1 development direction of natural gas
Natural gas has the characteristics of low carbon, environmental protection, extensive resources, high calorific value and low price. With the support of national policies, it is favored by construction units. From project establishment, approval, site selection, preparation to civil engineering, equipment orders, installation and operation, the construction of gas filling station project is in the ascendant and will become the development trend of energy in the future. Since 20 10, our project department has been fortunate to participate in the construction of these projects. Six natural gas village entrance projects have been completed, and the pipeline project is more than 50 kilometers. There are five gas stations under construction: Yangyu Road Gas Station, Niangziguan Gas Station of National Highway 307, Pingding South Outer Ring Station, Pingding Suburb Gas Station and Xiyang Xinyuan Gas Station.
2. The nature and characteristics of the project and the present situation of the project supervisors.
Natural gas (80% methane) belongs to flammable and explosive compressed gas and liquefied gas, which is mainly stored in LNG storage tank of pressure vessel, and the inner cylinder temperature is-196℃; CNG is a kind of compressed gas, which is compressed into the gas storage well by a compressor at a pressure of 25MPa. After the filling station is completed and put into operation, its station area is a relatively dangerous park, and the level requirements of fire prevention, lightning protection and anti-static in the whole station area are quite high. The production, management, storage, transportation and use of natural gas must comply with the Regulations on the Safety Management of Hazardous Chemicals, so the construction of natural gas filling station project puts forward higher requirements for all parties involved in the construction. We have only been involved in similar projects for two years. Because of its particularity, the project site selection is independent, and most of them are far away from urban areas and towns. It can be said that the village is in front and the store is not behind. Transportation is often inaccessible, living and working conditions are simple, there is no office rest place, and dining is extremely inconvenient. The working environment of supervision institutions is extremely difficult, which requires our supervisors to be prepared for hardship, overcome the cold and heat, get tired, have a high sense of responsibility and professionalism, and have a sense of safety and risk. At present, there are insufficient engineering supervisors in our center who are related or close to related majors. We recruit talents for the society through supervision training.
3 Quality control measures of gas station engineering supervision
1) Qualification examination of construction and installation units (unit qualification and personnel qualification). Due to the strong professionalism of equipment engineering, the installation of professional equipment (complete sets of equipment are assembled by the manufacturer and transported to the installation site) has higher requirements for the installation enterprise's own construction technical standards, quality assurance system, quality control and inspection system, so qualification examination is an important link, and its enterprise qualification business scope should meet the engineering requirements. Its welder must hold a valid qualified welder certificate, and the certified welder must work within the approved scope of its qualified project.
2) Acceptance of materials and components. A. Tubing: There are three kinds of tubing: the medium temperature is-196℃ ~-20℃, and the selection standard of tubing is GB/T 14976—2002 Stainless Steel Seamless Pipe for Fluid Transportation, and the material is 0cr18ni9; Carbon steel pipes in GB/T8 163—2008 Seamless Steel Pipe for Fluid Transmission are selected for pipes with medium temperature of -20℃ ~ 60℃, made of 20 # steel fire hose and galvanized pipe, and vacuum pipes are used for pipes with special requirements. Pipeline entry must have product certificate, material standard code, production batch number, inspection seal mark, production unit name and material related data, and the appearance inspection is free of defects. B. valves: low-temperature valves and normal-temperature valves. In principle, low-temperature valves are connected by welding, and normal-temperature valves are connected by flanges. Valves should be ordered and installed according to the technical requirements of valve ordering. Before installation of normal temperature valves, temperature test and leak test shall be carried out one by one according to the requirements of SH3064 Selection, Inspection and Acceptance of Steel General Valves in Petrochemical Industry. Safety valves and pressure gauges need to be verified by relevant technical and quality supervision departments. C pipe fittings: the pipe fittings manufacturer must have a pressure pipe manufacturing license, and the pipe production standard is GB 12459—2005 "steel butt welded seamless steel pipe system Ⅱ". D flange fasteners: flanges, bolts, nuts, gaskets and anchor bolts matched with LNG cryogenic equipment shall be provided by the equipment manufacturer. E. vacuum pipeline: according to the design requirements and the manufacturer's production standards. 