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1.1 System Overview High-temperature and high-pressure steam pipelines mainly include the main steam pipeline system and the high- and low-temperature reheat steam pipeline systems. This technical guide is applicable to the installation of main steam pipelines, high- and low-temperature reheat steam pipelines, as well as high- and low-pressure bypass pipelines. The main steam pipeline of this unit starts from the outlet of the boiler superheater header, and is led by steel pipes to the turbine hall where it connects to the main steam valve of the turbine system in two separate paths ； The low-temperature reheat pipeline branches off from the high-pressure cylinder and returns to the boiler’s low-temperature reheat header in two paths ； The high-temperature reheat steam pipeline starts from the outlet of the boiler’s high-temperature reheat header; it consists of steel pipes that, before reaching the turbine hall, split into two branches and connect to the automatic control valves of the turbine system. To ensure the safe and stable operation of the boiler and maintain a constant steam pressure, a high-pressure bypass pipe is installed in the main steam pipeline, while a low-pressure bypass pipe is installed in the high-temperature reheat steam pipeline. The bypass system plays an important role in the startup, shutdown, and load variation operations of the unit. 1.2 Main system parameters: The design pressure of the main steam pipeline is P=13.7 Mpa, and the design temperature is t=545°C. The main material used in the system is φ377×50 alloy steel pipe made of 12Cr1MoV. The design pressure of the low-temperature reheat steam pipeline is P=3.04755 Mpa, and the design temperature is t=335.6°C. The main material used in the system is φ660.4×17.5 steel pipes of grade ST45.8/Ⅲ. The design pressure of the high-temperature reheat steam pipeline is P=2.58 Mpa, and the design temperature is t=545°C. The main material used in the system is φ609.6×20 alloy steel pipe made of 10CrMo910. 1.3 System Layout 1.3.1 Main steam pipeline: Outlet of the boiler superheater header (elevation 44.54 meters) → right side of the boiler at elevation 37 meters → from 27 meters to 15.5 meters in front of the furnace → turbine hall (in two pipelines at elevation 3.6 meters) → high-pressure main valve room of the turbine system. 1.3.2 Low-temperature reheat steam pipeline: Turbine high-pressure cylinder exhaust port (elevation 8.05 meters) → Turbine room (elevation 3.6 meters) → Levels 14.5 meters and 27.98 meters in front of the furnace → Boiler low-temperature reheater inlet header. 1.3.3 High-temperature reheat steam piping: Outlet of the boiler’s high-temperature reheater header (elevation 45 meters) → right side of the boiler at elevation 39.6 meters → from elevation 39.6 meters to 19.6 meters in front of the furnace → turbine hall (dividing into two routes at elevation 7.6 meters) → automatic control valves. 1.3.4 High-pressure bypass pipeline: Main steam pipe in front of the furnace (elevation 15.5 meters) → High-pressure bypass valve (elevation 7.17 meters) → Low-temperature reheat pipe in the turbine hall (elevation 3.6 meters). 1.3.5 Low-pressure bypass pipeline: High-temperature reheat steam pipeline in front of the furnace (elevation 17.3 meters) → Low-pressure bypass valve (elevation 7.5 meters) → Condenser temperature and pressure reduction device (elevation 6 meters). 1.4 Main quantities of work 1.4.1 Main steam pipeline: Total weight 43,752 Kg. For DN＞80: The pipeline is 129 meters long, there is 1 valve, and 19 sets of supports and hangers are required. DN≤80: There are 120 meters of pipes in total, 6 valves, and approximately 40 sets of supports and hangers. 1.4.2 High-temperature reheat steam pipeline: Total weight 22,391 Kg; DN > 80: The pipeline is 86.5 meters long, there is 1 valve, and 13 sets of supports and hangers are used. DN≤80: The pipeline is 20 meters long in total, there are 4 valves, and approximately 10 sets of supports and hangers. 1.4.3 Low-temperature reheat steam pipeline: Total weight 30,967 Kg; DN > 80: The pipeline is 67 meters long, there are 2 valves, and 10 sets of supports and hangers. DN≤80: The pipeline is 100 meters long in total, there are 4 valves, and approximately 40 sets of supports and hangers. 2 Basis for preparation 2.1 Design drawings from Central South Electric Power Design Institute: F0833S-J0501, F0833S-J0502, F0833S-J0503. 2.2 Technical Specifications for Construction and Acceptance of Electric Power Engineering – Pipeline Section, DL5031-94. 