1. Structural materials (classification). Ferrous metals. Steel, carbon, classification, marking, identification of markings, scope of application (aggressive environmental influences, pressure, temperature).

K.M. - materials from which parts of structures (machines and structures) that bear force load are made. The defining parameters of K.M. are mechanical properties. To the main quality criteria K.M. include: strength, toughness, reliability, service life, etc. The main structural material for petrochemical equipment is steel. Cast iron and non-ferrous metals are also used. Non-metallic materials; including polymer ones, they are rarely used as structural ones; they serve mainly for facing or lining equipment and individual components and parts.

Steel and cast iron make up the group of ferrous metals. Ferrous metals is an alloy of iron with carbon and other chemical elements, and the iron content must be at least 45%, and carbon up to 4.5%.

Steel has good strength, is very technologically advanced in processing and manufacturing semi-finished products, has a low cost compared to other structural materials, and can withstand high temperatures and the aggressive effects of corrosive environments.

Steel - an alloy of iron with carbon (up to 2.1%) and other chemical elements.

Impurities called chemical elements, transferred into the composition of steel during its production as technological additives or as components of charge materials.

By chemical composition Steels and alloys of ferrous metals are conventionally divided into carbon (without alloying elements), low-alloy, medium-alloy, high-alloy, and iron-based alloys.

Carbon steels do not contain specially introduced alloying elements.

Bypurpose Steels are divided into structural, tool and steels with special physical and chemical properties. Within the classification, there are narrower divisions of steels both by purpose and by properties.

By quality Steels are divided into ordinary quality steel, high quality steel, high quality steel and especially high quality steel. The main characteristics of steel quality are more stringent requirements for the chemical composition and, above all, for the content of harmful impurities such as phosphorus and sulfur.

Carbon steels are divided into two subgroups - carbon structural steels ordinary quality and carbon steel quality .

Structural carbon steel of ordinary quality

They are widely used in construction and mechanical engineering, as they are the cheapest, most technologically advanced and have the necessary set of properties for the manufacture of structures for mass use.

Steel group A supplied with regulated mechanical properties. Their chemical composition is not regulated.

Group B steel supplied with a regulated chemical composition, without guarantee of mechanical properties.

Steel group B supplied with regulated mechanical properties and chemical composition. Currently, carbon steels are not divided into groups and are not marked with the letters B and B.

, there are calm (sp), semi-calm (ps) and boiling (kp) . They contain different silicon contents.

Carbon steels of ordinary quality are designated by the letters "St", followed by a number indicating the serial number of the steel grade, and not the average carbon content in it, although as the number increases from St1 to St6, the carbon content in the steel increases. The letters B and C indicate in front of the brand.

Carbon structural quality steels denoted by a two-digit number indicating the average carbon content in hundredths of a percent to indicate boiler rooms stamps have the letter K at the end.

When designing technological equipment, the following requirements must be met for structural materials:

1) sufficient general chemical and corrosion resistance material in an aggressive environment with a given concentration, temperature and pressure at which the technological process is carried out, as well as resistance to other possible types of corrosion destruction (intercrystalline corrosion, electrochemical corrosion of conjugated metals in electrolytes, stress corrosion, etc.);

2) sufficient mechanical strength at a given pressure and temperature of the technological process, taking into account the specific requirements when testing devices for strength, tightness, etc. and in operating conditions when additional loads of various kinds are applied to the devices (wind load, deflection from its own weight, etc.);

2. Structural materials (classification). Ferrous metals. Alloy steel, classification (according to various criteria), bimetals marking, marking interpretation, scope of application (aggressive environmental influences, pressure, temperature).

K.M. - materials from which parts of structures (machines and structures) that can withstand force loads are made. The defining parameters of K.M. are mechanical properties. To the main quality criteria K.M. include: strength, toughness, reliability, service life, etc. The main structural material for petrochemical equipment is steel. Cast iron and non-ferrous metals are also used. Non-metallic materials; including polymer ones, are rarely used as structural ones; they serve mainly for facing or lining equipment and individual components and parts.

Steel and cast iron make up the group of ferrous metals. Ferrous metals are an alloy of iron with carbon and other chemical elements, and the iron content must be at least 45%, and carbon up to 4.5%.

Steel is an alloy of iron with carbon (up to 2.1%) and other chemical elements (impurities and alloying additives).

Alloying elements are chemical elements specially introduced into steel to obtain the required structure, structure, physical, chemical and mechanical properties.

Impurities are chemical elements that have passed into the composition of steel during its production as technological additives or as components of charge materials.

According to the chemical composition, steels and alloys of ferrous metals are conventionally divided into carbon (without alloying elements), low-alloy, medium-alloy, high-alloy, and iron-based alloys.

Carbon steels do not contain specially introduced alloying elements.

According to their purpose, steels are divided into structural, tool and steels with special physical and chemical properties. Within the classification, there are narrower divisions of steels both by purpose and by properties.

According to the quality of steel, they are divided into steel of ordinary quality, high-quality, high-quality and especially high-quality. The main characteristics of steel quality are more stringent requirements for the chemical composition and, above all, for the content of harmful impurities such as phosphorus and sulfur.

Alloy steels are iron-based alloys, in the chemical composition of which alloying elements are specially introduced, providing the required structure and properties under certain methods of production and processing. In alloy steels the content individual elements more than the same elements in the form of impurities.

Designations in steel grades: G – manganese, C – silicon, X – chromium, N – nickel, M – molybdenum, V – tungsten, F – vanadium, T – titanium, D – copper, Yu – aluminum, B – niobium, P – boron, A – nitrogen (no designation at the end). The letter “A” at the end indicates that the steel is high quality, if the letter in the middle of the grade means the steel is alloyed with nitrogen.

1. low alloy with an alloying element content of up to 2.5%,

2. medium alloyed (alloyed) with an alloying element content from 2.5% to 10%,

3. highly alloyed with an alloying element content > 10%.

Low-alloy structural steels include low-carbon weldable steels that contain inexpensive and abundant alloying elements (up to 2.5%) and have increased strength and a reduced susceptibility to brittle fractures compared to carbon steels. Most widely used in capital construction and for the manufacture of pipes for main gas pipelines, metal structures of machines and mechanisms, in shipbuilding and other industries national economy.

Alloyed structural steels are used for the most critical and heavily loaded machine parts.

According to the main properties (special properties), depending on the purpose, alloy steel is divided into the following groups:

1. High strength steel. Usually these are low-alloy steels. They are used for equipment operating at high pressures and temperatures up to 4750 C. These are steel grades 16GS; 09G2S. Steels are unstable in many aggressive environments.

2. Heat-resistant steels. The mechanical properties of these steels change slightly with increasing temperature: they are distinguished by high creep resistance and long-term strength. Heat-resistant steels are intended for the manufacture of parts operating under load at temperatures from 200 to 600°C for a long time. The main alloying element is Mo. These steels include steel grades: 15M; 15Х5М. Typically these are low and medium alloy steels.

3. Corrosion-resistant (non-rust or acid-resistant) steels are resistant to various types corrosion and have good resistance to acidic environments. The most common steels are type 18–8 (18% Cr and 8% Ni). 12Х18Н10Т.

