75/63, 65/54 HDPE‑EVOH double‑wall composite fuel pipes are typical double‑containment underground piping products specially designed for gas station fuel conveyance. The figures represent outer‑wall outer diameter / inner‑wall outer‑diameter specifications, namely 75 mm outer pipe with 63 mm inner carrier pipe and 65 mm outer containment pipe matched with 54 mm inner fuel‑carrying pipe. Produced by multi‑layer co‑extrusion forming process, each pipe integrates high‑strength HDPE structural layers, adhesive tie‑layers and high‑barrier EVOH functional layers into one unified structure.
The inner pipe serves as the primary carrier for gasoline, diesel and ethanol‑blended fuels, while the outer pipe forms a secondary containment shell. An interstitial cavity exists between inner and outer pipes, which can connect with leak monitoring sensors. If the inner pipe suffers damage, leaked fuel will be confined within the interlayer space instead of seeping into surrounding soil and groundwater, enabling real‑time leakage alarm for underground station piping systems. Built‑in EVOH barrier layer delivers outstanding hydrocarbon permeation resistance, effectively restraining fuel vapor diffusion, lowering VOCs emissions and meeting stringent international environmental requirements for gas station underground infrastructure.
Manufactured from high‑grade HDPE raw materials, these double‑wall composite pipes exhibit favorable chemical tolerance against various petroleum products and underground corrosive media. Different from steel pipelines, they will not generate rust or pitting corrosion during long‑term underground burial. Reliable molecular bonding between each material layer avoids inter‑layer delamination caused by fuel immersion, temperature cycling and ground stress. The pipes are provided in long coiled lengths, minimizing the quantity of on‑site joints and reducing leakage hazards brought by field connections.
Complete supporting electrofusion fittings are available for both 75/63 and 65/54 sizes, including couplers, elbows, tees, reducers and saddle tapping units. Electrofusion welding creates homogeneous molecular‑bonded joints whose mechanical strength is comparable to the pipe body. Barcode‑marked fittings support parameter automatic reading for standardized welding operations, convenient for construction quality control and project file traceability. Anti‑static modification can be offered upon request to dissipate static charges generated by internal fuel flow, complying with explosion‑proof safety standards of hazardous fuel zones.
These two dimension specifications cover mainstream small‑and‑medium‑diameter application scenarios for gas stations, applicable to fuel supply pipelines between oil tanks and dispensers for new‑build gas stations, as well as replacement and renovation of old station underground piping. The coiled‑delivery feature adapts to narrow‑trench construction conditions. Matching with corresponding electrofusion accessories, the 75/63 and 65/54 HDPE‑EVOH double‑wall composite fuel pipes realize dual‑barrier anti‑seepage protection, cut later‑stage maintenance workload and extend service life of underground fuel transmission networks, becoming practical size options for gas station underground fuel piping engineering.