Shut-off valves are a type of pipeline valves that perform the function of shutting off the flow of a liquid (water, gas or any other fluid). This type of reinforcement is characterized by a wide distribution - about 80% of total parts used. Trial-bleed and control-bleed valves used to control the level of liquid (water, gas or any other fluid) in tanks, sampling, expelling air from upper cavities, drainage, etc. - also types of shut-off valves.

The material for the manufacture of these parts can only be ductile iron or stainless steel. This is due to the fact that inner surface valves are constantly in contact with water, steam, gas, oils and other chemically active media - however, metal corrosion in this case is categorically unacceptable due to the fact that if the integrity of the wall is damaged, the medium will leak.

Important! Due to its functionality, shut-off valves has found application in a variety of industries.

Depending on the area of ​​​​use, it can be divided into two types:

1. Shut-off valves, which are used in special conditions (“narrow profile” use);
2. Shut-off valves with some general technical application;

Examples of full-opening shut-off valves are plug valves, valves, valves with a through channel, which has the structure of a Venturi tube.

Important!!! What types of parts are used the most?

Cork faucet

Production reached its maximum volumes in industrial scale the following parts from the category of shut-off valves:

1. Cranes,
2. Valves (valves),
3. gate valves
4. dampers.

Brief description of each type of part

It should immediately be noted distinguishing feature shut-off valves - their dimensions do not exceed 300 mm in the diameter of the passage. These parts are applicable exclusively in dead-end sections of the liquid supply system (water, gas or any other fluid). In addition, they can also be used for spindle bellows seals.

In addition to this variety of parts, the so-called ball valves and dampers of a simple design have gained recognition among hydraulic masters due to their reliability and multifunctionality.

An important advantage of gate valves is their relatively simple structure: short length, low hydraulic resistance. They are classified into two types: parallel two-disk and wedge. In the event that the pressure exerted by a liquid or gaseous medium is insignificant, then double-disk valves should be used, high pressure necessitates the installation of wedges (the wedge itself can be solid, elastic or composite).

Detailed characteristics of cranes. Their classification, functional characteristics and scope.

It is difficult to even imagine how wide the scope of their application is - pipelines, water pipelines, steam pipelines and gas pipelines are necessarily equipped with these parts. As a rule, taps with small dimensions and low resistance are used. The mass of this kind of part is from 0.881 kg to 8.64 kg. Diameter d in inches from one to three.

According to another classification (structural), most often used the following types valves: cork and ball. They, in turn, are divided into tension and stuffing boxes (the main criterion for the difference is the way they are sealed). Connection to the pipeline is carried out using a coupling, flange or welding. Plug valves (gas, coupling, cast iron) have found application on pipelines through which natural gas. Attachment is carried out using a threaded coupling. It should be noted that the normal functioning of these types of cranes is possible with the following indicators: operating pressure— Pp=0.1 MPa, tp< 50°С.

Another type of cranes is stuffing box (coupling cast iron). They are necessary on pipelines, through which the transit of water or oil is carried out. Required temperature for successful functioning is tp< 100°С. Особенности строения заключаются в том, что основные детали крана (корпус, пробка, сальник, заполненный пенькой или резиной) сделаны из чугуна.

In the event that it is necessary to install a valve on the pipeline large diameter, you should opt for a ball valve with small size, low resistance and high quality. If a gas or liquid (water, or any other fluid) will be supplied over a wide temperature range through the same pipeline, it is necessary to use a flanged steel valve with lubrication or with nozzles for welding. It can be controlled both remotely and manually, using a flywheel.

control valve

Detailed characteristics of shut-off valves. How are they divided, what do they consist of, what is the scope of their application?

In this case, as a rule, devices (valves) with remote control or with flywheel control are used.
The choice of the valve is based on the temperature of the liquid or gas that will be transported through the pipeline.

1. In the event that it is intended to transport water (gas or any other fluid), the temperature of which does not exceed 50 ° C, it makes sense to install cast-iron shut-off coupling valves.
2. If the temperature of the transported will be in the range strictly from 45 to 50 degrees Celsius, then it makes sense to use shut-off valves with an electromagnetic drive, which can be controlled manually, since they work from an electromagnetic drive.

The main functions and structural features that characterize dampers

The use of these parts is justified only if the diameter of the pipeline is about 2200 mm. These parts are characterized by a number of very advantageous advantages:

1. The maximum possible simplicity of the device, in which, as always, it shows the greatest efficiency.
2. They are easy to manage.
3. Their price is quite acceptable and weight. As a rule, dampers are controlled manually, however, reinforced dampers are sometimes produced using a hydraulic or pneumatic drive. Important point- remote control is possible only in the case of dampers with a diameter of 300-1600 mm at Ru = 1.0 MPa.
4. Very rarely repairs are needed.

