- №1.Classification and diameter of gas pipelines
- №2.Method of laying gas pipes
- № 3.Material pipe gas pipeline
- №4.Steel gas pipes
- №5.Pipes for the gas pipeline from polyethylene of low pressure( PND)
- No. 6.Copper pipes for gas pipeline
- №7.Metal pipes for gas pipeline
- №8.Safety requirements when laying the gas pipeline
The organization of the gas pipeline is an important step towards ensuring the comfort of your own home, but at the same time, these are complex technical works associated with a great danger. It is better to entrust the design, selection and installation of pipes of a certain material and diameter to professionals, but everyone needs to know the basic principles and nuances of arranging gas supply. We understand which pipes for a gas pipeline are better to choose, which can be used everywhere, and which ones are suitable only for underground installation.
№1.Classification and diameter of gas pipelines
. When choosing gas pipes, first of all, it is necessary to take into account
.Depending on this indicator, gas pipelines are divided into the following
- I-A - a network with a pressure of more than 1.2 MPa. For such sections, pipes with a diameter of 1000-1200 mm are chosen; they are usually used for connecting steam plants, thermal power plants and turbines;
- I - high pressure gas pipelines 0.6-1.2 MPa, such systems operate in places of distribution of gas and its transportation;
- II - high pressure gas pipelines , but its performance is slightly lower than in the previous case, 300-600 kPa. The diameter of the pipe is 500-1000 mm, they are used to supply gas from gas distribution facilities to houses, industrial, social and other facilities;
- III - gas pipelines of medium pressure , 5-300 kPa, pipes with a diameter of 300-500 mm are used. Such networks are used to pump gas from the pipeline to an inlet gas pipeline near residential buildings;
- IV - low pressure gas pipelines , up to 5 kPa. Pipe diameter up to 300 mm. Such pipes are used to transport gas from the inlet pipeline to the houses and directly through the house to gas consumption points. It is with this type of pipe that consumers face when organizing a gas pipeline within a private house or apartment.
gas pipe installation method Gas pressure is, of course, the fundamental factor of choice, but not the only one. It is also necessary to take into account the operating conditions of the pipeline, i.e.features of its laying.
According to the method of installation, the gas pipeline is divided into the following types of :
- underground .It is considered the safest, especially when it comes to high pressure gas pipelines. However, with this method of laying it is necessary to take into account such factors as the depth of soil freezing, its density and the likelihood of corrosion processes. For transporting dry gas, the depth of the pipeline must be about 0.8 m. Installation of pipes for transporting wet gas is carried out below the ground freezing level. steel and polyethylene pipes are suitable for underground installation. The latter are used more frequently today;
- above ground .In terms of reliability, it is inferior to the underground and is used only when it is impossible to lay pipes underground. These are rivers, canals, ravines and other difficult areas in terms of relief. Overhead installation is allowed to be performed on the territory of enterprises. steel pipes are best suited for this purpose;
- domestic gas pipeline in the house and apartment is open. In order not to draw attention to the pipes, they are allowed to be mounted into pre-prepared grooves, but it is necessary to hide the gas pipeline only behind easily removable panels - there must always be access to the pipes. The internal gas pipeline is organized with the help of steel, less often copper pipes.
# 3.Pipeline Material Pipeline
Not so long ago there was not much choice, and only steel pipes were used in all sections of the pipeline, from large nodes to consumption points in houses. Today, an alternative in the form of low pressure polyethylene pipes has appeared. Copper pipes are also used. The agony of choice is unlikely to suffer, since each of these materials has strictly defined operating conditions:
- steel pipes can be with different wall thickness. Thick-walled products are used to equip high-pressure gas pipelines .If we are talking about an above-ground installation, then there is no alternative to steel pipes. These are durable, durable and reliable pipes that will cope with a serious load. Thin-walled pipes are suitable for organizing low-pressure gas pipelines, includingfor arranging the gas supply system inside the house;
- polyethylene pipes are used for underground installation of gas pipeline with different pressure. There are products that can withstand operation at a pressure of 1.2 MPa. They win the steel equivalent in weight, price and ease of installation. Not suitable for above ground or indoor installation;
- copper pipes are superior to steel ones in many ways, but their mass use is impossible due to the high price. Overhead installation using such pipes is not carried out, but this is a great option for organizing a gas pipeline inside the apartment.
