Range circular pipe: steel, stainless steel, flare in Table

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A variety of metal pipe sections are common in industry, construction, architecture, urban utilities. Application are they and at home. The correct choice of gauge and circular cross-sectional dimensions of the tube is carried out in two stages. Initially set the mass and the technological characteristics of the rental. Then pipes from the range calculated expected estimate of the strength and corrosion resistance of the product, given the conditions of its operation.

Classification of steel profiles of circular cross-section

Viewed rental distinguished by the following parameters:

  1. According to production technology. These products can be obtained on the rolling mills (hot and cold), drawing on the round mandrels, compression through round spinnerets and convolution of metal strips or bands followed by electrical or flame welding. Accordingly say rolled, drawn, extruded and welded tubes.
  2. By the size of the cross-section - with constant or variable (flare connection) section.
  3. According to the source material.
  4. For dimensional accuracy.
Rolled steel pipes

They have the greatest strength seamless pipe. They, in turn, can be divided into:

  • Hot rolled seamless.
  • Cold Drawn (hot drawing does not apply in the modern metallurgical production).
  • Hot- and cold-.
  • Precision steel high precision.
Process of cold drawing pipe rolled
Welded steel pipes

Seamless steel tubes show a good performance in pressure pipelines and gas pipelines trunk lines.

Push-fit connections

Welded steel pipes technologically easier to manufacture, and require less energy to manufacture.

They differ:

  • Welding method (flame, electric, resistance welding).
  • The direction of relative movement of the welding head (only with respect to the electrically welded blanks!) - straight or spiral.
Welding, electric circular profile
Flame welding pipes

Welded steel pipe formed by welding a steel plate rolled into a tubular shape by means of a seam which extends along the entire product. Such profiles are used in the water main pressure medium, Internal pipelines, heating and air conditioning systems as well as the laying housing electrical networks.

The following standards are for the tubular rolled steel domestic production:

  • GOST 8732-78, which establishes technical requirements for seamless pipes of hot deformation.
  • GOST 10705-91 regarding electric-welded longitudinal pipes.
  • GOST 3262-75 defining assortment and technical requirements for round steel pipes for water supply systems mounting.
  • GOST 10704-91, the rules which apply to a thin-walled tubular products (see. Fig. 8).
  • GOST 20295-85, which shows the various round pipes for trunk pipelines.
welded pipes
Thin-walled steel pipes

Some special types of profiles, in particular drill or stainless steel tubes, are manufactured by industry standards and specifications. Domestic assortment of round steel pipes - metric, an assortment of foreign - often inch.

Basic geometric characteristics of the section of the tubular metal of

To assess the performance capabilities of round pipes are important parameters such as a circular cross-section moment of resistance, the moment of inertia and radius of gyration.

Under the resistance torque W, mm3It realizes a power factor which is caused by internal stresses which arise in a pipe subjected to external elastic deformations. The strength of materials, this parameter depends on the moment of inertia of a plane section I, mm4And the distance between the outer diameter of the outer tube and the e axis, mm

W = I / e

modulus characterizes the section's ability to withstand external force factors. For ring (flat shape defining section a conventional, not the thin-walled, circular tube) drag torque does not depend on the direction of coordinates and is set depending on

W = πD3/ 32 (1-c4),

Where:

  • D - outside diameter profile mm;
  • c = d / D - d ratio of the internal and external diameters D section.

Tube profile characterized by a high moment of resistance. This allows it to cope with external force factors, for example, than a continuous profile with the same cross-sectional area. Thus, such pipes are used in such mechanical and hydraulic systems, which during operation are subjected to considerable bending stresses. Often these voltage changes in sign and time.

Moment of inertia - a term used to measure or quantify amounts of mass located in the most remote points of the object between them. The moment of inertia is calculated symmetrical with respect to a hypothetical axis of rotation, and therefore will be the same for both the x axis and y axis. In this case, by selecting the rotational axis of the ring, its cross-sectional moment of inertia is equal to

I = πD4/ 64 (1 - a4)

The moment of inertia is considered to be the energy section of the property in the calculation of how much energy will be stored in a rotating object, the energy is proportional to the moment of inertia. Thus always try to choose the rotation axis and the shape of the object, which would provide the greatest moment of inertia at the maximum stored energy. Ring this condition is satisfied automatically. Therefore, from the viewpoint Strength inertia ring is the maximum resistance of the object expand it axially when trying.