How is a damper different from a valve, which is used much more?

Considering that dampers are, by definition, short devices and their use is justified only on highways and technological productions. The structure of the valves implies the presence of a movable or immovable spindle. Actually, it is for this reason that there are different types of valves. Naturally, their repair also depends on the type.

In the event that the spindle is movable, then such valves can be electrically driven. Wedge gate valves have a fixed, flanged, cast-iron spindle. Naturally, thanks to this, they are characterized by remote control.

The use of double-disc gate valves with a fixed stem made of cast iron is justified if fuel gas or water with a temperature of up to 100 ° C is transported through the pipeline.

If fuels and lubricants are being transported, then it is necessary to install steel valves so that they do not have to be constantly repaired.

What fittings are needed when working with aggressive media?

All valves that are applicable in the case of transporting substances that are in themselves an aggressive environment, without bringing them to a temperature, are subject to exactly the same classification, but with a slight difference - it is divided into the following types: taps, valves, gate valves.

The most common shut-off devices will be: diaphragm valves, ball valves, hose valves, but the most famous and frequently used are stainless steel bellows shut-off valves (if used, repairs to these parts are almost never required).

But just the valves, on the contrary, did not gain popularity in Russian Federation(precisely during the transportation of aggressive media through the pipeline), for a number of reasons, one of which is the repair that these parts will constantly need during such operation.

So it turns out that in the vast majority of metallurgical enterprises that are successfully operating in our country, the most common chemically aggressive substance is sulphuric acid. It is precisely this that is supplied through the pipeline and provides a continuous process for the production of steel and many other alloys, for which it received the second name - the bread of ferrous metallurgy. So the impact of this particular substance has become the most common reason for the need to repair installed valves.

conclusions

The use of various elements of valves is necessary for the normal functioning of any pipeline, regardless of what is supplied through it - be it gas, water or some other chemically active liquid. By controlling the elements of the shut-off valves (this happens both manually and automatically), it is possible to regulate the pressure in the system. Thanks to advanced technologies, a large number of the most diverse elements of shutoff valves (valves, taps, gate valves, dampers) have already been designed, each of which ideally performs a particular function. In the photos above, there are images of various parts that are already installed in the pipeline (or just manufactured) and thanks to them, the safe control of the entire fluid supply system is ensured.

You may be interested in:

→ Types and types of pipeline fittings

• Ball valves, valves, shut-off valves, gate valves, butterfly valves, pressure regulators, temperature regulators, elevators, hydraulic elevators, filters, vibration compensators, subscriber mud collectors, locking devices and level indicator frames.
• Mixing and control valves, taps and distribution valves.
• Safety and non-return valves, impulse-safety and diaphragm-bursting devices.
• Check valves and three-eccentric gate valves, non-return-shut-off and non-return-operated valves, gate valves(guillotine type).
• Steam traps.

1. Shutoff valve

The main purpose of valves is to block the flow of the working medium in the pipeline. For this, four main types of pipeline fittings are used: taps, valves, gate valves and butterfly valves (you should not forget about the difference between gates, as one of the elements of a shut-off body, and a gate - a type of pipeline fittings). They differ in the way the flow is blocked, i.e. the shape of the main part (or parts) of the shutter, the nature of the movement of the shutter relative to the seat (or seats) of the body, as well as the direction of movement of the shutter in relation to the direction of the medium flow.

In a ball valve, the valve has the form of a body of revolution (i.e. a cone, ball or cylinder) with an opening for the passage of the medium. When the flow is blocked, the valve rotates around its axis in one revolution.

Depending on the shape of the valve, which is called a cork in ball valves, valves are divided into cone, ball and cylindrical.

In cone ball valves, it is necessary to create the necessary pressing force on the conical surfaces of the plug and body. This can be done in two ways. One of them is using a threaded pair (the nut is screwed onto the threaded shank of the plug) or a spring. Such cranes are called tension. The second way is by tightening the stuffing box, which presses the plug against the conical surface of the housing and at the same time blocks the outlet of the working medium to the atmosphere. Such a valve is called stuffing box or plug-gland.

According to the shape of the flow part, it is possible to distinguish between two-way and three-way valves.

In a valve, the plug (commonly referred to as the spool) moves back and forth in a direction that matches the direction of fluid flow through the seat.

With all the variety of designs of shut-off valves, we note only their differences in the shape of the flow path for the passage of the working medium - straight and angular. Among the check valves, direct-flow valves stand out, the external sign of which is the location of the spindle not perpendicular, but obliquely to the axis of the passage of the body.

