Pipes

Gas pipe: steel, polyethylene and their features

July 27, 2020

A gas pipe is a product, used in the installation of gas pipelines. Previously, only steel products were used for these purposes, however, with the development of industry, pipes made of modern polymer material — polyethylene — began to be used (PE). Polymer products have high technical characteristics, but still have some operational limitations.

Steel and polymer pipes are used for the installation of gas pipelines

Types of gas pipelines

Today, gas pipeline communications can be divided into 4 types depending on the pressure indicator, which they can tolerate. Consider them:

  • the first type includes products 1 categories, which are able to withstand pressure from 6 to 12 atmospheres;
  • the second type includes details 2 categories, which are able to withstand pressure indicators of the working environment from 3 to 6 atmospheres;
  • medium pressure pipes belong to the third type. Indicators of the pressure of the working environment in such communication can be from 0,5 to 3 atmospheres;
  • the fourth type of pipes is represented by low pressure products. Such a gas pipeline can have a pressure of 0 to 0,05 atmospheres.

pay attention! Material, from which elements of gas pipeline structures are made, is selected not only by pressure indicators, but also in accordance with others, no less important factors, including: capacity, strength, laying method, etc. d.

Gas pipes for a specific area are selected according to the following parameters:

  • built-up density of the settlement;
  • soil characteristics;
  • indicator of stray currents in the soil.

Not all pipes are equally applicable to all gas networks, in many cases it is allowed to use only steel

In any case, the products, along which the gas will be transported, must be very reliable, to exclude the possibility of dangerous emergency situations.

Gas pipes made of polyethylene (PE)

Gas pipes, which are made of this polymer material, have a number of advantages:

  • polyethylene products are distinguished by good resistance to atmospheric precipitation;
  • polyethylene gas pipeline is resistant to the harmful effects of corrosion;
  • polyethylene gas pipes have good resistance to aggressive chemical compounds;
  • the material is plastic, however, such products have good strength characteristics;
  • polyethylene pipes can be laid even in adverse climatic conditions. They can tolerate very low temperatures (to ?60 °C);
  • they have dielectric properties, therefore, it is allowed to lay them in soils with stray currents without fear, that this will affect their performance;
  • the cost of products from this material is lower, than steel counterparts, which is also an important factor.

It is worth noting, that polyethylene products have one major drawback — weak resistance to ultraviolet rays. Therefore, it is not recommended to mount polyethylene products in an open manner. Let's consider other recommendations and restrictions on the installation of communications from this material:

  • minimum temperature, which polyethylene can withstand, as mentioned above, is ?60 °C, but, it is not recommended to use pipes made of this material at a lower temperature ?45 °C;
  • it is forbidden to lay such products in seismically active areas, where seismic activity may be more 6 points;
  • plastic products cannot be mounted within the city limits in that case, if the pressure indicators in the gas pipeline structure refer to 1 and 2 categories.

Polyethylene pipes are intended for use in difficult climatic and seismic conditions

In the listed situations, it is necessary to lay a gas pipeline from steel elements.

Steel gas pipes

Steel pipes for gas pipelines must be additionally treated with anti-corrosion and electrochemical materials. It has to do with that, that steel products themselves have a weak resistance to corrosion, and are also destroyed under the action of stray currents in the soil. Treatment of steel pipes increases their cost, therefore they are quite expensive, but, are very strong and reliable and are widely used in the installation of gas pipelines of any type.

Steel products are divided into types according to several indicators. Consider the classification of steel parts for gas pipelines in the presence of welds:

  • welded;
  • seamless.

It is used for the manufacture of gas pipes:

  • low carbon steel;
  • high quality structural steel, to which various elements are added (example, phosphorus).

Pipes for gas pipelines can be made of steel with various additives

Importantly! According to GOST, the wall thickness of steel products should be approx 3 mm, for those pipes, which will be used when closed (underground) gas pipeline laying. And for open ones (terrestrial) works use details, the wall thickness of which is not less 2 mm. Products should have the same thickness, which are used for laying an indoor gas pipeline.

Let's consider other characteristics, which are considered important for gas pipes:

  • capacity of any gas pipe;
  • index of the section of the part.

The diameter of the steel gas pipe can be from 15 to 100 mm. Steelwork, as well as plastic, are classified into categories depending on pressure indicators, which they are able to withstand:

  • for a closed gasket (in the soil) products are used, which are able to withstand pressure up to 1,2 MPa (12 atmospheres). At the same time, the ambient temperature can reach ?30 °C;
  • pipes are used for closed laying, able to withstand pressure, which is 1,2 MPa at ambient temperature up to ?10 °C;
  • steel parts are used for indoor installation, which are able to withstand up to 0,3 MPa (3 atmosphere). At the same time, the indicators of the external cross-section of such pipes do not exceed 159 mm

Any gas pipe, which has undergone mandatory anti-corrosion treatment, has a characteristic yellow color. Steel and polyethylene products, used for gas pipeline structures must necessarily meet the necessary standards of DSTU, and the selection of these products is carried out individually for each specific case. Installation of any gas pipes should be carried out, following all building codes and regulations, prescribed in the relevant documentation.