1. Understanding Pipe Structure: Single-Layer vs. Double-Layer Composite Pipes
The first decision point in selecting an underground piping system is understanding the structural differences between single-layer and double-layer composite pipes. Ai Yuan brand HDPE composite pipes from Luoyang Wohong Petrochemical are available in both configurations to meet varied project requirements.
Single-layer composite pipes (available in 110mm, 90mm, and 63mm specifications) are constructed from HDPE blended with conductive masterbatch. These pipes provide reliable static dissipation and are suitable for standard fuel dispensing applications where secondary containment is provided by other means or where local codes allow single-wall systems.
Double-layer composite pipes (available in 125/110mm and 75/63mm specifications) incorporate an inner HDPE layer, an EVOH (ethylene vinyl alcohol) barrier layer, and an outer HDPE layer, bonded together with imported adhesive. The EVOH barrier provides superior permeation resistance against hydrocarbon vapors, making double-layer pipes the preferred choice for environmental-sensitive installations. The 75/63mm double-layer pipes also have the flexibility of being supplied in coil form (100m, 75m, or 50m per coil) for continuous runs with fewer joints.
2. Evaluating Pipe Diameter and Flow Requirements
Pipe diameter directly affects flow rate and pressure drop across the underground piping network. For a typical fuel station, the selection should be based on expected fuel throughput, number of dispensers, and distance from tank to dispenser.
125/110mm Double-Layer Pipe
This is the largest diameter option in the Ai Yuan product line, designed for main supply lines in high-throughput stations. A 125/110mm pipe can handle multiple dispensers simultaneously without significant pressure loss. It is supplied as 6-meter straight sections, requiring electrofusion couplers for connection.
110mm and 90mm Single-Layer Pipes
These medium-diameter pipes work well as branch lines or for stations with moderate fuel throughput. Both are supplied as 6-meter straight sections. The 110mm size is commonly used for diesel and gasoline supply lines in a typical 4-dispenser station layout.
75/63mm Double-Layer Pipe
The 75/63mm double-layer pipe offers a unique advantage: it is available as coiled pipe (100m, 75m, or 50m per coil) as well as 6-meter straight sections. The coil form significantly reduces the number of electrofusion joints required for long runs, which lowers installation time and potential leak points. This is particularly valuable for retrofit projects where existing trench work limits access.
63mm Single-Layer Pipe
Suitable for individual dispenser connections or low-flow applications. Available in both coil and straight sections for maximum installation flexibility.
65/54mm Double-Layer Pipe
A specialized size for specific configurations, this pipe comes in coil form (100m or 50m per coil). Its smaller diameter makes it ideal for vapor recovery lines or monitoring tube applications where space is constrained.
3. Fittings Compatibility: The Electrofusion Advantage
All Ai Yuan pipe fittings are manufactured from imported PE raw materials and are electrofusion type fittings. This is a critical selection criterion because electrofusion fittings create homogeneous, leak-free joints when properly installed.
When selecting fittings, consider the following:
- Electrofusion couplers — for joining straight pipe sections end-to-end. Available for all pipe diameters.
- Electrofusion elbows — 45-degree and 90-degree configurations for directional changes. Important to minimize the number of fittings to reduce pressure drop.
- Electrofusion tees — for branch connections to individual dispensers.
- Electrofusion reducers — when transitioning between different pipe diameters, such as from a 125/110mm main line to a 75/63mm branch line.
- Electrofusion end caps — for future expansion points or test port terminations.
Because all fittings are electrofusion type, the installation crew must be trained in electrofusion welding procedures. The imported PE material used in Ai Yuan fittings ensures consistent melt flow characteristics with the pipes, creating joints that are as strong as the pipe itself.
4. Installation Environment Considerations
Soil Conditions
The local soil type influences pipe selection. In sandy or well-drained soils, standard backfill procedures apply. In clay or expansive soils, additional bedding material may be required. The double-layer pipe’s EVOH barrier provides extra protection against ground moisture and chemical aggression, making it suitable for challenging soil environments.
Climate and Temperature
HDPE pipes perform well across a wide temperature range, but installation temperature affects handling. In hot climates, pipes have more flexibility and are easier to coil or bend to gentle radii. In cold weather, pipes become stiffer — the coiled 75/63mm and 65/54mm pipes should be warmed gradually before installation to prevent cracking during uncoiling.
Traffic Load
For areas subject to vehicle traffic, pipes must be installed at adequate depth with proper compaction of backfill material. The double-layer construction provides additional ring stiffness compared to single-layer pipes of the same diameter. If the pipe run passes under driveways or tanker access roads, consider increasing cover depth or using concrete encasement for protection.
5. Comparing Coil vs. Straight Pipe for Your Layout
One of the most practical decisions in pipe selection is whether to use coiled or straight pipe sections:
| Factor | Coil Pipe (75/63mm, 65/54mm) | Straight Pipe (All sizes) |
|---|---|---|
| Number of joints | Fewer (long continuous runs) | More (each section requires coupling) |
| Transportation | Compact coil form | Requires long vehicle or multiple trips |
| Installation speed | Faster for long, straight runs | Slower due to joint welding time |
| Available diameters | 75/63mm, 65/54mm, 63mm | All sizes including 125/110mm, 110mm, 90mm |
| Best application | Long trench runs, retrofit, limited access | New construction, complex pipe networks |
6. Vapor Recovery System Compatibility
Stage III vapor recovery systems require pipes with excellent permeation resistance. The Ai Yuan double-layer composite pipes with EVOH barrier layer are specifically designed for this purpose. The EVOH layer acts as a molecular barrier, preventing fuel vapor molecules from migrating through the pipe wall into the surrounding soil.
When selecting pipes for a vapor recovery system, always specify double-layer construction for the vapor return lines. The 65/54mm double-layer pipe in coil form is an excellent choice for vapor recovery lines due to its compact diameter and barrier properties. For the liquid supply lines in the same system, 75/63mm double-layer or 63mm single-layer pipes can be used depending on flow requirements.
7. Cost-Benefit Analysis: Making the Final Decision
The selection process ultimately comes down to balancing initial cost against long-term reliability and maintenance requirements:
- Double-layer pipes have a higher upfront cost but provide superior environmental protection, longer service life, and may satisfy regulatory requirements that would otherwise require additional secondary containment measures.
- Single-layer pipes are more economical for applications where secondary containment is provided separately or where regulations permit single-wall systems for specific fuel types.
- Coil-form pipes reduce installation labor costs through fewer joints, which can offset the material cost premium for double-layer construction.
- Imported PE fittings from Ai Yuan ensure joint quality and consistency — using lower-cost fittings from unknown sources can compromise the entire piping system’s integrity.
For procurement teams and station designers, the recommended approach is to create a piping schematic of the entire station layout, identify all segments by function (supply, return, monitoring), and then match each segment with the appropriate pipe type and diameter from the Ai Yuan product range. This structured selection process ensures both technical adequacy and cost efficiency.
Conclusion
Selecting the right HDPE composite underground pipe for a fuel station project requires careful evaluation of pipe structure, diameter, fitting compatibility, installation conditions, and long-term operational needs. By understanding the full product range offered by Ai Yuan composite pipes from Luoyang Wohong Petrochemical — from 125/110mm double-layer straight pipes to 65/54mm double-layer coil pipes — engineers and procurement professionals can make informed decisions that balance performance, cost, and installation practicality.