Water and gas pipes and electrowelded difference. Types of round pipes and their manufacture. These products have found application in construction

04.06.2018

Engineering networks are an integral part of any residential, commercial or industrial facility. When designing communications, special attention is paid to water supply, sewerage and gas distribution networks. For the device of all engineering networks, vGP pipe... Depending on the manufacturing technology, this type of product can be divided into several groups. The most popular pipe products for the laying of communications today are VGP pipes and longitudinal electric-welded products. They are supplied without threads and are available in a wide range.

Scope of application of the VGP pipe

As mentioned earlier, this type of metal product is universal. The VGP pipe is equally successfully used for laying gas and water pipelines. There are no restrictions on the nature of the objects either. It has long been successfully used to provide gas and water to residential buildings, commercial buildings, industrial complexes.

VGP pipe production technologies

High-quality steel is used as a raw material for the manufacture of pipe products in this category. To date, domestic enterprises have launched the production of two variants of VGP pipes: galvanized and not galvanized. In the first case, due to the zinc coating, a high degree of resistance to metal corrosion is achieved. However, galvanized products are more expensive. The second version of pipe products is recommended for use as plumbing systems. They meet all sanitary and hygienic requirements, and are also more affordable.

All products are manufactured in accordance with GOST 3262-75, GOST 380, GOST 1050 and GOST 1050. Each of the standards regulates the technical parameters of the product and its scope. Depending on GOST, a VGP pipe can be selected for water supply, gas distribution networks, sewerage or heating systems.

Longitudinal electric-welded pipe and VGP: main differences

Longitudinal electric-welded pipe products are manufactured by the method of continuous reduction.
The VGP pipe has a threaded or rolled cylindrical thread, and also differ in nominal bore.

In fact, longitudinal electric-welded pipe products are the main ones for the production of high-quality water and gas pipeline elements of utilities. Due to the technology of reduction vGP pipe gets a smaller diameter, it becomes resistant to corrosion and is durable.

Electric welded pipes and water and gas pipes - welded pipes having a similar production method, appearance, but differing in some parameters. AND gOST steel water and gas pipes(steel pipe VGP) , electric-welded (ES pipes) pipes are made from tape, sheet metal, the workpiece is molded on special mills, and then welded to form a seam, which gives the rolled product high strength and wear resistance. GOST electric-welded steel pipes are longitudinal seam, a straight seam is formed when welding along the longitudinal axis. This seam is performed first from the outside, then from the inside. Have gOST water and gas pipes the seam is even more reinforced. Also, VGP pipes can undergo reduction - drawing of the billet on mills to reduce their cross-section, while the wall thickness can change, or it can remain the same. Straight seam pipes are the most demanded on the market.

Longitudinal seam pipes electro-welded can be additionally processed thermally along the entire seam or throughout the entire pipe and be hot-alternated. ES pipes, which have low alloying elements in their composition, can undergo recrystallization annealing. Rolled steel from the St1 grade is not subject to thermal effects. Heat treatment in a protective environment is previously agreed with the buyer at the plant. A certain type of heat treatment electro welded pipes the mills have the right to choose themselves.

It is believed that because of the seam, welded pipes are not very reliable in use, however, the production of pipes on high-precision equipment and high-quality welding of the seam, strength tests, seam control (X-ray) and the issuance of quality certificates for these products guarantee the receipt of durable, reliable material, which will last for more than one year. Only a rough external influence can violate the integrity of this rolled product, in particular, bending of pipes leads to damage to the seam. For pipelines, steel round pipes are used, since plastic and metal-plastic pipes cannot withstand the required gas or water pressure.

