Pipeline fittings are a range of structures installed on pipelines for the purpose of controlling the transported medium by changing the actual cross-sectional area of the pipe. Technical requirements and nomenclature of pipe fittings of industrial and domestic type are given in the regulatory document GOST No. 52720 “Pipeline fittings”.
This article presents the classification of pipeline fittings. We will consider its varieties, functional purpose, design features and study the marking of reinforcement products.
Contents of the article
Classification of pipe fittings
According to the provisions of GOST, pipe fittings divided into groups based on the following factors:
- functional purpose;
- scope of application;
- device control method;
- method of connection to the pipeline;
- sealing principle.
The main classification parameter is the functional purpose; according to it, the following types of pipeline fittings are distinguished:
- Shut-off valves are structures designed to completely shut off the flow of medium circulating through a pipeline. Shut-off products, in turn, are divided into drain valves (used to remove the transported medium from the pipeline) and control valves (blocks the flow and supplies the working medium to instrumentation).
- Control valves - used to regulate the throughput of a pipeline. It is divided into throttle valves - due to an increase in hydraulic flow resistance, and shut-off and control valves - which combines the functions of two types of fittings and is the most commonly used pipe fittings today.
- Protective (cut-off) valves - installation of shut-off valves is carried out to protect the equipment connected to the pipeline and the pipeline itself in emergency situations. The fittings block and disconnect the failed part of the pipeline from the circulation ring, which makes it possible to carry out the required renovation work. A type of protective fitting is one that prevents the possibility of reverse flow of the circulating medium.
- Safety valves are structures that automatically relieve excess pressure in the system, which protects equipment and the pipeline from overloads.
- Distribution fittings - installation is carried out in two adjacent pipelines if it is necessary to combine and mix their flows.
- - structures used for either routing a highway into several channels. This group includes all kinds of bends, crosses, etc. The material of manufacture of the connecting fittings corresponds to the material of the pipeline (production of both steel and polypropylene and polymer products has been established).
Depending on the scope of application, all pipeline fittings are divided into industrial and household. Household fittings are used for gas pipelines, water pipes and heating pipes. The class of industrial fittings, in turn, is divided into the following groups:
- steam;
- water;
- oil;
- chemical;
- gas;
- food
A separate subgroup includes ship fittings used on military and civilian ships, which have an increased reliability class.
According to the control method, pipeline fittings are divided into two types - automatic and controlled. Controlled valves can have several types of drives:
- manual drive;
- mechanical drive (electric, pneumatic, hydraulic or electromagnetic type);
- remote drive - a control structure that is remote from the valve and connected to it through a transmission (shaft, cable, gears or bearings)
Depending on the method of connection to the pipeline, pipe shut-off valves are:
- flanged;
- coupling;
- tsapkova;
- fitting;
- welding
The last classification factor is principle of sealing fittings, according to which structures are divided into:
- stuffing box - at the junction of the fittings and the end part of the pipeline, seals made of asbestos, graphite, fluoroplastic or;
- bellows - instead of elastic materials, metal ones are used for sealing;
- membrane - structures in which the membrane simultaneously performs a sealing and locking function;
- hose - a compressible rubber hose is used as a sealing material.
Marking of pipeline fittings
Marking of pipeline fittings is carried out in accordance with the provisions of GOST No. 4666-75 “Pipeline fittings”. The marking consists of a series alternating letters and numbers, example - 30s941nzh2, where:
- 30 — type of fittings (valve);
- c — material of manufacture (carbon steel);
- 9 — drive type (electric);
- 41 — model number;
- nzh - type of sealing material (stainless steel bellows seal);
- 2 - execution option.
You can find a breakdown of each nomenclature component of the marking in the tables of TsKBA (Central Design Bureau of Valve Engineering).
Operating principle of pipeline fittings (video)
Types of pipeline fittings
Shut-off pipeline valves, the most common type of fittings, have several design options. Pipe shut-off valves are divided into the following types:
- damper (butterfly valve);
- valve (valve);
- tap.
In which the covering structure moves parallel to the movement of the circulating flow. There are two types of valves - wedge and parallel. The flow is blocked by a valve in which the seals are placed at an angle to each other. The shutter, depending on the design, can be rigid, elastic, or made in the form of two alloy steel disks.
Valves are divided into types according to. Designs with a rotating (not retractable) spindle are used in pipelines transporting corrosively neutral media, in which long-term exposure of the spindle does not provoke destruction of the material (oil, water); in the chemical industry, the installation of plugs with a retractable spindle is practiced. Powerful steel valves can withstand flow pressure up to 25 mPa.
A valve is a fitting that shuts off the flow due to the reciprocating movement of the valve inside the pipeline. The valve, in most cases, has a flat valve, the cross-section of which corresponds to the internal diameter of the pipe. The valves are manufactured with a flange connection, providing high level tightness.
Depending on the material, steel (stainless steel or alloy steel) or bronze. There are linear, angle and mixing valves; the latter are installed when it is necessary to maintain the required temperature, concentration or density of the transported medium.
A valve is a fitting that shuts off a pipeline by rotating around its own axis of the locking disk. Dampers are structurally similar to valves, however, they have significantly smaller dimensions and a wider scope of use - these fittings, in addition to industry, are in demand in heat and water supply, and sewerage systems.
The tap is the most common type of shut-off and control valve in household use. The locking part in the faucet is located in the direction of the flow of the circulating medium; it can be made in the form of a conical element.
Shut-off valves can be installed on pipelines transporting liquid or gaseous media. The advantages of this fitting include compact dimensions, simplicity and maintainability of the design, and minimal activation time.
Depending on the type of design, the valves can be straight-through, corner or (three-way) in which two inlet pipes are connected to the central outlet, which allows mixing several working media with each other.
Shut-off valves
In the “Accessories” section we will look at shut-off valves. Without shut-off valves, it is impossible to imagine any pipeline system. Shut-off valves – These are pipeline fittings that are widely used and usually account for up to 80% of the total number of products used. The name “shut-off valves” means well-known valves, ball valves, gate valves, and so on. With their help, you can open or, on the contrary, close the movement of liquid or gases in the desired direction or depending on the requirements of the ongoing technological process. Shut-off valves are used in various pipeline systems, be it a heating system, gas supply, steam pipelines, water supply, sewerage or other engineering systems. Without fittings it is impossible to imagine the stable operation of various equipment, both industrial and household use. Of the variety of types of fittings, valves, ball valves, gate valves and gate valves are most widely used. Some of the main parameters of any type of shut-off valve are: the connecting diameter to the response device, the materials from which the body and working part are made, and the closing speed. For reliable and long term operation, shut-off pipeline valves must have high strength, corrosion resistance, tightness and high reliability. Regarding the installation method, all shut-off valves are designed so that their installation does not take much time. Depending on the area of use, fittings are made from various synthetic and polymer materials, as well as cast iron, bronze, steel, brass, titanium and aluminum.
