4.1 Design Unit Selection: The selection of a design unit for the LPG storage tank system engineering design shall be responsible by the project organization department of the provincial (municipal, district) companies. It should be chosen from the shortlisted design institutes, and the designated supervisor must sign and approve. The design unit should be qualified with petrochemical engineering design资质 and industrial pipeline (GC2) design资质. 4.2 Site Survey: 4.2.1 The site survey should be conducted by the project organization department of the provincial (municipal, district) companies, organizing the construction, pipeline, safety, and design departments from the branch company where the gas station is located to carry out the site survey. 4.2.2 For the gas station survey, the layout and burial depth of the existing underground pipelines and cable laying should be understood. For stations that cannot provide site pipeline data, pipeline detection technology should be used to determine the existing processes, electrical, and water supply and drainage pipelines. 4.2.3 The construction department of the branch company where the gas station is located should propose suggestions for the scope and methods of renovation (including oil unloading vapor recovery systems, fuel vapor recovery systems [dispersed, centralized], and oil-gas emission treatment units], and related equipment and facility renovations, based on the principles of economic applicability and relevant local government requirements. After approval by the designated supervisor and the project organization department of the provincial (municipal, district) company, the design unit shall proceed with the design based on these suggestions. 4.3 Design Proposal: 4.3.1 The design proposal 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 proposal should be submitted to the project organization department of the provincial (municipal, district) company, which will organize the pipeline, safety, and other departments, as well as construction personnel from the branch company where the gas station is located, and the design institute for proposal review, and then submitted for approval by the designated supervisor. 4.4 Construction Drawing Design: 4.4.1 The selection of equipment should be provided by the project organization department of the provincial (municipal, district) companies with a list of shortlisted 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, economic practicality, and compliance with emission standards, and should use products that are easy to install, convenient, and have minimal on-site modification. The following points should also be considered: 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 volume of over 3,000 tons and more than 10 gasoline nozzles should use centralized fuel vapor recovery systems; others should use dispersed systems. 4.4.1.3 Different types of fuel vapor recovery technology and equipment should be selected based on the internal space of the fuel dispenser. For example, a secondary recovery dispersed vacuum pump should use a lower power, utilizing the existing power supply of the fuel dispenser, and it should not require additional power cable laying. 4.4.1.4 The oil-gas emission treatment unit should be selected based on the surrounding environment, site size, and business volume of the gas station. The maximum oil-gas treatment capacity of the unit should be 10% to 20% of the maximum fuel volume. 4.4.2 Construction Drawing Design: 4.4.2.1 The design institute will carry out construction drawing design based on the approved design proposal. 4.4.2.2 The LPG storage tank pipeline should be made of seamless steel pipe that complies with the current national standard "Seamless Steel Pipe for Fluid Transmission" GB/T8163, with a design pressure for oil pipeline not less than 0.6 MPa, and a design pressure for oil vapor recovery pipeline not less than 0.13 MPa. Flexible materials such as thermoplastic plastic pipelines should not be used.

The diaphragm liquefied gas tank is mainly composed of an electric motor, base, crankcase, crank and connecting rod mechanism, cylinder components, oil and gas piping, electrical control system, and some accessories. It increases gas pressure through single or multi-stage compression to meet customer requirements for pressure, flow rate, temperature, and other process parameters. The motor drives the crank, connecting rod, and piston to propel hydraulic oil, which in turn drives the diaphragm. The diaphragm vibrates to compress the medium. The membrane press is a special volume liquefied gas storage tank, with its working cylinder divided into two parts by a diaphragm. The top of the diaphragm is called the gas chamber, and the bottom is called the oil chamber. During operation, the piston moves upwards to drive the hydraulic oil, which then drives the diaphragm to expel the compressed medium outside the membrane cavity. The diaphragm liquefied gas tank compresses the gas through diaphragm deformation, ensuring a tight fit between the diaphragm and the cylinder head membrane cavity surface, with a small gap between the diaphragm and the cylinder body membrane cavity surface. Through theoretical analysis and scientific selection of the membrane cavity curve radius, maximum deflection, and deflection index, a larger volume is guaranteed, allowing the diaphragm to work under approximately equal strength.

Liquefied gas storage tanks offer the following advantages and features:

1) The overall structural design is rational, ensuring smooth and reliable operation with minimal vibration and low noise, and is easy to operate and maintain. 2) The cylinder components use a structure without oil distribution plates, reducing assembly difficulty and the number of sealing surfaces; alarms are triggered upon leakage of the compressed medium, enhancing the overall reliability. 3) The new diaphragm cavity curve improves the volumetric efficiency of the liquefied gas storage tank and extends the lifespan of the vulnerable diaphragm and gas valve components. 4) The built-in oil pump station provides a stable pressure, clean quality, and fully cooled lubricant for the liquefied gas storage tank and cylinder operation, addressing the issue of oil leakage in the original external storage tank. 5) A highly automated control system ensures the safe operation of the equipment. 6) The entire unit is mounted on a skid base, facilitating transportation, installation, and management of the equipment.