Those and other pipes can be additionally galvanized, which makes them suitable for use in domestic water supply systems. Such pipes serve for a long time, rust does not appear inside the pipe, various waste does not adhere to them, but the weight of the pipe increases. Galvanized pipe can be a quarter heavier than non-galvanized. The steel grade from which the pipe is made also affects the anti-corrosion properties of rolled pipes. In addition, galvanized pipes are resistant to high temperatures, so they are used for heating networks, in which water temperature is over 140 degrees C. To prevent pipelines from rusting underground, a bituminous coating is used, it increases the service life of pipes. Professionals connect galvanized pipes with caution, since the coating can be damaged; threads or welding are used to connect the pipes. Zinc plating of pipes is carried out by immersion in a zinc melt or using toxic zinc salts.

The difference between the VGP pipe and the ES:

1. According to GOST:

Water-gas and electric-welded pipes have their own quality standard. Steel pipes VGP are produced according to GOST 3262-75 (this State standard regulates the range and technical conditions of pipes), and ES pipes - according to GOST 10704-91 (implies the range longitudinal electric-welded pipes ) and

GOST 10705-80 (standardizes technologies for the manufacture of electric-welded pipes).

2. The difference between black pipes in size:

VGP and eS pipes differ in wall thickness, outer section, inner diameter, nominal bore. Nominal bore is the average value of the internal section of the pipe in mm. Water and gas pipes are measured and designated according to the conditional passage; steel pipeslongitudinal electric welded - standardized by outer diameter.

Pipe type	Outside diameter(overall diameter)	CONV. passage	Wall thickness
VGP pipes GOST3262	10.2 - 165.0 mm	6 - 150 mm	2.0mm to 5.5mm.
Electric-welded pipes GOST 10705 80	10 - 530 mm		1- 32 mm
Electric-welded pipe GOST 10704 91	10 - 1420 mm		1- 32 mm

Maximum deviations for the mass of pipes, wall thickness are prescribed in GOSTs.

Water and gas pipelines pipes gost 3262 in the days of the USSR it was measured in inches, and many people still use this designation.

For example, an inch pipe is considered a pipe with a nominal bore of 25 mm ( pipe vgp DN 25), half-inch - 15mm ( pipe vgp du 15),

three quarters of an inch - pipe vgp DN 20,

inch and a quarter - water and gas pipe with a nominal bore of 32 mm;

1.5 inches - DN 40,

two-inch pipe - 50mm nominal bore ( pipe vgp du 50).

Table pipe diameters vgp, assortment of longitudinal electric-welded pipes is available on our website in the section "Rolled metal". There is also a division of VGP pipes by wall thickness into: light, ordinary and reinforced.

Thus, water and gas pipe with nominal bore 50 mm ( pipe vgp 50) has an outer diameter of 60 mm, it corresponds to an analog - electric-welded steel pipe GOST 10704 91 60th - with an outer diameter of 60 mm.

For VGP pipes DN 15 analog outer diameter of electrowelded pipes = 21,3

3. By application:

Electrowelded pipes gost 10704used for external water and gas pipelines with different pressures, oil pipelines, heating networks; in the manufacture of furniture, in the construction of buildings and for the construction of structures: fences, poles, supports, for laying cables. GOST 10705 applies to pipes that are designed for pipelines and various designs. ES pipes are used in food, chemical, automotive, mechanical engineering, nuclear technology, as well as for the manufacture of shafts, bearings, etc.

VGP pipes 3262 75 used mainly for internal (drinking) water supply, they are intended for small gas pipelines, supplying communications to rooms, pipe 3262 it is used for heating systems, the manufacture of metal structures, in mechanical engineering and aircraft construction, in industrial construction, in agriculture; thick pipes are needed for main pipelines; some pipes are threaded. The water and gas pipe is widely used by housing and communal services.

The required section, the diameter of the pipe is selected for the water supply system, taking into account the throughput of the water supply system, the number of pipe joints and the total length of the water supply system, as well as the number of pipe turns. For risers, a pipe vgp Du 25 and 20 is usually used, for supplying water to the equipment, a 15th pipe and 10 mm are taken.

4. By steel grades and GOSTs for the applied steel.

Steel water and gas pipes GOST 3262 are made of St1 - St3 (ps / cn / kp), steel 10, steel 20, 08ps / kp in accordance with GOST 380 and GOST 1050. These carbon steels do not have chemical composition and mechanical properties.