By purpose shut-off pipeline valves divided into the following categories: industrial, sanitary, marine, special order. Industrial fittings are divided into general industrial pipeline fittings for special conditions work and special.
- Industrial pipeline fittings are used in various industries and the national economy. It is produced serially and in large quantities, intended for heating systems, for water supply systems, steam pipelines, city gas pipelines, etc.
- general industrial pipeline fittings for special operating conditions are used for operation in conditions high pressures and temperatures, low temperatures, on corrosive, toxic, radioactive, viscous, abrasive and granular media. This category of fittings includes: corrosion-resistant, cryogenic, fountain, heated fittings, fittings for abrasive hydraulic mixtures and for bulk materials.
- Special The fittings are developed and manufactured according to special orders and their use is specified by technical regulations.
- Ship's pipeline fittings are manufactured and used for operation in special operating conditions, on river and sea fleet vessels, taking into account special requirements for minimum weight, increased reliability, vibration resistance, as well as special control and operating conditions.
- Plumbing pipeline fittings are mounted on various household appliances: gas stoves, boilers, columns, bathtubs, showers, sinks, etc. These products are produced in batches in huge quantities at specialized enterprises. It has small connection diameters and is operated manually, with the exception of pressure regulators and gas safety valves.
- By special order developed and manufactured according to special orders and special technical requirements. These can be experimental or unique industrial installations. For example: fittings for nuclear power plants.
Main classes of shut-off valves
According to its functional purpose, pipeline shut-off valves is divided into the following main classes:
- "constipation" used to block or stop the flow of working fluid or gas with a certain tightness;
- "regulating" used to regulate the flow of liquid or gas by controlling process parameters (pressure, temperature, etc.);
- "distribution - mixing" used to distribute the flow of working fluid or gas in given directions or to mix their flows;
- "safety" designed for automatic protection of pipelines and equipment from unacceptable excess pressure by relieving excess liquid or gas pressure,
- "protective" (cut-off) intended for automatic protection of pipelines and equipment from unacceptable or unforeseen technological process changes in parameters or direction of flow of working fluid or gas, as well as to shut off the flow;
- "phase separating"(condensate drains, air vents, oil separators) are used for automatic separation of working liquid or gas depending on their condition and phase.
In this article we will look at shut-off valves. This class of devices is mounted on pipelines and is designed to change the flow rate of liquids or gases, up to its complete cessation. Shut-off valves include:
- Valves;
- Valves;
- Cranes;
- Valves;
- Shutters.
Gate valve is a product of industrial pipeline shut-off valves in which the regulating or shut-off element, a valve in the form of a sheet, disk or wedge, performs reciprocating movements perpendicular to the axis of the flow of the working medium. This is the most common type of fittings . Valves can be found at facilities belonging to housing and communal services, at industrial facilities and various pipelines. Valves are divided into full bore, in which the diameter of the seat is equal to the diameter of the pipeline, and truncated, where the diameter of the seat is less than the diameter of the pipeline. Valves are mounted on pipelines with a connecting diameter of more than 50 mm, where it is necessary to smoothly regulate the flow rate in order to prevent the occurrence of The valve design is shown in (Fig. 1).
The valve consists of the following main components. The body (Fig. 1) is made of cast iron or steel. On the rod (Pos. 6), when the flywheel (Pos. 7) rotates, the disk (Pos. 2) performs reciprocating movements. The cover (Pos. 5) is attached to the valve body using tightening bolts and nuts (Pos. 4).
Such widespread use of valves can be explained by a number of their advantages, including:
- simple design;
- small construction length;
- used in various operating conditions;
- low hydraulic resistance.
The last advantage of valves is especially valuable when used in main pipelines, where very high fluid movement is characteristic.
The main disadvantages of valves include:
- large construction height (in valves with a rising spindle, this is due to the fact that the full stroke of the valve is one passage diameter);
- long time required to open or close;
- development of sealing surfaces in the valve and body;
- difficulty in carrying out repairs during operation.
The industry produces valves with a retractable spindle or stem, and with a non-retractable stem. They differ in the design of the screw pair with which the shutter moves. Valves with a non-rising stem have a significantly smaller construction size. Thanks to their symmetrical design, the valves can be mounted on pipelines without taking into account the direction of movement of the working medium. Gate valves come in wedge and parallel types. This fitting is used at pressures from 2 to 200 atmospheres (bar). The nominal diameter ranges from 8 mm to 2 m. In air conditioning and ventilation systems, an analogue of valves is a gate valve, which is a rectangular a metal sheet, moving in the guides perpendicular to the central axis of the air duct. Now, due to the rapid development of technology and technology, valves are increasingly being replaced when laying new pipelines by products for shutting off water with a circular movement of the actuator, gates, or as they are often called “Butterfly” type valves.
Valve It is a control pipe fitting, with the help of which it is possible to change the flow rate in the pipeline. With the help of valves, the required pressure in the pipeline is maintained, or liquids are mixed in a given proportion. The locking element in the device is located on the spindle. The rotational movements of the flywheel in one direction or the other are converted into reciprocating movements of the spindle and the locking element. The shut-off element regulates the flow of liquid passing through it. The spindle rotates either manually, with little effort, or using servo drives. Most consumers most often encounter this type of valve in everyday life; it can be found in apartments and cottages or in suburban areas, etc. The most common type of valve is a walk-through valve, which is mounted on straight sections of pipelines. In apartments, valves are installed on the cold and hot water supply pipelines. The main disadvantage of valves is the rather large hydraulic resistance. Direct-flow valves do not have this disadvantage, which are installed in those places of pipelines where it is unacceptable to reduce the liquid flow rate at its outlet. The valve structure is shown in (Fig. 2).
The valve also consists of a housing (Pos. 1). The housings are made of cast iron, steel, brass or bronze. Cast iron valves are general technical shut-off valves, which have become very widely used, are manufactured with flange and coupling connections, are characterized by a low price and are easily accessible. Steel valves are most often used in technological processes with harsh operating environment parameters, as well as with high reliability requirements, and are manufactured with a flange connection. Brass and bronze valves are manufactured in a coupling design and are very often installed in heating systems, hot and cold water supply of buildings and structures. The product is connected to pipelines, depending on the design, using flanges (Pos. 8), coupling connections or welding. The direction of flow of the working medium is always indicated on the body of the device (Pos. 9). The flow of the working medium is adjusted using a spool valve (Pos. 2) mounted on the rod (Pos. 5). The rod seal (Pos. 4) is designed to prevent the working fluid from flowing through the rod. The spindle sealing assembly may use a gland, bellows or membrane design. The rod rotates using a flywheel (Pos. 6). The cover (Pos. 10) is sealed using a gasket (Pos. 7) and secured to the valve body using bolts and nuts (Pos. 3). This design of the valve allows it to be easily repaired during operation.