In gate valves, the shut-off body has the shape of a wedge or disk (s), moves, as in valves, reciprocating, but perpendicular to the flow axis. This closes or opens the passage of the working medium through the annular seats of the body.

Depending on the design of the shutoff valve, valves are divided into parallel, wedge, hose and gate valves.

In parallel gate valves (30ch6br - the brightest representative of this type), the body seats and, accordingly, two gate discs are located parallel to each other. The shutter is pressed against the body in the “Closed” position, as a rule, due to the wedge device placed between the shutter disks. In wedge gate valves (30ch39r type MZV) the body seats are located at an angle to each other. The shutter is made in the form of a wedge or two disks located at an angle. There are also valves with only one flat closing element working with self-sealing. Such valves are called gate valves (guillotine type).

Wedge and parallel gate valves are available with a non-rising or rising stem. They differ in the location of the spindle thread - inside the valve or outside the working environment. The former are smaller in size, but they have less favorable conditions for the operation of the threaded pair, the spindle - running nut.

There is also a shut-off valve, in which the flow of the medium is shut off by pinching an elastic (usually rubber) hose, inside which the medium passes. The hose - a special branch pipe - is placed inside the body. The movement of the parts that pinch the hose is reciprocating and perpendicular to the direction of the medium flow - as in gate valves. Such products are called - SHINGED VALVES.

In butterfly valves, the locking element (shutter) has the shape of a disk. Opening and closing of the passage of the medium through the annular seat in the body occurs by turning (usually by 90 degrees) the shutter around the axis perpendicular to the direction of the flow of the medium. In this case, the axis of rotation of the disk is not its own axis. It should be noted that the shape of the disc, in the middle of which its axis of rotation passes, somewhat resembles a butterfly, because of this, sometimes butterfly valves are called “Butterfly-type shutter”.

Very often it is necessary to control the liquid level in vessels, containers, boilers. For this, level indication systems are used, consisting of water gauge glasses (Klinger glass) and locking devices (12b1bk, 12b2bk, 12b3bk, 12s13bk, 12nzh13bk, 12kch11bk). The shut-off devices of the level indicators are adjacent to the shut-off valves (as intended) and are used to release air when filling the system, as well as when replacing the water gauge glass.

A complete set of shut-off devices, including top and bottom devices (respectively installed above and below the glass) and a drain cock for purging. Locking devices are of tap or valve type. The latter usually have special valves, automatically blocking the passage of the medium in case of glass breakage. Locking devices are operated manually.

2. Control valves

Adjusting the parameters of the working environment includes many functions. This includes adjusting the flow rate of the medium, maintaining the pressure of the medium within the specified limits, and mixing various environments in the required proportions, and maintaining a given level of liquid in the vessels, and others. However, depending on various conditions operation apply different types control valves. Usually, this is control using external energy sources on command from sensors that record the parameters of the medium in the pipeline. Automatic control directly from the working environment is also used.

At the same time, although not so common, manual control is used - the shutter is manually set to a certain constant position relative to the seat in the body. This ensures the given maximum flow working medium through the passage section of the regulating body.

The requirements for each type of control, taking into account the parameters of the working media (pressure, temperature, chemical composition, etc.), determine the variety of design types of control valves. The most common are control valves, direct acting pressure regulators, level regulators and mixing valves.

3. Distribution fittings

Of the most commonly used, two types should be mentioned: three-way valves and electromagnetic distribution valves (or electromagnetic distributors).

The three-way distribution valve is similar in terms of its main design characteristics passage crane. But if the latter has two branch pipes for connecting to the pipeline, then the distribution valve is three-way, i.e. has three connecting branch pipes; one input and two output. Accordingly, the design of the valve gate allows, when it is turned, to direct the flow of the working medium in the required direction. The control of such cranes is usually manual.

The distribution valve (distributor) with an electromagnetic drive is intended for remote control hydraulic or pneumatic actuators of valves, by sampling air from several objects and for some other functions.

Four-way distributors are serially produced, which have connecting pipes for receiving the working medium, supplying it to the right direction and for the release of the spent environment. They are used to control double-acting actuators. The control is carried out by an electromagnetic drive. There are also various designs of three-way, four-way and multi-way valves with various types electromagnetic drives.

4. Safety fittings

To ensure the protection of the pipeline and equipment in the system from overpressure, three types of fittings are mainly used: safety valves, impulse safety devices and diaphragm rupture devices. General principle their action is as follows: if the process mode in the system is violated, the pressure of the working medium rises to a value that can lead to damage to the pipeline and equipment. Under these conditions, the safety devices automatically operate, relieving excess working medium until normal working pressure in the pipeline is restored.