For the production of ES pipes, grades are used: St1-4, 08, 20, 10 according to the same GOST 380 and GOST 1050. ES pipes are made of low-alloy and carbon steels. Electric-welded pipes are divided into quality groups: A, B, C, D, mechanical properties are determined, chemical composition, pressure test.

5. By pressure test. All pipes are checked for tightness and strength using hydraulic pressure. This is one of the types of non-destructive testing.

VGP pipes gost 3262 must withstand hydraulic pressure:

light and ordinary pipes
2.4 MPa,
reinforced - 3.1MPa.

For ES pipes, these indicators are equal:

for pipes with a diameter of up to 102 mm, the pressure gauge shows 6MPa,
more diameter of steel electrowelded pipes - 3MPa.

Also various electrowelded pipes are subjected to impact bending, flattening, expansion test, bending test, tensile test and other strength tests.

Electric-welded pipe to buy, vgp pipe to buy

Electric welded pipe price per ton, water and gas pipe price, water and gas pipe diameters the client can independently find it on the company's website. Pipe vgp price, pipe es price depend on the manufacturer, steel grade and wall thickness, pipe weight, zinc coating. Than smaller wall pipes, the lighter it is, respectively, the easier the structure to be manufactured, the lower the cost of metal and its delivery by transport.

You can always get the following information from our managers: gOST 10704 longitudinal electric-welded steel pipes price per meter, pipe steel electrowelded price for the amount you need, 102 * 3.5 electric-welded pipe price per meter, steel water-gas pipe price per meter . We are always happy to help the buyer with the delivery of pipes to the facility and ordering a small batch from other regions, which will be significantly more profitable for the client than his on their own... We also carry out carriage deliveries of rolled tubular products.

Without round pipes it is still difficult to build cities: to lay heating and gas pipelines, communications for residential buildings, to erect popular frame objects, as well as to manufacture transport, various units, units, furniture.

It is clear that "creative" enterprises need high quality products. The popularity of round pipes is easy to explain: products in constant demand are produced, focusing on GOSTs, and sold at affordable prices.

The requirements for the manufacture of these products, the range of round pipes are described in detail in the following documents:

GOST 10704-91 (On longitudinal electric-welded steel pipes),

10705-80 (About electric-welded steel pipes),

10705-91 (About electric-welded steel pipes with a diameter from minimum 10 to maximum 530 mm),

10706-76 (About longitudinal electric-welded steel pipes),

20295-85 (On welded steel pipes for main gas and oil pipelines),

GOST 3262-75 (On steel water and gas pipes).

Assortment, round steel pipe (GOST 8732-78) - requirements for steel pipes, seamless, obtained by hot deformation, while seamless, cold-deformed pipes are detailed in GOST 8734-75.

Types of round pipes and their manufacture

In conditions difficult situationexisting in the global and domestic market of rolled metal products, consumers are extremely interested in the assortment of round pipes: longitudinal welded, spiral welded, seamless products obtained different ways, including water and gas pipes (VGP). The reliability of the communications, buildings, transport, household items - in a word, the comfort of the human environment depends on the quality of these products.

Welded seam pipes

The production of welded pipes accounts for more than half of the total. By the way, it was with welded pipes in 1852 that this industry began to develop. The advantages of a welded pipe are still appreciated today: thanks to the latest developments of scientists, modern products have acquired excellent characteristics and are not inferior in activity to the use of seamless varieties. The range of round steel pipes has expanded significantly since the end of the 19th century.

Manufacturing of welded pipes is much cheaper than seamless pipes. The production technology allows you to save metal: the products are much cheaper in price, while they are lightweight, which is extremely convenient and in demand during transportation and installation. In addition, raw materials (sheet steel) make it possible to obtain products of the highest quality with minimal deviations in thickness.