Shut-off valve (ball)- another type of shut-off pipeline equipment used in Lately very popular and has come to replace valves. The device of a shut-off valve is a very simple body and a shut-off element, which can be made in the form of a ball (ball) or in the form of a cylinder (cylindrical) and, most rarely, with a conical shut-off device. Based on performance, shut-off valves are divided into full bore and non-full bore. A full bore ball valve has a bore hole equal to the diameter of the connecting hole. A non-full bore valve has a flow hole that is smaller in diameter than the connecting diameter. The shut-off valve operates in two modes, open or closed. Its main task is to block the flow of the working environment passing through it. The shut-off valve design can be seen in (Fig. 3)
The ball valve consists of a body (Pos. 1) made of brass or stainless steel or plastic. The closing element ball (Pos. 2) is made of brass. The seats are sealed on both sides with Teflon O-rings (Pos. 3). After assembling the ball valve, the entire structure is closed with a nut (Pos. 4) made of brass. Using a rod (Pos. 5) made of brass, you can control the position of the ball (open or closed). A handle (Pos. 6) made of steel or aluminum is mounted on the rod, which is secured with a nut (Pos. 7).
The most widely used ball valves are made of brass and various grades of steel. These are stainless steel, molybdenum steel and regular carbon steel. There are also ball valves that are made of plastic, polyethylene or polypropylene, materials resistant to aggressive environments. Plastic products have low tightness and are sensitive to mechanical impurities in the working environment. Their main difference from products made of metal is the scope of application. Plastic ball valves are sensitive to the high temperature of the working environment, and it is best to install them in cold water supply systems and hot water supply systems with hot water temperatures up to 65 C. Due to the large coefficient of linear expansion, approximately ten times more than in metals, in systems These products should not be used for heating. The impact of high temperature on the plastic parts of the ball valve causes them to deform and the seal is broken. Application area stainless steel taps- This main pipelines with a diameter of 50 mm. They are designed to operate at high pressure and temperature. For domestic purposes, the use of stainless steel taps is too expensive.
Check valves is a protective pipe fitting that prevents the reverse flow of liquid or gas in pipelines. The purpose and types of check valves were discussed in more detail
Gates This is a compact shut-off valve made of steel or special alloys, providing high tightness when closing. In this case, the flow of the working medium can be adjusted so that it flows in the optimal mode or is completely blocked. This pipeline fittings are the simplest and most convenient to use and have affordable price. In the gate, the regulating (closing) element rotates around the axis on which it is fixed. Butterfly type butterfly valve is the most common type of this type of pipeline fittings. Butterfly valves, according to the type of materials used to seal the shutoff of the flow of the working medium, are used with a soft seat seal, with a metal-to-metal seal, with a Teflon coating of the shutting parts of the valve. The butterfly valve design is shown in (Fig. 4)
Butterfly valve device
The Butterfly valve is a body (Pos. 1), which can be made of steel or cast iron. Inside the housing there is a moving part, a rotary disk (Pos. 3), which rotates around its axis. The rotary disk is pressed against the rubber O-ring (Pos. 2). Thus, the flow of the working medium is blocked. For ease of installation, the valve body has special eyes (Pos. 4). The handle (Pos. 5) and the handle position lock (Pos. 6) are used to rotate and lock the rotary disk in various angular positions. You can control the position of the shutter, depending on the required applied force, using a handle, through a gearbox or using an electric drive. Such operational properties Butterfly rotary dampers, such as ease of installation and replacement of sealing elements, small construction dimensions and weight, as well as durability (up to 100 thousand openings and closings) and relatively low price, have given impetus to their widespread use in heating, water supply and air conditioning systems.
Methods of installation to the pipeline
Depending on the method of connection to pipelines, the following types of industrial shut-off valves: coupling, nipple, welding fittings, coupling, pin, flange, fitting.
- Coupling fittings its connection to pipelines is made using couplings with internal threads.
- Nipple fittings it is attached to pipelines using nipples.
- Weld fittings its installation to the pipeline is carried out by welding. This method of installation to the pipeline has both advantages and disadvantages. Thus, high-quality installation of fittings has absolute tightness in the connection, the weld does not require maintenance (tightening of flange connections), but has certain problems in the case of repairs when replacing fittings elements.
- Tightening fittings (wafer) its fastening to pipelines is carried out using studs and nuts;
- Flange fittings its connection to pipelines occurs using flanges. This method of fastening makes it possible to repeatedly install and dismantle the fittings. Very high installation strength and the ability to operate the valves in a wide range of operating pressures and diameters. The disadvantages of this installation method include loosening of fasteners during operation and loss of tightness of connections, as well as large weight and dimensions.
- C upholstery fittings (American women) its installation to the pipeline is carried out on an external thread with a collar for sealing using union nuts.
- Union fittings attached to the pipeline using fittings.
Working pressure
Depending on the nominal pressure of the working medium, pipeline fittings can be divided into: vacuum, low, medium, high and ultra-high pressure.
- Vacuum(medium pressure less than 1 atmosphere)
- Low pressure(from 0 to 16 atmospheres)
- Medium pressure(from 16 to 100 atmospheres)
- High pressure(from 100 to 800 atmospheres)
- Ultra high pressure(from 800 atmospheres).
Temperature
Depending on the operating temperature, shut-off valves are divided into:
- Cryogenic (working temperature below minus 153°C)
- For refrigeration(working temperature from minus 153°С to minus 70°С)
- For low temperatures(working temperature from minus 70°С to minus 30°С)
- For medium temperatures(working temperature up to 455°C)
- For high temperatures(working temperature up to 600°C)
- Heat resistant(working temperature over 600°C)
Control methods
Remote control fittings does not have a direct control, but is connected to it using rods, speakers and other devices.
Drive fittings control is carried out using an actuator (directly mounted on the valve or remotely).
Automatic valves The gate is controlled without the participation of the operator, but directly under the influence of the parameters of the working environment, on the gate or on the sensor, or through the influence of the control environment on the valve drive, as well as by signals received by the drive from ACS devices.
Manual valves Control is carried out manually by the operator, remotely or directly.
Thank you for your attention
Gate valves include locking devices in which the passage is blocked by translational movement of the gate in the direction perpendicular to the flow of the transported medium. Valves are widely used to shut off flows of gaseous or liquid media in pipelines with nominal diameters from 50 to 2000 mm at operating pressures of 4-200 kgf/cm 2 and medium temperatures up to 450 °C. Sometimes valves are made for higher pressures.
In the gas industry, valves are used to equip wellheads, at field collection points, main and distribution gas pipelines, pipelines of compressor and gas distribution stations.
Compared to other types of shut-off valves, gate valves have the following advantages: low hydraulic resistance with a completely open passage; no turns in the flow of the working medium; Possibility of use for shutting off flows of highly viscous media; ease of maintenance; relatively short construction length; Possibility of supplying the medium in any direction.
