Pipe longitudinal seam electrowelded GOST 10704 91

Round pipe is an ideal option for transporting liquid and gaseous media at any distance. This form of pipe resists pressure equally well in any direction. These products are manufactured using various technologies, the features of which, in fact, determine their specific properties. The most popular ones include electric-welded (straight-seam pipes meeting the requirements of GOST 10704 91.

GOST 10704-91 governs the production of longitudinal and spiral welded pipes

Steel pipe classification

In general, depending on the presence or absence of a weld, pipe metal products are divided into two groups.

1. Seamless pipes. For the manufacture of pipes of this type, a solid metal billet is used. The production process is quite complicated. The final product is characterized by high accuracy and increased mechanical strength, but at a considerable price.

2. Electric-welded pipes. There is a seam on the finished product. Such a manufacturing method is simpler and requires less cost to complete it, which is why the cost of an electric-welded pipe GOST 10704 91 is much less. These products, in turn, are of two types:

• longitudinal pipe. It has a longitudinal seam. The parameters of these pipes are regulated by the above GOST 10704 91;
• spiral seam pipe. Formed seam is a spiral. Such products of pipe rolling are characterized by high tensile strength.

In longitudinal pipes, the seam is located along the product along its entire length

Features and Specifications

Of the features of pipes with a longitudinal seam, experts distinguish:

• the possibility of producing products of a relatively small diameter. Spiral tubes are available only with a large cross-section;
• the cost of such a pipe is less than the price of a spiral analogue;
• universality of application.

Important! GOST 10704 91 describes the main characteristics and assortment of steel longitudinal seam welded pipes of circular cross section. Do not confuse them with products of a different profile. Those are covered by GOST 8645 68 and GOST 8639 82.

When choosing, it is necessary to take into account that in the assortment of electric-welded pipes GOST 10704 91 there is a product with rather heterogeneous characteristics. In this standard 4 groups of longitudinal products are designated.

1. Group A. This includes pipes that can withstand high mechanical loads.
2. Group B. Resistant to various kinds of chemical influences.
3. Group B. These pipes are characterized by the properties of products of groups A and B.
4. Group G. Characterized by increased resistance to both internal and external pressure.

Along with the geometric parameters, when selecting pipes of electric welded straight-seam GOST 10704 91, their weight characteristics must be taken into account. A selection of the most popular samples can be found in table No. 1.

Table 1

Note! Some data is rounded to the first decimal place due to the infinity of the fraction.

Spiral tubes are produced only in large diameters, and they are distinguished by their large weight

The table shows that all products are characterized by high weight. This is important from the point of view of the need to strengthen the weld. The data presented in the table are calculated theoretically. In fact, the mass may be different.Firstly, reinforcing the seam increases the calculated value by approximately 0.01. Secondly, in calculating the average specific gravity of steel is taken.

As for the length, the following figures are stated in GOST 10704 91:

Length unmeasured.

if the pipe diameter (Dt) is less than 30 mm, the length should be greater than or equal to 2 m;

• 30 ≤ D_t≤ 70 mm - the value of this parameter is not less than 3 m;
• 70 ≤ D_t≤ 152 mm - length not less than 4 m;
• Dt> 152.0 mm - length over 5 m.

Length is measured.

• Dt ≤ 70.0 mm; the length may be 5–9 m;
• 70 t ≤ 219 mm - length varies in the range of 6-9 m;
• 219 ≤ Dt ≤ 530 mm - length from 10 to 12 m.

Good to know! In accordance with GOST 10704 91 products of larger diameter can only be excessive.

The production of electric-welded pipes is carried out with ordinary and increased accuracy. This factor imposes specific restrictions on the deviation of the outer diameter from the nominal values.

• D_t> 1200 mm ± 0.6%: (normal accuracy) and ± 6 mm (increased accuracy);
• 426 ≤ Dt ≤ 1200 mm: ± 0.70% and ± 0.65%, respectively;
• 193.7 ≤ Dt ≤ 426 mm: ± 0.75% and ± 0.65%;
• 51 ≤ Dt ≤ 193.7 mm: ± 0.80% and ± 0.70%;
• 30 ≤ Dt ≤ 51 mm: ± 0.40% and ± 0.35%
• 10 ≤ Dt ≤ 30 mm: ± 0.3% and ± 0.25%.

Welded pipes are available with a length limitation of both dimensional and non-dimensional

GOST 10704 91 requires that the magnitude of the ovality and difference of the electric welded products, the cross section of which is not more than 530 mm, does not exceed the permissible deviations in the outer section and wall thickness, respectively. Regarding curvature, the regulation of this standard is as follows: for one meter of pipe length it should not be more than 1.5 mm.

Pipe production

As a material for the manufacture of products of this type are steel sheets supplied in the form of rolls of the corresponding thickness - strips. The technological process includes the following steps:

1. Cutting sheets into strips, followed by welding them into an endless ribbon.
2. Forming from a tape on rolling mills blanks with a circular cross section. The seam remains open.
3. Weld seam. Currently, at least 4 methods are used for this. Each of them has advantages and disadvantages. PWhen choosing a priority is the reliability and strength of the seam. These characteristics determine the class of pipes.
4. Calibration to a predetermined size of wall thickness and diameter.
5. Seam control. This procedure is performed by ultrasound or eddy currents.
6. The finished pipe is cut into segments of the required length, and then sent to the warehouse.

Galvanized electric welded pipe

As you know, steel is not able to withstand negative environmental factors, and is very susceptible to corrosion. The galvanizing procedure solves this problem.

Galvanized welded pipes are more resistant to corrosion and have a long service life.

But the features of the process impose restrictions on the galvanized pipes.

This concerns, first of all, the following parameters of these products:

• outer diameter (D int.) ranges from 17 ≤ D_vn ≤ 159 mm;
• Conditional pass value (Du): 10≤ D_condition ≤ 150 mm;
• wall thickness: 2 ... 4 mm (light pipes); 2.20 ... 2.40 mm (ordinary pipes); 4.50 ... 5.0 mm (reinforced).

Helpful information! There is no defined standard for galvanized pipe products. Therefore, production is regulated by the requirements of GOST 10704 91.

There are also nuances of installing a pipeline of galvanized pipes. It should be carried out only by a threaded connection. Welding galvanized products is a gross violation of technology. This is especially true for the assembly of plumbing systems. When the material is heated to a high temperature, zinc simply burns out. As a result, the corrosion resistance of the pipes is lost.

In addition, in order to correctly perform the installation, you will need a special threading machine. Of course, if we are talking about creating a home water supply system from a galvanized galvanized pipe GOST 10704 91, it is allowed to use a small manual fixture. But installing the same riser will be problematic.

This is not the only moment.You will have to master the skills of high-quality sealing of the threaded connection of galvanized pipes. And know: FUM tapes and all kinds of modern threads are not here. For reliable packaging of such water supply elements, it is necessary to use only tow and ordinary oil or nitro paint

To complete the installation of galvanized pipes, you will need fittings. The use of conventional bends, tees, couplings and angles is not allowed here. These elements must also have a zinc coating.

In conclusion, it should be noted that the scope of galvanized pipes is much wider than the creation of plumbing communications. In particular, it perfectly serves as protection for electrical cables when laying them under the floor or in the ground.