4. Heat-resistant steels and alloys (scale-resistant), resistant to chemical destruction of the surface in gas environments at t> 5500C, operating in an unloaded or lightly loaded state. Scale resistance of steels is given mainly by Cr; Si; AI; Ni. Scale-resistant steels include grade 10X17; 08Х13, etc., chromium-nickel steels type 18–8 and nichrome type alloys: with 80% Ni and 20% Cr.

Marking of brands of heat-resistant and heat-resistant alloys on iron-nickel and nickel bases consists only of letter designations of elements, with the exception of nickel, after which a number indicating its average content in percentage is indicated.

Steels for castings are marked in the same way as wrought steel, but with the addition of the letter “L” at the end of the mark.

5. Heat-resistant steels and alloys that are capable of working in a loaded state for a certain time and at the same time possessing sufficient heat resistance, that is, having simultaneously the properties of heat resistance and scale resistance (that is, they are used at t> 5500C).

These steels are alloyed mainly with Cr and Mo; 15Х5М; Cr and Ni; 14Х17Н2; 20Х23Н18; 15Х5ВФ.

When choosing a grade of alloy steel, it is necessary to carefully study the requirements for its operating conditions: strength at operating temperature and corrosion resistance in a given environment.

When designing technological equipment, the following requirements must be met for structural materials:

1) sufficient general chemical and corrosion resistance of the material in an aggressive environment with a given concentration, temperature and pressure at which the technological process is carried out, as well as resistance to other possible types of corrosion destruction (intercrystalline corrosion, electrochemical corrosion of conjugate metals in electrolytes, stress corrosion, etc.);

2) sufficient mechanical strength at a given pressure and temperature of the technological process, taking into account the specific requirements presented when testing devices for strength, tightness, etc. and in operating conditions when additional devices are exposed to loads of various kinds (wind load, deflection from its own weight, etc.);

3. Basic design parameters. Temperature, pressure, permissible voltage.

The main design parameters for choosing a structural material and calculating the strength of apparatus elements are the temperature and pressure of the working process.

Temperature There are operating and design temperatures . Operating temperature t is the temperature of the contained or processed medium in the apparatus during the normal course of the technological process in it. Design temperaturet p- this is the temperature that is used to determine the physical and mechanical characteristics of the material and permissible stresses. It is determined on the basis of thermal calculations or test results. The highest value of the wall temperature is taken as the calculated temperature of the wall of the vessel or apparatus. At a temperature below 20, the design temperature when determining permissible stresses is taken to be a temperature of 20. If it is impossible to carry out thermal calculations or measurements and if during operation the wall temperature rises to the temperature of the medium in contact with the wall, then the highest temperature of the medium should be taken as the design temperature, but not below 20. When heating with an open flame, exhaust gases or electric heaters, the calculated temperature is taken to be equal to the temperature of the medium increased by 20 for closed heating and by 50 for direct heating, unless more accurate data is available.

If the device has thermal insulation, the calculated temperature of its walls is taken to be equal to the temperature of the insulation surface in contact with the wall, plus 20. If the element has a negative operating temperature, the calculated temperature is taken to be equal to 20, i.e. the design temperature can be determined using the following formula

Pressure There are working, design, conditional and test pressures.

Working pressure P is the maximum internal excess or external pressure that occurs during the normal course of the working process. Without taking into account the permissible short-term increase in pressure during the operation of the safety valve or other safety devices. If the process in the apparatus occurs under vacuum, then the working pressure is vacuum.

Design pressure determined for operating conditions and test conditions.

The design pressure under operating conditions for elements of vessels and apparatus should be understood as the pressure at which the strength is calculated. As a rule, the design pressure is assumed to be equal to or higher than the operating pressure. The design pressure may be higher than the working pressure in the following cases: if, during the operation of the safety devices, the pressure in the device can increase by more than 10% of the working pressure, then the design pressure should be equal to 90% of the pressure in the device when the safety device is fully opened; if an element is subject to hydrostatic pressure from the liquid column in the apparatus, the value of which is more than 5% of the calculated one, then the calculated pressure for this element accordingly increases by the value of the hydrostatic pressure.

That. for operating conditions design pressure

where p slave – working pressure in the apparatus, MPa;

Hydrostatic pressure of the medium, MPa, which is calculated using the formula: density of the medium, kg/m 3 (density values for some liquids are given in Appendix I);

g – gravitational acceleration, m/s 2 ;h – height of the working fluid, m, which is determined by the type of technological process a in the apparatus.

For mass transfer columns in a liquid–gas (steam) system, the height of the working fluid can be taken equal to where is the height of the bottom part of the apparatus;

H DN – height of the bottom of the apparatus, m, which is determined depending on the type of bottom.

Under design pressure In test conditions for elements of vessels and apparatus, the pressure to which it is subjected during the test pressure should be understood, including hydrostatic pressure if it is 5% or more of the test pressure, i.e. the design pressure for test conditions is determined by the formula

Where P PR is the test pressure, MPa, which is calculated by the formula

where P 20 G is the hydrostatic pressure of water at t = 20 0 C, MPa, which is calculated by the formula where is the specific gravity of water, MN/m 3; H is the height of the body (without support) filled with water, m; [σ] 20 – permissible stress, MPa, at temperature t=20 ºС.

Conditional (nominal) pressureр у – excess operating pressure at a temperature of the apparatus element of 20°С (without taking into account hydrostatic pressure).

For higher temperatures of the apparatus elements, the conditional pressure decreases according to the decrease in the strength of the structural material.

Conventional pressures are used when standardizing devices and their components.

This pressure is always not lower than the operating and design pressure.

At t slave >20°C, the conditional pressure decreases in proportion to the decrease in permissible stresses at these temperatures.

Test pressure P pr - test pressure in a vessel and apparatus should be understood as the pressure at which the vessel or apparatus is tested.

The test pressure of the hydraulic test of the vessel must be determined taking into account the minimum values of the design pressure and the ratio of the permissible stresses of the material of the assembly units (parts), i.e. ,the ratio sigma20/sigmat is taken according to the material used in the vessel elements for which it is the smallest.

Determination of the permissible stress for the material of the device body is made for operating conditions and for test conditions:

- for working conditions at the design temperature is made according to the formula

[σ] t =η·σ * t, where σ * t is the standard permissible stress, MPa,

η – correction factor to permissible stresses. It must be equal to unity, with the exception of steel castings, for which this coefficient has the following meanings:

0.8 - for castings subjected to individual testing using non-destructive methods;

0.7 - for other castings.

Thus, for welded machines η = 1.

For test conditions the design temperature for the body of the column apparatus is assumed to be 20. For test conditions, the permissible stresses are determined by the formula where σ 20 T is the yield strength at t = 20 0 C;

n T – safety factor for the yield strength.

Main parameters

Under the term "pipeline fittings" understand a device installed on pipelines, units, vessels and intended for control (switching off, distribution, regulation, discharge, mixing, phase separation) flows of working media (liquid, gaseous, gas-liquid, powder, suspension, etc.) by changing the area of the passage sections.

Pipeline fittings are characterized by two main parameters:

nominal bore (nominal size),
conditional (nominal) pressure.

