Pipes

Polyethylene pipes for gas supply: features and characteristics

April 8, 2020

Polyethylene pipes for gas pipelines are products, which are made by continuous extrusion. Such pipes are used in the construction of various highways for gas transportation. To date, due to its technical characteristics and relative cheapness of PE products have gained great popularity in various fields (including in gas supply).

Polyethylene pipes are applicable for installation of various communications, including gas networks

The main advantages and disadvantages

Like any other product, PE gas pipe has a number of positive qualities, which is due ??their effectiveness. Consider the main benefits of this product:

  • are resistant to corrosion, unlike many metal pipes;

pay attention! The light weight of such products allows to simplify their transportation as much as possible, storage and installation. Steel pipes due to their weight are difficult to install and transport and, therefore, more and more people prefer PE products.

  • installation of such pipes is simple. exept this, the speed of installation of polyethylene parts is higher, compared to metal pipes;
  • polyethylene is resistant to aggressive chemicals and does not require additional electrochemical protection;
  • do not require installation of waterproofing materials, as they themselves have excellent characteristics;
  • polyethylene parts meet all state quality standards;
  • smooth walls of such products provide high throughput. Unlike metal parts, salt deposits and others do not settle on their walls, which narrow the lumen of the pipe, shares;
  • polyethylene pipes are environmentally friendly and do not emit harmful substances, which may be harmful to human health.
  • the service life of polyethylene pipelines is much higher, than metal analogues. Under normal operation, it can reach 50 years, and in some cases more;
  • the cost of such products is lower, than on metal, which for many construction companies is a fundamental factor.
  • also worth mentioning, that they have low air permeability and gas permeability. This is a very important point, given that fact, which is among the transported by polyethylene pipelines.

Gas PE pipes are produced by extrusion and have high performance characteristics

Now consider the main disadvantages of polyethylene products:

  • installation of polyethylene communications should be carried out only underground (closed) method;
  • such pipes have good temperature resistance, however, at sharp differences of temperatures their use is not recommended. This is especially true of low temperatures;
  • exept this, there are restrictions on the depth of laying such pipelines - no less 1 m;
  • under autoploys or other engineering construction laying of a gas pipeline from polyethylene pipes is made with use of special protective cases. Such cases, usually, are made of steel;
  • installation of HDPE pipes should be carried out by specialists, who have permission to do so and have construction skills in the field.

Scope of polyethylene pipes

Such communications, as polyethylene gas pipelines (including HDPE) used quite often, however, due to the large number of requirements, put forward to them - their scope is not so numerous.

Low resistance of PE to ultraviolet pipes determines the method of laying such products - only underground method

That fact, that such tubes have poor resistance to ultraviolet rays, prevents their laying indoors. And if you still do an open installation, then they will quickly lose their qualities and become unusable. This cannot be allowed, as the working environment in such constructions is flammable explosive gas. Therefore such communications mount, usually, underground, in a closed way.

It is also worth noting, that pipes for low pressure pipelines, relating to 1 and 2 categories, it is strictly forbidden to lay in places, where transitions through any obstacles in cities and other settlements can be laid.

Characteristics of PE pipes for gas pipelines

Polyethylene pipes for the gas pipeline are made of special brands, relating to tubular. Usually, these brands are two main: PE 80 and PE 100. The class of pipes is established by means of pressure tests. Such checks are performed more 1 year, which allows to determine the class of polyethylene products with high accuracy, as well as the maximum operating pressure, in which the product will last at least 50 years.

So, pipe, which is made of polyethylene 100, able to withstand (even with the same wall thickness) pressure readings are higher, than marked parts 80.

Useful Information! Polyethylene pipes, used for gas supply, are carried out only with the use of primary polyethylene. This is due to increased safety requirements for gas pipelines.

Only products are used in gas systems, able to withstand pressure, characteristic of the gas supply line

The diameter of polyethylene pipes for gas pipelines varies from 20 to 630 mm, and for underground highways gas consumption and gas distribution reach 1200 mm. This range allows you to expand the scope of polyethylene pipes.

