Pipes for gas: a comparative overview of all types of gas pipes + how to choose the best option
One of the most important issues in the autonomous gasification of the house is compliance with the norms and requirements of fire safety. Even at the design stage, you need to clearly know which gas pipes are applicable for outdoor and indoor installation.
The successful combination of their various types will ensure maximum reliability of the pipeline.
The main classification of gas pipelines
The category of the pipeline, depending on the magnitude of the gas pressure, is one of the most important criteria that have a significant impact on the choice of pipe material.
There are 5 main categories of the gas network:
- IA is a design with the highest pressure exceeding 1.2 MPa. The diameter of the pipe is 1000-1200 mm, the purpose is to connect thermal power plants, turbines and steam installations.
- I - system with high pressure, which is in the range of 0.6-1.2 MPa. Its purpose is the transportation of gas and the arrangement of gas distribution points.
- II - the pressure is lower than in the previous category, but still considered high. It ranges from 300-600 kPa. The diameter of the pipe is 500-1000 mm, the purpose of the gas pipeline is the delivery of gas from gas distributors to industrial facilities, houses for residential and social purposes.
- III - medium pressure design with indicators of 5-300 kPa. Use of pipes with a diameter of 300-500 mm is allowed. Its purpose is to transport gas from the main line to gas distribution points located in residential buildings.
- IV - system with minimum pressure (less than 5 kPa). The diameter of the pipe does not exceed 300 mm, the purpose is to deliver gas from the introductory gas pipeline to residential buildings and directly to final gas consumption devices.
In addition to the category of the pipeline and the magnitude of pressure, an important influence on the choice of pipes has the characteristics of their laying and operating conditions - external or internal installation, ground or underground. If they are laid in the ground, you will have to reckon with such factors as the depth of freezing, the density and thickness of the soil layer, the likelihood of corrosion processes, the presence of stray currents.
To ensure stable and durable gas pipeline operation, it is necessary even at the preparatory and design stage to take into account the specifics of installation and operation, to perform all the analyzes that prescribe gasification norms.
Types of materials for gas pipes
The main requirements for the gas transportation system are their fire safety, which is achieved by complete sealing of the butt joints. Previously, only steel products were used for network construction, the life of which depended on the thickness of the material and the pressure in the system.
Today, along with steel pipes, industrial products made of copper and polyethylene are very actively used in the creation and arrangement of gas pipelines. A direct influence on the choice of material has a scope.
So, steel pipes are suitable for aboveground and underground gas pipelines. They are successfully used both for house wiring and for creating high pressure lines.Polyethylene pipes are suitable only for underground installation, and copper - for the installation of gas systems inside apartments and houses.
In order to figure out which pipes can be used for gas transportation, one has to become familiar not only with the norms of gas pipeline construction, but also understand the strengths and weaknesses of each of their materials.
Characteristics and use of steel pipes
At present, steel pipelines are the most common. This is due to the high reliability of the material and a wide range of applications.
General description of steel products
The requirements of the construction standards of gasification meet welded pipes with a spiral or straight seam or seamless products of hot or cold rolling. They are everywhere and are used in the construction of gas ducts.
For the manufacture of steel pipes used for gasification, low carbon steel is used (up to 0.25%). Sulfur (content not more than 0.056%) and phosphorus (content not more than 0.046%) are removed from it. This is necessary to give the material the desired properties.
The main parameters of the pipes are the steel wall thickness and diameter, which are determined by calculation and depend on the volume of gas being pumped and the pressure in the system. In addition to the calculated values, steel pipe rolling must comply with GOST, the main requirements of which are in the following parameters:
- the diameter of the internal gas pipeline should be 25 mm and more;
- pipe diameter for gas distribution systems - 50 mm;
- for the construction of the above-ground gas duct, it is allowed to use the product, in the manufacture of which steel 2 mm thick and above is used;
- the thickness of the steel underground gazovoda should be not less than 3 mm.
In addition to the method of laying a gas pipeline, the seismic and climatic features of the territory where construction is carried out can affect the diameter and wall thickness of steel products.
