing squeezed out of the thread shall be removed.
4.9.2 The lead monoxide glycerin mixture should be used up within ten minutes, and all kinds of fillers can only be used once in the thread. If it needs to be disassembled and reassembled, the fillers should be replaced again.
4.11 pipeline installation
before pipeline installation, the pipeline positioning method is to use truck crane or other auxiliary tools (such as chain hoist, homemade trolley, hanging basket, scaffolding, etc.) to make it enter the site in place when manpower is difficult to position.
the pipeline installation shall meet the following conditions:
a the civil works related to the pipeline have passed the inspection and meet the installation requirements.
b the equipment connected to the pipeline has been aligned and fixed.
c relevant processes such as cleaning and anticorrosion must be completed before pipeline installation.
d pipes, fittings and valves have passed the inspection and have relevant technical documents.
e pipes, fittings and valves have been checked as designed, and the interior has been cleaned without sundries.
4.11.1 installation of carbon removal air pipeline
a pipeline connection: DN≤51mm oxygen-acetylene welding, but the welded steel pipe with DN≤51mm can be connected by thread. Seamless steel pipes with DN > 51 mm are connected by electric welding.
the branch pipe b should be connected from the upper part or side of the main pipe. For the convenience of construction, the connection angles between the branch pipe and the main pipe are generally 91, 61, 31, 15, etc. When the pipe passes through the wall or floor, a sleeve should be set.
c during installation, pay attention to that the slope conforms to the design or specification.
d the pipes at the top of the furnace and the resisting wall must be connected after the oven temperature reaches 611 degrees.
e pipeline pressure test adopts hydraulic pressure test, with strength test Ps=1.5P, P=1.8Mpa and test time of 11 minutes. The leak test pressure Ps=P, and the leak test is qualified if the pressure does not drop or there is no leakage within 31 minutes.
4.11.2 installation of heating pipes under the furnace
The limit deviations of elevation and centerline of distribution main pipe are all 5 mm, and the limit deviations of centerline and center distance of branch pipes are all 3 mm..
the branch pipe b should be connected from the standard pipe fitting tee of the main pipe, and the branch pipe should be arranged in typesetting before opening the hole on the main pipe to avoid cross welds. The diameter of the opening is not more than 5mm, and the depth of inserting the branch pipe into the main pipe is not more than 3 mm..
the tolerance of levelness and verticality of c main and branch pipe flanges is 1/511. Flanges of each branch pipe shall be in the same plane,