The disadvantages of valves include: the impossibility of using for media with crystallizing inclusions, a small permissible pressure drop across the valve (compared to valves), low valve actuation speed, the possibility of water hammer at the end of the stroke, large height, difficulties in repairing worn sealing surfaces of the valve when operation.
The working cavity of the valve (Fig. 13.3.), into which the medium transported under pressure is supplied, is formed by the body 3 and the top cover 7. This cavity is sealed using a gasket 5, which is pressed by the cover to the body. The valve body is a one-piece, cast or welded structure. As a rule, it has a height equal to two diameters of the blocked passage. On the body, symmetrically to the spindle axis, there are two pipes with which the valve is connected to the pipeline. The connection can be either welded or flanged.
Inside the body there are two annular seats 1 and a valve 2, which in this case is a wedge with welded sealing annular surfaces. In the closed position, the sealing surfaces of the valve are pressed against the working surfaces of the housing rings from the drive.
Fig. 13.3. Gate valve:
1-saddle; 2-shutter; 3-body; 4- running nut; 5-sealing gasket; 6-spindle; 7-top cover; 8-ring gasket; 9-oil seal; 10-press bushing; 11-flywheel.
Sometimes the sealing surfaces are obtained directly from the housing. However, such a design solution can hardly be acceptable for all valves, since when these surfaces wear out, it is easier and cheaper to replace replacement seats than to re-process the body during operation. In order to reduce wear and friction forces arising when the valve moves, the sealing surfaces of the seats and the valve are usually made of materials different from the body material by pressing, which allows them to be changed during operation.
In the upper part of the shutter 2 there is a running nut, into which a spindle 6 is screwed, rigidly connected to the flywheel. The screw-nut system serves to convert the rotational movement of the flywheel (when opening or closing the valve) into translational movement of the valve.
When the passage is blocked from one-sided pressure of the medium, quite significant forces arise on the valve, which are transmitted to the sealing surfaces of the seat. The magnitude of these forces depends on the pressure difference of the working medium in the pipeline before and after the valve and on the magnitude of the specific pressures on the sealing surfaces of the valve and seats, which must be ensured to hermetically shut off the flow of the working medium at a given operating pressure in the pipeline. The screw-nut system is the most rational, since it allows you to obtain a compact and simple-design drive with translational movement of the output element. It also makes it possible to obtain a translational movement of the drive with greater force in the direction of travel. In addition, since this design is self-braking, it virtually eliminates the possibility of spontaneous movement of the valve when the drive is turned off, which is very important for shut-off valves during operation.
The disadvantage of this system in this particular case should be considered that the screw-nut pair is located in the medium flowing through the working cavity of the valve.
The environment washes away the lubricant, hence increased wear of the pair. In addition, this design may not be applicable to all media.
Usually the valve is placed entirely in the operating environment, even when the passage is completely open. The seal at the point where the spindle exits the working cavity of the valve is ensured along the diameter of the spindle by a stuffing box device 9, which prevents the leakage of the working medium into the atmosphere.
The design of the stuffing box device is similar to the designs in valves and control valves. The stuffing box packing, usually made of asbestos cord impregnated with graphite to reduce the coefficient of friction, is pressed using a pressure sleeve 10. The stuffing box body is attached to the top cover 7. The connector area is sealed with an annular gasket 8.
There are a wide variety of valve designs. They are trying to classify them according to various criteria, associated with specific operating conditions, according to the chemical composition of the working environment and its parameters. Valves are classified by size operating pressures, operating fluid temperatures, drive type etc.
Classifications of this kind are incomplete, since they do not take into account the design features that allow, in addition to working in certain environments, to meet a number of requirements for valves in operation, and place many completely different types of valves into one class.
The most appropriate is classification valves according to shutter designs. Based on this feature, numerous valve designs can be grouped according to the main types: wedge and parallel gate valves.
By the same token wedge valves may be with solid, elastic or composite wedge.
Parallel gate valves can also be divided into single-disc and double-disc.
In a number of valve designs designed to operate at high pressure drops across the valve, in order to reduce the effort required to open and close the passage, the passage area is made slightly smaller than the cross-sectional area of the inlet pipes. Based on this feature, valves can be classified as full bore (gate diameter equal to the diameter of the pipeline) and with a narrowed passage.Depending on the design of the screw-nut system and its location (in the environment or outside the environment), valves can be with a retractable or non-retractable spindle.
Wedge valves
Wedge valves include valves whose gate looks like a flat wedge (Fig. 13.4.-13.5.).
In wedge gate valves, the seats and their sealing surfaces are parallel to the sealing surfaces of the valve and are located at a certain angle to the direction of movement of the valve. The gate in this type of valve is usually called a "wedge". The advantages of such valves are increased tightness of the passage in the closed position, as well as a relatively small amount of force required to ensure a seal.
Since the angle between the direction of the drive force and the forces acting on the sealing surfaces of the valve is close to 90°, even a small force transmitted by the spindle can cause significant forces in the seal.
The disadvantages of valves of this type include the need to use guides to move the valve, increased wear of the sealing surfaces of the valve, as well as technological difficulties in obtaining tightness in the valve.
Fig.3.14. Wedge valve:
1- spindle with long thread; 2- intermediate ring and graphite seal for PN 2.5 MPa and higher; for PN 1.6 MPa only graphite seal. Double graphite seal - upon request; 3- corrugated steel seal for valves of class 1.6 MPa, spiral seal for class 2.5 - 4.0 MPa and 8.0 - 10.0 MPa and connecting ring for 12.5 MPa and above; 4-guides in the valve body ensure centering of the wedge when opening and closing; 5- flexible wedge allows you to compensate for distortion of the seat surface and deformation of the body caused by water hammer in the pipeline; 6-spindle design prevents ejection; 7-way nut made of soft alloys, allows in case of emergency situation prevent the rod from breaking at the junction with the wedge due to stripping the nut thread; an 8-replaceable welded seal is included in the standard design, a screw-on seal is available upon request.
Fig. 13.5. Wedge gate valve with prestressed seal:
A 1-part thrust ring reliably holds internal pressure; a 2-piece thrust ring prevents deformation of the seal; 3-stainless steel insert ensures noiselessness and corrosion resistance; 4-Forged steel seal provides a larger contact area, increasing seal reliability; 5-sealed rod; A 6-flexible wedge allows you to compensate for the distortion of the surface of the seat and the deformation of the housing caused by water hammer in the pipeline; A 7-o-ring seat with #6 stellite coating is a standard design.
Solid wedge valves
An example of a valve design of this type is a valve with a rising spindle (Fig. 13.6). It consists of a cast body 1 into which sealing seats 2 are screwed. As a rule, they are made of alloyed, wear-resistant steel. Together with the body, guides 3 are cast and then machined to fix the direction of movement of the shutter (wedge).