Round pipes are made in several ways. The most famous of them:

furnace welding;
electric welding;
gas welding;

Hot-deformed pipes are produced by furnace welding. This method is based on the processing of a steel billet using special equipment: furnace and molding and welding mill. For example, a round steel pipe (GOST 3262-75), made of steel of type 2 kp with reduction (reduction in diameter), can "boast" of high ductility of the metal and a high-quality welded seam.

The steel strip GOST (3262-75), which can be found on the website, heats up to about 1300 ° C and is blown, while the edges are descaled, which is designed to ensure a high quality of the weld. In a word, the workpiece is brought to the required state in order to carry out the main welding procedure on the forming-welding mill and give it the desired shape with a given diameter.

Straight seam are perhaps the most popular. Their production accounts for about half of all rolled pipes. The most in demand are thin-walled steel products of impressive diameter, characterized by a hermetically sealed smooth seam and high surface performance characteristics.

The process of making electric-welded round pipes is simple: a steel strip with the required performance characteristics is rolled up to the required diameter, and then the edges are butt-welded, often by arc welding. Further procedures for molding, calibration, testing allow you to bring the product to the requirements specified in GOST.

Welded spiral seam pipes

Coiled sheet steel is also used to produce spiral pipes. This type of product has a number of advantages: the very arrangement of the seams "inhibits" the formation of longitudinal cracks leading to the failure of pipelines, facilitates repair work.

There is also the possibility of producing products with a small diameter and thin walls. However, these products also have a significant drawback - for their manufacture, more metal is required.

Seamless pipes and pipes VGP

Seamless pipes, water and gas supply (WGP) products are highly demanded product, as they can withstand powerful mechanical loads. Seamless pipes are made by hot and cold forming methods on special equipment.

For the manufacture, for example, of a very wide range of round steel pipes GOST R 52079-2003 “Welded steel pipes for main gas pipelines, oil pipelines and oil product pipelines. Technical conditions "one more technology is applied - welding in a protective environment. All the advantages of gas and electric welding are linked here. Shielding gases, displacing air from the working chamber, contribute to the creation of a special environment where the welding process using tungsten electrodes is as efficient as possible. Pipes made in this way are characterized by a high degree of tightness, strong and wear-resistant. In terms of their performance characteristics, they are not inferior to their seamless counterparts.

Scope of application - enterprises of the oil and gas industry, the production of various units. Made in accordance with GOSTs, the round steel pipe VGP is a product that is indispensable for the construction of life support systems. Her "duties" - supply of water, gas, installation of adjustable, spacer fittings. Along with seamless pipes VGP, especially their galvanized version, is necessary for the construction of boiler houses to provide urban residents with warmth in the cold season.

Despite the saturation of the market with many varieties of high-tech polymer pipes, metal for the installation of heating systems, hot and cold water supply is widely used today. Metal pipes for these purposes, they are mainly made from steel and copper, less often from aluminum. Each type of such pipes, depending on the material of manufacture, has a set of individual characteristics that provide the consumer with enough room for maneuver when choosing.

One of the common types of pipes is zinc-coated steel products - a material that has many positive characteristics, but is specific in application. Consider what kind of material it is, and how to properly use galvanized pipes for heating.

The main enemy of steel pipes is corrosion. One of the ways to protect against it is to apply a protective zinc layer to the surface of the steel pipe, after which the material is classified as a separate subgroup - galvanized pipe for water supply and heating systems.

The method is moderately expensive, so the cost of a steel pipe after galvanizing remains affordable - an approximate price ratio can be found according to the table:

Zinc coating can be applied to steel pipes made according to any technology - longitudinal seam, with a spiral seam, seamless, therefore, galvanized pipes are classified in the same way as ordinary ones according to the seam factor.

There is no independent standard for galvanized products. Zinc-protected steel pipes are manufactured in accordance with regulatory documents for electric-welded products with a straight seam (GOST 10704) and material for gas pipelines (GOST 3262-75).

Zinc coating methods

Zinc coating, depending on the operating conditions of the pipe, can be performed both on its outer surface and on its inner surface.