Differences in actuation methods and, accordingly, designs protective devices determined by the specific conditions of their operation.

Safety fittings also include breathing valves, which protect oil tanks from an unacceptable increase or decrease in pressure arising under the action of temperature conditions environment.

The safety valve, preventing an emergency increase in pressure, opens and releases part of the working medium from the pipeline, after which it closes, restoring the working pressure. The valve plug in the closed position is pressed against the seat by a force that counteracts the pressure on it from the working medium. According to the method of creating this force, the valves are divided into lever-truck and springs. In lever-load valves, the pressure of the medium on the spool is counteracted by the force transmitted from the load fixed on the lever. V spring valve- spring force.

The manufactured valves provide for the possibility of using them in various pressure ranges of the working medium at which the valve must operate.

In lever-loaders, this is done by setting a load of a certain mass on the corresponding lever arm, in spring ones, by more or less preload (adjustment) of the spring.

In lever-load valves, a lever is used for this, on which the load is fixed. In spring - a lever specially designed for this purpose.

An important characteristic is the lift height of the spool when actuated, since this determines the capacity of the valve. According to this characteristic, safety valves are divided into full-lift, in which the lift height is 1/4 or more of the seat diameter, and low-lift, where this figure is not more than 1/20.

Lever-load valves - low-lift, spring - both small and full-lift.

The impulse safety device (SPU) performs the same function as the safety valve, but is used to protect systems with high operating parameters when it is necessary to discharge large quantities of the working medium. IPU consists of a main safety valve with a large throughput and a pulse valve that controls the main valve actuator.

The impulse valve opens on command from the sensor at the appropriate pressure of the working fluid and directs it to the piston actuator of the main valve, which at the same time opens and dumps the excess amount of fluid. IPUs are used at thermal power plants for steam at high pressures and temperatures, as well as in systems of nuclear power plants.

The diaphragm rupture device is used on pipelines with high toxicity or aggressiveness of the working environment, when leakage through the shut-off body of the safety valve is absolutely unacceptable. The purpose of such a device is to reliably separate the process line from the outlet under normal operating conditions of the plant, and in the event of emergency pressure by breaking the membrane, open the exit for the excess medium. Of course, after operation, the destroyed membrane should be replaced.

Breather valves are designed to protect tanks of oil and light oil products from destruction and deformation due to excessive pressure increase or vacuum formation.

In these cases, the valves automatically provide communication between the gas space of the tank and the atmosphere. The valve body has two seats (one for pressure, one for vacuum). On each saddle there is a shutter pressed by weights. When the pressure in the tank changes beyond allowable limits, a passage is opened for entering the tank atmospheric air under vacuum, or for the release of the vapor-air mixture from the tank at excess pressure.

5. Protective fittings

During the operation of the pipeline system, situations may arise when separate sections pipeline, a technological or emergency pressure drop occurs, and the operating pressure is maintained in neighboring sections. In such cases, the so-called reverse flow of the working medium occurs, which is unacceptable in relation to the equipment and pipeline (water hammer, pump failure, etc.). To prevent the formation of reverse flow environments, such types of automatically operating fittings as check valves and check valves are used.

Such fittings are installed, for example, behind pumping unit to protect it from backflow of the medium.

Check valves have a gate in the form of a spool and, in rare cases, a ball that reciprocates along the direction of the medium flow through the body seat. Basically, they are intended for installation only on horizontal sections of the pipeline. Exceptions are valves with a spring to seat the spool on the seat, valves specially designed for vertical positioning, as well as valves with mesh (receiver) for installation in a vertical suction line before the pump.

In check gates, the gate element (gate) rotates around a horizontal axis located above the axis of the valve seat, as a rule, outside through hole saddles. The shutter is made in the form of a disk, often called a flap.

Check valves can be installed on both horizontal and vertical pipelines. There are several valves that are installed only on horizontal pipelines of large diameters.

In addition to working only automatically, there is a protective fitting, the design of which provides for forced control. check valve or a gate having forced closing is called a non-return shut-off valve, and having forced closing and opening is called a non-return-controlled valve.

6. Phase separation fittings

During the operation of power and heating installations, part of the steam, condensing, turns into water. For automatic removal of condensate from the system, which is not involved in the working or technological process, condensate traps are used.

There are steam traps - thermodynamic, float and thermostatic.

In a thermodynamic steam trap, the valve is a plate that lies freely on the body seat. The plate rises above the seat, opening the condensate outlet, and is pressed against the seat after it exits. This process occurs automatically with changes in pressure under the plate and above it, which is caused by differences in densities and temperatures of steam and condensate.

Some thermodynamic steam traps are equipped with a device (bypass) for forced opening and purging.