The network has information on the use of metal-plastic and even polypropylene products as pipes for the gas pipeline, but these are not the most suitable options.
№4.Steel gas pipes
Steel pipes were previously the only way to organize gas supply. Today, when there are alternative solutions, steel still remains in the lead, winning in terms of universality and breadth of the scope of use. For gas pipelines, steel structures are made in a different way. Seamless pipes of cold and hot rolling, as well as welded pipes with a spiral seam are suitable. The use of a particular type of pipe depends on the pressure in the gas pipeline, the temperature and the characteristics of the transported gas.
In any case, uses high-quality steel with low carbon content( up to 0.25%), sulfur( no more than 0.056%) and phosphorus( up to 0.046%) to create gas pipes. It is even better if the steel passes anti-corrosion treatment, which can significantly increase the life of the pipeline.
The main advantages of the steel gas pipeline are :
- is high strength, but in order for the structure to be airtight, the welds must be of the highest quality possible;
- versatility. Steel pipes can be laid aboveground and underground, inside and outside the premises;
- functioning over a wide temperature range;
- ability to withstand high pressure;
- relatively long life. At observance of all rules of installation and operation it is possible to count on the uninterrupted work period about 40 years.
Among the shortcomings of the it is worth noting:
- the complexity of the installation work;
- high cost;
- poor flexibility;
- prone to corrosion and condensation;
- heavy weight.
The versatility of steel pipes is achieved by a wide variety of products: products with different wall thicknesses and diameters can be found on the market. Pipes may differ in other properties, with all the basic information about the product can tell the marking.
The main parameter of the steel pipe - nominal diameter , is marked as a remote control. This is, in fact, the internal diameter of the pipe, which determines its throughput. It can vary from 6 to 150 mm. For an internal gas pipeline, for example, pipes with a diameter of 25 mm are chosen, for gas distribution systems pipes of at least 50 mm in diameter are needed.
The outer diameter of the depends on the wall thickness of the .The last parameter ranges from 1.8 to 5.5 mm and sometimes more. For above-ground gaskets, pipes with a wall thickness of at least 2 mm are used, for underground pipes at least 3 mm. In some cases( under difficult operating conditions), reinforced pipes with a wall thickness of 5.5 mm or more may be required.
Keep in mind that thin-walled pipes are used only in low pressure systems. Such products are characterized by low weight, sufficient flexibility, so they can be used to install networks of complex configuration. The connection is due to soldering or through the creation of threaded connections. On the other hand, such pipes have a high thermal conductivity: they can accumulate condensate, which negatively affects the material itself, leading to corrosion. That is why gas pipes protect several layers of oil paint.
On high pressure areas, use pipes with thick walls .These are durable structures, but the functionality of the entire system will largely depend on the quality of the connection of individual sections. After welding, control is required.
On pipes with a remote control more than 159 mm and a wall thickness of more than 3.5 mm marking is applied directly to the product. In other cases, all information about the pipes are on the label, which must be present on the packaging. If the letter contains the letter H, then we are talking about pipes with knurled thread, the letter P is threaded, D is an elongated thread, and M is the presence of a coupling.
The quality certificates for steel must contain information on the manufacturer, brand, steel category and group, smelting number and batch, confirmation of compliance with GOST.The manufacturer must conduct tests and check whether the product is coping with regulatory pressure. There should be no defects on the pipe.
If you delve into the theory, then it is worth highlighting a very important point - , depending on the production conditions, the steel may be:
- boiling .In the manufacturing process, it is not completely deoxidized, therefore, it contains an increased amount of unnecessary impurities. This is a more brittle and corrosive steel, not very good weldability. It can be used for domestic gas pipeline and in seismically stable conditions;
- quiet steel has a more uniform structure and is characterized by a minimum content of impurities. This is a durable material that is well welded and withstands decent loads. Such pipes are allowed to use even where there is a vibration load;
- Semi-Quiet Steel - in composition and performance, something between a boiling and a calm one. It is strong enough and often used instead of calm.
No. 5.Pipes for a gas pipeline from low-density polyethylene( HDPE)
HDPE pipes have recently enjoyed no less demand than steel ones. It should be noted immediately that the phrase "low pressure", which appears in the name of the material, refers to the peculiarities of the production of pipes, and not to the operating conditions of the pipeline. There are polyethylene pipes that can withstand pressures up to 1.2 MPa. What makes us abandon the proven version with steel pipes and use polymer? The answer to this question lies in the benefits of the material.