There are 4 methods of galvanizing pipes, each of which is used depending on the size of the products and the requirements for the thickness and strength of the zinc coating:

Parameters of zinc coated steel pipes

Main technical parameters steel pipes with zinc coating are:

outer diameter (10.2 - 165 mm);
weight of 1 m of pipe (0.4 - 22 kg);
nominal bore (6 - 150 mm);
wall thickness (1.8 - 5.5 m);
length (4 - 12 m).

As with ordinary pipes, the walls of galvanized products can be light, reinforced or standard, the accuracy is assigned ordinary or increased.

Important! A protective zinc coating must be applied to the entire surface of the product and have a thickness of 30 microns. Peeling of the protective layer, peeling and swelling on it are not allowed ("Steel water and gas pipes", Technical conditions, GOST 3262-75, rev. No. 4.6).

Advantages and disadvantages

Most of the characteristics of galvanized VGP pipes, both positive and negative, coincide with the parameters of products made of black steel, but there are also individual qualities.

Advantages

Strength (especially tensile strength).
Fire resistance.
Low coefficient of thermal elongation.
Absolute tightness.
Durability.
Can be used as a heat exchanger.
The possibility of installation, including maintenance, do it yourself.
Two assembly methods (welding, threaded connection).
Ease of disposal.

In favor of steel GWP pipes is the fact that the external laying of the gas pipeline from the main to consumers is allowed only from steel material.

disadvantages

Significant share.
Electrical conductivity.
High thermal conductivity (the need to insulate pipes in heating and hot water systems).
Corrosion susceptibility when zinc protection is damaged.

Installation and assembly methods

Galvanized pipes that form a heating or hot water system are mounted in three ways:

welding;
flange connection;
threaded connection;
soldering.

Each of these methods has its own pros and cons. Consider these installation methods and the nuances associated with them.

Welding galvanized pipes

Zinc-coated water and gas pipes can be connected by electric or gas welding - both types of installation are convenient because they take little time. But there is one negative factor, the effect of which must be minimized, since it will not be possible to completely eliminate it.

The fact is that the temperature of the welding seam reaches 1200 degrees, and zinc boils at 906 degrees and begins to evaporate from heating during the welding process. In this case, the following happens:

the harmful effects of zinc vapors on the welder, up to the onset of suffocation, as they are poisonous;
evaporating zinc exposes steel and makes it vulnerable to corrosion;
zinc vapors contribute to the formation of pores and cracks in the weld, which reduce the strength of the joint.

For the maximum localization of these processes, before starting welding, not counting the mandatory device for efficient ventilation of the room, the following actions must be performed.

to weld the joint followed by cleaning the weld seam from slag and coating the bare pipe section with zinc-containing paint (zinc dust content - 94%, binder - 6%) - cold galvanizing.

To prevent the zinc layer from boiling, you can treat the junction with hydrochloric acid 5 cm in both directions, but in this case, acid fumes will form during welding.

Important! According to clause 4.6 of the joint venture (Construction Rules) 73.13330.2012, the device of welded joints on galvanized steel pipelines is not allowed, since zinc is not removed from the inner surface of the pipe before welding, and zinc vapors, the formation of which cannot be avoided, cause the formation in the seam pores and shells. But this document is voluntary, and if there is no reference to the mandatory use of this item in the project, then the installation of galvanized pipes by welding is permissible.

In order to minimize the effect of zinc on the quality of electric welding, installation should be carried out in accordance with the following recommendations:

perform welding at a low speed, but avoiding pipe burning, and with an increased value of the current strength;
use rutile-coated electrodes (the electrode contains titanium oxide).

Welding zinc-coated pipes requires certain skills from the welder. In addition to the composition of the outer coating of the electrode, the quality of the weld is affected by the thickness of its rod, which determines the power of the arc - an excessively thick electrode will burn through the wall, and a thin one will not provide the necessary strength of the welded joint. For welding galvanized pipes with a wall thickness of 1.5 - 5 mm, electrodes with a diameter of 2-3 mm are used.

