Aboveground and underground gas pipelines: features of design and installation

Fuel is supplied to the consumer through the arrangement of a gas distribution system - a complex of interconnected facilities and communications.Part of the system includes above-ground and underground gas pipelines through which fuel is supplied to points of use - to residential buildings and businesses.

The choice of pipe laying location depends on a number of criteria, which are analyzed at the design stage. Gas can be supplied to private homes in different ways: by laying pipes in the ground or above the ground. Let's consider both methods and the features of their choice.

General rules for pipeline construction

Gas pipelines are pipe lines, supporting and protective elements, additional equipment. They serve to transport “blue fuel” from the source or gas distribution station to the place of consumption.

Based on the location of installation, gas communications are divided into two large categories:

• above ground – running above the surface of the earth at a certain distance, installed on special supports, placed in casings and cases;
• underground – placed in the ground, in specially dug trenches.

In modern construction, both methods of laying pipes are used.

Gas pipeline installation sites are classified as particularly dangerous areas, therefore special signs or limiters are installed along the entire length of the pipeline.

Designation plates are painted in different colors. They can be white with blue or red trim, just blue, but the “brand” color of any gas equipment is yellow.

What determines the choice of communications?

A special commission is responsible for the project of a new gas pipeline, which determines the route of the pipeline, the method of its construction, and the points for construction of the gas distribution station.

When choosing a laying method, the following criteria are taken into account:

• population of the territory where the gas pipeline is planned to be laid;
• the presence of already extended underground communications on the territory;
• type of soil, type and condition of coatings;
• consumer characteristics - industrial or household;
• the possibilities of various types of resources - natural, technical, material, human resources.

Underground installation is considered preferable, which reduces the risk of accidental damage to pipes and ensures stable temperature conditions. This type is used more often if it is necessary to supply gas to residential areas or separate buildings.

At industrial enterprises, highways are laid overhead - on specially installed supports, along the walls. Open laying is also observed inside buildings.

In rare cases gas pipes It is allowed to camouflage under a concrete floor - in laboratories, public catering places or consumer services. For safety reasons, the gas pipeline is placed in anti-corrosion insulation, filled with cement mortar, and in places where it exits outside it is placed in reliable cases that ensure stability.

Features of the installation of gas pipelines

When the purpose of the gas pipeline is clear, it is easier to choose the method of its construction or installation material. For example, if you need to connect a detached cottage to the highway, they first analyze the topography of the territory, take soil samples, calculate the distance and the shortest route, and look for ways to save resources.

Let us consider in more detail the technical and legal aspects of the construction of these types of gas pipelines - underground and aboveground.

Option #1 - underground gas pipeline

When laying underground communications, it is important to calculate all the nuances in advance: the length of the main line, the depth of the trench, the type of pipe material.

According to the installation rules, the depth of the underground gas pipeline is 0.8 m - it is not the bottom of the trench that is taken into account, but the distance to the top point of the pipe or casing

If the area is deserted, without roads or buildings, the depth allowed is reduced to 0.6 m

On the contrary, the trenches will have to be deepened if the following factors are identified at the site:

• difficult soil and climatic conditions;
• increased dynamic loads;
• The groundwater.

Dynamic loads are typical for cities and industrial zones - these are sharp temperature fluctuations, the presence of highways, trams and railways.

If a road runs through the territory of a summer cottage, the trench for the gas pipeline passing under it is made deeper. In some cases, another type of highway is used - overhead

If underground gas pipelines intersect with other communications, certain distances must be maintained between them:

• 0.1 m or more - to rainwater or drainage sewerage;
• 0.2 m or more vertically – to drains, sewer or heat pipes;
• 0.5 m or more - to a telephone, network or electrical cable.

The last distance can be reduced if both lines - gas and electric - are enclosed in protective cases.

Reliable cases are also used to enhance protection if underground gas lines cross railroad tracks or highways.In this case, the ends of the cases are sealed - packed with pre-tarred flax strands, and then sealed with bitumen.

Not far from the intersection, at a distance of no more than 1 km, shallow wells are dug and shut-off valves are installed in them. Ring gas pipelines require two shut-off devices, while dead-end gas pipelines require one, located on the fuel supply side.

