Polyethylene (PE) gas pipes have become the first choice of many urban and industrial gas distribution companies over the past three decades. Their inherent flexibility, remarkable resistance to corrosion, low weight, and the ability to make homogeneous melt-fusion joints have made this piping system a suitable replacement for carbon-steel and cast-iron pipes. Chemically, polyethylene is a thermoplastic polymer with a simple linear chain that, depending on density and molecular-weight distribution, is divided into different grades. A yellow stripe or a fully yellow pipe commonly indicates use in low- to medium-pressure natural gas supply and distribution lines.
Material structure and common grades
Polyethylene used in gas-distribution infrastructure is mainly supplied in two classes, PE80 and PE100. PE80 has lower density and relatively lower strength, but due to better processability it is still widely used in many municipal projects; whereas PE100, with higher density and a more coherent crystalline structure, provides better hydrostatic resistance at higher pressures and varying ambient temperatures. The dual amorphous–crystalline microstructure and the stable presence of antioxidants play a major role in the designed 50-year service life of these pipes.
International and national standards
The key technical documents for PE pipes used for gas are as follows:
- ISO 4437-1 to ISO 4437-5: requirements for raw materials, pipe dimensions, couplings, test methods, and system specifications.
- EN 1555 (European Union): the European equivalent to the ISO standards with details specific to pressures up to 10 bar.
- ASTM F2619 (North America): requirements for pipe and fittings in IPS and CTS with dimension ratio (DR) indices.
- Iran National Standard 11233 and National Iranian Gas Company guidelines: including pressure classification, impact testing, and failure tolerances.
Mechanical and performance characteristics
The prominent mechanical properties of these pipes include: long-term creep resistance, low impact modulus at cold temperatures, tolerance of bending without creating stress-cracking, and suitable abrasion resistance in soil routes containing sharp particles. The smooth internal surface and low hydraulic friction factor reduce pressure loss and allow the selection of a smaller diameter for a given flow rate.
Manufacturing methods and quality control
Continuous extrusion with a standard annular die along with gradual cooling is the most common production method. Dimensional control is performed online using laser measuring rings, and offline tests such as the Rapid Crack Propagation (RCP) test, OIT, and the Notched Constant Tensile Load (NCTL) test are conducted to verify service life.
Joining techniques
The three main technologies for creating leak-tight joints in PE gas networks are:
- Butt fusion: uniform melting of the two pipe ends at 210–225 °C and application of controlled pressure until a uniform bead is formed.
- Electrofusion: using a coupling containing a resistive wire and applying controlled current via RFID for repair projects or confined spaces.
- Mechanical compression coupling: suitable for emergency repair or joining dissimilar materials, with a maximum working pressure of 4 bar.
Dimensional range and pressure classes
Outside diameter (mm) SDR11 series – pressure up to 10 bar SDR17.6 series – pressure up to 6 bar Minimum wall (mm) Approx. weight (kg/m)
32 ✅ ✅ 3.0 0.43
63 ✅ ✅ 5.8 1.67
90 ✅ ✅ 8.2 3.77
160 ✅ ✅ 14.6 11.16
250 ✅ ✅ 22.7 27.19
Note: thickness values comply with the minimum requirements of ISO 4437-2 for PE100 materials at a reference temperature of 20 °C.
Comparison with steel pipe and other options
Performance index PE pipe Carbon-steel pipe Cast-iron pipe
Corrosion resistance Excellent (no coating needed) Requires coating and cathodic protection Moderate
Flexibility High (bend radius 20–30×OD) Low Very low
Joining method Homogeneous thermal fusion Arc welding or flanges Clamps and gaskets
Installation cost Low due to light weight Medium to high High
Long-term leak potential Very low Dependent on flanges and seams Moderate
Fatigue life High Medium Low
Design requirements for gas distribution networks
In low-pressure urban networks, a gas velocity ratio up to 10 m/s and a minimum end pressure of 21 mbar are observed. Diameter selection is based on Qn peak-hour consumption and an allowable pressure drop of 5% on the main branch. Hydraulic software such as Synergi Gas or AFT Arrow primarily uses the Darcy–Weisbach relation for pressure drop, while an equivalent roughness factor of 0.010 mm is considered for PE.
Installation, trenching, and pressure testing requirements
Both open-cut trenching and horizontal directional drilling (HDD) are permitted; however, the bend radius must not be less than 25 times the outside diameter. After installation, an air leak test at 150 kPa is performed followed by a hydrostatic test according to ISO 4437-5.
Maintenance, operation, and repairs
PE pipes in normal operation generally do not require periodic repair; however, system monitoring with pressure and temperature data logging and visual inspection of electrofusion joints at two-year intervals is recommended. For localized repairs, the use of Erbil couplings or two-part resin couplings is permitted in accordance with gas company instructions.
Safety and environmental notes
Polyethylene contains no heavy metals, chlorine, or halogen compounds; therefore, at end of life it can be easily shredded and recycled. However, in a fire it releases black smoke with light hydrocarbons, and safety distances to high-voltage electrical installations must be observed. All joints must be checked with a methane leak detector before final commissioning.
Service life and end-of-life management
Service-life assessment of PE pipes is based on creep-rupture testing at 20 °C and the Minimum Required Strength (MRS) principle. With a design factor C = 1.25 for PE100, a 50-year life at 8 bar is achieved. After decommissioning, mechanical shredding and re-extrusion can be used to manufacture small-diameter pipes or automotive products.
Economic aspects
Savings of 25–40% in installation cost compared to steel pipe, elimination of painting and anti-corrosion coating, and reduced need for periodic maintenance mean that the life-cycle cost of PE pipe is about half that of steel. This difference is more pronounced in rural projects with hard soil or steep routes, as the high transport cost of heavy steel pipes is eliminated.
Brand presence and domestic market
In Iran, more than 15 licensed extrusion units operate under National Iranian Gas Company permits, and the annual production capacity of PE gas pipe has reached 120,000 tons. Well-known trade names such as Sepehr Polymer, Kimia Bonyan, Azargostar, and Pars Pipe hold major shares. Raw materials are mainly supplied by the Bandar Imam and Maroun petrochemical complexes, with a smaller imported portion. Distribution is based on regional dealership networks and B2B online stores.
Tamam Baha: services and offering
Tamam Baha’s specialist store offers a complete portfolio of PE80 and PE100 pipes from 20 to 250 mm, with direct delivery from Tehran and Isfahan warehouses for gas-distribution contractors across Iran. Alongside transparent pricing, the company provides on-site cutting, supplies electrofusion fittings, and offers short butt-fusion training tailored for field crews.