2.3 “Quality Inspection and Evaluation Standards for Thermal Power Plant Construction” – Pipeline Section, 2000 edition. 2.4 Code for Technical Supervision of Metals in Thermal Power Plants SD107-83. 2.5 Safety Regulations for Electric Power Construction DL5009.1-2002. 2.6 “Regulations on Safe Construction Management in Electric Power Projects”. 3 Preparation for the work and requirements 3.1 Preparation for the work 3.1.1 Number of workers required: Fitters: 16 people ； Crane operators: 3 people ； General workers: 6. 3.1.2 Equipment of main tools and machinery: chain hoist ； Angle grinder ； Grinding wheel cutter ； Grooving machine ； winch ； Automatic gas cutting machine ； level ； Oxycut torch ； Gantry crane ； Tank crane ； dump truck ； Impact drills and other tools can be used flexibly as needed. 3.1.3 Supply of mechanical energy: Oxygen, acetylene, hydrocarbon gases, and argon are supplied via cylinders or through piping systems. The construction power supply and welding machines are located in the assembly area, the main plant (at 0 meters, 12 meters, 22 meters, etc.), and the boiler area. 3.1.4 Construction site layout: The inspection of pipes and fittings, material delivery, processing, prefabrication and assembly are mainly carried out at the pipe assembly site. 3.1.5 Before construction, all workers shall carefully study the operation instructions. 3.1.6 Before construction, all workers must be familiar with the construction drawings and the on-site layout. 3.1.7 Before construction, all workers must become familiar with the technical specifications for pipeline installation, operating procedures, quality acceptance standards, and other relevant regulations. 3.1.8 Prepare the assembled platform before construction, along with the stools used for alignment, alignment clamps, and welding sheds. 3.2 Operating Conditions 3.2.1 The materials must be inspected and counted; their specifications and quantities must meet the design requirements. The materials shall come with certificates of conformity, and alloy materials must undergo spectral analysis before they can be used. 3.2.2 Steel pipes shall be inspected individually for appearance, wall thickness, metallography, and hardness, with original records to be kept. 3.2.3 Materials should be waterproof and dustproof, stored in categories with clear labeling. 3.2.4 In cases where the quantity of materials does not match or there are defects, detailed records should be kept, and the situation should be reported to the technical staff. 3.2.5 The foundation has been inspected, verified, and is ready for handover. 3.2.6 The holes passing through the wall have been inspected, and their positions have been verified to meet the design requirements. 3.2.7 The roads for transporting and placing materials must be clear, and the site must be clean. 3.2.8 The construction site must be equipped with adequate fire-fighting facilities. 3.2.9 Thoroughly prepare the records for measurement and inspection at all stages of construction. 4 Operation Steps and Process Requirements 4.1 Operation Steps: 4.1.1 Preparation of supports and hangers: Material receipt and inventory checking → Preparation of the pipe sections of the supports and hangers and assembly of their bases → Hanging and installation of the supports and hangers → Adjustment of the supports and hangers. 4.1.2 Pipe installation: Receiving and counting of pipes and fittings → Inspection of pipes and fittings (spectroscopy, thickness measurement, metallography, hardness, etc.) → Cutting and beveling → Prefabrication and assembly → Lifting and installation. 4.1.3 Valve installation: Retrieval and model verification → Visual inspection → Disassembly inspection (spectral recording) → Hydrostatic test and installation adjustment → Inspection and cleaning. 4.2 Process Requirements 4.2.1 Installation of Supports and Hangers ★The installation of supports and hangers should take into account the position of the pipes, ensuring that their elevation and horizontal centers are aligned properly. The fixings must be secure, and the connection to the pipes should be firm. ★The hanger should be installed according to the construction drawings at its base; the tie rods must not be bent or deformed, the threads must be intact and fit well with the nuts, and the welding must be secure. ★ The holes in the lifting rings and shims at the base of supports and hangers should be created using mechanical drilling; cutting torches must not be used for this purpose. ★ The fixing supports of the pipeline should be installed in strict accordance with the design drawings; no two or more fixing supports shall be installed simultaneously on straight