Rice. 13.6.Full bore valve with solid wedge:
1 – body; 2 – saddle; 3 – wedge movement guide; 4 – wedge; 5 – spindle; 6 – top cover; 7 – hairpin; 8 – sealing gasket; 9 – guide sleeve; 10 – oil seal; 11 – pressure flange; 12 – yoke; 13 – nut; 14- flywheel.
Wedge 4 has two annular sealing surfaces and is hinged to spindle 5 through a spherical support. Top cover 6 is connected to the body by means of bolts or studs 7. To center the cover in relation to the body, the latter has an annular protrusion that fits into the groove of the body. The seal between the cover and the body is ensured by gasket 8, which is placed in the groove of the body. To prevent distortions of the spindle, a guide sleeve 9 is pressed into the upper part of the cover.
The stuffing box consists of a groove in the body where the packing is placed, an annular pressure sleeve and flange 11. The stuffing box is sealed by pressure flange 11.
A yoke 12 is mounted on the cover, on which a running nut 13 is located, usually made of antifriction alloys. The flywheel is rigidly connected to the running nut.
As the flywheel rotates, the nut causes the spindle and associated wedge to rise or fall. In the design of the connection between the gate (wedge) and the spindle (see Fig. 13.6.), the wedge can move in a direction perpendicular to the spindle axis. In this case, in the final position, the wedge freely enters the space between the seats even if the spindle axis does not coincide with the axis of symmetry of the valve. The use of such a connection somewhat reduces the cost of manufacturing valves and facilitates their installation after repairs under operating conditions.
The solid wedge gate valve is widely used because its design is simple and, therefore, low in manufacturing cost. The one-piece wedge, which is a very rigid structure, is quite reliable under operating conditions and can be used to shut off flows at fairly large pressure drops across the valve.
However, one cannot fail to note a number of significant disadvantages of this design, which include: increased wear of the sealing surfaces, the need for individual fitting of the seats and wedge during assembly to ensure tightness (this completely eliminates the interchangeability of the wedge and seats and complicates repairs), the possibility of the wedge jamming in the closed position as a result of wear, corrosion or under the influence of temperature (in this case, it is sometimes impossible to open the valve); the need for drives with high starting torque.
To avoid jamming, the sealing surfaces of the wedge and seats are made of dissimilar materials.
Valves with a solid wedge are produced with both a rising and a non-rising spindle.
Gate valves with elastic wedge
The gate design of this type of valve provides better seal passage in the closed position without individual technological adjustment, since the shutter is made in the form of a cut (or half-cut) wedge, both parts of which are connected to each other by an elastic (spring) element. Under the influence of the pressing force, which is transmitted through the spindle, in the closed position the latter can bend within the limits of elastic deformations, ensuring a tight fit of both sealing surfaces of the wedge to the seats.
This valve design is very promising, since, having the advantages of a valve with a solid wedge, a valve with an elastic wedge eliminates a number of its disadvantages. The resilient wedge valve allows for interchangeable gates and increased reliability at high temperatures (by reducing the risk of uneven thermal expansion causing the valve to jam). However, the danger of jamming in the closed position is still not completely eliminated.
Rice. 13.7. Gate valve with narrowed passage and elastic wedge:
1- body; 2-saddle; 3-shutter; 4-rack; 5-spindle; 6-top cover; 7 way nut; 8-rib.
Figure 13.8. Gate valve with elastic wedge and retractable
spindle:
1-body; 2-saddle; 3-shutter; 4-spindle; 5 way nut; 6-flywheel; 7-lin; 8-rack
In a valve with an elastic wedge (Fig. 13.7), gate 3 is a cut wedge with an elastic rib 8, which allows the sealing surfaces of the wedge to rotate relative to each other at a certain angle, which ensures a better fit to the sealing surfaces of the seats. This feature of the elastic wedge eliminates the need for individual technological adjustment of the seal and reduces the risk of jamming. Gate valves of this type are manufactured both with a non-retractable spindle (Fig. 3.7.) and with a retractable spindle (Fig. 13.8).
The drive force when opening such valves is somewhat greater than that of valves with a solid wedge, but the tightness of the valve is much higher.
Related information.
Federal Agency for Education
State educational institution of higher education
vocational education
"Ufa State Petroleum Technical University"
Department: “Transport and storage of oil and gas”
Test
on the topic: “Types of shut-off valves, their purpose and design”
Completed by: student of group GRz-07-02
Politaev M.A.
Checked by: teacher
Fazletdinov R.A.
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). This includes gate valves, taps, shut-off valves, and butterfly valves. The main purpose of shut-off and control valves is to shut off the flow of the working medium through the pipeline and let the medium in again, as well as to ensure the necessary tightness. The pipeline fittings plant monitors the quality of its products. Fittings are installed on pipelines of high and low pressure, units and vessels. Shut-off valves are designed to control: water, gaseous, vapor, gas-liquid mass by changing the area of the diameter of the opening. It must ensure reliable and complete overlap of the flow area. In principle, it should provide only two states - open or closed - and may not be intended for operation in an intermediate position of the working body.
According to their functional purpose, pipeline fittings are divided into the following main classes:
Shut-off valve - designed to shut off the flow of the working medium with a certain tightness;
Regulating - designed to regulate flow by changing the amount of working medium flowing through the pipeline. The control valves are controlled from an external energy source;
Distribution - designed to distribute the flow of the working medium in certain directions or to mix flows;
Safety - designed to automatically protect equipment and pipelines from unacceptable excess pressure by discharging excess working fluid., protective (cut-off) designed to automatically protect equipment and pipelines from unacceptable or unforeseen technological process changes in parameters or direction of flow of the working fluid, as well as to shut off the flow .
Phase separation - designed for automatic separation of working media depending on their phase and condition. These include steam traps, air vents and oil separators.
A gate valve is one of the shut-off valve devices. Here, unlike taps, the shut-off element does not perform a rotational movement, but a reciprocating one. The movement of the locking element occurs perpendicular to the movement of the liquid.
Chronologically, valves appeared as one of the first devices to shut off water flow. This is due to their sufficient simplicity and unpretentiousness in operation and repair. At present, due to the rapid development of technology and technological processes, valves are increasingly being replaced when laying pipelines by water shut-off devices with a circular movement of the actuator. Gate valves, like shut-off valves, are used mainly in two modes: open and closed, i.e. when the shut-off element is in its extreme positions. When using the valve in an intermediate position, it is destroyed work surface due to vibration caused by high-frequency movement of the actuator along and across the flow of liquid as it moves through the pipeline. The fastening elements of the actuator also become loose. As a result, the valve fails ahead of schedule.
Valves are divided into several types. Wedge, parallel, with retractable and non-retractable stem. They are used at pressures from 2 to 200 atmospheres. Nominal diameter from 8 mm to 2 m.