Flange connection of galvanized pipes

This method is based on bolting together fragments of pipes, at the ends of which flanges are welded - steel rings with an inner diameter equal to the outer diameter of the pipe, and holes around the perimeter for mounting bolts. Two flanges of different fragments are applied to each other using an intermediate gasket and tightened with bolt-nuts or studs.

In this method of installation, the same negative factor is present as in the welded joint - in the process of welding the flanges to the pipes, zinc boils and the protective layer in the area of \u200b\u200bthe weld is destroyed. Therefore, it is also necessary to take measures to localize the temperature effect on the zinc layer, and after the end of welding, clean the seam and apply an anti-corrosion zinc-containing coating on it (cold galvanizing).

The flange connection is not compact, therefore it is used in most cases when laying pipelines in utility rooms or outside. On the abutting side of the flange there is an annular area called a mirror. A paronite gasket with a hole, the diameter of which must match the inner diameter of the pipe, is installed between the two mirrors of the abutting flanges before they are pulled together. The outer diameter of the gasket is made equal to the distance between the opposite mounting bolts.

Threaded connection

This installation method eliminates the need for thermal connection methods and is performed using fittings of various types, designed to connect individual fragments of the pipeline after threading them.

Threaded assembly also has its disadvantages:

the threading process is laborious and time-consuming;
a cutting tool (die) removes a layer of steel of a certain thickness along with a protective zinc coating when cutting a thread.
the tightness of the threaded connection is ensured by winding the thread with FUM tape, sealing paste or tow with paint, which eventually lose their properties and require replacement.

Brazing galvanized pipes

To mount a heating system or hot water supply from galvanized pipes without damaging the zinc layer, brazing is used, which is performed in the following sequence:

the pipe ends to be connected are butted and, if the wall thickness is more than 3 mm, beveled at the outer edges;
the joints are degreased by heating, after which the flux (composition HLS-B) heated to plasticity is also applied in a thick layer to the surface adjacent to the planned joint;
the ends are positioned with a gap of 2-3 m;
the burner flame is exposed to excess oxygen.

The size of the burner is selected depending on the diameter and wall thickness of the galvanized pipe:

For high-quality brazing of a galvanized pipe, it is necessary to adhere to the rule: the size of the burner must be one unit smaller than when welding a pipe of the same dimensions without a zinc coating. In the process of brazing, the flame should be concentrated on the edges to be joined and the joint gap in order to exclude heating and evaporation of zinc from under the flux layer.

Joint seams of high-quality brazing of galvanized pipes do not need additional anti-corrosion protection, but applying on zinc-containing paint as a safety operation will not be superfluous.

The specifics of the use of galvanized pipes in heating and hot water systems

Zinc coated pipes in heating systems and water supply systems are used taking into account the operating conditions.

If the temperature of the coolant does not exceed 65 degrees, then the zinc coating successfully performs its functions. In the northern regions, where this parameter is much higher, the inner zinc layer reacts with water under the influence of high temperature:

Zn + H2O \u003d ZnO + H2.

Both substances resulting from this interaction are negative factors:

ZnO is a floc that precipitates and clogs the lumen of small-diameter pipelines;
H2 is hydrogen, which, when mixed with air in a certain proportion, is explosive or, at least, forms plugs in the system.

Therefore, in hot water and heating systems with a coolant temperature above 60 degrees, it is allowed to use pipes that have only an outer protective zinc coating, which will protect the pipeline from corrosion during periods of inactivity. However, if water hits the surface hot pipe the zinc sheathing begins to peel off from the base, therefore, to avoid this, it is necessary to paint such pipelines over zinc, which will further increase the cost of the system.

Output: the use of pipes galvanized on the outside in hot water and heating systems with a coolant temperature above 60 degrees is unreasonably expensive, and galvanized pipes from the inside are harmful and dangerous.

Conclusion

A water and gas galvanized steel pipe is a material in demand today, but it must be used and installed taking into account the features of the protective coating so that the advantages of zinc are used rationally, and not become a factor that only increases the cost of work.