Nominal size (nominal size) (D y or DN) is a parameter used for pipeline systems as a characteristic of the connected parts, for example, pipeline connections, fittings and fittings. The nominal diameter (nominal size) is approximately equal to the internal diameter of the connected pipeline, expressed in millimeters. The values of the nominal diameters must correspond to the numbers of the parametric series established by GOST 28338-89 (a total of 50 indicators from 2.5 to 4000).

The nominal bore or nominal size is indicated using the designation Dу or DN and numerical value, selected from a series. For example, nominal diameter (nominal size) 200 should be designated: Dy 200 or DN 200.

Conditional (nominal) pressure (P y or PN)- the highest excess operating pressure at a working medium temperature of 20°C, at which the specified service life of pipeline connections and fittings having certain dimensions, justified by strength calculations for the selected materials and their strength characteristics at a temperature of 20°C, is ensured.

GOST 26349-84 defines a parametric series of nominal pressures, consisting of 27 parameters from 0.1 to 1000 kgf/cm 2

Conditional (nominal) pressures less than 0.1 kgf/cm 2 are determined according to GOST 8032-56.

In contrast to conditional pressure, a distinction is made between test and working pressures.

Test pressure (P pr)- this is the excess pressure at which hydraulic testing of fittings and pipeline parts must be carried out for strength and density with water at a temperature of not less than 5 ° C and not more than 70 ° C, unless the specific value of this temperature is indicated in the regulatory and technical documentation.

Working pressure (P)- this is the highest excess pressure at which the specified operating mode of fittings and pipeline parts is ensured, that is, at a given operating temperature. The temperature of the environment must be taken equal to the temperature at which long-term operation of the product occurs without taking into account short-term deviations allowed by the relevant regulatory and technical documentation.

Working pressures are equal to the conventional ones for fittings made of carbon steel at an ambient temperature from -20 to +200°C, for fittings made of gray cast iron from -15 to +120°С, for fittings made of ductile cast iron from -30 to +120°С, for fittings made of brass and bronze from -30 to +120°С, for titanium alloys from -40 to +50°С. As the operating temperature of the medium increases, the permissible operating pressure is reduced depending on the material of the valve body parts. Fittings are made from carbon steel for operating temperatures up to 445°C, from gray cast iron - up to 300°C, from malleable cast iron - up to 400°C, from bronze and brass - up to 250°C, from titanium - up to 350°C.

The test pressure value for fittings and pipeline parts intended for operating pressure less than 1 kgf/cm 2 and for operation in vacuum is assumed to be equal to:

at operating pressure less than 1 kgf/cm 2 P pr = P + 1 kgf/cm 2
in vacuum P pr = 1.5 kgf/cm 2

Examples of designations according to GOST 356-80

conditional pressure 40 kgf/cm 2 - Р у 40 or PN 40
test pressure 60 kgf/cm 2 - P pr 60
operating pressure 250 kgf/cm 2 at a temperature of 530°C - P 250 t 530

General basic terms and concepts

Along with the listed main concepts in valve engineering, the following terms are most often used, reflecting specific elements, objects and parameters of manufactured products.

Type of fittings- a classification unit characterized by the interaction of the movable element of the valve (locking body) with the flow of the working medium and defining the main design features of pipeline fittings. For example, gate valve, faucet, valve, etc.
Type of fittings- a classification unit characterizing the functional value of pipeline fittings. For example, shut-off, regulating, etc.
Valve size- design of pipeline fittings, regulated by nominal bore and nominal pressure and having the designation of a group main design document (main design of the product).
Valve version- the design of one of the types of pipeline fittings, regulated, in addition to the nominal diameter and nominal pressure, by variable data: material of the main parts, connection to the pipeline, type of control, etc., information about which is contained in one group or basic design document. The execution corresponds to a specific OKP code.
Constructive series- pipeline fittings of the same design, differing only in nominal diameters.
Parametric series- designs of pipeline fittings various conditions passages having the same nominal parameters.
Ratings- pressure and temperature of the working medium specified to take into account deviations in tolerances.
Working environment- liquid, gas, pulp or mixtures thereof and other substances for the control of which (switching off, distribution, regulation, discharge, mixing, phase separation) pipeline fittings are intended.
External (environmental) environment- atmospheric air, gas, liquid or other substances surrounding pipeline fittings.
Control environment- liquid, gas or other substances used as a working fluid in valve actuators, that is, creating a shifting force on a locking or control element.
Team environment- liquid, gas or other substances used to transmit command signals to the valve actuator.
Absolute pressure (P abs)- pressure measured taking into account atmospheric pressure.
Excess pressure (P)- pressure measured without taking into account the effect of atmospheric pressure - atmospheric pressure (P, a) is taken as the zero reference, P = P abs - P a. When P abs > P, and the pressure P is also called manometric.
Vacuum (W)- positive difference between atmospheric pressure and absolute - W = P, a - P abs (when P, a > P abs). In engineering calculations, P, a = 1 kgf/cm2 is usually accepted.
Operating temperature (T p, °C)- the maximum temperature of the working environment operating during the normal course of the technological process without taking into account random short-term increases.
Construction length of reinforcement (L)- linear size of the fittings between the outer end planes of its connecting parts (flanges, couplings, fittings, nipples, welding pipes).
Construction height of reinforcement (N)- distance from the axis of the passage pipes of the valve body to highest point structure (spindle or drive) when the product is open.
Hydraulic resistance coefficient- the ratio of the lost pressure to the velocity (dynamic) pressure in the agreed (accepted) flow section.
vFlow section is the area formed by the relative position of the movable and fixed elements of the valve.
Leak (leak)- the volume or weight of the working medium passing through a valve closed with nominal pressure per unit time at given parameters (pressure, temperature, density).
Tightness- the property of a connection (detachable, permanent, with a moving or fixed contact) to prevent leakage.
The tightness class for shut-off valves is indicated in technical conditions for a specific type of fittings. The leakage values correspond to the case of leakage into the atmosphere. When determining leaks, the nominal diameter is taken in millimeters.
Impenetrability- a property of the material of a part, characterized by the absence of cracks, looseness, and gas inclusions through which the working medium can penetrate.
Reliability- the property of pipeline fittings to perform specified functions, maintaining over time the established values of operational indicators within the required limits and taking into account the mode of its operation, the conditions of its use and maintenance, as well as taking into account repairs, storage and transportation. The property is complex and includes requirements such as reliability, durability, etc. These requirements can be considered separately or included in the form of a certain combination in assessing the reliability of the reinforcement or its individual components and parts.
Reliability- a single indicator of the reliability of pipeline fittings, characterizing the ability of the fittings to remain operational continuously for some time or some operating time.
Durability- a single indicator of reliability, characterizing the ability of the valve to maintain operability until the onset of the limit state with the necessary breaks determined by the established system of maintenance and repairs. An indicator of durability is the service life or resource.
Performance- a state in which pipeline fittings can perform specified functions.
Operating time- duration of operation of pipeline fittings in time or in quantitative terms in the form of “closed-open” response cycles. The operating time can continue continuously or intermittently; in the latter case, the total operating time is taken into account.
Cycle- movement of the locking element from starting position(“closed”, “open”) to the opposite and vice versa, associated with the performance of the main function of this type of fittings.
Service life- calendar duration of operation of the valve from its beginning or renewal after an average or overhaul until the limit state of the reinforcement occurs.
Resource- operating time of the valves from the start of operation or its restoration after medium or major repairs until the onset of the limit state specified by the regulatory and technical documentation.
Limit state- the state of pipeline fittings in which it performs its functions, but cannot be used for further operation, which must be stopped due to an irreparable violation of safety requirements. The limit state may occur either as a result of the specified parameters leaving the established limits, or due to the need for medium or major repairs, as well as due to a decrease in the operating efficiency of the valves.
Long lasting strength- the ability of the part material to maintain strength under prolonged stress (especially important at high temperatures).
Cyclic strength- the ability of the part material to maintain strength when stress occurs periodically in it.
Thermal shock - sudden action to high-temperature metal (when a highly heated liquid, for example, a metal coolant, suddenly enters the fittings).
Thermal cycle strength- the property of a material to maintain strength when exposed to thermal shocks.
Fire, explosive or toxic environment- a gas or liquid that may ignite, explode or cause harmful effects on humans or animals.