Figure 1 Gate valve ZMS-65-14 K1 HL (Baku)
Table 1 Specifications valves ZMS-65-14 K1 HL
| Specifications |
|
| 14 (140) | |
| 2.Nominal bore, mm | 65 |
| 393 (120) | |
| 4. Valve design | K1 |
| 5. Gate valve | Cast housing |
| 6. Established service life of the ZMS | At least 12-15 years |
| 7. Gate valve design | Non-retractable spindle |
| 8. Replacing cuffs | Under pressure |
Christmas tree equipment is designed for sealing wellheads, monitoring and regulating their operating mode, as well as for carrying out various technological operations in moderate and cold macroclimatic regions for environments containing CO2, H2S, and formation water. Assembled according to tee and cross type schemes in accordance with GOST 13846 - 84.
The following designations are adopted in the code for the Christmas tree fixtures: AF – Christmas tree fittings; design according to GOST 13846 – 84 schemes; a – double-row concentric suspension of lifting pipes; K – suspension of the lifting string on the thread of the pipe head sub (the letter is not written on the coupling suspension); E – for operating wells with ESP; B – method of valve control (remote and automatic); the first number is the nominal diameter of the barrel and side strings in mm; the second number is the working pressure; HL – Climatic performance for cold areas; corrosion resistance version: K1 – for environments containing CO2 up to 6%; K2 – for environments containing CO2 up to 6%; K3 – the same, H2S and CO2 up to 25%; K2I - for Christmas tree equipment made of low-alloy and low-carbon steel, using an inhibitor in the well.
The fittings include a pipe head, a fountain tree, shut-off devices with manual and pneumatic control, and chokes.
The pipe head is designed for hanging one or two rows of tubing, sealing them, as well as for performing technological operations during the development, operation and repair of a well.
The riser pipe columns are suspended on threads and coupling suspensions.
Hanging of columns on the thread is carried out: with a single-row elevator - on the thread of the stem coil; with a two-row elevator: the inner column is on the thread of the stem coil, the outer column is on the thread of the tee (cross) of the pipe head.
Hanging of columns on a coupling suspension is carried out: with a single-row elevator - on a coupling in the crosspiece of the pipe head; with a two-row elevator: internal - on the coupling in the tee of the pipe head, external - on the coupling in the cross.
Figure 2 Christmas tree fittings AFK 1 E65x21M K1 HL
(for ESP, RPM and flowing wells)
The tree is designed to direct well production to the flow line for regulating the operating mode, for installation special devices, when lowering downhole instruments or pigs to clean pipes from paraffin, measure the pressure and temperature of the medium, as well as for carrying out some technological operations.
Pass-through plug valves and direct-flow gate valves with forced or automatic feeding lubricants They are designed to cover flow holes in Xmas trees and wellhead equipment.
Table 2 Technical characteristics of the Christmas tree fittings AFK 1 E65x21M K1 HL
| Specifications |
|
| 1. Working pressure, MPa (kg/cm2) | 21 (210) |
| 2.Conventional bore, mm: trunk/side branches | 65/65 |
| 3. Temperature of the working environment is not more than K (C 0) | 393 (120) |
| 4. Hanging pipe | NKT-73 GOST 633-80 |
| 5. Type of locking device | Gate valve ZMS 65x21 |
| 6. Ensuring the replacement of cuffs in the MZS under pressure | 21 MPa |
| 7. Tee | Cast housing |
| 8. Gate valve | Cast housing |
| 9. Cross | Cast/forged body |
| 10. Adapter | Cast/forged body |
| Established service life of fittings and protective structures | At least 12-15 years |
To regulate the operating mode, adjustable or non-adjustable throttles with a replaceable bushing made of wear-resistant material are installed on the side strings of the tree.
Christmas tree fittings are classified according to their design and strength characteristics:
Working pressure (7, 14, 21, 35, 70, 105 MPa);
Execution scheme (6 schemes);
The number of rows of pipes lowered into the well;
Designs of locking devices;
The dimensions of the flow section along the wellbore (50-150 mm) and side branches (50-100 mm).
All Christmas trees are used with column heads OOK1 10"" ´ 9 5/8 ´ 6 5/8 - 210 or column heads designed by TsNIL "" GANG "".
Column heads, like casing pipes, are an integral part of the well design as an engineering structure. They are designed to suspend the next casing string, seal and control the pressure in the annular space between adjacent pipe strings.
Figure 3 Column head piping OKK1-35 K1 HL
The design of the column head, fountain fittings, and their piping schemes should ensure optimal modes well operation, sealing of the pipe, annulus and annulus space, the possibility of technological operations at the well, deep research, sampling and control of wellhead pressure and temperature.
The operating conditions of the casing head are quite complex: the load from the weight of the casing strings can exceed several hundred kilonewtons in deep wells. The elements of the column head also perceive the pressure of the medium in contact with them. Violation of the reliability of the column head inevitably leads to serious accidents and damage environment, and in some cases can cause fires, explosions, and accidents.
Figure 4 Rotary shutter
A valve is an element of pipeline shut-off valves, where the regulating (shut-off) element rotates around an axis that is not its own axis. The most common type of this type of pipeline valve is a butterfly valve, in which the control element is made in the form of a disk.
Depending on the type of ensuring the tightness of shutting off the flow of liquid, butterfly valves can be with a metal-to-metal seal, with a soft seat seal, or with a Teflon coating of the shutting parts of the valve. Depending on the type of connection to the water (pipe) wire system, the valves come with flanges for welding and for threaded connections.
The shutter can be controlled, depending on the force required to bring its moving part into working position, using a simple handle, through a gearbox, through a pneumatic drive or electric. The material and design of the valve must be such that it can work for the required period not only to open and close the substance passing through it, but also to regulate the volume passing through. To do this, the bolt handle is most often made with a lock, which allows you to lock the handle in various angular positions.
Such operational properties of valves as convenience and ease of installation and replacement of sealing elements, sufficient durability (up to 100 thousand openings and closures), and relatively low cost have led to their widespread use in the pipeline industry.
Figure 5 Stopcock
Shut-off valve is one of the types of shut-off equipment. Can be made from various materials: steel, brass, some kind of plastic, etc. But they all have the same device - a body and a locking element. The shut-off element can be made in the form of a cylinder (cylindrical valve) or in the form of a ball (ball valve). Less often in everyday life you can find a faucet with a conical shut-off device.
In terms of performance, shut-off valves can be full bore or semi bore. Half-bore valve - if the hole to be closed is smaller in diameter than the diameter of the pipes connected to the inlet and outlet. And, accordingly, full bore - when it is the same.
