Types of metal gas pipes and their area of application. Basic performance characteristics of steel and copper products. Advantages and disadvantages of metal highways. The price of metal pipes for gas.
Metal pipes for gas are versatile products for creating an above-ground or underground gas pipeline and an inter-house wiring system. Their characteristics make it possible to operate structures in any conditions. In the article you will find useful information about steel and copper pipes, which will help you with self-arrangement of an internal gas network.
Basic information about gas metal pipes
In the photo, metal pipes for a gas pipeline
A gas pipeline made of metal pipes is built to move flammable gases. Therefore, special requirements are imposed on structural elements that exclude their leakage and ensure the fire safety of the structure. These characteristics are possessed by pipes made of steel and copper, manufactured using a special technology.
The most widespread are gas pipelines made of steel parts. They are made of low-carbon steel (up to 0.25%) without sulfur (the allowable amount is up to 0.056%) and phosphorus (up to 0.046%). Steel grades for the production of billets are given in GOST 280-2005.
The chemical composition of the metal affects the following characteristics:
- The pressure in the line is distinguished between high, medium and low.
- The product is laid overhead, underground or indoors.
- The purpose of the structure is main or distribution. The latter option is used to deliver gas from the main route to consumption points.
According to the requirements of building codes, gas pipelines from metal pipes are assembled from the following types of parts:
- Seamless… Products are made by the method of metal cylinders piercing. After the procedure, a hollow cylinder is obtained, which is passed through a rolling line. The complexity of manufacturing is quite high, so the blanks are expensive. Seamless pipes can be hot-woven and cold-woven. The first ones have walls up to 75 mm thick, therefore they are used in the construction of a high-pressure gas pipeline and for operation in especially harsh conditions. Cold-deformed parts are produced with a diameter of up to 250 mm with a wall thickness of up to 24 mm. They are designed for more modest pressure.
- Welded… Such pipes are produced by the method of giving a metal sheet a given shape, followed by welding of joints. The process takes place in an automatic mode, which ensures high reliability of connections. They are manufactured with different wall thicknesses, so they have a wide range of applications. Welded pipes can be longitudinal or spiral seam.
- Straight seam… The joint line runs parallel to the product axis. They have acceptable characteristics, but insufficient safety margin. Under high pressure, the pipe may burst along the seam. They are relatively inexpensive due to the simplified welding technology. Such parts make up the majority of all steel pipes. Typically, workpieces are TIG welded using a tungsten electrode in a shielded gas environment. Recently, welding has been carried out using HF technology (welding with high-frequency induction currents), which makes it possible to obtain a high-quality joint while reducing the cost of production.
- Spiral seam pipes… It goes all over the surface. Less durable and used at a pressure of no more than 16 atmospheres.They are used for local system wiring and when creating an in-house gas pipeline. Such products have a lower cost compared to the longitudinal seam option.
- Water-gas pipes… In gas systems, water-gas pipes are often used, from which the water supply is also collected. They are made from metal strip by welding. Such products are used in indoor systems with low pressure.
It is generally accepted that steel pipes are the best option for the line, but there are other options. Copper products in their characteristics are not inferior to steel ones, and in many characteristics they surpass them. Therefore, experts recommend making the wiring in apartments of copper. For this, it is necessary that they comply with the norms of SNiP 42-01-2002 and SP 42-101-2003.
Copper pipes are made by welding or pulling. The first type differs from the second by the presence of a welded seam. Both options are suitable for gas pipelines, but users prefer the latter. Seamless parts have always been considered more reliable because there are no “weak” areas on them.
In stores, you can buy metal pipes for gas with additional insulation made of foamed polyethylene or polyvinyl chloride to protect against external mechanical stress. The coating makes the track less visible in the interior.
Gas pipes are mainly installed underground. On the supports, the line is laid in the presence of unremovable obstacles. In the house, the track is assembled in an open way, which corresponds to the conditions for the safe operation of the system.
Advantages and disadvantages of metal pipes for gas
Photo of a gas pipeline made of steel pipes
Steel pipes today compete with plastic products, but have no alternative when creating gas systems in apartments and houses.