Steel Pipe Marking
Any specialist is obliged to understand the marking of pipes, since there is important information behind a set of simple letters and numbers. So, the abbreviation VGP means that before you is a gas and water pipe, the production of which should be regulated by GOST 3262-75.
The main parameter of the gas pipe is the nominal diameter, marked as a remote control. In manufactured products with remote control 6-150 mm, the standard wall thickness is in the range of 1.8-4 mm. Reinforced pipes are manufactured industrially. Steel is used for their manufacture, the thickness of which can exceed 5.5 mm.
Marking is present directly on the pipe, whose thickness is more than 3.5 mm, and the DU exceeds 159 mm. Otherwise, a package of products is marked, on which a label is posted containing information on the length and diameter, and the grade of steel used. Be sure that the label should contain the mark of the manufacturer's QCD. The letters in the marking of steel pipes correspond to the following parameters:
- P - steel of high accuracy;
- H - the presence of knurled thread;
- Р - presence of the cut thread;
- D - elongated thread;
- M - clutch equipment.
The standard length of steel pipes VGP is 4-12 m. They are called dimensional. With a length of more than 12 m they are called unmeasured.
Features of steel pipelines
Thin-walled lightweight steel pipes are used exclusively in low pressure gas ducts. The low weight of the material facilitates the work with pipes and allows you to easily lay the network, which is characterized by complex structural features. Lightweight products can be bent at a slight angle without resorting to a pipe bender.
Pipes made of steel with thin walls are characterized by high thermal conductivity, which often leads to the formation of condensate. It is possible to avoid premature aging as a result of corrosion if, after the installation of the pipeline, their surface is treated with oil paint. The more of its layers will be applied, the more effective the protection of steel will be. Such products can be easily connected by soldering, and also threaded connections are allowed using fittings.
If necessary, the device gas outlet, which can withstand the highest pressure, it is customary to use more massive thick-walled reinforced pipes. The highest strength of the pipeline is achieved with high-quality connection of seamless pipes made of steel, by welding, at the final stage, control of connections is mandatory.
Advantages and disadvantages of structures
Due to their physical qualities, steel products are characterized by high strength, and high-quality welding works ensure the reliability and tightness of the seam. They can be considered universal due to the possibility of performing surface and underground installation. And also they are suitable for both indoor and outdoor use.
Along with the positive moments, there are also a number of shortcomings that cannot be ignored when choosing pipes and carrying out measures to optimize the service life of steel gas producers:
- the complexity of the installation work;
- low corrosion resistance;
- tendency to the formation of condensate, especially actively manifested in light tubes;
- high mass;
- high cost;
- poor flexibility.
If the building codes, the rules of installation, operation and the provision of high-quality insulation are observed, the uninterrupted operation of the steel gas pipeline will be at least four decades.
Features of polyethylene gas pipes
Along with steel structures in recent years other products are actively used, for the manufacture of which polymeric materials are used.
Installation work on the device of the polyethylene pipeline is performed much faster than in the case of steel pipes, which is explained by the absence of threaded connections and the need to use heavy electric and gas welding equipment.
Methods of joining polymeric structures
Today, the quality of polyethylene pipes makes it possible to build reliable underground gas pipelines with a service life of 80-90 years. Most often, a network of polyethylene materials is arranged for leading the line to private homes. In addition, such products can be used to transport gas in systems whose pressure does not exceed 1.2 MPa.
The tightness of the connection of polyethylene pipes of good quality is ensured by welding, which can be performed in two ways:
- Pipes whose edges are preheated with a special soldering iron, are mounted end-to-end. Similarly, fittings are mounted. Heating must be done before viscosity is reached.
- The edges of the product are turned into a special coupling, inside of which there are heating elements. The applied voltage provides heating elements and fixing the pipes in the fitting. The joint obtained by electrofusion welding withstands pressures up to 16 MPa.