Legend

The use of a system of symbols for fittings allows us to briefly record some of the main technical parameters of the product. The use of an index system makes it possible the right choice reinforcement, its use for its intended purpose and increases the ability to control the fittings during installation. The most widely used system is the TsKBA (Central Design Bureau for Valve Manufacturing) system, which contains a digital and alphabetic code for the basic data of valves. According to the TsKBA system, the product index includes five elements arranged in series (in the absence of a drive, the product index consists of four elements).

The first two digits indicate the type of valve (table 1), the letters behind them indicate the body material (table 2), one or two digits after the letters indicate the model number (design features of the product), if there are three digits: the first of them indicates the type of drive (table 3), and the next two are the model number; the last letters are the material of the sealing surfaces (Table 4) or the method of applying the internal coating of the housing (Table 5).

In some cases, after the letters indicating the material of the sealing surfaces, a number is added that indicates the version of this product or its manufacture from a different material. A product without inserted or welded-on rings, that is, with sealing surfaces made directly on the body or valve, is designated by the letters "bk" (without rings).

For example:

15s922nzh Steel shut-off valve, straight through, flanged with electric drive
15 - according to table 1 - shut-off valve
c - according to table 2 - carbon steel
9 - according to table 3 - with electric drive
22 - model number
NZh - according to table 4 - sealing surfaces overlaid with corrosion-resistant steel

For valves with electric drives in an explosion-proof design, the letter B is added at the end of the symbol (for example, 30ch906brB), and in a tropical version - the letter T (for example, 30ch906brT). The letters B and T are indicated when ordering.

Along with the TsKBA system, they use a code obtained by abbreviating the name of the product, for example, KTS - three-way steel valve, etc. Individual designs are indicated only by the number of the drawing according to which they are manufactured. Sometimes a letter is entered into the designation indicating the manufacturer of the fittings.

The symbol for valves intended for the oil refining and oil production industries consists of letters and numbers. The letters indicate the type of valve, the numbers behind the letters indicate the product parameters, for example, ZKL-200-16 - a cast wedge valve with a nominal bore of 200 mm, for a nominal pressure of 16 kgf/cm 2 or YUL-160 - a supply valve for a nominal pressure of 160 kgf/cm2 cm 2. Products that do not have a symbol are designated by the drawing number.

Currently, many new symbols for fittings have appeared that do not lend themselves to any systematization. These designations are given in the reference book as adopted by the manufacturer (or developer)

Tables!

Classification of fittings

1. By area of application:

General purpose industrial pipeline fittings- used in various sectors of the national economy. It is mass-produced in large quantities and is intended for environments with frequently used pressures and temperatures. This fittings are used to equip water pipelines, steam pipelines, city gas pipelines, heating systems, etc.
Industrial pipeline fittings for special conditions work- intended for operation at relatively high pressures and temperatures, at low temperatures, on corrosive, toxic, radioactive, viscous, abrasive or granular media. These fittings include: energy fittings with high energy parameters, cryogenic, corrosion-resistant, fountain, heated fittings, fittings for abrasive slurries and for bulk materials.
Special fittings developed and manufactured according to individual orders based on special technical requirements. Often such fittings are manufactured, for example, for experimental or unique industrial installations, including nuclear power plants.
Ship fittings is produced for operation in specific operating conditions on river and river vessels navy taking into account increased requirements for minimum weight, vibration resistance, increased reliability, special control and operating conditions.
Plumbing fittings Various household appliances are equipped: gas stoves, bathroom units, kitchen sinks, etc. These fittings are manufactured in large quantities at specialized enterprises, have small passage diameters and are mostly operated manually, with the exception of pressure regulators and safety valves for gas.

2. By functional purpose (type):

Shut-off valves designed to completely shut off the flow of the working medium in the pipeline and start the medium depending on the requirements of the technological process (open-close cycle). The main purpose of shut-off valves is to shut off the flow of the working medium through the pipeline and re-release the medium depending on the requirements of the technological process served by the pipeline, ensuring tightness both in the valve and in relation to the external environment. Shut-off valves by the number of units used account for 80% of all valves.
Control valves designed to regulate the parameters of the working medium by changing its flow rate. This includes control valves, pressure regulators, liquid level regulators, throttling valves, etc.
Distribution and mixing (three-way or multi-way) fittings designed to distribute the working environment in certain directions or to mix flows of the environment (for example, cold and hot water). This includes distribution valves and taps.
Safety fittings designed to automatically protect equipment and pipelines from unacceptable pressure by releasing excess working fluid. These include safety valves, impulse safety devices, diaphragm burst devices, and bypass valves.
Protective fittings designed for automatic protection of equipment and pipelines from unacceptable or technological process changes in parameters or direction of flow of the working medium and to shut off the flow without releasing the working medium from the technological system. This includes check valves, shut-off valves.
Control fittings used to check the presence and determine the level of liquid in boilers, tanks and vessels, as well as to connect instrumentation in hydraulic and pneumatic systems. These include test valves, level indicators, stopcocks and pressure gauge valves.
Phase separating fittings designed for automatic separation of working media depending on their phase and condition. These include steam traps, air vents and oil separators.

3. By design type:

Gate valve- pipeline fittings in which the locking element moves back and forth perpendicular to the direction of flow of the working medium. It is used primarily as a shut-off valve: the locking element is in the extreme positions “open” and “closed”. A variation of this type of fittings are hose valves, in which the flow of the medium is blocked by a shut-off element that pinches an elastic hose, inside which the transported working medium passes.
Valve- pipeline fittings in which the locking or control element moves back and forth parallel to the axis of the flow of the working medium in the seat of the valve body. A valve in which the closing element is moved by a screw pair and controlled manually is called a valve. This name is now obsolete. A variation of this type of fitting is a diaphragm valve, in which a membrane is used as a shut-off element. The membrane is fixed along the outer perimeter between the body and the lid and performs the function of sealing body parts and moving elements relative to external environment, as well as the function of sealing the locking organ.
Tap- pipeline fittings in which the locking or control element has the shape of a rotating body or part thereof; rotates around its axis, perpendicular to the direction of flow of the working medium.
Valve (disk valve)- pipeline fittings in which the locking or control element has the shape of a disk and rotates around an axis perpendicular to the axis of the pipeline.

