HDPE double‑wall composite fuel pipeline adopts pipe‑in‑pipe structural design, which is widely applied to underground fuel delivery, suction and vapor transmission systems of gas stations. The inner primary pipe undertakes the transportation of gasoline, diesel and alcohol‑blended fuels, while the outer HDPE secondary containment pipe forms a protective interlayer space. If leakage occurs on the inner pipe, leaked fuel will be confined within the interlayer instead of permeating into surrounding soil and groundwater, which effectively avoids soil and underground water contamination. An EVOH barrier layer is integrated inside the primary pipe through co‑extrusion process, delivering outstanding anti‑permeation performance against hydrocarbon molecules, and significantly cuts down fuel vapor diffusion across pipe wall materials. Modified conductive formula is adopted for inner surface to dissipate static charges generated by high‑speed fuel flow, lowering static spark risks in underground fuel systems.
Traditional steel fuel pipelines face obvious defects in long‑term underground burial scenarios. Metal pipes are vulnerable to electrochemical corrosion from soil moisture, saline‑alkali components and stray current. Corrosion pits gradually expand and eventually trigger underground leakage, which brings hidden dangers to environmental safety. Rigid steel pipe installation requires a large quantity of threaded or welded joints, and each joint becomes a potential leakage risk point. Single‑wall plastic pipes without secondary containment lack backup protection. Once pipe body gets damaged by external impact or ground settlement, leaked fuel will directly infiltrate subsurface environment without early warning.
HDPE double‑wall composite fuel pipeline features excellent chemical compatibility. The HDPE base material resists erosion from various petroleum products, alcohol‑added fuels and soil chemical media, and maintains stable physical performance under long‑term underground burial conditions. The interlayer cavity between inner and outer pipes supports leak monitoring configuration. Pressure or vacuum detection can be implemented inside interlayer space, and abnormal pressure variation will give early warning of inner pipe failure, so that operators can locate hidden troubles before actual fuel spillage happens. Manufactured in continuous coil forms, the pipeline greatly reduces the total number of field joints compared with rigid metal pipes. Fewer joints mean fewer potential failure points for the whole underground network. Electro‑fusion welding is adopted for field connection. Under controlled heating parameters, molecular fusion forms homogeneous, high‑strength sealed joints, avoiding defects caused by manual threading or arc welding.
Flexible property enables the pipeline to accommodate slight ground displacement and foundation settlement, resisting crack fracture from external ground stress. It can adapt to complex trench routes without processing numerous special elbow fittings, shortening excavation workload and site construction cycle. When designing the piping system, working pressure, burial depth, soil condition, fuel type and actual layout of gas station shall be taken into full consideration. Proper pipe diameter selection matches required fuel flow rate of dispensers. Burial backfill materials shall be reasonably selected to prevent sharp gravel from scratching outer pipe wall. After installation, pressure and tightness test shall be carried out for both primary pipe and secondary containment interlayer, verifying the integrity of pipe body and welded joints. Scientific layout, standardized installation and regular interlayer leak inspection can ensure long‑term safe operation of underground fuel transmission network, satisfying environmental protection and safety requirements for gas station fuel storage and distribution system.