5 Common Mistakes When Installing Underground Composite Pipes at Fuel Stations
Installing underground composite pipelines at fuel stations is a task that demands precision. Even experienced crews can overlook details that lead to leaks, pressure drops, or premature pipe failure. At Luoyang Wohong Petrochemical (brand: Ai Yuan), we have supplied HDPE-based composite pipes for hundreds of fuel station projects worldwide. Based on field feedback, here are the five most frequent installation mistakes and how to avoid them.
Mistake #1: Improper Trench Preparation
Many installers rush the trench work. They assume the pipe will simply conform to the ground. This is a serious error. A poorly prepared trench — with rocks, sharp debris, or uneven compaction — creates concentrated stress points on the pipe wall.
Correct approach: Excavate the trench to at least 15 cm wider than the pipe on each side. Remove all stones larger than 2 cm. Lay a 10 cm sand bed and compact it evenly. For our 125/110 double-layer composite pipe and other straight-pipe products (6 m per section), this bed provides uniform support along the entire length. For coiled products such as the 75/63 double-layer composite pipe (supplied in 100 m, 75 m, or 50 m coils), take extra care when uncoiling — let the pipe relax before positioning it in the trench.
Mistake #2: Ignoring Pipe Ovality Before Electrofusion
Electrofusion couplings from Ai Yuan are manufactured from imported PE raw materials and deliver reliable joints when used correctly. However, if the pipe end is oval (out-of-round) when inserted into the coupling, the fusion zone will be uneven. Hot and cold spots develop, and the joint may fail under pressure.
Correct approach: Before every electrofusion joint, check the pipe end for ovality. Use an ovality gauge or a simple caliper. The maximum allowable ovality is 1.5% of the nominal outer diameter. If the pipe end is out of round, use a pipe re-rounding tool or cut back to a round section. All Ai Yuan fittings — for all models including 110 single-layer, 90 single-layer, and 65/54 double-layer pipe — are electrofusion fittings and require a round pipe end for proper fusion.
Mistake #3: Skipping the Scraping Step
HDPE develops a surface oxidation layer within hours of exposure to air and sunlight. This layer — roughly 0.1–0.2 mm thick — prevents proper fusion if not removed. We see many field failures where crews either skip scraping entirely or do it too lightly.
Correct approach: Use a dedicated pipe scraper to remove at least 0.2 mm from the entire circumference of the pipe end. The scraped length should equal the insertion depth marked on the electrofusion fitting plus 5 mm. Clean the scraped surface immediately with isopropyl alcohol and a lint-free cloth. Do not touch the scraped area with bare hands afterward — skin oils contaminate the fusion surface. This applies equally to all Ai Yuan pipe models, from the 63 single-layer pipe (available in coils and straight sections) to the larger 125/110 double-layer system.
Mistake #4: Insufficient Cooling Time After Fusion
After the electrofusion cycle completes, the joint area is hot — typically 180–220 °C at the interface. The PE material needs time to crystallize and cool evenly. Moving the pipe or applying load before the joint has fully cooled can introduce internal stresses and micro-cracks.
Correct approach: Follow the cooling time specified on the electrofusion fitting’s barcode sticker. For Ai Yuan fittings, the standard cooling time at 20 °C ambient temperature is:
- Smaller fittings (up to 63 mm): minimum 10 minutes
- Medium fittings (75–90 mm): minimum 20 minutes
- Large fittings (110 mm and above): minimum 30 minutes
At lower ambient temperatures, subtract roughly 10% per 5 °C drop. At higher temperatures, add 10% per 5 °C rise. Never accelerate cooling with water or compressed air — this causes uneven crystallization and weakens the joint.
Mistake #5: Backfilling With Unsuitable Material
Many contractors backfill the trench with the excavated soil from the same site. This often contains sharp gravel, construction debris, or organic material that can damage the pipe over time — especially the outer conductive layer of double-layer pipes.
Correct approach: Use a classified backfill material. The first 20 cm above the pipe should be fine sand or 3–6 mm crushed stone (free of sharp edges). Compact in layers of 15–20 cm with light compaction equipment. Avoid heavy vibratory rollers over the pipe zone. Our Ai Yuan double-layer composite pipes (models 125/110, 75/63, 65/54) have a conductive outer layer for static dissipation — while this layer is durable, sharp rocks can still score or penetrate it, compromising long-term corrosion protection.
Final Recommendation
Installation quality determines 80% of a fuel station underground piping system’s service life. The pipe itself — manufactured from HDPE, EVOH, conductive masterbatch, and imported adhesive through extrusion compounding — is engineered for decades of service. But that engineering depends on correct installation practices.
For project-specific installation guidance or technical drawings, contact the WoHong Petrochemical International Department. Our technical team can review your site conditions and recommend the right pipe model and fitting specifications for your fuel station project.
Remember: a quality installation starts with preparation, continues with discipline on every joint, and finishes with proper backfill. Get these five fundamentals right, and your underground composite piping system will perform reliably for decades.