4. Depending on the nominal pressure of the working environment:

vacuum(medium pressure below 1 kgf/cm abs),
low pressure (from 0 to 16 kgf/cm 2 excess),
medium pressure(from 16 to 100 kgf/cm 2),
high pressure(from 100 to 800 kgf/cm 2),
ultra high pressure(from 800 kgf/cm2).

5. According to temperature conditions:

cryogenic(operating temperatures below -153°C),
for refrigeration technology(operating temperatures from -153 to -70°C),
For low temperatures (operating temperatures from -70 to -30°C),
for medium temperatures(operating temperatures up to +455°C),
for high temperatures(operating temperatures up to +600°C),
heat-resistant(operating temperatures above +600°C).

6. According to the method of connection to the pipeline:

Coupling fittings. Connects to a pipeline or container using couplings with internal threads.
Pin fittings. Connects to a pipeline or container on an external thread with a collar for sealing.
Weld fittings. Attached to a pipeline or container by welding. The advantages are complete and reliable tightness of the connection, minimum maintenance (no tightening of main flange connections is required). The disadvantage is the increased complexity of dismantling and replacing fittings.
Tightening fittings. The connection of the inlet and outlet pipes with the flanges on the pipeline is carried out using studs with nuts running along the valve body.
Flange fittings. Connects to a pipeline or container using flanges. The advantages are the possibility of repeated installation and dismantling on the pipeline, good sealing of joints and ease of tightening them, greater strength and applicability for a wide range of pressures and passages. Disadvantages - the possibility of loosening and loss of tightness over time, large overall dimensions and weight.
Fittings (nipple). It is connected to a pipeline or container using a fitting (nipple).

7. According to the method of sealing (sealing) relative to the external environment:

Stuffing box fittings. Sealing of the rod or spindle relative to the external environment is ensured by an elastic element in contact with the movable rod (spindle) under a load that prevents leakage of the working medium.
Membrane fittings. A membrane is used as a sensitive element. It can perform the functions of sealing body parts, moving elements relative to the external environment, as well as sealing the valve.
Bellows fittings. To seal moving parts (rod, spindle) relative to the external environment, a bellows is used, which is also a sensitive or power element of the structure.
Hose fittings. The elastic hose ensures a tight seal throughout internal cavity fittings in relation to the external environment.

8. By control method:

Remote controlled fittings. It does not have a direct control element, but is connected to it using columns, rods and other transition devices.
Drive fittings. Control is carried out using a drive (directly or remotely).
Automatic valves. The valve is controlled without the participation of the operator under the direct influence of the working environment on the valve or on the sensitive element, or through the influence of the control medium on the valve drive, or by a command signal sent to the valve drive from ACS devices.
Fittings with manual control . Control is carried out manually by the operator, remotely or directly.

Industrial pipeline fittings are the name of a number of devices intended for installation on units, vessels or pipelines. The main operational task of pipeline fittings is to control (distribution, shutdown, discharge, regulation, etc.) flows of gaseous, powdery, liquid, gas-liquid working media by increasing or decreasing the flow area.

Traditionally distinguished two main operational parameters pipeline fittings: nominal size (nominal diameter) and nominal (nominal) pressure.

Conditional bore (DN or DN) is a parameter by which the connecting elements of a pipeline are characterized: the nominal bore (nominal size of the fittings) is expressed in millimeters and is approximately equal to the internal diameter area of the connected element.

Conditional passage according to GOST 28338-89
2,5;3	40	300	1600
4	50	350	1800
5	63*	400	2000
6	65	450	2200
8	80	500	2400
10	100	600	2600**
12	125	700	2800
15	150	800	3000
16*	160*	900	3200**
20	175**	1000	3400
25	200	1200	3600**
32	250	1400	3800**; 4000

* Suitable for use with hydraulic and pneumatic devices.
** Not allowed for general purpose fittings.

Nominal (conditional) pressure (PN or PN) is the maximum excess pressure in the system at a working medium temperature of 20 ° C, which allows to ensure the operational service life of individual elements of connecting fittings and pipelines. Designations and values of conditional pressure must correspond to the ratings specified in GOST 26349-84.

		Designation of nominal (conditional) pressure	Nominal (conditional) pressure value, MPa (kgf/cm³)
PN 0.1	0,01 (0,1)	PN 63	6,3 (63,0)
PN 0.16	0,016 (0,16)	PN 80	8,0 (80,0)
PN 0.25	0,025 (0,25)	PN 100	10,0 (100,0)
PN 0.4	0,040 (0,40)	PN 125	12,5 (125,0)
PN 0.63	0,063 (0,63)	PN 160	16,0 (160,0)
PN 1	0,1 (1,0)	PN 200	20,0 (200,0)
PN 1.6	0,16 (1,6)	PN 250	25,0 (250,0)
PN 2.5	0,25 (2,5)	PN 320	32,0 (320,0)
PN 4	0,4 (4,0)	PN 400	40,0 (400,0)
PN 6.3	0,63 (6,3)	PN 500	50,0 (500,0)
PN 10	1,0 (10,0)	PN 630	63,0 (630,0)
PN 16	1,6 (16,0)	PN 800	80,0 (800,0)
PN 25	2,5 (25,0)	PN 1000	100,0 (1000,0)
PN 40	4,0 (40,0)

The choice of nominal pressures less than 0.01 MPa is carried out from the R5 series, more than 100 MPa - from the R20 series (according to GOST 8032-84).

When marking pipeline fittings, the design of which was developed before 01/01/1992, the use of the nominal pressure designation Ru is allowed. The designation of conditional pressure PN6 can be used instead of the designation PN 6.3.

Operating pressure Pр – maximum excess pressure at operating temperatures that ensure the specified operating mode of pipeline fittings.

Test pressure Ppr is an excess pressure at which hydraulic tests of pipeline fittings and connecting elements can be carried out for tightness and strength. Test pressure values are determined in accordance with GOST 356-80. If the operating pressure value is below 20 MPa, then the test pressure will be approximately 1.5 times higher than Pр.

The classification of industrial pipeline fittings is carried out taking into account several technical, functional and operational characteristics.

Scope of application

Depending on the area and scope of application, there are the following types industrial pipeline fittings: general purpose pipeline fittings, fittings for special operating conditions, special fittings, transport and ship fittings, sanitary fittings.

General purpose pipeline fittings It is mass-produced and intended for use in all areas and industries.
Pipe fittings for special operating conditions designed for operation in energy systems with high technological characteristics. Besides this, industrial fittings This type is used for the installation of pipelines through which highly toxic and aggressive working media are transported.
Development and production special fittings carried out, as a rule, on special orders from individual departments or state enterprises. The scope of application of special fittings is ship power plants, Ministry of Defense facilities, nuclear power plants, etc.
Transport and ship fittings produced for use in the transport industry and, in particular, used in shipbuilding. The fittings of this class are subject to increased technical requirements: in the production of transport fittings, the dimensions, weight of the products, the possibility of operating the fittings in different climatic zones and other characteristics are taken into account.
Plumbing fittings used to complete and organize the functionality of various types of household equipment. Fittings of this type, as a rule, have a small diameter and do not cause any difficulties during operation. The production and release of sanitary fittings is carried out on production lines. In the production of sanitary fittings special attention traditionally focused on consumer performance and, in particular, product design.