If the issue of individual connection to the gas network is decided, then it is better to prefer a cheaper installation option that assumes butt-welding. With the collective gasification of cottage settlements, dacha societies, villages it is better to resort to more expensive electrofusion welding of polyethylene elements of the gas pipeline. This method provides maximum tightness and reliability of the connection.
Characteristics of polyethylene pipes
Polyethylene pipes are manufactured in diameters from 20 to 400 mm, standard sizes are marked with SDR11 and SDR17,6.Depending on the strength class, there are products marked with PE80 (black with yellow inserts) and PE100 (black with blue inserts).
PE80 polyethylene pipes are suitable for individual gasification and arrangement of the low-pressure pipeline. In turn, PE100 products have higher strength, and their use is allowed to create gas ducts with pressures up to 1.2 MPa. It should be noted that the installation of PE100 pipes will require great efforts, since they will have to be heated to a higher temperature, however, these costs are compensated for by the excellent connection quality.
Advantages and disadvantages of gas polymer pipes
Popular earlier steel pipe-rolling is noticeably replaced by polyethylene analogues. This fact has many reasonable explanations that lie in the useful qualities of PE pipes:
- Good corrosion resistance, ability to withstand exposure to chemically aggressive compounds.
- High strength, resistance to mechanical stress.
- Excellent throughput with no roughness. If you compare the plastic products with steel of the same diameter, then the throughput of the gazovod from PE pipes will be 30% higher.
- Ease of production installation work. Welding PET does not require heavy gas and electric welding equipment, as when installing a steel gas pipeline. In addition, pipes made of polyethylene easily bend, which allows you to bypass the obstacles that arise in the path of the pipeline.
- Low cost of polyethylene products in comparison with similar ones made of copper and steel.
Polyethylene pipes are quite actively used for gas pipelines. This is due to a number of positive qualities. However, there are some features of their use, which limit or even completely exclude the possibility of erecting a gas network from polyethylene structures.
Thus, it is impossible to use PET in seismic active zones, in areas where the temperature drops to -45 degrees, in gas pipelines with a pressure of more than 1.2 MPa.
In addition, polyethylene pipes are completely incompatible with network installation in tunnels and collectors, while steel pipes allow this option.It is necessary to take into account that when polyethylene is heated to 80 degrees, its deformation occurs and is followed by destruction.
The use of PET for the creation of ground-based gas ducts is not recommended, since the material quickly collapses under the influence of ultraviolet radiation. If, however, a decision has been made about the installation of a land pipeline, the pipes should be coated with a special protective polymer composition.
Nuances of the construction of a copper gas pipeline
Copper pipes have recently begun to be used for the installation of a gas network. It is allowed to use drawn and cold-rolled copper pipes with a wall thickness of not less than 1 mm for the implementation of internal wiring.
Copper is a rather expensive material, however, its use is justified by the ease of installation work and the ability to create lines of complex configuration.
Another indisputable fact in favor of copper pipes is their attractive appearance. Since the gas pipeline cannot be hidden in the niches of the walls and ducts, steel structures can easily spoil the appearance of the room, while copper pipes will only enrich the interior.
Copper products have the following positive qualities that may be decisive when choosing them for a gas duct device:
- high plasticity, thanks to which the possibility of laying lines of complex configuration is realized;
- simplicity and ease of installation, the product is easily cut, the connection of pipes is carried out by using press fittings or soldering;
- attractive appearance;
- durability - the term of operation when technology is observed reaches 100 years;
- resistance to mechanical damage and resistance to chemically active compounds.
Copper pipes also have their weaknesses, the main one of which is high thermal conductivity, which contributes to the formation of condensate. As well as their strength is much lower than steel, and the price is much higher.
Conclusions and useful video on the topic
The video demonstrates the process of making steel seamless pipes:
Electrofusion welding of polyethylene pipes in video:
At present, copper and polymer pipes, although in some cases they are able to compete with steel pipes, they cannot completely replace them.Polyethylene structures are ideal for underground gas pipelines, copper - facilitates the installation of internal wiring, and steel - universal and can be used to create any type of gas network.