The main task of a stopcock is to stop the flow of liquid passing through it. That is, it has two working positions - open and closed. It is clear that if the faucet handle is turned not by 90 degrees, but, say, by 45, then the flow of passing liquid can be reduced, roughly speaking, by 2 times. Thus, by smoothly changing the angle of rotation of the handle, you can smoothly change the passing flow. However, this is not recommended, because depending on the pressure and composition of the liquid, the shut-off valve may be damaged, this especially applies to the sharp edges of the valve structure, which can wear off, as a result of which, when completely closed, the liquid may continue to ooze out at the outlet of the valve.
Shut-off valves are used both in industry (for transporting water, oil products, gas) and in everyday life, to shut off various parts of the water supply system if necessary.
Figure 6 Valve
Valves. This is another class of shut-off valve devices. Here the locking element is located on the spindle. The rotational movement in one direction or another of the spindle (using a simple flywheel or some devices) is converted into a reciprocating movement of the locking element, which regulates the flow of liquid passing through it. The spindle is rotated either manually (if the force is small) or using some kind of electric (hydraulic) motor.
The mass consumer is most familiar with this type of shut-off valves in everyday life, since various modifications of valves can be found in any apartment, in suburban area, in various kinds of public spaces, etc.
The most common type of valve is a straight-through valve, which is installed on straight sections of the pipeline. The main disadvantage is the fairly high hydraulic resistance and, as a consequence, the presence of a zone of stagnation of liquid in the area where such a valve is installed. A direct-flow valve, used in those places of the pipeline where a decrease in the liquid flow at the valve outlet is not allowed, does not have this drawback.
Also, the most common types of valves include angle valves (connects two mutually perpendicular parts of the pipeline) and mixing valves (they mix two liquid flows in order, for example, to maintain a given temperature).
Figure 7 Combined multifunctional valve type KKM
The combined multifunctional valve KKM-89x21 is designed for installation instead of a check valve in the tubing string assembly for oil production using electric centrifugal pumps (ESP)
Table 3 Technical characteristics of KKM
| Specifications | KKM-89x21 |
| ESP operating capacity for valve operation, m 3 /day | 80…800 |
| Outer diameter, mm | 89 |
| Length, mm, no more | 370 |
| Column lifting speed, no more, m/s | 0,3 |
| Nominal diameter of the passage hole, mm | 32 |
| Connecting thread according to GOST 633-80 | smooth tubing 73 |
| Weight, kg, no more | 10 |
| Working pressure, MPa | 21 |
In pipeline fittings, valves act as a kind of sensors combined with an actuator.
The main type is safety valves that automatically release (into the atmosphere or into special containers) excess liquid or gas (steam) from a pipeline when a pressure exceeds the permissible level. technical parameters, thereby preventing pipeline failure. According to the type of actuator, they can be spring and lever-load.
Regulating, bypass, distribution, mixing, and shut-off valves are also used, the purpose of which is easy to determine from their name.
Shut-off valves stop the flow of liquid or gas into the pipeline, starting from some section of it, when its flow is unacceptable (for example, when a pipe ruptures).
The bypass valve maintains a given pressure in a certain section of the pipeline circuit by partially opening and bypassing excess liquid or gas to another branch of the pipeline.
Distribution valves (three-way or multi-way) distribute flows of the working fluid into different sections of the pipeline, often from a control panel, and therefore they often have an electromagnetic drive.
Mixing valves are used when it is necessary to mix different media having both different temperatures, so different composition. Such valves are required to maintain a constant composition or temperature (or both).
Control valves. Their task is to regulate the flow of the medium flowing through the pipeline (liquid, gas). They are most often controlled from an external energy source.
Bibliography
1. Petroleum Production Engineer's Handbook
2. Shurov V.A. “Engineering and technology of oil production” M. Nedra, 1983
3. Boyko V.S. “Development and operation of oil fields” M. Nedra, 1990.
4. Catalogs of oil production equipment manufacturers
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→ Types and types of pipeline fittings
- Ball valves, gate valves, shut-off valves, gate valves, butterfly valves, pressure regulators, temperature regulators, elevators, hydraulic elevators, filters, vibration compensators, subscriber drains, locking devices and level indicator frames.
- Mixing and control valves, taps and distribution valves.
- Safety and check valves, pulse safety and membrane rupture devices.
- Check valves and three-eccentric gates, non-return shut-off and non-return controlled valves, gate valves (guillotine type).
- Steam traps.
1. Shut-off valves
The main purpose of shut-off valves is to block the flow of the working medium in the pipeline. For this purpose, four main types of pipeline fittings are used: taps, valves, gate valves and butterfly valves (it is worth not forgetting the difference between gates, as one of the elements of a shut-off valve, and a valve, a type of pipeline fitting). They differ in the way the flow is blocked, i.e. the shape of the main part (or parts) of the gate, the nature of the movement of the gate relative to the seat (or seats) of the body, as well as the direction of movement of the gate in relation to the direction of flow of the medium.
IN ball valve the valve has the shape of a body of rotation (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 in ball valves is called a plug, valves are divided into conical, ball and cylindrical.
In conical 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 cranes. The second method is by tightening the seal, which presses the plug against the conical surface of the housing and at the same time blocks the exit of the working medium into the atmosphere. Such a valve is called a stuffing box or plug-stuffing valve.
Based on the shape of the flow path, we can distinguish straight-through and three-way valves.
In a valve, the gate (usually called the spool) moves back and forth in a direction that coincides with the direction of flow of the working fluid through the seat.
With all the variety of designs of shut-off valves, we note only their differences in the shape of the flow part for the passage of the working medium - straight and angular. Among the straight-through valves, direct-flow valves stand out, external sign which is served by the location of the spindle not perpendicular, but oblique to the axis of the housing passage.
In gate valves, the shut-off element has the shape of a wedge or disk (disks), and moves, as in valves, back and forth, but perpendicular to the flow axis. In this case, the passage of the working medium through the annular seats of the housing is closed or opened.
Depending on the design of the shut-off element, valves are divided into parallel, wedge, hose and gate valves.
In parallel valves (30ch6br is the most striking representative of this type), the body seats and, accordingly, the two shutter disks are located parallel to each other. The shutter is pressed against the body in the “Closed” position, as a rule, due to a wedge device placed between the shutter discs. 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. Valves are also available with only one flat locking element, operating using self-sealing. Such valves are called gate valves (guillotine type).
Wedge and parallel gate valves are manufactured with a fixed or rising spindle. They differ in the location of the spindle thread - inside the valve or outside the working environment. The first ones are smaller in size, but they have less favorable conditions for the operation of the threaded pair spindle - running nut.
There are also shut-off valves in which the flow of the medium is blocked by pinching an elastic (usually rubber) hose, inside which the medium passes. The hose - a special pipe - is placed inside the housing. The movement of the parts that clamp the hose is reciprocating perpendicular to the direction of the medium flow - as in valves. Such products are called HOSE VALVES.