Functional purpose

Depending on the functional purpose, the following types of industrial pipeline valves are distinguished: shut-off, control, distribution and mixing, safety, protective and phase separating.

Functional purpose shut-off valves– complete opening or blocking of flow in the pipeline. The operation of shut-off valves is determined by technological requirements.
Pipeline control type fittings used to regulate the parameters of working media by changing the flow rate. Control valves are various models pressure regulators, liquid level regulators, throttling valves, control valves, etc.
Main purpose separation and mixing valves(valves, taps) – mixing flows of the working medium, redirecting flows in the required direction.
Safety fittings used for automatic protection of pipelines and equipment from overpressure. Warning when operating safety valves emergency situations is carried out by dumping excess working medium from the system. The most common types of safety valves are impulse safety devices, safety valves, bypass valves, and diaphragm bursting devices.
Functional purpose protective fittings(shut-off and check valves) – automatic protection of pipelines and equipment from failures technological process due to changes in the parameters of working media, changes in the direction of flows. When operating protective valves, emergency situations are prevented without the release of excess working fluid from the system.
Phase separating pipeline fittings are used when it is necessary to organize automatic separation of working environments, taking into account their current state and phases. The most common types of phase separation valves are gas separators, condensate traps, air separators and oil separators.

Construction types

Depending on the design features, the following types of industrial pipeline fittings are distinguished: gate valves, valves (gates), taps, gates.

Gate valve– a structural type of pipeline fittings, the movement of the working element of which is perpendicular to the direction of flow of the working medium. As a rule, valves are most often used as shut-off pipeline valves.
Valve– a structural type of industrial valves, the movement of the control or shut-off element of which is carried out parallel to the axis of the flow of the working medium. There is a variety of this type of fittings - diaphragm valves. In the design of a diaphragm valve, the role of a locking element is a membrane, which is fixed between the body and the cover along the outer perimeter and performs the function of sealing the shut-off body, body parts and moving elements relative to the external environment.
Tap– a structural type of industrial pipeline fittings, the regulating or shut-off element of which has the shape of a body of rotation (or part of it), rotates around its axis and is located arbitrarily in relation to the direction of flow.
Gate- a structural type of pipeline fittings, the regulating or shut-off element of which has the shape of a disk and rotates around a non-its own axis.

Conditional pressure of the working medium

Vacuum fittings (working medium pressure below 0.1 MPa abs.)
Low pressure (0-1.5 MPa)
Medium pressure fittings (1.5-10 MPa)
High pressure (10-80 MPa)
Ultra-high pressure pipeline fittings (80 or more MPa)

Method of connection to the pipeline

Depending on the method of fastening to the pipeline, the following types of industrial fittings are distinguished: coupling, nipple, welding fittings, clamping, pin, flange, fitting.

Accession coupling industrial fittings connection to the pipeline is carried out using couplings with internal threads.
Accession nipple fittings to the pipeline is done using a nipple.
Accession pipeline fittings intended for welding, is carried out by welding. This method connecting fittings to a pipeline has both advantages and obvious shortcomings. In particular, high-quality welding of fittings guarantees absolute tightness of the connection, does not require maintenance (tightening of flange connections), however, it can cause certain problems when carrying out repair work, work on replacing reinforcement elements.
Fastening tie rods to the pipeline is done using nuts and studs.
.Accession flanged fittings connection to the pipeline is made using flanges. This method fastening also has advantages (the possibility of repeated installation and dismantling of fittings, high strength, the ability to operate under a wide range of operating pressures and passages) and disadvantages (possible loosening of the fastening, loss of tightness of the connection, large weight and dimensions).
Installation pin fittings to the pipeline is made on an external thread with a collar for sealing.
Union fittings attached to the pipeline using fittings.

Sealing method

Depending on the sealing method, the following types of industrial pipeline fittings are distinguished: membrane, bellows, stuffing box.

With the help membrane fittings The housing elements and movable connecting elements are sealed relative to the external environment. In addition, the membrane fittings make it possible to ensure a seal in the valve.
Gland fittings allows for sealing of the spindle or rod relative to the external environment: the sealing of the connection is carried out using an stuffing box that is in direct contact with the movable spindle or rod.
Bellows fittings used to seal moving parts (spindle, rod) relative to the external environment. A bellows, which is a power or sensitive element of the structure, is used as a seal.

Control method

Depending on the control method, the following types of industrial pipeline valves are distinguished: drive valves, valves with remote, automatic and remote control.

Main feature fittings intended for remote control, - absence of a control body. The connection to the control is made using transition elements (columns, rods, etc.).
Control driven pipeline fittings carried out using a drive (remotely or directly).
Control industrial pipeline fittings designed for automatic control, is carried out without operator participation. Automatic control is ensured due to the direct influence of the working environment on the power or sensitive element, or with the help of signals supplied to the drive from instruments and devices of the automated control system.
Control manual valves carried out using an operator.

According to GOST 9544-93, for all types of shut-off valves (except for special valves and valves with electric drive), the following classes of tightness of connections are established at a nominal pressure of 0.1 MPa or more.

Table of minimum duration of hydraulic mash tests:

Table of dependence of media values and pressures for hydraulic tests on nominal (conditional) pressures and diameters:

The choice of medium for hydraulic testing is carried out depending on the functional purpose of the pipeline fittings and compliance with GOST requirements (water - GOST P 51232-98, air - class 0 GOST 17433-80). When conducting hydraulic tests, the temperature of the test medium must be less than 5° C, but not more than 40° C. Permissible error when measuring leaks: ±0.01 cm³/min. for leaks less than 0.1 cm³/min. and ±5% for leaks more than 0.1 cm³/min.

Symbol of fittings according to the TsKBA classification (table-figure)

Classifications of industrial pipeline fittings (TsKBA classification) are made on the basis of accepted symbols consisting of letters and numbers. The first two digits in the product labeling indicate the type of industrial fittings (see Table 1). The letter (or combination of letters) after the first two digits indicates what material the product body is made of (see Table 2). The letters (or combination of letters) are followed by one or two numbers indicating the model number. If three digits are indicated after the letter designation, then the first is the type of drive (see Table 3), and the next two digits are the model number. The last letters in the marking indicate the material from which the sealing surfaces are made (see Table 4) or indicate the method by which the internal coating of the product body was carried out (see Table 5). Reinforcement made without welded or insert rings is designated “bk”.

Table 1

Type of fittings	Symbol
Test valve	10
Pipe valve	11
Level indicator locking device	12
Shut-off valve	13, 14, 15
Shut-off valve	22, 24
Check valve	16
Safety valve	17
Reverse shutter	19
Bypass valve	20
Pressure regulator	18, 21
Distribution valve	23
Control valve	25, 26
Mixing valve	27
Gate valve	30, 31
Butterfly valve	32
Hose valve	33
Steam trap	45

Table 2

Table 3

Table 4

Table 5

In parallel with the TsKBA classification system, a system of codes obtained by abbreviating the factory name of products is often used to classify industrial fittings. For example, to indicate ball valve, having a nominal pressure of 16 kg/cm³ and a nominal bore of 15 mm, the designation KSh-16/15 is used. To designate some types of reinforcement structures, only the number of the drawing documentation according to which they were manufactured is used. Often, when classifying products, a letter is indicated indicating the name of the manufacturing plant.

