4.1 Design Requirements for Liquefied Gas Storage Tank Engineering The selection of a design unit for the liquefied gas storage tank system engineering shall be responsible by the project organization department of the provincial (city, district) companies. It should be chosen from the design institutes shortlisted in the sector, and the supervisor's signature of approval is required. The design unit should be qualified for petrochemical engineering design and industrial pipeline (GC2) design. 4.2 Site Survey 4.2.1 The site survey shall be organized by the project organization department of the provincial (city, district) companies, involving the construction, pipeline, safety, and design department personnel from the local branch of the gas station, as well as the design institute. 4.2.2 During the research and survey of the gas station, the layout and burial depth of the existing underground pipelines and cable laying should be understood. For stations that cannot provide site pipeline documents, pipeline detection technology should be used to determine the existing process, electrical, and water supply and drainage pipelines. 4.2.3 The construction department of the local branch of the gas station, based on the economic and practical principles and relevant local government requirements, should propose suggestions for the scope and method of renovation (including fuel offloading vapor recovery system, fuel vapor recovery system [dispersed, centralized], and oil and gas emission treatment facilities), and related equipment and facility renovations. After approval by the supervisor and the project organization department of the provincial (city, district) company, the design unit shall carry out the design based on these suggestions. 4.3 Design Proposals 4.3.1 The design proposals submitted by the design institute should include technical documents such as general layout, oil vapor recovery process diagrams, and lists of main equipment and materials. 4.3.2 The design proposals shall be submitted to the project organization department of the provincial (city, district) company, which will then organize the pipeline, safety, and other departments, as well as the construction personnel from the local branch and the design institute to review the proposals before reporting to the supervisor for approval. 4.4 Construction Drawings 4.4.1 Equipment selection: The project organization department of the provincial (city, district) companies will provide a list of pre-qualified suppliers for oil vapor recovery equipment. The design institute will select the relevant equipment based on this list. The selection should follow principles of safety, reliability, advanced technology, practicality, and compliance with emission standards, and should use products that are easy to install, convenient, and require minimal site modifications. Note the following: 4.4.1.2 It is preferable to select equipment from the same manufacturer in the same region for ease of after-sales service. 4.4.1.2 Gas stations with an annual gasoline filling volume of more than 3,000 tons and more than 10 fuel dispensers should opt for a centralized fuel vapor recovery system; others should choose a dispersed system. 4.4.1.3 Different types of fuel vapor recovery technologies and equipment should be selected based on the internal space of the fuel dispensers. For example, secondary recovery dispersed vacuum pumps should be powered by a smaller motor, utilizing the existing power supply of the fuel dispenser, and should not require additional power cable laying. 4.4.1.4 The oil and gas emission treatment facilities should be selected based on the surrounding environment, site size, and business volume of the gas station. The maximum oil and gas treatment capacity of the emission treatment facilities should be 10% to 20% of the maximum fuel filling volume. 4.4.2 Construction drawings: 4.4.2.1 The design institute will carry out the construction drawings based on the approved design proposals. 4.4.2.2 The pipelines for liquefied gas storage tanks should be made of seamless steel tubes that comply with the current national standard GB/T8163 for fluid conveying. The design pressure for oil pipelines should not be less than 0.6 MPa, and the design pressure for oil vapor recovery pipelines should not be less than 0.13 MPa. Flexible materials such as thermoplastic plastic pipes should not be used.