In a float trap (sometimes referred to as a “steam pot”), as condensate accumulates, the float floats up, controlling the release of condensate.

In a thermostatic steam trap, the shutter opens the condensate outlet under the influence of a bellows thermostat or a bimetallic element, the operation of which is based on the use of the expansion of bodies during heating and the temperature difference between steam and condensate. The use of certain types of steam traps is determined by the specific conditions of the installations and their operation.

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Under shutoff valves understand a variety of devices designed to control the flow of fluid transported through a pipeline.

Depending on the purpose, it is divided into:

1. Shut-off - which is designed to completely shut off the flow of fluid from pipelines (gate valves, valves, taps, valves).

2. Shut-off - non-return fittings - which serves to pass fluid in one direction and lock in the opposite direction (check valves).

3. Safety - which provides a partial release or bypass of the working fluid when the pressure rises to a value that threatens the strength of the system, and also prevents the reverse flow of fluid (safety valves).

4. Control valves - for flow control and level maintenance (valve control and level controllers).

gate valve- a locking device in which the passage is blocked by the translational movement of the shutter in the direction perpendicular to the flow of the transported medium.

Compared to other types of valves, gate valves have the following advantages: low hydraulic resistance with a fully open passage; lack of turns in the flow of the working medium; the possibility of using high-viscosity media to shut off flows; ease of maintenance; relatively small building length, the possibility of supplying the medium in any direction.

Disadvantages common to all designs of gate valves include: impossibility of application for media with crystallizing inclusions: small allowable pressure drop across the gate (compared to valves) low gate actuation speed; the possibility of obtaining a hydraulic shock at the end of the stroke; high height of the difficulty of repairing worn sealing surfaces of the shutter during operation.

Gate valves are divided into:

1. steel - for high pressure

2. cast iron - for pressure up to 16 kgf / cm 2.

Gate valves come with a rising spindle and non-rising, when the flywheel itself rises when opened. They come with parallel dies, maple, the passage section overlaps in a vertical plane.

At sight constructive type valves should be based on the following:

1. type of working environment;

2. chemical composition working environment;

3. working environment pressure;

4. operating temperature;

5. the presence of reasonable requirements for the tightness of the shutter;

6. pipeline diameter.

Wedge gate valves with a solid wedge are mainly designed for tight shutoff of pipelines with high operating pressure of non-aggressive media, both liquid and gaseous.

Wedge gate valves with an elastic wedge are mainly used for tight shut-off of pipelines with oil and gas media high temperature and high operating pressure. It is not recommended to use valves of this type for operation in crystallizing media or in media with mechanical impurities.

Gate valves with a compound wedge are mainly recommended for pipelines with an average working pressure of the medium, both liquid and gaseous, without solid and abrasive inclusions. The temperature of the working medium is set depending on the materials of the sealing surfaces of the valve.

Parallel valves are designed for installation in pipelines in processes where sufficient shutoff of the pipeline is not required at large values working pressure. The medium may contain a small amount of mechanical impurities.

Single disc gate valves are used, as a rule, for pipelines with high t and average pressure of the working medium, in which it is required to ensure the passage of the medium in case of incomplete blocking of the pipeline. With increased requirements for the tightness of the passage overlap, the most acceptable medium is non-crystallizing liquids with a sufficiently high viscosity, for example, oil, fuel oil, etc.

Double-disc gate valves are recommended for tight closing of pipelines with medium pressure of the working medium (both liquid and gaseous) containing a small amount of mechanical impurities. The medium temperature depends on the material of the valve sealing surfaces.

Gate valves with elastic sealing of the gate are designed for hermetic closing of pipelines with low temperature and medium pressure of the working medium, both liquid and gaseous.

Gate valves with a rubberized coating of the inner cavity are used for tight shutoff of pipelines with working media that are highly aggressive at low operating temperatures, as well as containing abrasive inclusions.

Gate valves with a bypass (bypass) are mainly used for pipelines with a high pressure of the working medium.

Valve- the locking device is mounted on the spindle, the flow area is blocked in the horizontal plane.

According to the design of the body, the valves are divided into: straight-through, angular, direct-flow and mixing.

Essentially important is the classification of valves according to their purpose: shut-off, shut-off and control and special. In turn, regulators can be subdivided according to the design of throttle devices into valves with profiled spools and needle valves. Similarly, shut-off valves are divided into poppet and diaphragm valves according to the design of the valves, and according to the method of sealing the spindle into stuffing box and bellows valves.

Globe valves are designed for installation in straight pipelines.

Disadvantages: relatively high hydraulic resistance; the presence of a stagnation zone; large building dimensions; the complexity of the hull design and relatively large weight.