To classify valves intended for use in industries such as oil refining and oil production, a symbol consisting of numbers and letters is also used. If the letters indicate the type of fittings, then the digital value indicates the operational parameters of the product. For example, a cast wedge valve of the 2nd modification, having a nominal pressure of 16 kg/cm³ and a nominal diameter of 200 mm, is designated as ZKL2-200-16.

To designate the working environment in catalogs of industrial pipeline fittings, it is customary to use abbreviations (see Table 6).

Table 6

Type of fittings	Symbol
Aggressive	ah
Nitrogen	az
Ammonia	am
Acetylene	ac
Air	vz
Air-oxygen mixture	vzkd
Gases, gaseous media	G
Liquids, liquid media	and
Oxygen	cd
Oil, oil with solvents	ms
Natural or associated petroleum gas	ng
Petroleum products, diesel fuel, kerosene, gasoline	np
Oil and gas mixture	nf-ng
Steam	n
Neutral	n
Non-aggressive	naked
Water	vd
Hydrogen sulfide	With
Carbon dioxide	uk

Selection of shut-off valves for gas distribution systems

When choosing pipeline shut-off valves intended for use in gas distribution systems, it is necessary to be guided by the following provisions and regulatory documents: PB 12-529-03, SNiP 42-01-2002 and SP 42-101-2003. In gas supply networks with pressures up to 1.6 MPa, it is recommended (depending on operating conditions) to use the types of pipeline fittings indicated in the table:

Type of fittings	Scope of application
1. Cone tension valves	External above-ground and internal low-pressure gas pipelines, including LPG vapor phase.
2. Stuffing box cone valves	External and internal gas pipelines, including the vapor phase of LPG with pressure up to 0.6 MPa inclusive.
3. Ball valves
4. Valves	External and internal gas pipelines natural gas, as well as vapor and liquid phases of LPG with pressure up to 1.6 MPa inclusive.
5. Valves (valves)	External and internal gas pipelines of natural gas, as well as steam and liquid phases of LPG with pressure up to 1.6 MPa inclusive.

When installing pipeline fittings on external gas pipelines in areas with cold climatic conditions, it is necessary to use products in the climatic design UHL1, UHL2, HL1, HL2. When carrying out installation work of pipeline fittings on internal gas pipelines in heated rooms, it is necessary to choose products in climatic modifications U1, U2, U3, U5, UHL4, UHL5, KHL5, and for unheated rooms it is recommended to use UHL3, KHL3 (according to GOST 15150-69).

When installing pipeline fittings on internal (in unheated rooms) and external gas pipelines in areas with a moderately cold climate, it is necessary to select products in the climatic version U1, U2, U3, UHL1, UHL2, UHL3 (according to GOST 15150-69).

Select pipeline fittings for external and internal gas pipelines in unheated rooms, taking into account the operating pressure in the system, climatic conditions, housing material, recommended based on the data given in the table:

Carbon steel

Material	Gas pressure, MPa	DN, mm	Operating temperature, °C
Material	inclusive
Gray cast iron	up to 0.05 up to 100 up to –45
Malleable iron	up to 0.6	without restrictions	up to –35
	up to 0.05	up to 100	up to –45
	up to 1.6	without restrictions	up to –40
up to 1.6	without restrictions	up to –45
Alloy steel	up to 1.6	without restrictions	up to –60
Copper alloys	up to 1.6	without restrictions	up to –60
Aluminum alloys*	up to 1.6	up to 100	up to –60

* Production of body parts of fittings must be carried out from the following materials: stamped and forged products - deformable alloy grade D-16 (alloy D-1 can be used), cast products - guaranteed quality with mechanical properties not lower than grade AK - 7ch (AL-9) (according to GOST 1583-93).

As design temperature operation of the valves and the temperature of the working environment, it is customary to choose the temperature of the coldest week with a probability of 0.92 (according to SNiP 23-01-99).

The hermetic tightness of the valves and gate valves with a nominal bore up to 80 mm must correspond to class B. If there is a nominal bore above 80 mm, it must correspond to class C (according to GOST 9544-93).

The hermetic tightness of the valve of tension cone valves with a nominal pressure of up to 0.1 MPa, which are not covered by GOST 9544-93, must comply with the class standards for a working pressure of 0.1 MPa (according to GOST 9544-93).

The hermetic tightness of valve closures, which are installed on gas pipelines of the liquid phase of LPG, must correspond to class A. When installing valve closures on other types of gas pipelines, compliance with class B (according to GOST 9544-93).

Industrial pipeline fittings used in gas supply systems must have a passport that states that the working medium for this product is liquefied or natural gas.

In a number of cases (subject to compliance with the requirements for the tightness of products; provided that the sealing materials of the valve and body connectors are resistant to the transported gas), the operation of valves intended for natural or liquefied gas, possible for steam, water and ammonia.

The choice of operating and conditional pressure of shut-off valves is carried out depending on the operating pressure parameters in the system and must correspond to the data specified in the following table:

According to the requirements of GOST 4666-75, all types of pipeline shut-off valves must be marked and distinctively painted. The marking is applied to the product body and must contain the manufacturer’s trademark, operating or nominal pressure, nominal diameter and, if necessary, an indication of the direction of flow of the working fluid. The cover and body of the shut-off valves are painted depending on the material.

The electric drive of the shut-off valves must be manufactured in an explosion-proof design.

What are DN, Du and PN? Plumbers and engineers must know these parameters!

DN – Standard denoting nominal internal diameter.

PN – Standard indicating nominal pressure.

What is Du?

Du– formed from two words: Diameter and Conditional. DN = DN. Du is the same as DN. Just DN more international standard. Du is the Russian-language representation of DN. Now it is absolutely necessary to abandon this name for Du.

What is DN?

DN- Standardized representation of diameter. GOST 28338-89 and GOST R 52720

Nominal diameter DN(nominal diameter; nominal bore; nominal size; nominal diameter; nominal bore): A parameter used for pipeline systems as a characteristic of the connected parts of the fittings.

Note - The nominal diameter is approximately equal to the internal diameter of the connected pipeline, expressed in millimeters and corresponding to the nearest value from a series of numbers adopted in the established order.

What is DN usually measured in?

According to the terms of the standard, it seems that it is not strictly tied to the unit of measurement (written in the documents). But it just means the diameter. And diameter is measured by length. And because the unit of length may be different. For example, inch, foot, meter and the like. For Russian documents we simply measure in mm by default. Although the documents say that it is still measured in mm. GOST 28338-89. But it does not have a unit of measurement:

How can it not, if it does? Can you write in the comments how to understand this phrase?

It seems that it has arrived... DN (diameter number expressed in millimeters). That is, it does not have a unit of measurement, but rather contains constant values (digital discrete values like: 15,20,25,32...). But it cannot be designated, for example, as DN 24. Because the number 24 is not in GOST 28338-89. There are strict values in order like: 15,20,25,32... And only these need to be selected for designation.

DN is measured by the nominal diameter in mm (millimeter = 0.001 m). And if in Russian documents you will see DN15 then this will indicate an internal diameter of approximately 15 mm.