A metal line has a number of advantages over plastic structures:
- The pipes are highly durable and can withstand high pressure.
- The workpieces are connected by welding, which ensures high reliability of the joints.
- They can be used in any climate.
- The products are universal and are used in outdoor and indoor gas pipelines.
- Steel structures have a low coefficient of expansion with temperature changes.
- The metal does not react with chemical elements that are in the composition of the gas.
When designing gas pipelines from metal pipes, it is necessary to remember the disadvantages of such a design:
- The installation of the line is quite complicated, because parts are connected by welding.
- It takes a long time to install the system.
- Metal parts will rust over time, which will shorten the life of the system. Galvanized products and pipes with an anti-corrosion layer are devoid of such disadvantages. Often the problem is solved by applying a polymer or polyurethane foam coating.
- The blanks are expensive, which increases the cost of building the system. For example, the price of a 25 mm metal pipe for gas averages 49, 7 UAH. for 1 m, which is several times more expensive than plastic samples of a similar purpose.
- Large weight leads to higher costs of transportation and installation of products.
- Steel structures require cathodic protection.
- There are restrictions on the method of installation: pipes with threaded connections must not be laid underground, and in the presence of flange joints, special wells must be provided for their control.
- Various layers settle on the inner walls, which leads to clogging of the system.
In the photo, a gas pipeline made of copper pipes
Copper gas pipes have a number of advantages over steel ones:
- The service life is several decades.
- Small diameter products bend well.
- The pipes are highly resistant to corrosion.
- They do not crack, deform and withstand very low and very high temperatures.
- The installation technology involves the use of fittings for joining workpieces, so the work is carried out as soon as possible.
The main drawback of the material is its high cost: such systems cost many times more than steel and plastic. The products can only be used in low pressure systems.
How to choose metal pipes for gas?
When designing and building gas pipelines from metal pipes, many factors are taken into account. What you need to pay attention to when choosing blanks is described below.
All gas handling structures are divided into 4 categories:
- Category 1… It includes highways with a diameter of 1000-1200 mm with a pressure of 0.5-1, 2 MPa or more between distribution stations. Installation of structures is carried out according to separate specially developed projects.
- Category 2… The system is operated under a pressure of 0.3-0.6 MPa. It is built from distribution stations to enterprises, residential buildings, etc. The pipeline is assembled from parts 500-1000 mm in diameter.
- Category 3… The line is assembled from blanks with a diameter of 300-500 mm, withstanding a pressure of 0.05-0.3 MPa. The design is intended for pumping gas from the city main to regional distribution stations, which are located near houses and other consumption points.
- Category 4… The pipelines are operated with a minimum pressure of up to 0.05 MPa, which is permissible for an intra-house system. Gas is supplied via branches directly to household appliances.
Steel products can be used for the construction of all categories of gas pipelines. Copper - to create a category 4 system when installing intra-house networks. Corrugated steel products are installed in gas pipelines of category 4 for connecting household appliances to in-house highways.
Characteristics of steel pipes for gas pipeline
When choosing pipes, first of all, attention is paid to the wall thickness and diameter, which determine the permissible pressure in the system.
Examine the following options:
- Du is the nominal diameter of the metal pipe. The value is obtained after rounding up the nominal value.
- Дн - the outer diameter of the pipe. According to this indicator, the products are divided into 3 groups: small - 5-12 mm; medium - 102-426 mm; large - more than 426 mm.
- S is the thickness of the metal pipe.
- Dvn - internal size, calculated by the formula Dvn = Dn - 2S.
The dimensions of steel pipes for gas are standardized. Parameters of products for intra-house highways:
|Diameter, mm||Outside diameter, mm||Pipes|
|inch||mm||Wall thickness, mm||Weight 1 m, kg||Wall thickness, mm||Weight 1 m, kg||Wall thickness, mm||Weight 1 m, kg|
A feature of the operation of systems in apartments is the low pressure in the line - within 0.05 kgf / cm2therefore it can be assembled from thin-walled blanks. According to GOST, the diameter of steel pipes for gasification of a house or apartment must meet the following criteria: for wiring inside the house - at least 25 mm; for gas supply to the house - at least 50 mm. When laying the mains underground, the thickness of the product must be at least 3 mm, overground - at least 2 mm.