Angle valves are designed to connect two parts of the pipeline, located perpendicular to each other or for installation at a turn. They operate at working medium pressures less than 64 kg/cm2 and at low temperatures.

Straight valves. Advantages: relatively low hydraulic resistance; compact design; no dead zones. Disadvantages: long length and relatively large weight.

Mixing valves are used for mixing two streams of a liquid medium in order to stabilize its temperature, concentration of reagents, dilute the main medium, maintain quality, etc. A simpler solution to the mixing scheme is obtained by using mixing valves, in which two streams are mixed directly in the body of one valve. Their use gives a high economic effect due to the fact that instead of 2 valves and a special mixer, only one valve is used.

Diaphragm valves (membrane) are designed to shut off media flows at low temperatures (up to 100-1500C) and the absence of a stuffing box; stagnation zones and pockets; low hydraulic resistance; small dimensions and weight. The main disadvantage is the relatively short service life of the membrane.

Bellows valves are designed to operate in environments where leakage into the surrounding atmosphere is unacceptable due to high cost, aggressiveness, toxicity, explosion or fire hazard, poisonousness, etc. The advantages are the complete elimination of leakage of the working medium and the reliability of the sealing element.

Shutoff and control valves provide the possibility of manual or remote control of the flow of the medium by changing the hydraulic resistance of the throttle pair with reliable fixation of intermediate positions even in case of accidents in the drive supply line or with difficult access to the valve, and also reliably shut off the pipeline.

Needle valves can be either shut-off valves or control valves. They have found wide application in the regulation and throttling of small gas flows, with large pressure drops across the throttling device.

Tap- the passage section is opened or closed with a plug, used for diameters up to 50 mm, for pressures up to 40 kgf / cm 2

Conical valves can be divided into the following types: tension, gland valves with lubrication and valves with clamping (or lifting) plugs.

Tension valves are used for mass production and normal service conditions (for example, kitchen gas valves). They are mainly used for free-flowing or viscous media where high liquid or gas tightness is not required. Tension valves are mainly used for low operating pressures (up to 10 kg / cm 2) or for media, the passage of which in environment not dangerous.

Stuffing valves are widely used in liquid and gaseous media at pressures of 6-40 kg/cm 2 .

Lifting plug valves are not recommended for media containing solids and slurries, as the ingress of solids between the body and the plug can cause loss of tightness with damage to the sealing surfaces, as well as for polymerizing or very viscous media.

Cylindrical valves can be divided into 2 groups: metal seal valves and elastic seal valves.

Valves with a metal seal are mainly used for high-viscosity media (fuel oil, coal tar pitch, etc.)

Valves with an elastic seal are mostly used with a metal plug and a non-metallic elastic seal in the seat.

Ball Valves are used with lubrication and for high media pressures and large passages (mainly for gas and oil pipelines). They are divided into 2 types: floating plug faucets and floating ring faucets.

Floating plug valves come in 2 main types: lubricated metal rings, non-metal rings made of pure plastics, rubbers.

Bellows valves are very expensive to manufacture due to the increased requirements for manufacturing accuracy. The presence of a lifting plug - do not allow it to be used in viscous and polymerizing media.

Shut-off valves are one of the most common types of pipeline valves and are designed to shut off the flow of the working medium with a certain tightness. According to experts, the number of valves is about 80% of the total number of applied pipeline valves. As a result of archaeological excavations, it was found that people used shutoff valves already more than 5 thousand years ago. In ancient Egyptian manuscripts, information was found on the organization of water supply and the use of rotary and disc valves. With a more careful study of the scope of valves and a certain share of the assumption, one can see the principles of its operation even in humans and animals: with the help of the so-called “living valves”, the flow of fluid removed from the body is blocked.

To shut-off valves, depending on design, include taps, valves, gate valves and butterfly valves. Sometimes the term valve is erroneously replaced by the term valve - this is wrong and in serious technical literature such a replacement is not allowed. It should also be noted that according to GOST R 52720-2007 2007 “Pipeline fittings. Terms and definitions” it is not recommended to use the terms damper; butterfly valve; hermetic valve; hermetic valve instead of the term butterfly valve.

Tap

A valve is a type of pipe fittings in which a locking or regulating element, having the shape of a body of revolution or part of it, rotates around its own axis. Cranes are made of metals and their alloys or plastic. Cranes are non-full bore and full bore. In non-full bore valves, the diameter of the inner hole is less than the diameter of the pipe to which it is connected, and in full bore valves, these diameters are the same.