Conditional passage- indicates that this is the internal diameter of the pipe, expressed in millimeters - conventionally. The term “Conditionally” indicates that the diameter value is not exact. Conventionally, we assume that it is approximately equal to certain values of the standard.

The nominal bore (nominal size) is understood as a parameter used for pipeline systems as a characteristic of the connected parts, such as pipeline connections, fittings and fittings. The nominal diameter (nominal size) is approximately equal to the internal diameter of the connected pipeline, expressed in millimeters.

According to the standard from: GOST 28338-89 It is customary to choose the numbers that have been agreed upon. And you shouldn’t come up with your own numbers with commas. For example, DN 14.9 would be a designation error.

Nominal diameter approximately equal to the internal diameter of the connected pipeline, expressed in millimeters and corresponding to the nearest value from a series of numbers adopted in the prescribed manner.

These are the numbers:

For example, if the real internal diameter is 13 mm, then we write it as: DN 12. If the internal diameter is 14 mm. then we accept the value DN 15. That is, we select the closest number from the list of the standard: GOST 28338-89.

If in projects it is necessary to indicate both the diameter and thickness of the pipe wall, then it should be indicated as follows: d20x2.2 where the outer diameter is 20 mm. And the internal diameter is equal to the difference in wall thickness. In this case, the internal diameter is 15.6 mm. GOST 21.206–2012

Alas, we have to submit to other people's standards

Any materials imported from abroad were most often developed using a different length dimension: Inch

Therefore, most often the dimensions are oriented to inches. Usually a quotation mark is written in place of the word inch.

1 inch = 25.4 mm. Which is the same 1” = 25.4 mm.

Dimensions table. Usually a quotation mark is written in place of the word inch.

1/2 “ = 25.4 / 2 = 12.7. But in reality, this size of 1/2 “is equal to a passage of 15 mm. More precisely it might be 14.9mm. for steel pipe. In general, dimensions may vary by a few mm. Therefore, in such cases for accurate calculations you need to find out the internal diameter of a specific model separately.

For example, size 3/4” = 25.4 x 3/4 = 19 mm. But we write in the documents “conditionally” DN20 - approximately the internal diameter is 20 mm.

Here are the actual sizes that most often correspond to the Russian translation.

The table shows the internal diameter in mm.

Nominal pressure PN: More details in GOST 26349 and GOST R 52720.

Has a unit of measurement: kgf/cm2. The designation kgf means kg x s (kilogram times s). c=1. c characterizes, as it were, a force coefficient. That is, by multiplying a kilogram (mass) by force, we convert mass into force. This is a correction for meticulous physicists. If you designate kg/cm2, in principle you will not be mistaken if you assume that we perceive mass as force. Also, such a unit as kg/cm2 is erroneous in that pressure is formed from two units (force and area). Mass is another parameter. Because the mass only on the surface of the earth creates the force that presses on the earth (gravitational force). Value c=1 on the surface of the earth. And if you fly to another planet, then the force of gravity will be different, and the mass will create a different force. And on another planet the coefficient c=1 will be equal to a different value. For example, c=0.5 will create pressure twice as low.

What is PN for?

The PN value is needed to indicate to the device a pressure limit that cannot be exceeded for normal operation device for which this value is set. That is, when designing, the designer must know in advance what maximum pressure the device is designed for.

For example, if the device is given the value PN15, this means that the device is designed for operation with a pressure not exceeding 15 kgf/cm2. Which is approximately equal to 15 Bar.

1 kgf/cm2 = 0.98 Bar. Roughly speaking, the PN value is approximately equal to Bar or atmosphere.

For example, if a device is given a value of PN10, then it is designed for a pressure not exceeding 10 Bar.

Determination of PN according to the standard

The highest excess operating pressure at a working medium temperature of 293 K (20 °C), which ensures a given service life (resource) of valve body parts having certain dimensions, justified by strength calculations for the selected materials and their strength characteristics at a temperature of 293 K (20 °C).

Russian standards: GOST 26349-84, GOST 356-80, GOST R 54432-2011

European standards: DIN EN 1092-1-2008

American standards: ANSI/ASME B16.5-2009, ANSI/ASME B16.47-2006


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A series of video tutorials on a private home
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Page 1

Test pressure at hydraulic test pipelines is maintained for 5 minutes, after which it decreases to the operating value. At operating pressure, the pipeline is inspected and the welds are tapped with a hammer to identify welding defects. The results of the pipeline test are considered satisfactory if during the test there is no pressure drop on the pressure gauge, and no signs of rupture, leakage or fogging are found in the welds, pipes, housings, fittings and other elements.

The test pressure is maintained for 5 minutes, after which it is reduced to working pressure. At operating pressure, the pipeline is inspected by tapping the welds with a hammer weighing no more than 0 5 kg. The results of the hydraulic test are considered satisfactory if the pressure has not decreased, and no signs of rupture, leakage or sweating are found in welds, pipes, valve bodies and other parts.

The test pressure during hydraulic testing of pipelines must be maintained for 5 minutes, after which the pressure must be reduced to operating pressure. At operating pressure, the pipeline is inspected and the welds are tapped with a hammer weighing no more than 1-5 kgf.

The test pressure must be maintained for 5 minutes, after which it is reduced to working pressure. At operating pressure, inspect the steam pipeline and tap the welded joints with a hammer weighing no more than 1-5 kg. A hydraulic test is considered satisfactory if there is no pressure drop on the pressure gauge while maintaining the test pressure in the steam pipeline and its elements (in welds, valve bodies, flange connections, etc.

The test pressure for cylinders made of a material whose tensile strength to yield strength ratio is more than 2 can be reduced to 1 25 working pressure.

The test pressure in the boiler must be created by a hand pump. When using machine driven pumps, a gradual and planned increase in pressure must be ensured.

Test pressure is an excess pressure at which the fittings must be subjected to a hydraulic test with water for the strength and density of the material at a temperature not exceeding 100 C.

The test pressure for hydraulic tests is 1 25 rrab, but not less than 3 kgf/cm.

Test pressure during hydraulic testing is selected in accordance with the nominal pressure. For all pipes, as well as fittings, flanges and studs supplied for installation, the manufacturer draws up a factory certificate, which indicates their design characteristics and the grade of steel used.

The test pressure for cylinders made of a material whose tensile strength to yield strength ratio is more than 2 can be reduced to 1 25 working pressure.

The test pressure for cylinders made of a material whose ratio of tensile strength to yield strength is more than 2 can be reduced to 1 25 of the working pressure.

The test pressure for cylinders made of a material whose tensile strength to yield strength ratio is more than 2 can be reduced to 1 25 working pressure.

The test pressure determined from this table at temperatures from 200 to 400 C should not exceed the working pressure by more than 15 times, and at a wall temperature above 400 C - by more than 2 times. When testing tall apparatus, it is necessary to take into account the hydrostatic pressure of the liquid column, therefore, for example, when columns are tested hydraulically before installation in a horizontal position, then to the value of the hydraulic test pressure determined from Table. 3, add hydrostatic pressure, which will be when filling the column with water in a vertical position. In all cases, the stress in the walls of the vessel during hydraulic testing should not be more than 90% of the yield strength of the material at 20 C.