Underground composite fuel pipe installation demands precise fusion control, correct bedding, and careful trench preparation. This guide covers the practical, field-level workflow for laying Ai Yuan dual-layer and single-layer HDPE/EVOH composite pipes at service stations.
Understanding the Ai Yuan Composite Pipe Construction
The Ai Yuan fuel pipe from Luoyang Wohong Petrochemical is not a single-material product. It is a co-extruded multilayer pipe combining high-density polyethylene (HDPE), an ethylene-vinyl alcohol (EVOH) barrier layer, conductive masterbatch, and imported adhesive, all fused in a single extrusion pass. The EVOH layer gives the pipe its low-permeation barrier against hydrocarbons, while the conductive masterbatch provides electrostatic continuity for safe fuel transfer.
All fittings in the range are electrofusion fittings manufactured from imported PE raw material. This means the joints are not solvent-welded or glued; they rely on embedded heating coils that fuse the fitting to the pipe wall under controlled electrical power. Getting the fusion right is far more important than any single brand choice.
Which Product Line Fits Your Site
Selecting the correct pipe configuration is the first decision on site. The choice depends on the fuel type, the flow path, and the physical layout of the dispenser island and tank farm.
- 125/110 dual-layer – 6 m straight lengths; primary suction or pressure lines where larger bore is needed.
- 110 single-layer – 6 m straights; compatible lines where a single-layer barrier suffices.
- 90 single-layer – 6 m straights; smaller-flow branch runs.
- 75/63 dual-layer – available as 100 m, 75 m, or 50 m coils and 6 m straights; flexible runs with fewer joints.
- 63 single-layer – both coils and straights; small-diameter vent or low-flow applications.
- 65/54 dual-layer – coils of 100 m or 50 m; compact routing for tight station layouts.
Recommended Bedding and Trench Preparation
Underground pipe performance depends as much on the soil envelope as on the pipe itself. A poorly bedded trench will transfer vehicle and soil loads directly to the pipe, regardless of how well the joints are fused.
- Excavate the trench wide enough to allow 150 mm of select backfill on each side and at least 150 mm below the pipe.
- Use clean, free-draining granular material — sand or fine gravel — as the bedding layer. Remove sharp stones, rocks, and construction debris that could notch the pipe wall.
- Compact the bedding in layers, not in one pass, to avoid voids that allow subsequent settlement.
- For dual-layer lines, keep the same bedding discipline at every fitting location. Fittings are stiff sections and need firm support to avoid bending stress at the joint.
Electrofusion Jointing Procedure
Correct electrofusion is a sequence of small, disciplined steps. Skipping any one of them risks a cold joint or a burned fitting.
Preparation Before Fusion
- Cut the pipe square and clean. Use a proper pipe scraper to remove the oxidized surface layer — scraping is mandatory, not optional, on polyethylene.
- Remove loose shavings and wipe the fusion surfaces with a clean, lint-free cloth and an approved cleaning agent. Do not touch the prepared surface afterward.
- Align the pipe and fitting so that they are coaxial and free of axial or angular stress before applying power.
Fusion Parameters and Cool-Down
- Apply the fusion cycle using the settings specified for the pipe wall thickness and diameter. Record the machine-reported fusion time and energy for quality control.
- Do not move, load, or backfill the joint during the cool-down period. Cool-down is part of the weld. Interrupting it introduces residual stress and even hairline cracks that are invisible on the surface.
- After cool-down, mark each joint with its fusion data (date, operator, parameter set) as a permanent traceability record.
Dual-Layer versus Single-Layer Selection Logic
The practical difference between the dual-layer (with EVOH barrier) and single-layer lines is permeation resistance. If the site stores or dispenses fuels that require very low vapor emission through the pipe wall, the dual-layer construction is the appropriate choice. For lower-risk or venting duty, a single-layer line can meet the requirement at a lower material cost.
For the field engineer, the handling difference also matters: dual-layer pipe is stiffer and should be handled and bedded more carefully to avoid kinking the softer EVOH layer, especially on coil deliveries. Coils of the 75/63 and 65/54 lines must be laid out flat and allowed to relax before cutting and fusion.
Maintenance and Inspection Checklist
Routine site maintenance of underground composite pipes is limited because the system is buried. The practices that matter happen before backfill and during periodic checks.
- Pre-backfill inspection: verify every joint visually and with the fusion log before the trench is covered.
- Record keeping: keep the fusion records, pipe batch numbers, and fitting batch numbers for each run. This is the documentation that supports later troubleshooting.
- Leak testing: perform a hydrostatic or pneumatic pressure test on the completed run, following the design test pressure, before commissioning.
- Cathodic/scoping check: on dual-layer lines with conductive layer continuity, verify electrical continuity across the run to confirm the conductive masterbatch network is intact.
Common Field Errors to Avoid
- Omitting the scraper: fusing onto the glossy oxidized layer produces a joint that looks bonded but has no strength.
- Loading joints during cool-down: the most common cause of premature joint failure on site.
- Sharp backfill: rubble in the trench creates point loads that eventually notch and crack the pipe wall.
- Coil spring-back: installed while still coiled under spring tension, the pipe tries to straighten and pulls on the fittings over time.
Summary
Reliable underground fuel piping at a service station comes from controlled trench preparation, disciplined electrofusion of the imported-PE fittings, and patient cool-down. The Ai Yuan dual-layer and single-layer composite lines, co-extruded from HDPE, EVOH, conductive masterbatch, and imported adhesive by Luoyang Wohong Petrochemical, provide the base product; the crew’s fusion and bedding discipline determines how long the installation serves. For engineering, procurement, and installation teams specifying underground composite pipe, choosing the right diameter and layer configuration — then following a strict jointing and inspection routine — is what keeps the system performing safely for years.