The main advantages of polyethylene gas pipes:
- light weight;
- quick and easy installation without the use of sophisticated expensive equipment that requires special skills;
- strength, ductility and flexibility allow you to simply bypass possible obstacles in the path of the pipeline. The maximum allowable bending radius is 25 pipe radii. Flexibility allows the pipeline to remain complete with small ground movements;
- the ability to withstand pressures up to 1.2 MPa, so that such pipes can be used on virtually all sections of the pipeline;
- corrosion resistance, ability to withstand exposure to aggressive substances;
- high throughput, as the inner surface of the pipe is smooth. At the same diameter as the steel pipe, polyethylene will have a capacity of about 30% higher;
- pipes from HDPE produce a large length, which allows you to do with fewer connections, thereby achieving the integrity and reliability of the structure;
- polymeric materials do not conduct stray current;
- low cost, when compared with steel or copper counterparts;
- durability of at least 50 years, and under all conditions up to 80-90 years.
There are also disadvantages:
- polyethylene pipes can not be used in areas where the temperature falls below -450C.Such a gas pipeline is located at a depth of not less than 1 m, at winter temperatures of -400С the depth increases to 1.4 m, and in some cases, the laying of HDPE pipes is completely impossible. At low temperatures, performance may deteriorate, and durability may decrease;
- does not fit pipes also for seismically active areas;
- pressure more than 1.2 MPa pipes from PND will not stand - only thick-walled steel will help here;
- sensitivity to ultraviolet rays does not allow overhead laying - polyethylene pipes are only suitable for installation underground;
- because of the increased level of flammability of polyethylene such pipes are not recommended to be used indoors. Already at + 800 ° C, the material tends to deform and collapse;
- HDPE pipes are not suitable for laying gas pipelines in sewers and tunnels. In such places use steel analog;
- at the intersection of the pipeline with roads and other communications pipe must be hidden in a metal case.
It is better not to use polyethylene pipes for the installation of a gas pipeline inside the building, but they are being used more and more for underground installation.
For the production of pipes, uses special pipe brands of polyethylene :
- PE 80 - black pipes with yellow inserts, withstand pressures up to 0.3-0.6 MPa;
- PE 100 - pipes with a blue strip, withstand pressures up to 1.2 MPa. When installing them, more serious efforts are made, since the material has to be heated to higher temperatures, but the quality of the connection in this case is at a height.
The diameter of the HDPE pipes can vary from 20 to 630 mm and more; even pipes with a diameter of 1200 mm are used. When choosing, it is also worth taking into account such indicator as SDR - this is the ratio of the diameter to the wall thickness. The smaller this value, the thicker the walls and the more durable the product in front of us. SDR ranges from 9 to 26.
Joining polyethylene pipes is done in one of the following ways:
- butt-welding .The edges of individual elements are heated by a special soldering iron until a viscous consistency is reached, which allows you to easily connect two pipes into one;
- electrofusion welding involves the installation of the edges of the pipe in a special coupling, to which voltage is applied, due to which the heating and connection of two segments. Such a connection is more durable than the pipe itself and withstands a pressure of 16 MPa.
When individually connected to the network, there will be enough end-to-end welding, and if, for example, gasification of the whole area passes, it is better to use electrofusion welding - it is more reliable and hermetic.
Special elements are used to connect the steel and polyethylene pipelines, one side of which is welded to steel and the other to polyethylene.
№6.Copper pipes for gas pipeline
Copper pipes are used in the organization of the gas pipeline system relatively recently. They can only be used for laying pipes inside the house at pressures up to 0.005 MPa. For these purposes, drawn or cold-rolled pipes with a wall thickness of at least 1 mm are used.
- attractive appearance. Gas pipes can not be hidden in the walls or boxes - they should be easy access. Steel pipes can hardly be called interior decoration, in contrast to the copper counterpart. It is unnecessary to hide such pipes - they look neat and attractive, they will perfectly fit into many interior styles;
- is relatively simple installation, which is carried out using press fittings or soldering. In addition, copper pipes are easily cut;
- plasticity and the ability to create a network of complex configuration;
- sufficient mechanical resistance;
- resistance to aggressive substances;
- durability up to 100 years.
