Miscellaneous

Laying of the gas pipeline: methods and their main characteristics

December 4, 2019

Laying a gas pipeline is quite complicated, from a technical point of view, process, which should be conducted by specially trained people. To date, there are several ways to install gas pipelines. The pipelines themselves are classified according to some important parameters, which are worth considering.

Gas pipelines are laid by ground or underground method, different types of pipes are used

types of gas pipelines

Gas pipelines, usually, divided into types according to two main indicators:

  • location;
  • pressure.

Consider, what indicator of gas pressure these communications can have:

  • low;
  • average;
  • high.

The maximum allowable gas pressure in low pressure gas pipeline communications is up to 5 kPa. Constructions, the maximum pressure at which it reaches 0,3 MPa, refer to medium pressure gas pipelines. High pressure gas pipelines can withstand the maximum pressure of the environment up to 1,2 MPa. High pressure communications are used to supply gas to large industrial plants or gas distribution facilities. Such structures are called trunk.

Medium pressure pipelines supply gas to gas distribution points of residential buildings. Low-pressure communications deliver gas directly to consumers.

All gas mains have their own operating pressure, its highest figure - 1,2 MPa is typical for a high-pressure gas pipeline

And all gas pipelines are classified by their location on:

  • are laid underground (underground);
  • mounted overhead;
  • external;
  • internal.

Installation of each of these types differs in its features and nuances.

Laying of underground gas pipelines

Usually, when carrying out installation of the gas pipeline by an underground way pipes are put in in advance prepared channels (trenches). It is very important to remember, that the depth of the communication wiring must correspond to the figure, which is specified in the project.

Today, trenchless method of laying such structures is increasingly used. Equipment is used for the trenchless method, which performs horizontal directional drilling (GNB). This option is more budget-friendly and reduces the financial cost of gasification 2,5-3 times. Consider other benefits of this method:

  • the GNB method allows to reduce not only the financial costs of the gas pipeline, but also reduces installation time;
  • thanks to GNB it is not necessary to dig trenches, in accordance, there is no need to violate the integrity of the canvas (if the pipe passes through the road), and the well can easily bypass various obstacles, including existing pipelines.

In urban areas with dense buildings use a modern trenchless method of laying pipes

pay attention! exept this, after laying the gas pipeline with the help of GNB it is not necessary to restore greenery. Therefore, we can conclude, that this method is as harmless to the environment.

After, as arranged previous (pilot) well, its diameter is expanded to the required dimensions. The walls of the well must be strengthened. A special solution is used for these purposes, after solidification of which, gas pipes extend through the well.

In some cases, a special case is used for GNB, in which the pipeline is stretched. The case is used to protect the inner tube from mechanical impact, as well as from stray currents in the soil. Protection against mechanical loads is necessary in those cases, when the gas pipe passes under the roadway or railway.

Steel pipes are used as a case for good protective performance, which have high strength. exept this, it is worth noting, that cases of the small sizes are mounted at an exit of a gas pipeline from under the earth, as well as at its entrance to the building.

Laying of overhead gas pipelines

The cost of installing the pipeline overhead, usually, much lower, compared to the underground option. In some cases, savings can be achieved 60%, what, undoubtedly, is a big plus. But the trumpets, conducted in this way must have maximum protection from environmental influences.

Construction of an onshore gas pipeline is a less expensive method, though, that the pipes need extra protection

Overhead gas pipelines must be insulated from temperature changes, precipitation, etc.. D. The type of protection is selected depending on the climatic conditions of a particular region.

exept this, such communications require constant security monitoring, to eliminate the possibility of unauthorized connection to the network. Based on all the above factors, the reliability of such a highway is lower, than in the pipeline, laid in the ground.

However, if the gas pipes run above the ground in your area, which is well guarded, then this option is acceptable. And also worth noting, that such a gasket is popular in those cases, when it is not possible to run pipes underground through a dense network of communications.

Laying of external and internal gas pipelines

Consider two options for the location of gas pipelines in relation to residential or industrial buildings:

External. Such a gasket, usually, is carried out in the yard of a private house or in the case, when the pipe is adjacent to the facade of the building. The location of the gas pipeline communication by the external method should limit the access of third parties to it as much as possible. To do this, the structural elements are located at a considerable height.

The external gas pipeline is located on the street and access to these pipes should be limited

Fixing the pipes to the facade of the building is a very important point. Fixing elements must be reliable, to eliminate the possibility of falling gas pipe.

Importantly! Gas pipe laying should be carried out only by highly qualified specialists. Installation is carried out in accordance with building codes and regulations (SNiP), as well as all necessary technical documents.

Internal. To the internal, include all gas pipelines, conducted directly inside the buildings. There is one important rule, which you need to remember: at installation of gas pipelines any decorating of pipes is excluded, as well as their location inside the walls. It has to do with that, that such communication should be located so, so that it is always freely accessible for preventive inspections or repairs.

Which way to choose: underground or aboveground?