Underground (underwater) laying of pipes is also possible in more difficult conditions, when crossing water barriers - canals, rivers, streams. Select straight areas with a stable, stable bed, calm current, and strong gentle banks that are not washed away by water. Reinforced insulation is used for pipes

To save resources and increase the speed of work, it is allowed to lay 2 or more gas pipelines in one trench. They are located on the same level or in steps so that quick access and repairs are possible. The distance between pipes up to 30 cm in diameter is at least 0.4 m.

In some cases, the slope must be observed, for example, if undrained gas is introduced into the building. When installing pipes in frozen ground, condensate collectors are installed, and then the slope should lead in their direction.

To prevent sagging of the pipeline, causing bending of pipes and deformation of joints, soil subsidence in the trench is prevented. To do this, a dense backfill of hard rock is placed on the bottom, and then a layer of sand.

Installation procedure:

Digging trenches is not the only way to install an underground gas pipeline. There is also a trenchless installation method - horizontal drilling.

It reduces installation costs by 25-30% and has the following advantages:

• significantly reduces time;
• preserves established communications and road surfaces;
• protects the environment, including plantings.

Briefly about the drilling process: they create a pilot well, expand it to the specified parameters, concrete the walls, and stretch polymer pipes for the gas pipeline.

But in any case, underground pipelines are more expensive than above-ground ones and require increased resource costs in case of repairs. In buried mains, it is more difficult to find an emergency area, so increased requirements are placed on the installation and protection of pipes.

The rules regarding the operation of gas pipelines can be found in “Rules of technical operation and occupational safety requirements in the gas industry of the Russian Federation”.

Option #2 – overhead gas pipeline

Aboveground gas pipelines are installed where there are no conditions for underground installation or it is considered impractical. When designing and installing industrial networks, they are based on the requirements SNiP 2.09.03-85 And SNiP II-89-80.

For the installation of pipes, supports, columns, trestles and shelves made of non-combustible materials are used.Installation can also be done on the walls of buildings, but not all. For example, for industrial premises of categories B, D, D, gas pipelines of no more than 0.6 MPa can be installed, and for children's institutions, schools and hospitals, pipelines of any pressure cannot be used.

The metal supports on which the pipes are located must be protected as much as possible from corrosion, mechanical damage and atmospheric influences - moisture and temperature changes

On the walls of residential buildings and public buildings only overhead low pressure gas pipelines – no more than 0.3 MPa. It is also impossible to lay gas pipelines if the walls of buildings of categories A and B are sheathed with metal panels or polymer thermal insulation.

High-pressure gas lines are laid along the walls of industrial buildings of fire hazard categories B, D, D. The pipes are installed above window and door openings; if the building is multi-story, above the windows of the upper floor.

Detachable connections cannot be placed under balconies and windows of residential and public buildings - if you need to connect two pipes, welding is used

Requirements for the height of laying overhead gas pipelines are set out in SNiP II-89-80. The distance from the ground surface to the bottom surface of the pipe or protective case is 0.35 m if the structure is installed on low supports. For groups of pipes more than 1.5 m wide, the height increases to 0.5 m.

If pipes are placed on high supports, the standards are as follows:

• in pedestrian areas - 2.2 m;
• at intersections with highways – 5 m;
• at the intersection with tram tracks - 7.1 m;
• at intersections with trolleybus wires - 7.3 m.

The height when crossing internal railway tracks is adjustable GOST 9238.

For the production of pipes for above-ground use, special grades of steel are used, the wall thickness is at least 2 mm. Polyethylene pipe material is not used for above-ground gas pipelines.

When installing combined communications, hard cases are installed at the exit points of underground highways - except for areas where the possibility of damage is excluded

For pipelines supplying undrained gas, a slope towards condensate collectors of at least 3% is provided.

The distance to overhead power lines, as well as joint laying with electrical cables, is regulated by the PUE.

The choice of distances between fixed supports is subject to the requirements SNiP 2.04.12-86. If the diameter of the pipes is up to 30 cm, then the maximum distance is 100 m. As the diameter increases, the distance also increases - it is calculated using the formula.

Conclusions and useful video on the topic

The modern method is trenchless installation and repair:

How to quickly dig a trench:

More information about the trench method of laying pipes:

In order to establish an uninterrupted supply of gas to the consumer, it is important to choose the correct method of installing the gas pipeline and carry out the work in accordance with regulatory requirements. For a private household, the underground method of laying pipes is preferable, which guarantees maximum protection from accidental damage and interference from others.

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