One of the modern and most progressive types of valves is the so-called ball valve, which is increasingly used in various fields of technology and in everyday life. The design of the ball valve is quite simple and has been known for over 100 years. However, initially it was not as widespread as it is now, due to the inability to provide reliable overlap working environment flow. Later, new materials appeared that made it possible to guarantee the reliability of shutting off the flow of the working medium and significantly reduce the effort required to operate the crane. In ball valves, the flow of the working medium is shut off by a rotating spherical plug, inside which there is a through hole. Depending on the problem being solved, when the sphere is rotated by 90o, either the working medium flow is completely blocked or this flow is completely opened. Intermediate positions of the sphere are possible. In this case, the ball valve acts as a regulator of the flow of the working medium. Ball valves undoubtedly have a number of advantages over other types of valves. These advantages include:

• simplicity and reliability of the design;
• high tightness;
• relatively small size;
• the simple shape of the flow part and the absence of stagnant zones in it;
• convenient management;
• short time and little effort required to turn.

A valve is a type of pipe fittings in which a locking or regulating element in the form of a body of revolution or part of it rotates around its own axis, arbitrarily located in relation to the direction of the flow of the working medium. In essence, the valve is a temporary obstruction in the pipe and is most often used to automatically release excess fluid. This prevents accidents caused by excessive pressure of the working medium on the pipeline walls. Structurally, the valve consists of a body, a cover, a seat, a shutter (flap) and a stem. The working medium enters the valve body and, depending on the task being solved, completely or partially blocks its flow. In this case, the flow of the working medium can either change its direction of movement or keep it unchanged.

A gate valve is a type of pipeline fittings in which the locking or regulating element moves perpendicular to the axis of the flow of the working medium. The locking element of the gate valve is a gate valve, which slightly goes beyond the flow of the working medium. The tightness of the flow shutoff is ensured by pressing the gate against the seat by the pressure of the flow of the working medium. It is not recommended to use valves to partially shut off the flow of the working medium, because in this case, vibrations arise, which will soon lead to the destruction of the reinforcement. Gate valves are available in parallel, wedge, rising or static stem.

A butterfly valve is a type of valve in which the locking or regulating element is in the form of a disk that rotates around an axis perpendicular or at an angle to the direction of flow of the working medium.

Most often, butterfly valves are used on pipelines of large diameter and at low pressures of the flow of the working medium. Most typical applications butterfly valves are:

• water, heat and gas supply and distribution systems;
• ventilation and air conditioning systems;
• fire extinguishing systems;
• when working with abrasive and slightly aggressive working environments.

It is to the operation of butterfly valves in such areas that increased requirements to reliability and tightness.

As noted at the beginning of the article, up to 80% of pipeline valves belong to the category of shut-off valves. The scope of its application is unusually wide - these are ultra-high and ultra-low pressures, ultra-high and ultra-low temperatures, the toxic and abrasive nature of the working environment, etc. Thanks to the improvement of the design and the use of new materials, there is a constant expansion of the scope of stop valves and the tasks solved in this case. Selecting the required fittings is sometimes extremely difficult. In such cases, it is preferable to turn to the services of specialists with a large amount of versatile knowledge and rich experience. Often only such specialists can solve the problem of selecting the required fittings, their installation and maintenance.

Shut-off valves are necessary to control various gases and liquids transported through the pipeline. It can be divided into fittings for general technical purposes and used in special conditions.

The material for the creation of fittings are cast iron and steel. This choice of material is due to the fact that the inner surface of the reinforcement must withstand interaction with chemically active media and be resistant to corrosion, which can lead to seal failure and leakage of the medium.

Without armature safe use pipeline is not possible.

Fully opening fittings, namely plug valves, valves, fittings with a through channel, having the structure of a Venturi tube, belong to shut-off valves.

Any locking device has the following characteristics:

• the diameter of the pipeline on which it is mounted;
• meaning overpressure in a pipe at a temperature of 20 °C.

There are four types of valves.

Cranes are the most popular type of locking parts. It is used when working with different media: liquids, gas, steam. Its size can be from two and a half centimeters to eight, and its weight can be from 0.5 to nine kilograms. Attach valves to the pipe using a flange, coupling or welding.

By structure, valves are divided into cork and ball.

Plug valves are commonly used in the transportation of natural gas, oil, water, steam, lubricating oils. Devices of this type have a number of significant disadvantages:

• it is necessary to constantly monitor that the crane does not stick to the body;
• the need to use a gearbox to create a large torque;
• they can wear unevenly, which can cause pipe depressurization.

Ball valves are a part consisting of a body and a plug, and are used for pipelines with a large diameter, if the temperature of the working medium is constant. These cranes are characterized small size. Currently, they are mainly used in living conditions: in plumbing and heating systems, household appliances using water, etc.