sections of pipe without compensation devices. ★In the installation of multiple parallel pipes, the hangers shall not be used to lift any two pipes that are moving in opposite directions or with different displacement amounts. ★ When temporary supports and hangers are used for pipeline installation, they must be clearly marked and must not overlap with the positions of the permanent supports and hangers. They should be removed after the pipeline installation and hydrostatic testing are completed. ★ When fixing the anchorages of the supports and hangers to the concrete foundation using expansion bolts, these bolts must be driven to the specified depth. ★The sliding surfaces of the guide brackets and sliding brackets should be clean and smooth, and moving parts such as balls, rollers, and idlers should make good contact with their supporting elements to ensure that the pipeline can expand freely. ★The moving parts of all movable supports shall be exposed and not covered by insulation material. ★ For pipes with thermal displacement, when they expand due to heat, the supports and hangers should be inspected and adjusted as follows in a timely manner. a: Whether the displacement direction, amount of displacement, and guiding performance of the movable bracket meet the design requirements. b: Check whether the pipe supports have fallen off. c: Whether the fixing bracket is firm and reliable. d: Whether the installation height of the spring bracket and the working height of the spring meet the design requirements. ★ The setting spring should be installed in accordance with the design requirements. The fixing pins should be removed only after the pipeline system has been installed, the integrity tests have been completed, and insulation work has been done; they should be pulled out completely and stored properly. ★Constant-force hangers should be installed and adjusted in accordance with the design requirements. ★After adjusting the supports and hangers, the screw threads of all connecting parts must be fully engaged, and the lock nuts should be tightened to prevent loosening. ★ The bolt holes in the hanger and the holes for the spring seats must meet the requirements. ★ The spacing between supports should be installed correctly in accordance with the design requirements. 4.2.2 Combined installation of pipes ★ When combining pipes, consideration should be given to the convenience of lifting them. ★Piping assemblies shall have sufficient rigidity, shall not suffer permanent deformation after lifting, and temporary fixations shall be firm and reliable. ★ Before piping is assembled or the components are installed, the inside of the pipes must be cleaned thoroughly; no debris should remain inside them, and they should be temporarily sealed. ★ The slope direction and gradient of the horizontal section of the pipeline shall meet the design requirements. ★ The position of the butt weld on the pipe shall comply with the design specifications; otherwise, it shall meet the following requirements: a. The position of the weld shall be at least the outer diameter of the pipe away from the starting point of the bend, or at least 100 mm away. b. The distance between the two butt welds on the pipe should not be less than the outer diameter of the pipe, nor less than 150 mm. c. The position of the pipe section of the support or hanger must not overlap with the butt weld of the pipe; the distance between the weld and the edge of the support or hanger must be at least 50 mm. For joints that require heat treatment after welding, this distance must be at least 5 times the width of the weld. d. The pipe connections should be located away from openings for steam traps, exhaust pipes, and instrumentation pipes, with a distance of at least 50 mm from the edge of such openings. e. When pipes pass through wall panels or floor slabs, the sections of the pipes located within the walls or floors must not have joints. ★ When the two molded parts on the pipe are welded to each other, short pipes should be added as required by the design. ★ Unless the design specifies cold drawing or thermal tightening, forceful alignment should not be used when connecting the pipes. The connection between the pipes and the equipment should be carried out naturally after the equipment has been installed in position and its foundation bolts have been tightened properly. ★ The paint, scale, rust, and other contaminants within 10–15 mm of the inner and outer walls of the grooves in pipes and fittings must be removed completely before welding, until a metallic shine is achieved. For grooves with a wall thickness of 20 mm