Lightweight metal pipes allow quick installation of lines inside the building. They easily bend to small angles without using a pipe bender. Such structures are characterized by high thermal conductivity, which causes condensation and the appearance of rust. The problem can be avoided by painting products in several layers after the installation of the structure. Workpieces are connected by welding or threaded fittings.
Steel water and gas pipes differ in the following main characteristics:
- By the presence of a coating - galvanized surfaces or without it;
- By the method of manufacturing and threading - external or internal, rolled or cut, with or without a cylindrical pitch of a cylindrical thread;
- Lengthwise - measured or unmeasured;
- By wall thickness - light, standard and reinforced;
- In terms of manufacturing accuracy - normal and high accuracy.The first option is used for the construction of a gas pipeline, the second - for the production of connecting elements;
Photo of steel gas pipes
In home systems, corrugated metal pipes for gas are often installed, which can withstand pressures up to 15 bar. They are very popular due to their simple installation technology that does not require special equipment. Corrugated products do not transmit electric current, are not afraid of mechanical stress, and are operated without expansion joints. The blanks are always sold in a polyethylene sheath that protects the surface from condensation. They are made of stainless steel.
Steel parts are connected in three ways:
- By screwing. For docking, threaded fittings and couplings are used. The joints are sealed with various seals.
- Autogenous welding. It is used to connect samples with smooth ends.
- Flanged connection. In this way, workpieces with flanges are attached.
Characteristics of copper gas pipes
In gas supply systems, only pipes made of pure copper of the M2p, M2 or Ml brands are used, in which the carbon content is minimal. Requirements for the composition of copper for pipes are given in GOST 617-90. Imported samples must be labeled CU-DHP.
Note! It is forbidden to mount a structure made of copper alloys.
A special oxide layer is applied to the inner surface of the pipes, which does not react to oxygen, sulfates, alkalis and other elements. The same requirements are imposed on copper lines as for steel lines - they must comply with GOST R 50838-95.
Main characteristics of soft copper pipes for gas pipelines in coils:
|External diameter, mm||6, 35||6, 35||9, 52||9, 52||12, 7||12, 7||15, 88||15, 88||19, 05||19, 05|
|Wall thickness, mm||0, 65||0, 76||0, 76||0, 81||0, 76||0, 81||0, 81||0, 89||0, 81||0, 89|
|Weight of 1 rm, kg||0, 104||0, 119||0, 186||0, 198||0, 254||0, 270||0, 341||0, 372||0, 413||0, 594|
|Allowable pressure, atm||104||123||79||84||58||62||49||54||40||44|
The main characteristics of copper pipes for gas pipelines in sections of 3-5 m:
|External diameter, mm||9, 52||12, 7||15, 88||19, 05||22, 23||22, 23||25, 4||25, 4||28, 57||28, 57|
|Wall thickness, mm||0, 76||0, 76||0, 81||0, 81||0, 9||1, 14||1, 0||1, 14||1, 0||1, 27|
|Weight of 1 rm, kg||0, 186||0, 254||0, 341||0, 411||0, 536||0, 672||0, 682||0, 771||0, 773||0, 969|
|Allowable pressure, atm||124||97||77||64||60||77||59||67||52||67|
Note! Most often, domestic gas pipelines use pipes with a diameter of 10-28 mm and 35-54 mm, with a wall thickness of 1.0-1.5 mm.
When choosing copper pipes for gas, consider the following points:
- Parts are made of three types: tall, hard and soft. For gas pipelines, only samples of the first and second types are used. Parts made of soft copper are used only for connecting household appliances to the mains. The wall thickness cannot be less than 1 mm.