According to the principle of sealing, cranes are classified into tension and stuffing box. The main parts of stuffing box valves are made of cast iron. They are installed on pipes through which fluids are transported. Gland valves are operated at temperatures up to 100 °C.

valves

Shut-off valves are used only to shut off the flow and do not allow to influence the pressure in the pipeline. The size is not more than 300 mm in the diameter of the passage. The design includes a spool mounted on a descending spindle. When the working medium is shut off, the spool is lowered onto the seat. To avoid water hammer, it moves parallel to the flow.

According to the method of sealing, valves are:

• stuffing boxes;
• bellows;
• diaphragmatic.

As a rule, large valves are connected to the pipe by means of a flange connection, and couplings are used to secure small valves. For high pressure applications, thick-walled devices are used, which are connected to pipes by welding.

The control is carried out using a flywheel or an electric drive. Some of them can be controlled from a distance.

When choosing a valve, you need to focus on the temperature of the substance that will be transported through the pipes.

For the medium, the temperature of which will not rise above 50 °C, devices made of cast iron are used, connected to the pipeline by means of a coupling. Sealing ring they are made of leather, and the pads are paronite. The glands are filled with asbestos.

If the temperature range is narrow and strictly between 45 and 50 °C, electromagnetically driven devices can be installed. The spool and cover are steel, and the body is made of ductile iron. During installation, the actuator must be installed in the top position.

Valves are installed only in the dead ends of the fluid supply system, and are also used for the bellows seal of the spindle.

damper

The dampers are mounted on pipelines with a diameter of about 2200 mm. They can be used provided that the pressure in the pipes is low. Management is carried out manually, using a hydraulic or electric drive. The drive is available only for dampers with a diameter of 300 to 1600 mm and a nominal pressure of 1.0 MPa.

Motorized dampers must be installed with the motor at the top with the drive shaft vertical. There are no installation restrictions for non-actuated dampers.

The damper is arranged very simply, but at the same time it is not inferior to other types of valves in terms of efficiency.

The locking mechanism is a rotary disk, which can move around its axis, which is perpendicular or at an angle to the flow. For most dampers, the body is made of cast iron, and the rotary disc is made of steel. Due to the fact that cast iron is capable of contact with chemicals, the damper can be used for pipelines transporting acids and alkalis.

Flanged connection or welding is used for installation.

Flanged dampers are installed on the water supply. A rubber ring is inserted into the groove of the rotary disk of such a damper, sealing the locking mechanism. The body is made of cast iron, the rotary shaft is steel.

This type of shut-off valve has a number of advantages:

• low price;
• light weight;
• they are easy to operate;
• able to pass the working environment, which contains solid particles;
• they practically do not break and rarely need repair.

Gate valve and its differences from the valve

Due to the structural features, the use of dampers is advisable only on highways and technological productions. In contrast to them, the design of gate valves includes a spindle, which, depending on the type, can be retractable or non-retractable.

Rising stem valves can be optionally equipped with an electric drive. Thanks to this, they can be controlled from a distance.

Gate valves are used in pipelines with non-aggressive working media. They are able to withstand high temperatures and pressures.

When working with fuel gas, the temperature of which can reach 100 °C, two-disc wedge gate valves from cast iron. Their spindle is non-retractable. The lining material is paronite. There are cast iron rings on the discs and body, which serve to increase the tightness of the locking mechanism. These shutters do not have a remote control.

To work with coke oven gas, two-disc wedge gate valves are mounted on pipes, in which the spindle extends. All parts, except for the steel spindle, are made of ductile iron. Gate valves with a diameter of 1300 mm can withstand a temperature of 200 °C and a working pressure of 1.8 MPa. Devices with a diameter of 1500 mm are used at a working pressure of 0.05 MPa and 85 °C.

The control is carried out using an electric drive with a power of 3 kW.

Welded steel wedge gate valves are installed on the pipes through which oil and oil are pumped. The spindle is retractable. They withstand up to 250 °C. The installation position can be any.

What shut-off valves are needed when working with aggressive media

When working with aggressive media, taps, valves and gate valves are used. To choose the right reinforcement, you need to take into account the substance with which it will come into contact.

Due to the hermetically sealed seat/spool connection and low friction, valves are predominantly used in these applications. To work in liquid media It is recommended to use valves made of brass. If you have to work in high temperature conditions, bellows valves are installed that can operate at temperatures up to 350 ° C.

In order for the valves to be used when working with aggressive substances, they must have corrosion resistance, therefore steels flanged valves made of porcelain and glazed to resist corrosion. Diaphragm valves coated with rubber are also used.

Valves are least often used to work with aggressive substances, since they must be covered with corrosion-resistant steel, which is unprofitable. In addition, if the valve has a rising stem, then it requires regular maintenance.