or more, it is necessary to check for any defects such as cracks or delaminations. ★ When aligning pipes, they should generally be straight. The deformation at the welding joint is measured 200 mm from the center of the joint; unless otherwise specified, the allowable deviation d for such deformation is: d≯2 mm for DN＜100 mm, and d≯3 mm for DN≥100 mm. ★ When aligning thick-walled pipes, wedges should be used for alignment; upon removal, the base material must not be damaged, and any remaining weld scars should be completely removed and the surface polished to perfection. ★ When aligning the pipes, they must be secured firmly to prevent movement during welding or heat treatment. ★ If there are interruptions in pipeline installation, the pipe openings should be sealed promptly. ★ The installation of supports and hangers should be carried out simultaneously with the pipeline installation. ★ When installing instruments, drain pipes, and steam exhaust pipe bases on pipelines, mechanical drilling should be used for making openings whenever possible. . ★ When locally correcting the bend of alloy steel pipes, the heating temperature should be kept below the lower critical temperature of the pipe. ★ The expansion indicator shall be installed correctly in accordance with the design specifications, and its indication shall be adjusted to zero before flushing the pipeline. ★ When installing creep measurement points on steam pipes, such points and the monitoring sections must be installed in accordance with the design specifications. For the monitoring sections, pipes with the maximum negative wall thickness tolerance from among those in the same batch should be selected; no openings may be made in these sections, nor can instruments be installed there, nor supports or hangers be fitted. ★ The creepage measurement points should be installed before pipeline flushing; each set of points should be placed on the same cross-section of the pipeline and distributed evenly around the circumference. ★ After the installation of the alloy steel pipes in the entire system, a spectral recheck should be conducted to ensure that the material quality is correct; any remaining materials should also have their material specifications marked accordingly. ★ Holes in the pipes should be made before the pipes are installed. After making the holes, the interior must be cleaned thoroughly, with no drill debris or other contaminants remaining. ★Arc testing currents or welding of temporary supports shall not be applied to the surface of alloy steel pipes. ★ The weld locations of alloy steel pipes should be indicated on the drawings in a timely manner. ★ When installing drain pipes and steam exhaust pipes, the installation of the pipe fittings must comply with the design requirements. ★When the drain pipe is connected to the main drain pipe. It should be tilted slightly in the direction of fluid flow; the design cannot be altered arbitrarily, and drain and discharge pipes for different fluids or under different pressures must not be connected to the same main pipe or container. ★ The layout of the drain pipes and main pipes should be as short as possible, without interfering with the operation of passages and other equipment; necessary compensation measures should be taken for those subject to thermal expansion. ★ The center of the water discharge pipe should be slightly offset from the center of the funnel, and the diameter of the pipe after passing through the funnel should be larger than that of the inlet pipe. 4.2.3 Lifting of pipes ★ Before lifting the pipes into place, the bases of all supports and hangers should be installed and welded firmly. Temporary pipe support beams should be installed in areas where hanging is not feasible. When designing such temporary support beams, consideration must be given to the weight of the pipes to be hung, their length, and the position of their center of gravity. ★ Once the pipes are in place, equipment such as cranes in the turbine room, crawler cranes, and winches can be used to lift the pipe sections and valves to their respective installation locations, and they are secured in place using appropriate steel cables. For vertical pipe sections with a relatively large weight, straps should be used to prevent slipping. ★ When moving important components such as valves, a towing platform must be prepared before they can be moved, and the center of gravity of the towing point needs to be taken into account to prevent the component being pulled from tipping over and hitting other objects. ★ For pipe sections that are to be stored for an extended period of time, they