The choice of laying method depends on the specific case, namely: from soil characteristics, climatic conditions, built-up area, etc.. D. Therefore, it is impossible to give an unambiguous answer to this question.

Consider the basic tips for choosing a method of laying gas pipelines:

  • if the soil on the site has a high corrosion coefficient, then it is recommended to conduct the pipeline overhead.
  • if close to the site, on which installation works will take place, there is a high voltage power line, pipes are laid underground.
  • if the wiring of the gas pipeline is envisaged on the territory of neighboring sections, then it must be carried out in an open way (overhead).
  • exept this, if the gas pipeline will be conducted through autopairs, it is desirable to choose the combined option of installation of pipes. The combined option includes: underground laying under autoplots and above-ground on the territory of a site. This is the optimal solution to the problem.

In most cases, use the underground method of laying pipes, to protect the highway from the effects of various negative factors

Depending on that, which of the methods of installation of gas pipeline communication will be carried out, use pipes of different materials. There are two types of gas pipes based on the material of manufacture:

  • steel;
  • polyethylene (PE);

Steel pipes are versatile - they can be used for any gasket (aboveground and underground), but modern polyethylene products are used in the underground installation of gas pipelines. It has to do with that, that polyethylene has low resistance to ultraviolet radiation. Under the influence of ultraviolet rays, polyethylene loses its properties and breaks down. However, it has a number of useful benefits, which are worth paying attention to.

Advantages of polyethylene gas pipelines

Polyethylene pipes for gasification are in great demand in the modern construction market. It has to do with that, that they have a number of advantages, in comparison with other analogues:

  • have resistance to the harmful effects of corrosion and aggressive chemical compounds;
  • polyethylene pipes are easy to handle during installation (birch, fit);
  • the inner walls are phenomenally smooth, therefore, their throughputs are very high;
  • the polymer does not react chemically with any substances;
  • polyethylene products do not conduct electricity, so they are ideal for underground laying, after all, wandering currents in the soil they are not afraid;

Polyethylene pipes are used in gas pipelines quite often, since they are not prone to corrosion

Importantly! polyethylene products are much cheaper than steel counterparts, which is in some cases a determining factor.

  • weight of polyethylene pipes in 7 times lower, than products, made of steel, which simplifies their storage, transportation and laying;
  • such products have good resistance to temperature changes;
  • the service life of polyethylene products is under normal use 50 years.

In which cases the use of polyethylene pipes is not allowed?

However, despite all its advantages, polyethylene products have their limitations. Consider the cases, when the use of polyethylene pipes for gas transportation is unacceptable:

  • polyethylene pipelines are not allowed in those cases, when the conditions of a particular climatic region, the wall temperature of the pipeline may fall below -15 ° C. Such figures can be achieved in the case, if the ambient temperature drops below -45 ° C;
  • it is strictly forbidden to use polyethylene pipes for transportation of the liquefied hydrocarbon gas, as this will destroy their walls and lead to an emergency;
  • in seismically active areas, if the magnitude of the earthquake exceeds 7 points. However, if it is possible to establish ultrasonic control of welds, the use of polyethylene pipes is allowed when 7 and more points;
  • when installing overhead gas pipelines;
  • when laying communications, which transport gas, external and internal appearance;
  • when installing pipelines inside tunnels, channels, etc.. d.
  • it is also worth noting, that the laying of polyethylene pipes is strictly prohibited in the case, if the gas pipeline structure passes over automobiles or railways.

Only high-pressure steel pipes may be used in high-pressure and terrestrial gas networks.

Stages of laying gas communications

Consider the basics 3 stage of laying gas pipeline communication:

  1. Preparatory stage. At this stage, the project is being developed. Installation of the gas pipeline must be carried out strictly according to the project, which is prepared in advance, specialists. It must include the necessary equipment, which will be used to install the gas line. The project must indicate the path of the pipeline, as well as all possible buildings and other objects, located in the immediate vicinity of the pipeline. exept this, in the project must be: soil features on the site, on which the gas pipeline will pass, location and amount of groundwater, climatic conditions of the area, etc.. D.
  2. Construction works. At the second stage all works on installation of gas pipeline communication are carried out. Depending on the case, the range of installation work may vary. There are cases (example, when laying a gas pipe on the overpass), when a lot of construction equipment is used for installation.

Useful Information! Each gas pipeline construction includes a set of welding works, which are aimed at connecting individual steel or polyethylene parts into a single communication. Subsequently, each joint is numbered and marked.

  1. Stage of control. At the last stage, the installed gas pipeline is inspected. Usually, verification includes two stages:
  • strength test;
  • check of sealing indicators of a design.

Tests are performed only after installation of all auxiliary elements: fittings, measuring equipment, etc.. D. The finished gas pipeline structure is subjected to hydraulic tests (pressure check). To do this, use compressed air.

All the above work should be carried out only by highly qualified specialists in the gas industry in accordance with all safety regulations and rules..