Another important indicator of polyethylene gas pipes is SDR. This figure determines the ratio of the cross-sectional size of the pipe to the wall thickness. The lower the SDR, team, in accordance, the greater the wall thickness and the greater the pressure the product can withstand.

exept this, there is another very important indicator - MRS. This figure means that the HDPE pipe can withstand the pressure, which is expressed in megapascals. For PE pipes 80 MRS is 8 MPa, for PE 100 — 10 MPa.

exept this, polyethylene products may differ in color. The most common colors for such details:

  • black;
  • blue;
  • orange;
  • yellow.

Each pipe has its own marking, applied to the surface. The marking is repeated every meter of the product and contains the following information in a concise form:

  • material, of which it is made ??pipe;
  • product size;
  • appointment;
  • manufacturer and information about it;
  • party;
  • release date.

An important advantage of polyethylene pipes is their flexibility, therefore, they are used in the installation of underground gas pipelines in unstable soils

Properties of HDPE pipes

HDPE pipe has high flexibility, therefore it can be laid in mobile soils. This useful property allows you to mount it in seismically active areas. The bending radius of the HDPE parts is equal to 25 its diameters, which reduces the number of welded joints. The lower the number of joints, the more reliable is communication and HDPE pipelines in this sense are incredibly profitable.

exept this, HDPE products with cross-sectional indicators up to 180 mm are stored and transported in special coils. This greatly simplifies the process of transportation and installation.

pay attention! The operational capabilities of HDPE pipelines allow them to be used as a replacement for old communications. Such trenchless reconstruction is very popular today. And also for their installation use a modern method of horizontal directional drilling (GNB).

HDPE products have limited resistance to ultraviolet radiation and their installation is allowed only underground. The fire resistance of this material is also quite weak, therefore installation of such communications indoors is forbidden.

How gas pipelines are classified

Which pipeline will be used to transport fuel gas, depends on the working pressure in the communication. The higher the pressure level in the system, the more stringent requirements are set when selecting individual elements for the pipeline. It is also worth noting, that polyethylene pipes may not be used in all systems. There are systems with unacceptable gas pressure.

In gas pipelines 1 category the use of polymer pipes is prohibited, for installation of such highways it is admissible to apply only steel products

Communications, which transport gas to end users, are divided into 4 main categories. Consider them:

  1. The first category includes gas pipelines, which are able to withstand pressure from 6 to 12 atmospheres. For the transfer of liquefied hydrocarbon gases (ЗВГ) normal pressure is 16 atmospheres. Laying of such communications can be carried out as underground, and overhead, as they are made only of steel material. Operation of plastic pipes for gas pipelines, relating to 1 categories, strictly prohibited.

The choice of the type of pipe for the highway with a particular pressure can be made, based on the data of table №1.

Table 1

SDR indicator Pipe type
PE 80 PE 100
Pressure, atmosphere
17,6 3 6
17 3 6
9 10 6
11 6 6
13,6 6 6

  1. Gas pipelines, relating to 2 categories, usually, carry out transportation of the working environment under pressure from 3 to 6 atmospheres. SDR polyethylene pipes are perfect for this purpose 17 and SDR 17,6. Such systems transport gases between city stations, which perform the gas distribution function.
  2. The third category includes gas pipelines, which transport the working medium under pressure 0,005-0,3 MPa. They perform the function of delivering the medium to the distributors.
  3. The fourth category is presented ??pipelines, which distribute gas directly to individual, economic communications. Pressure indicators in such a system, usually, are less 0,005 MPa.

Installation of the gas pipeline from PE pipes is carried out by means of butt welding or fittings

Installation of a polyethylene gas pipeline

The polyethylene gas pipeline is mounted taking into account building norms and rules (SNiP), as well as the necessary safety precautions. All this is necessary, to avoid unforeseen accidents during the use of the pipeline.

Joining of two separate polyethylene details is carried out by means of special connecting elements - fittings. Fittings are connecting elements of various configurations and are mounted by means of butt or electric coupling welding..

Importantly! All parts must be well fixed during welding, to avoid their shift. Reliable fixation is a very important parameter for the tight connection of individual pipes.

Nozzles, which are used for welding, are mounted on pipes, after which heating and joining of details is carried out. After welding, the joint cools down fairly quickly (5-7 seconds). After, as the joint hardens, you need to wait at least 20 minutes and communication can be put into operation.