cannot be lifted using chain hoists; instead, they must be secured and lifted with steel wire ropes (the steel wire ropes used for lifting should form a wrap around the pipe). ★ To remove dirt and debris from inside the pipeline system, it should be cleaned (by steam cleaning), and approved technical, safety, and organizational measures must be in place. ★ After the pipeline has passed the steam cleaning process, no other activities that could affect the cleanliness inside the pipeline may be carried out, except for inspections and restoration work in accordance with technical, safety, and organizational measures. ★ After the steam purging is completed, effective protective measures should be taken. 5 Quality Requirements and Inspection Requirements 5.1 Quality Requirements 5.1.1 Pipes, pipe fittings, pipeline accessories, and valves must be accompanied by a certificate of conformity from the manufacturer, and their relevant specifications shall comply with current ** or industry technical standards. 5.1.2 Before use, pipes, pipe fittings, pipeline accessories, and valves shall have their specifications, materials, and technical parameters verified in accordance with the design requirements. A visual inspection shall be carried out prior to use, and the surface is required to be free from defects such as cracks, shrinkage cavities, inclusions, sand adhesion, folds, incomplete welding, and double layers. b. The surface should be smooth; there must be no sharp scratches. c. The depth of the depression shall not exceed 1.5 mm, and the maximum dimension of the depression shall not be greater than 5% of the tube’s circumference nor more than 40 mm. 5.1.3 Before use, alloy steel pipes, fittings, pipe accessories, and valves shall be subjected to spectral re-inspection one by one, and material markings shall be applied. 5.2 Inspection Requirements 5.2.1 The following tasks shall be inspected, accepted, and certified jointly by the construction unit, the project owner, and other relevant parties. a. Steam purging of the piping system. b. Hydrostatic test of the valve. c. Installation of the expansion indicator. d. Hidden works. e. Adjustment of the travel distance of electric valves. 5.3 The construction contractor shall submit the following documents: 5.3.1 Construction drawings (design changes shall be made on the original drawings). 5.3.2 Factory certificates and on-site inspection records for pipes, pipe fittings, and pipeline accessories. 5.3.3 Spring installation height record (no record is required for the set spring). 5.3.4 Single-line three-dimensional diagram of the expansion measurement points, expansion indicators, welds, and pipeline locations at supports and hangers. 6 Safe Production and Civilized Construction 6.1 Safe Production 6.1.1 Before starting construction, it is necessary to provide the workers with thorough technical and safety instructions, so that they understand the construction plan and methods as well as the safety precautions that need to be followed. 6.1.2 It is prohibited to use any pipes to suspend heavy objects. 6.1.3 When entering the construction site, a safety helmet must be worn. 6.1.4 It is strictly prohibited to enter the construction site wearing slippers, sandals, high heels, or shoes with spikes. 6.1.5 It is strictly prohibited to enter the construction site while under the influence of alcohol. 6.1.6 When working in areas with insufficient light, adequate lighting must be provided. 6.1.7 When working at heights, a safety belt must be worn, and it should be fastened securely to a reliable point above. 6.1.8 Workers must wear comfortable clothing with sleeves and trouser legs tied up, and soft-soled shoes. 6.1.9 When bending small tubes, the tubes must not be fixed in unstable positions. 6.1.10 When using a groove cutter to prepare grooves in tubes, the machine must be securely fixed and its center aligned properly; the cutting speed should be slow. 6.1.11 When creating grooves manually, protective glasses must be worn, and no one should stand opposite the person doing the work. 6.1.12 After the tubes are lifted into place, support brackets should be installed immediately. If temporary fixation is achieved using a chain hoist, the handle of the hoist should be attached to the lifting chain, along with a safety rope. 6.1.13 Pipe supports and hangers shall be welded firmly in one go; the hooks must not be released until the supports and hangers are properly welded. 6.2 Civilized Construction 6.2.1 Foster the mindset that \"safe production is everyone’s responsibility,\" study relevant regulations carefully, abide by them conscientiously, and avoid working in violation of rules. 