Among cons is a high price, a small range on the market and high thermal conductivity, which can lead to condensation. The strength of copper pipes is inferior to steel, but if we are talking about internal wiring, then it will not cause any special problems.
№7.Metal-plastic pipes for gas pipeline
This is not the most popular option, but, nevertheless, found. With such pipes, it is possible to create only a gas pipeline inside an apartment, to connect gas-flow devices. SNiP 42-01-2002 allows the use of such pipes in buildings with a height of no more than 3 floors. By means of a fitting it is possible to make connection with steel and polyethylene pipes.
Metal-plastic pipe is a multi-layer construction. The outer and inner layer is plastic, between them there is a thin layer of aluminum. Thanks to this design, numerous benefits are provided: :
- is easy to install, so you can cope even without the help of a professional and special tools;
- flexibility, you can do a minimum number of fittings;
- good tightness;
- low price.
Among the cons limited scope. Metal-plastic pipes are only suitable for laying inside buildings, they are afraid of prolonged exposure to ultraviolet rays, and when heated above +40 ° C, the tightness of the pipeline is lost, as it does when cooled to a temperature of -150 ° C.
№8.Safety requirements when laying the gas pipeline
The laying and operation of the gas pipeline is fraught with great risks. To ensure complete safety, you must follow a number of rules. Before starting work on connecting a private house to a centralized gas pipeline, you must notify the local gas service. He must inform about the pressure parameters in the gas pipeline to which the connection is made, and carry out a technical agreement, after which a design work is drawn up.
The relevant building codes and fire safety regulations state how and where gas pipes must pass in order to ensure maximum safety of their operation.
The overhead gas pipeline is used in enterprises, as well as in cases where the soil has an increased corrosivity. In this case, such s are guided by the norms:
- the height of the pipe in the crowded area must be at least 2.2 m, above the roadway more than 5 m;
- in places where there is no movement of people and vehicles, installation at a height of 0.35 m is allowed;
- in places of intersection with power supply systems it is necessary to organize electrical protection.
The following rules should be followed when underground laying gas pipes to a house:
- pipe location depends on the depth of soil freezing, but in any case, not less than 0.8 m. In areas where arable work or abundant irrigation is carried out, it is better to lay pipes at a depth of at least 1.2 m;
- gas pipeline distance from the road - at least 3 m;
- distance of the low pressure pipeline to the wall of the house - not less than 10 cm, input into the dwelling is carried out by means of a sleeve.
Now the most interesting thing is the of the norm for the installation of gas pipes inside apartments and houses :
- in residential premises gas pipes cannot be placed;
- prohibited the installation of gas pipes in hard-to-reach places, they can not be hidden behind the decorative casing. Exceptions are those cases in which the exterior decor can be easily removed if necessary, in order to provide access to the whole pipe;
- the height of the gas pipe from the floor - not less than 200 cm;
- installation of gas pipes is possible in rooms with a ceiling height of at least 220 cm and normal ventilation;
- when the gas pipeline is located in the kitchen, the ventilation of this room cannot be adjacent to the living rooms;
- gas pipe should not overlap window and door openings;
- the length of the flexible section of the pipeline should not be more than 300 cm;
- the ceiling over the pipeline must be finished with non-flammable plaster;
- requires a steel or galvanized exhaust pipe for mounting the gas column, but in no case aluminum corrugated. Naturally, it is necessary to provide in the design of the column the presence of a fuse that will shut off the gas supply if the flame goes out;
- the distance from the thin-walled metal pipe to the electric cable must be at least 25 cm, to the shield - 50 cm;
- is better to exclude the neighborhood of gas pipes and cooling devices;
- the laying of gas pipes in the kitchen on the floor, under the sink or near the dishwasher is prohibited;
- pipe should be securely fastened to the wall with clamps and brackets.
As for the , the diameter of the pipes, the calculation requires the use of parameters such as the length of the pipeline, the gas temperature, the allowable pressure drop, the heat capacity of the equipment and the gas flow. In order to correctly calculate the diameter of gas pipelines, it is necessary to use complex formulas — it is better to entrust this task to the designers. The network has online calculators that can quickly calculate the required diameter depending on the entered data. Special tables may also come to the rescue.