Polyethylene Gas Pipe: Colour, Standards, Sizes and Requirements

Polyethylene gas pipe is heavy-density polyethylene pipe used for natural gas distribution networks in city streets, housing estates, villages and customer service connections. It is buried and stays underground for years, so more than any other pipe it has to resist corrosion, cracking and soil stress; polyethylene does not rust and does not rot in wet or saline soil.

In our catalogue this product is P003, "PE gas pipe (yellow or black with a yellow stripe)", supplied in PE80 and PE100 and only in the SDR 11 series. Its published diameters run from 20 to 250 mm, with smaller diameters in coils and larger ones in bars.

In this guide we explain the colour and its reason, the reference standards, the size table, how gas pipe differs from water pipe, the jointing methods, storage, and the documents to prepare when you order for a gas project. Safety decisions and the allowable pressure of each line are always for the gas company and the design consultant, not the seller.

• PE gas pipe (SDR 11)
• PE gas pipes

Polyethylene gas pipe comes in solid yellow, or with a black body and yellow longitudinal stripes. The colour is not just appearance; it is a warning. Years after installation, when a contractor digs along the same route, yellow tells him he is dealing with a gas line, to carry on with care and not to confuse it with a water or sewer pipe. In the published rows of our catalogue the gas pipe colour is recorded as yellow.

PE water pipe is normally black with a blue stripe and sewer pipe black with a brown stripe, so yellow in a trench belongs to gas alone. On the same principle, pipe colour must never be changed for another line, nor uncoloured pipe used on a gas line.

In black pipe, the carbon black in the compound protects it from solar ultraviolet radiation. Yellow pipe does not have this carbon black and is more sensitive to direct sunlight, which is why its storage is explained separately below.

In our catalogue, PE gas pipe is listed to ISO 4437 and EN 1555-2 and to the requirements of the IGS standard of the National Iranian Gas Company. These standards set dimensions, tolerances, colour, raw material and long-term strength tests, and they are the basis on which the gas company approves a pipe.

The raw material of gas pipe must resist slow crack growth and rapid crack propagation. PE100, with its higher long-term strength (MRS of 10 MPa against 8 MPa for PE80), gives a larger safety margin in the same conditions and is preferred in higher-pressure networks; PE80 is also supplied in the gas range, and its choice is for the network designer.

Caspian Sanat ZAAL is a supplier and holds no certificate of its own; each gas project may ask the supplier for raw material documents and for the gas company's approval of the pipe maker. Get these documents from the project supervisor before ordering and put them in your enquiry so the supply matches them.

The table below shows every published diameter of our gas pipe in the SDR 11 series. SDR 11 means the outside diameter is 11 times the wall thickness; for example 110 mm pipe has a 10 mm wall (110 ÷ 11 = 10). The weight per metre helps estimate load and transport cost and is recorded as the same for PE80 and PE100 in our rows.

Diameters from 20 to 50 mm come only in coils (50, 100 and 200 m), diameters from 63 to 110 mm come both in coils and in 6 and 12 m bars, and from 125 mm up only 6 and 12 m bars are supplied. Coils suit continuous branch service lines in side streets, and bars suit straight distribution lines.

• 63 mm PE gas pipe
• 110 mm PE gas pipe
• PE pipe weight calculator

Water pipe comes in SDR 41 to SDR 7.4 and pressure classes PN4 to PN25, while gas pipe in our catalogue is SDR 11 only. A more important difference is allowable pressure: the working pressure allowed on a gas line does not equal the nominal pressure (PN) of the same pipe in water service, because gas calculations take a larger design safety factor. For this reason we give no allowable pressure for gas pipe; the number is set by the gas company and the design consultant and must come from the project documents.

Another difference is colour (yellow against blue), and a third is the jointing method: the compression fittings common on water and irrigation networks are not used on gas lines, which are jointed by electrofusion or butt fusion. Water pipe must not be used in place of gas pipe either, even if the wall thickness is the same.

• Gas pipe versus water pipe
• SDR and PN pressure class of PE pipe

Gas lines are joined by fusion, not compression fittings. In electrofusion, the coupler or tapping tee has an internal heating wire and the electrofusion unit sets voltage and time by reading the fitting's barcode; because the pipes do not move and the data of each weld is recorded, the method is very common on gas networks. Our electrofusion coupler runs from 20 to 250 mm, and the electrofusion tapping tee for 25 to 250 mm main pipe is on the site.

In butt fusion, two pipe ends are faced with a planer, melted on a heater plate and pressed together; butt-fusion elbows, tees, reducers and end caps are fitted this way. To connect to metal pipe or a meter, the PE-to-metal transition fitting is used, for 20 to 63 mm pipe.

Read the welding parameters, that is temperature, time and pressure, from the gas company's instructions and the pipe maker's table; we give no numbers for them in this article, because gas welding must be done only by a qualified welder and according to the supervisor's rules.

• Electrofusion coupler
• Electrofusion tapping tee
• PE-metal transition fitting
• How to connect polyethylene pipe

Keep yellow gas pipe in covered storage or in the shade and do not leave it in site sunshine for days, because ultraviolet radiation harms yellow pipe more than black. Stack the pipe on a flat surface, keep coils horizontal and do not drag it over rocks or rough ground.

In the trench the pipe must lie on a stone-free sand bed, with the gas warning tape and clearances from other utilities as the installation instructions require. Keep the pipe ends capped until jointing so that soil, water and animals stay out, and before service the line is tested and approved by the gas company's supervisor.

In your enquiry put the outside diameter, the grade (PE80 or PE100), the SDR 11 series, the supply form (coil or bar and its length), the total length and the fittings needed (couplers, tapping tees, transitions, elbows). If the gas supervisor has asked for particular documents or approvals, copy them word for word so that supply matches them.

We give technical advice on choosing size and fittings before you buy and issue an official invoice, but the allowable pressure and the method of building a gas line belong to the gas company and the design consultant. Send your list from the contact page and a pro-forma invoice will be prepared.

• Contact and quotation