In butterfly valves, the locking element (gate) has the shape of a disk. Opening and closing the passage of the medium through the annular seat in the housing occurs by rotating (usually 90 degrees) the valve around an axis perpendicular to the direction of the medium flow. In this case, the axis of rotation of the disk is not its own axis. It should be noted that the shape of the disk, in the middle of which its axis of rotation passes, somewhat resembles a butterfly, which is why butterfly valves are sometimes called “Butterfly valves”.
Very often it is necessary to control the liquid level in vessels, containers, and boilers. For this purpose, level indicating systems are used, consisting of water measuring glasses (Klinger glass) and locking devices (12b1bk, 12b2bk, 12b3bk, 12s13bk, 12nzh13bk, 12kch11bk). Level indicator shut-off devices 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 meter glass.
A complete set of shut-off devices includes upper and lower devices (installed above and below the glass, respectively) and a drain valve for purge. Shut-off devices are of tap or valve type. The latter, as a rule, have special valves, automatically blocking the passage of the medium when the glass breaks. The locking devices are controlled manually.
2. Control valves
Adjusting the working environment parameters includes many functions. This includes adjusting the flow of the medium, maintaining the pressure of the medium within specified limits, mixing various media in the required proportions, maintaining a given level of liquid in the vessels, and others. Moreover, depending on various conditions operation apply different types control of control valves. Typically this is controlled using external sources energy on command from sensors recording the parameters of the environment in the pipeline. Automatic control directly from the working environment is also used.
At the same time, although it is not so common, it is used manual control- the shutter is installed manually in a certain constant position relative to the seat in the body. This ensures the specified maximum flow rate of the working medium through the flow area of the regulatory body.
Requirements for each type of regulation, taking into account the parameters of working media (pressure, temperature, chemical composition etc.), determine the variety of design types of control valves. The most common types are control valves, direct acting pressure regulators, level regulators and mixing valves.
3. Distribution fittings
Among the most frequently used, two types should be mentioned: three-way valves and electromagnetic distribution valves (or electromagnetic distributors).
A three-way distribution valve is similar in basic design characteristics to a straight-through valve. But if the latter has two pipes for connection to the pipeline, then the distribution valve is a three-way valve, i.e. has three connecting pipes; one input and two output. Accordingly, the design of the valve valve allows, when turning it, 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 of hydraulic or pneumatic drives fittings, by taking air samples from several objects and for some other functions.
Four-way distributors are commercially produced, which have connecting pipes for receiving the working medium, supplying it in the desired direction and for releasing the spent medium. They are used to control double-acting drives. The control is carried out by an electromagnetic drive. Also available various designs 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 pressure increases above the permissible level, mainly three types of fittings are used: safety valves, impulse safety devices and membrane bursting devices. General principle their action is as follows: if the technological process in the system is disrupted, the pressure of the working medium increases to a value that can lead to damage to the pipeline and equipment. Under these conditions, protective devices are automatically activated, releasing excess working fluid until normal operating pressure in the pipeline is restored.
Differences in operation methods and corresponding designs protective devices determined by the specific conditions of their operation.
Safety valves also include breathing valves that protect oil tanks from unacceptable increases or decreases in pressure caused by 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 shutter 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, valves are divided into lever-weight and spring. IN lever-weight valves the pressure of the medium on the spool is counteracted by the force transmitted from the load attached to the lever. In a spring valve, the force of the spring.
The manufactured valves provide the possibility of using them in different pressure ranges of the working medium at which the valve must operate.
In lever-load ones, this is done by installing a load of a certain mass on the corresponding lever arm, in spring ones - by preloading (adjusting) the spring more or less.
In lever-weight valves, a lever on which a weight is mounted is used for this purpose. In spring ones, there is a lever specially designed for this purpose.
An important characteristic is the lifting height of the spool when activated, since this determines the throughput 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 no more than 1/20.
Lever-weight valves are low-lift, spring valves are both low- and full-lift.
An impulse safety device (ISD) performs the same function as a safety valve, but is used to protect systems with high operating parameters when it is necessary to discharge large quantities of the working fluid. The IPU consists of a high-capacity main safety valve and a pulse valve that controls the main valve drive.
The pulse valve opens on command from the sensor at the appropriate pressure of the working medium and directs it to the piston drive of the main valve, which opens and discharges the excess amount of medium. IPUs are used at thermal power plants for steam at high pressures and temperatures, as well as in nuclear power plant systems.
The diaphragm rupture device is used on pipelines with a highly toxic or aggressive working environment, when leakage through the shut-off member 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 installation, and in case of emergency emergency pressure by destroying the membrane, open the exit for excess medium. Of course, after operation, the damaged membrane should be replaced.
Breather valves are designed to protect tanks of oil and light petroleum products from destruction and deformation due to excessive pressure increase or vacuum formation.
In these cases, the valves automatically ensure communication between the gas space of the tank and the atmosphere. The valve body has two seats (one for pressure, the other for vacuum). Each saddle has a bolt pressed with weights. When the pressure in the tank changes beyond permissible limits, a passage opens for atmospheric air to enter the tank under vacuum, or for the steam-air mixture to be released from the tank under excess pressure.
5. Protective fittings
During the operation of a pipeline system, situations may arise when a technological or emergency pressure drop occurs in certain sections of the pipeline, while in adjacent sections the operating pressure is maintained. In such cases, a 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 possibility of a reverse flow of the medium, types of automatically activated fittings such as check valves and check valves are used.
Such fittings are installed, for example, behind pumping unit to protect it from the reverse flow of the medium.
Check valves have a valve in the form of a spool and, in rare cases, a ball that performs a reciprocating movement along the direction of the medium flow through the body seat. They are mainly intended to be installed only on horizontal sections pipeline. The exceptions are valves with a spring that ensures the spool is seated on the seat, valves specially designed for vertical placement, as well as valves with a mesh (intake) for installation on a vertical suction line in front of the pump.
In check valves, the valve element (gate) rotates around a horizontal axis located above the axis of the valve seat, usually outside the seat bore. 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 the one that operates only automatically, there is a protective valve whose design provides for forced control. A non-return valve or valve that has a forced closure is called a non-return valve stop valve, and having forced closing and opening is a non-return controlled valve.
6. Phase separating fittings
During the operation of energy and heating installations, part of the steam condenses and turns into water. For automatic removal of condensate from the system that is not involved in operating or technological process, condensate traps are used.
There are thermodynamic, float and thermostatic steam traps.
In a thermodynamic steam trap, the valve is a plate that rests freely on the housing 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 and above the plate, which is caused by differences in the 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 called a “sweat trap”), as condensate accumulates, a float floats to the surface, controlling the release of the condensate.
In a thermostatic steam trap, the valve opens a hole to release condensate under the influence of a bellows thermostat or bimetallic element, the operation of which is based on the use of expansion of bodies when heated and the temperature difference between steam and condensate. The use of certain types of condensate traps is determined by the specific conditions of the installations and their operation.
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