I radius of gyration is the distance from the pivot axis of the annular section to the point at which the concentrated mass of the ring material. The radius of gyration is defined by i = (I / F)0,5Where F - sectional area. The radius of gyration characterizes the flexibility and resilience of the pipe under the influence of external loads. The above characteristics are taken into account in the calculations for torsional rigidity. The corresponding formulas are summarized in the table:

The cross sectional shape The moment of inertia for torsion Torsional modulus Position of the point in which there are the greatest torsional stresses
The one-piece thick-walled pipe Ik = 0,1d4(1-c4) Wk = 0.2d3(1-c4) The perimeter of the outer contour of the pipe
The one-piece thin-walled tube Ik = πd3t / 4 (t - wall thickness) Wk = πd2t / 2 (t - wall thickness) Throughout the section the same voltage
Welded thin-walled tube Ik = πdt3/3 Wk = πdt2/3 The maximum stress occurs on the line opposite to the weld seam

Note! Thin-walled tubes are considered for which the ratio D / t> 40, or profiles with wall thickness less than 1.5 mm.

materials

For the production of the products in question are used:

  1. High-quality carbon steel according to GOST 1050-90.
  2. Structural alloyed steel according to GOST 4543-91 (except those containing a higher percentage of zinc - an element that enhances brittleness).
  3. Stainless steel according to GOST 5632-89.
  4. Some brands of construction steels in accordance with GOST 27772-2015.

The choice of material is determined by the standard of the applicable operating conditions and pipeline. For example, when pumping chemically aggressive environments, when operating in high humidity or when laying underground communications pipe must be subjected to anticorrosive treatment. Due to the increasing requirements operatives gauge stainless steel tubes of circular cross-section is constantly changing.

With an increase in the percentage of carbon increases the strength of the pipe, and ability to withstand dynamic loads falls. By reducing the carbon percentage is reduced production costs, and improve the conditions of plastic deformation of workpieces without cracking.

Pipes made of normal carbon steel is used for supplying drinking water, and therefore are widely used in sanitary ware, fire extinguishing devices, heating, ventilation and air conditioning. Such pipes are also ideally suited for use in other industries, if pre-coated paint, varnish or other metals (in particular nickel, chromium, zinc). This not only helps protect the profiles against rust, but also make life at work in critical conditions.

List the main positive features of low carbon steel pipes:

  • Relatively high values ​​of tensile strength / tear;
  • Plasticity, which is important in the formation of complex piping lines;
  • Low cost;
  • Good cvarivaemost;
  • A wide assortment of product range;
  • Long service life (at the surface anti-corrosion treatment - up to 100 years).

Since any steel has high heat conductivity, the steel pipe for pumping hot liquids or gases, require thermal insulation. Furthermore, at elevated temperatures, rolling resistance, made of conventional steels, it is drastically reduced; in such cases, the conduits are made of stainless steel tubes or of heat resistant steels.

Engineering pipeline computing

Divided into mechanical and hydraulic. The first related to the certain limitations of this type of steel. In particular, steel differs increased weight per meter (in comparison with aluminum or plastic profiles of the same cross section). Therefore, in the process of settlement and the design work is required always possible to accurately set the weight of the pipeline section, which will act on the supporting elements of metal constructions. Mass of product can be installed in several ways:

  • Meaningfully weight per meter pipe (this table is always given in the text of the relevant standard);
  • By calculation by multiplying the cross sectional area F = ρπ (D2 - d2) / 4 length of pipeline;
  • According to an online calculator mass, which in abundance on the Internet.

The need for hydraulic piping connected to the calculation mode motion variability of operating environments inside. In addition, the length L of the cross section diameter and arrangement of its axis and wall thickness may vary. The basic cross-sectional shape of pipelines:

  1. The flared.
  2. Stepped.
  3. Periodical.
  4. Bellows (ribbed).
  5. Spiral.
  6. With radiator.
Pipe-bellows

At individual design meet other options. For complicated piping is required to establish total hydraulic head losses that are accounted for so called Reynolds number.

The Reynolds number is a dimensionless parameter, which is determined by the dynamic pressure ratio ρu2 and shear stress μu / L (ρ - density of the pumped medium, u - its speed).

The Reynolds number can be used to determine whether a laminar flow, transition or turbulent. Thus, the flow:

  • Laminar when Re <2300;
  • The transient at 2300
  • Turbulent when Re> 4000.

Calculation of this parameter is performed according to the relationship:

Re = (ρu2) / (Μu / L)

For pipe or duct is the Reynolds number

Re = ρuDat/μ,

where Dat - hydraulic diameter of the pipeline on the settlement section.

When assembling several dissimilar portions are two main options: one-piece and detachable connection. In the first case to apply different connection fittings (flanges, connectors, sockets), in the second - welding (electric or gas flame).

pipe fittings

Pipe fittings and adapters should provide a hermetic, gas-tight seal, convenient for installation, disassembly, assembly. The main requirements to them are sufficient fatigue strength, vibration resistance, durability under conditions of high pressure and extreme temperatures.

Industrially manufactured connecting fittings made of steel, aluminum alloys, brass, copper, and more optimized in terms of strength, corrosion resistance, weldability, plasticity. Configuration it is subdivided into sleeves, bends, tees, caps, transition sleeve and the ferrules.

The use of steel pipes to reduce structural weight and save up to 40% of the metal, as well as increased use of mechanized assembly techniques. As a result, simplified construction, reduced investment and operating costs.