- Products made of high hardness copper are very tough and durable, which makes them difficult to process. To reduce stiffness, pipes are heated and slowly cooled, as a result of which the parts become ductile.
- Hard workpieces are sold in 5 m lengths, soft workpieces in 50 and 25 m bays.
- Copper billets change some properties during long-term storage, for example, they acquire increased hardness. Therefore, it is not recommended to purchase metal pipes for future use in large quantities in case of repair. To return the cuts to their original condition, it is necessary to subject them to additional annealing.
- Copper structures have a large linear elongation, therefore, expansion joints in the form of curved nodes are necessarily provided in the line.
Pictured are copper gas pipes
When installing copper pipes for gas, the following rules must be observed:
- Products are connected by soldering and pressing. However, the requirements for the installation of a gas pipeline made of this material differ from other pipelines. Such work is entrusted to highly skilled workers who have undergone special training. For brazing, only solid solder with a high melting point (PMFS6-0D5 or PMFOTsrb-4-0.03) is used, which does not require a flux. Large diameter pipes, which are mounted at the entrance to the house, are connected by gas or argon welding.
- The workpieces can also be connected with special copper fittings, which are assembled by pressing. Without a fitting, it is allowed to fasten cuts with a diameter of up to 54 mm.
- If the system contains parts made of different materials, their mutual contact is prohibited, because this will lead to corrosion. Therefore, rubber gaskets are installed between them.
Price of metal pipes for gas
Metal pipes are produced in a large assortment today. They differ not only in characteristics and scope, but also in cost. The factors that affect the price of a metal pipe for gas include the following:
- Blank manufacturing technology… It can be seamless or electrically welded. The second option is more loyal due to the simplified technology.
- Product material… Copper pipes are considered the most expensive, carbon steel pipes are the cheapest. The more impurities in the metal, the higher the cost of the workpiece.
- Geometric parameters… The cost of the goods depends on them - in the prices of manufacturing companies it is customary to indicate the price of a metal pipe per meter. The cost of the product is determined by the mass of the product per measured unit. The more metal is used to make 1 m of the workpiece, the more expensive it is.
- Distance from the place of pipe production to the point of sale… Transportation costs will be included in the price. the workpieces are heavy and large.
- Product quality… On sale you can find used goods. Its price is lower than that of new samples. In addition, the cost can be reduced if the pipe does not meet the requirements of GOST.
- Processing method… The cost of blanks rises if the pipes have undergone additional processing at the manufacturing plant - galvanizing, grinding, polishing.
Price of metal pipes for gas in Ukraine:
|Position||Options||Weight of 1 rm, kg||Price, UAH / m|
|Pipe VGP DN 15x2, 5 50x3, 5 GOST-3262||6.9 m||1, 23-4, 96||28, 84-115, 32|
|Electric-welded pipe f = 57x3 325, 7 GOST-10704||6, 9, 12 m||4, 15-55, 15||96, 48-1307, 055|
|Thin-walled pipe DN 20x1, 2 50x1, 5||6 m||0, 67-1, 99||14, 74-43, 78|
|Copper pipe f = 10x1 28, 1x1||Bay, cuts||-||120, 73-338, 84|
Price of metal pipes for gas in Russia:
|Position||Options||Weight of 1 rm, kg||Price, rub / m|
|Pipe VGP DN 15x2, 5 50x3, 5 GOST-3262||6.9 m||1, 23-4, 96||40, 24-215, 42|
|Electric-welded pipe f = 57x3 325, 7 GOST-10704||6, 9, 12 m||4, 15-55, 15||196, 45-2909, 15|
|Thin-walled pipe DN 20x1, 2 50x1, 5||6 m||0, 67-1, 99||25, 94-98, 76|
|Copper pipe f = 10x1 28, 1x1||Bay, cuts||-||259, 79-720, 94|
Watch a video about metal pipes for gas:
The technical characteristics of metal pipes for gas pipelines are determined by the relevant GOSTs. The workpieces are selected according to the design category, stacking method and many other criteria. If all requirements are met, the gas supply system will be in trouble-free operation for a long time - at least 50 years.