6.2.2 Do not operate tools, machinery, and electromechanical equipment that are unfamiliar to you or not used in your field of specialization. 6.2.3 At the end of work, carefully tidy up tools and equipment and clean the site, ensuring that all work is completed, materials are cleared away, and the area is clean. 7 Responsibilities of Workers 7.1 Responsibilities of the Team Leader 7.1.1 The team leader is the primary person responsible for ensuring safe construction within the team, and is accountable for the safety and health of the team members during the construction process. 7.1.2 Responsible for organizing and implementing the team’s safety construction management objectives. 7.1.3 Responsible for organizing the personnel in the team to study and implement the superior-level regulations, rules, and measures regarding safe construction; taking the lead in abiding by these rules and regulations, and promptly correcting and addressing any violations of them. 7.1.4 Organize the weekly safety day activities carefully, promptly summarize and arrange the safety work for the team, and keep proper records of these safety activities. 7.1.5 Conduct daily shift meetings and post-shift safety reviews thoroughly. 7.1.6 Regularly check (at least once a day) the safety conditions at the construction site to ensure that the personnel in this team use protective equipment and tools correctly during construction. 7.1.7 Responsible for conducting the third-level safety training for new employees, as well as safety training for employees changing their job roles. 7.1.8 Be responsible for organizing the construction workers in the team to receive safety instructions prior to the start of a project and have them sign accordingly; employees who have not signed shall not be assigned to carry out construction tasks. 7.1.9 Be responsible for checking and ensuring the safety conditions for construction before the start of projects under the team, and safety supervisors must be assigned to sites where hazardous operations are carried out. 7.1.10 Urge the team members to carry out construction in a civilized manner, and clean up the work site promptly upon completion. 7.1.11 Implement management measures that link safe construction to economic incentives, ensuring clear rewards and penalties. 7.1.12 Organize the team members to analyze the causes of accidents, draw lessons from them, and promptly improve the team’s safety practices. 7.2 Workers’ responsibilities for safe construction 7.2.1 Carefully study* and conscientiously follow the relevant regulations, rules, and measures regarding safe construction, and avoid working in violation of these rules. 7.2.2 Use, maintain, and store tools, machinery, and personal protective equipment and supplies properly, and inspect them before use. 7.2.3 Do not operate machinery, equipment, and tools that are unfamiliar to you or not used in your field of specialization. 7.2.4 Before the start of a construction project, carefully receive the instructions on safety measures for construction and sign the instruction document. 7.2.5 Inspect the work area before starting work and take safety measures to ensure that you do not harm yourself, others, or get harmed by others; tidy up the site promptly before leaving work. 7.2.6 Any potential safety hazards identified during construction should be properly addressed or reported to higher authorities; safety measures must be respected, and no unauthorized modifications shall be made. 7.2.7 Actively participate in safety activities, propose reasonable suggestions to improve safety practices, and assist new employees in enhancing their safety awareness and operational skills. 7.2.8 For construction projects that lack safety measures and for which no safety instructions have been provided, it is permissible to refuse to carry out the work and to appeal to higher authorities; one has the right to stop others from acting in violation of regulations, to refuse to follow unlawful instructions, and to raise objections, make reports, and file complaints regarding any actions that pose a threat to life safety and physical health. 7.2.9 Respect and support the work of safety inspectors, and comply with their supervision and guidance. 7.2.10 In the event of an injury accident, the injured persons must be rescued immediately, the accident scene must be preserved, and reports must be submitted promptly. When investigating the accident, the facts must be reported accurately, and improvements and preventive measures should be proposed actively during the analysis of the accident.