Gas transport pipes

Indications on the pipes used to convey the gas from the point of supply to the users

We are pleased to present you with a comprehensive guide on transporting gases through pipelines in three key materials: steel, copper and polyethylene. This guide provides a detailed overview of the different types of piping used to transport gas and provides essential information for the safe and efficient operation of gas distribution systems.

Transportation of gas is a critical part of many industries and of daily life, from the supply of natural gas for homes to the transportation of industrial gas for manufacturing processes. The choice of piping material is crucial to ensure system integrity, safety and durability. In this guide, we will explore the main characteristics and key considerations related to each material:

1. Steel pipes:

• Strength and durability.
• Resistance to high pressures and adverse environmental conditions.
• Wide range of diameters available.
• Common use in the natural gas and diesel industry.

2. Copper pipes:

• High thermal and electrical conductivity.
• Corrosion resistance.
• Suitable for moderate pressure applications.
• Commonly used in residential and small business applications.

3. Polyethylene pipes:

• Flexibility and ease of installation.
• Corrosion and abrasion resistance.
• Suitable for underground applications.
• Commonly used to transport natural gas and LPG.

In the guide, we will also review the installation, maintenance and safety procedures specific to each type of pipe, providing practical advice to ensure safe and efficient operation of the system.

Safety is an absolute priority in the transport of gas, and this guide, created by Itieffe, provides essential information on the precautions to be taken, periodic inspections and the regulations to follow to guarantee a safe working environment and environmental protection.

In conclusion, this guide is an invaluable tool for anyone involved in the operation, maintenance or installation of gas transmission systems. We hope it will help you make informed decisions and implement best practices to ensure the safety and efficiency of your gas piping systems, regardless of the material used. Enjoy the reading.

Gas transport pipes

The regulatory reference for the implementation of the current safety criteria and procedures for the transport and use of gas in the home (thermal capacity of the appliances <35kW) is UNI 7129/2008.

In addition to the minimum sections of the pipes that must guarantee a supply of gas sufficient to cover the maximum demand by limiting the loss of pressure between the meter and any appliance of use, the materials that make up the fixed part of the systems (pipes, joints , fittings, taps).

In particular, the pipes can be of:

• steel
• copper
• polyethylene

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I steel pipes

they can be seamless or with longitudinal welding and must have

characteristics prescribed by UNI EN 10255.

The minimum diameters and thicknesses are indicated in the following table:

Steel pipes - Diameters and thicknesses
External diameter Ø mm	17,2	21,3	26,9	33,7	42,4	48,3	60,3	76,1	88,9
Nominal diameter DN	10	15	20	25	32	40	50	65	80
Thickness mm	2	2,3	2,3	2,9	2,9	2,9	3,2	3,2	3,6

If underground, steel pipes with longitudinal welding must have characteristics equal to those of the pipes used for maximum operating pressure <5 bar (UNI EN 10208-1).

The joints of the steel pipes can be made using parts and fittings with threaded ends compliant with UNI EN 10226-1 and UNI EN 10226-2, or by means of butt welding by fusion.

To seal the threaded joints, sealing materials that meet the product standards and used in accordance with the manufacturer's instructions can be used:

- UNI EN 751-1 for hardening materials (anaerobic sealants);

- UNI EN 751-2 for non-hardening materials (gels, pastes, impregnants, etc.);

- UNI EN 751-3 for non-sintered PTFE tapes.

The use of hemp fibers, even if impregnated with the sealing compound, on pipe threads is prohibited

LPG conveyors or LPG-air mixtures. In any case, the use of white lead, lead and similar materials is prohibited.

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The copper pipes

they must have characteristics prescribed by UNI EN1057. The minimum diameters and thicknesses are indicated in the following table:

Copper pipes - Diameters and thicknesses
External diameter Ø mm	12	14	15	16	18	22	28	35	42	54
Thickness mm	1	1	1	1	1	1,5	1,5	1,5	1,5	2

The joints of the copper pipes can be made using fittings suitable for both soft capillary and hard brazing compliant with UNI EN 1254-1. The alloys for soft brazing must conform to UNI EN 29453 and those for hard brazing must conform to UNI EN 1044 - fittings suitable only for hard brazing conforming to UNI EN 1254-5.

The alloys for hard brazing must conform to UNI EN 1044 - mechanical compression fittings conform to UNI EN 1254-2; - mixed fittings for joining copper pipes with steel pipes and also for connecting taps, hose connectors, etc. compliant with UNI EN1254-4.

Direct junctions (bell mouth, T-junction, etc.) between sections of piping are not allowed without the use of special fittings.

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The polyethylene pipes

to be used only for underground pipes (and in any case they must be protected against solar radiation and provided that the pipe does not enter the building), they must have qualitative and dimensional characteristics not less than those prescribed by UNI EN 1555 -2.

For diameters in current use, the minimum thicknesses are indicated in the following table:

Polyethylene pipes - Diameters and thicknesses
External diameter Ø mm	20	25	32	40	50	63	75	90	110
Thickness mm	3	3	3	3	3	3,6	4,3	5,2	6,3

The joints of the polyethylene pipes can be made by:

- polyethylene fittings compliant with UNI EN 1555-3 with electrofusion welding carried out in compliance with UNI 10521;

- polyethylene fittings in compliance with UNI EN 1555-3 with fusion welding by means of heated elements in compliance with UNI 1052O;

- mechanical fittings compliant with UNI EN 1555-3;

- mechanical fittings with mixed polyethylene - metal joints, compliant with UNI 9736. The mechanical fittings can be installed above ground or in inspection wells.

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General information and precautions

The gas pipes must preferably be laid outside the building, limiting the path inside the premises as much as possible.

It is forbidden to install gas systems with a relative density greater than 0,8 in rooms with floors below the ground level.

The pipes can be placed in sight, concealed or buried, in sheaths.

The crossing of closed cavities, of solid or perforated walls, of slabs (floors and ceilings) is allowed as long as the piping in the crossing has no joints of any kind (welded, threaded or mechanical) and is placed inside a through sheath tube.

In the case of a closed cavity, the sheath must be made of steel with a diameter of at least 10 mm greater than the external diameter of the gas pipe and a minimum thickness of 2 mm with sealing of the end facing inwards only.

In the cases of figures A and B, the sheath must consist of metal pipes or flame retardant plastic pipes with an internal diameter greater than at least 10 mm than the external diameter of the gas pipe.

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Fig. A Crossing of external perimeter walls in solid bricks

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Fig. B Crossing of floors (floors or ceilings)

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