Design and construction quality control of the hot

2022-08-11
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Quality control of the design and construction of liquefied petroleum gas stations

liquefied petroleum gas has the characteristics of flammability and explosion. The safety is not only from the fundamental transformation of the plastic granulator process, but also from the aspects of the design and construction quality of liquefied petroleum gas stations. This paper puts forward some views on the following issues for reference

1 in terms of design

1.1 the building design of liquefied petroleum gas stations generally pays attention to the requirements of ventilation, but often ignores the pressure relief requirements of buildings. According to the fire protection design code, buildings should have sufficient pressure relief area and correct pressure relief direction, which can relieve pressure to safety in case of local explosion accidents, so as to avoid greater losses caused by chain reactions

1.2 equipment selection is an important part of the design. According to the characteristics of LPG, the following suggestions are put forward: (1) in the process flow, the compressor and pump should be combined and configured, and only the compressor station should be set. It may be difficult to unload and reverse the horizontal tensile testing machine tank when the saturated vapor pressure of LPG drops in winter; (2) The hot water gasifier is preferred, and the gasification temperature can be controlled in a low range to avoid the polymerization of dienes in LPG into colloids, reduce heat transfer efficiency, block pipelines and pressure regulators; (3) The process system should be equipped with gas-liquid separator, blowdown valve and other drainage devices. The existence of water in LPG will accelerate the corrosion of oxygen and sulfide to pipeline equipment, and hydrate will be generated at low temperature, blocking the pipeline, increasing flow resistance and energy consumption

1.3 the setting of vane pump should consider the problem of cavitation, which brings noise and vibration, affects the normal flow of fluid, reduces the lift, flow and efficiency of the pump, and shortens the service life. The measures that can be taken in design are: (1) make the minimum liquid level in the storage tank more than 0.6m above the center line of the pump; (2) Anti vortex baffle is set at the liquid outlet of the storage tank; (3) The horizontal distance of pump suction pipeline should be less than 3.6m; (4) A vent valve is set at the inlet of the pump for exhaust

1.4 the safety devices should be fully equipped. In addition to the basic configuration of pressure gauge and safety valve, the key inspection is: (1) whether the storage tank system is equipped with check valve, overflow valve and emergency shut-off valve; (2) Whether the pump system is equipped with return safety valve and check valve; (3) Whether the unloading system is equipped with filling check valve and pull off safety valve

1.5 other aspects that should be paid attention to include: (1) the elevation of the pipeline should not be changed at will, so as to avoid the formation of U-shaped pipeline, which will lead to air resistance and silt deposition; (2) The sealing surface of each flange should adopt the form of concave and convex surface, and the oil-resistant asbestos rubber gasket is routinely used. Considering the characteristics of low viscosity of liquefied petroleum gas to consumers and easy leakage, it is recommended to choose the PTFE gasket that is not easy to crush and has good sealing performance; (3) The drainage system with water sealed well, valve and oil separator is set to separate the drainage system of the gas station from the civil sewage discharge pipe

2 in terms of construction

2.1 it is the most common accident that the underground storage tank floats up and destroys the pipeline. The main reason is the improper anti-seepage and drainage measures of the pit. In addition to the construction of the anti-seepage wall of the pit and the setting of pumping holes, the following measures can be taken: (1) fill dry sand around the storage tank to reduce the buoyancy of water; (2) Improve the grouting quality of anchor bolt holes, completely remove the silt and water in the reserved holes before grouting, and use high-grade cement for grouting; (3) Install steel belt on the side wall of the pit to fix the storage tank without warping

2.2 construction quality control mainly focuses on materials, welding and inspection. The main contents include: (1) each valve, pressure gauge and safety valve should be inspected and qualified one by one; (2) The chemical composition of the material shall be rechecked to ensure its good weldability. Boiling steel materials and castings are not allowed; (3) The butt weld shall be welded by argon arc welding, and the fillet weld shall be fully welded. It is recommended to use tee pipe fittings to turn the fillet weld into a butt weld; (4) Radiographic inspection should spot check welded junctions with poor weld formation and large amount of misalignment. The important thing is to ensure that the spot check results are true and reliable and to prevent fraud

2.3 cathodic protection is the main Anti-corrosion Measure for underground storage tanks, which is highly technical. During the construction process, the following aspects should be monitored to prevent the cathodic protection system from failure: (1) whether the magnesium anode is firmly welded to the conductor, and whether the insulation assurance layer is sealed; (2) Whether the anode surface is activated and coated with chemical filler; (3) Whether the relative potential of the storage tank is lower than -0.85v relative to the saturated copper sulfate reference electrode

in the construction process, it is often found that the requirements of cathodic protection are contradictory to the requirements of anti-static and lightning protection. Cathodic assurance requires that the storage tank and the pipeline be separated by insulating flanges to prevent the loss of protective current on the storage tank. For anti-static and lightning protection, the resistance between conductors should be as small as possible in order to dissipate static charges and prevent inductive lightning strikes. Our practice is to give priority to ensuring the safety of anti-static and lightning protection. It is required to cancel the insulating flange, and at the same time, regularly detect the protective potential of the storage tank to ensure the effectiveness of cathodic protection

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