3) Installation quality control. A. pipeline anticorrosion. Quality control: derusting, anticorrosion and leak detection. Quality control content: the buried carbon steel process pipeline adopts extruded polyethylene three-layer structure to strengthen anti-corrosion. After derusting, the overhead carbon steel pipeline is coated with two anti-corrosion primers matched with epoxy paint, and then two epoxy topcoats; Stainless steel pipes and vacuum steel pipes do not need corrosion protection. B. welding. Key points of quality control: welder qualification, welding environment, weld appearance quality and first pass rate of weld detection. Quality control content: Welders must obtain the certificate of special equipment operators. Welding equipment meets the requirements of welding process, and check whether all measuring instruments on welding equipment are within the validity period of verification. Check whether the pipes and welding materials meet the requirements of welding process and whether the welding materials meet the requirements of product specifications when stored. Nondestructive testing. Key points of quality control: qualification examination of weld inspection unit. Quality control content: weld appearance, X-ray inspection and ultrasonic inspection. Purge and pressure test. Key points of quality control: instrument verification, qualified installation and test, pressure grade, stabilizing time and pressure drop. Quality control content: According to the purging pressure test plan approved by the owner and the supervisor, the pressure gauge used for pressure test must be verified by the metrological verification department, and the accuracy of the pressure gauge must meet the specification requirements within the validity period of verification. E. cold preservation and precooling of the pipeline. Key points of quality control: the appearance quality should strictly meet the design requirements and the relevant provisions in GB 50 126-2008 Industrial Equipment and Pipeline Construction. F. Installation of electrical instruments. The storage tank area, gas filling area, loading and unloading area and discharge pipeline in the station belong to the explosion danger area: the environmentally dangerous process production device area. Except for the independent lightning rod in the equipment area, grounding devices are used for lightning protection, anti-static and grounding protection of the whole station, and TN-S system is used for wiring system. The field test of grounding resistance shall not be greater than 1ω. The first is the panel, cabinet and secondary circuit. Key points of quality control: bus lap and secondary circuit wiring. Quality control content: GB50 17 1 Code for Construction and Acceptance of Wiring of Disks, Cabinets and Secondary Circuits of Electrical Equipment Installation Project shall be implemented. Bus lap must be tinned and evenly coated with power compound grease, and the secondary circuit wiring should be fastened without looseness. Second, cables and grounding devices. Key points of quality control: buried depth of top surface of grounding body and grounding of electrical equipment. Quality control content: GB50 169 Code for Construction and Acceptance of Grounding Devices in Electrical Equipment Engineering shall be implemented. The buried depth of the top surface of grounding body is 0.6m, and the welding parts must be treated with anti-corrosion; The grounding of electrical equipment must be connected separately from the grounding trunk line, and series connection is not allowed. Third, explosion-proof electrical installation. Key points of quality control: junction box, junction box and cable pass through different dangerous areas to protect the connection of steel pipes. Content of quality control: GB50257 Code for Installation of Electrical Devices, Construction and Acceptance of Electrical Devices in Explosive and Fire Dangerous Environments shall be implemented. There should be no sand holes and mechanical scars on the explosion-proof surfaces of junction boxes and junction boxes. Cable lines should pass through different dangerous areas, and dry sand should be filled in the cable trench at the joint. The nozzles at both ends shall be tightly blocked with glass fiber cloth and filled with sealant mud. Connections in steel pipes and connections between steel pipes, electrical equipment and steel pipe accessories shall be protected by threaded connections, and the threaded joints shall be coated with electric compound grease. Fourth, instrument installation. Key points of quality control: debugging and verification, cable, wire and insulation test, protective grounding of instrument and equipment shell. Quality control content: SH352 1 Technical Specification for Instrument Engineering Construction in Petrochemical Industry shall be implemented. Before installation, it shall be verified as qualified. Before laying cables and wires, continuity and insulation tests should be carried out, and the instrument equipment shell, instrument panel (box) and junction box should be grounded. Alarm system. Key points of quality control: combustible gas detector and alarm device. Quality control contents: First, gas filling stations and gas filling stations should be equipped with combustible gas detection and alarm systems; Secondly, LNG equipment and CNG equipment (tanks, bottles, pumps, compressors) should be installed at the filling station and the filling station, and combustible gas detectors should be installed under the shed; Third, the general alarm setting value of combustible gas detector should not be greater than 25% of the lower explosion limit of combustible gas; Fourthly, LNG storage tanks should be equipped with upper and lower liquid level alarm devices and upper pressure alarm devices; Fifth, the alarm should be set in the control room or duty room; Sixth, the alarm system should be equipped with uninterrupted power supply; 7. The selection and installation of combustible gas detectors and alarms shall comply with the relevant provisions of the current Code for Design of Detection and Alarm of Combustible and Toxic Gases in Petrochemical Industry (GB50493); Eighth, LNG pumps should be equipped with over-temperature, over-pressure and automatic pump stop protection devices. H. emergency cut-off system. Key points of quality control: emergency cut-off system, start switch and operation stop. Quality control content: The filling station should be equipped with an emergency cut-off system, which can quickly cut off the power supply of LNG pump and CNG lifting and contracting machine and close CNG and LNG pipeline valves in case of accident, and should have fault protection function. First, the power supply of LNG pump, CNG compressor and emergency cut-off valve on the pipeline of filling station should be controlled by manual start-up process, and the system should be shut down; Second, the emergency cut-off system should be equipped with a start switch at the following positions: within 5 from the gas unloading point of the gas filling station; The site staff of the gas filling station are easy to get close to the location; In the control room or duty room; Third, the emergency cut-off system should be reset manually.
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