The term "stop valves" refers to devices that control the flow force of a certain medium. Most often, elements of shutoff valves are present on pipelines. Next, we will understand what types of valves are divided into, what it is and where it is used.
Stop valves in pipelines are used to control the flow of liquids or gases. It is able to regulate the flow in piping systems from a minimum reduction in flow to its complete stop.
Some types of this equipment:
- cast-iron valves;
- control valves;
- cranes
- butterfly valves.
Application area
All these products are widely used in engineering systems and can be manufactured both for general technical use and for work in special conditions. If the valve is used only to completely block the flow, then valves that can be controlled by valves (valves and taps) can not only block the flow, but also regulate its intensity.
Device
All locking devices have a similar design. This is a closed sealed enclosure in which a stop valve assembly is located. In the case most often there are two (in some cases more) ends, through which it is tightly attached to the pipeline. The purpose of the locking unit is the hermetic separation of the pipeline system into parts. It consists of a saddle and a locking body, constantly in contact on the sealing surfaces.
Cranes
Cranes are used for installation on pipelines with water, steam and gas carriers. They are characterized by compact dimensions (1-9 kg) and low resistance. The diameter of the crane can be from 1 to 3 inches. The most common types of cranes are ball and cork. In accordance with the method of sealing, they are stuffing box and tension.
The tap is connected to the pipeline using a flange, a coupling, or by welding to it. On gas pipelines, gas coupling valves are used. The material for them is cast iron. A threaded sleeve is required to ensure that the pipeline is connected to the tap. Gas valves are designed to operate under pressure of 0.1 MPa and temperatures up to 50 ° C.
Higher loads withstand stuffing box valves. They serve oil pipelines and water pipelines, their main parts are made of cast iron. At the same time, cast iron stuffing box is stuffed with rubber or hemp. Such cranes are capable of operating at pressures up to 1 MPa and can withstand temperatures up to 100 ° C.
The smallest sizes are ball valves. This equipment is famous for its high quality work, which predetermined its use in large diameter pipelines. They are made of cast iron, and the o-rings are made of fluoroplast-4. The operating parameters of ball valves correspond to the characteristics of stuffing box valves.
Using flanges, flanged steel valves are connected to the pipelines. If the crane is large, it is equipped with a worm gear. To adjust the flow in such a valve is a flywheel. This equipment is used on gas pipelines operating in the temperature range from -40 ° C to +70 ° C. Such cranes are mounted only vertically. Management can be both remote and by means of a flywheel.
Stop valves
Valves play a critical role in a large number of pipeline network regulators. This is the most common stop valve. What is it can be seen in the picture.
These are parts that have a shutter having the shape of a cone or flat plate that moves parallel to the axis of the sealing surface of the body seat back and forth or in an arc.
Valve - a type of valve, the movement of the shutter of which is carried out by means of a threaded pair.
The most common shut-off valves installed on pipelines. Adjustment in them occurs in manual mode using a flywheel or remotely using an electric drive.
The strength of the seal is provided by rings made of leather, rubber or PTFE-4. Shut-off valves are used in pipelines whose working medium is air, steam or water. A threaded sleeve is used to connect to the pipe. To fill the gland, the AP-31 asbestos packing is used - a cord of woven asbestos threads with antifriction impregnation.
In water supply systems with a water temperature of less than 50 ° C, shut-off valves for couplings are installed. This equipment is able to work in any position. In this case, water enters under the spool. The device case is cast-iron, gaskets are paronite, the o-ring is made of leather, and the stuffing box packing is asbestos-based.
In pipelines for transporting air or water, the medium warms up to a temperature of +45 ° . In such engineering networks, it is permissible to use an electromagnetic drive in the shutoff valves. It is designed to operate at temperatures up to +50 ° C. It should be directed up. The body of the device is cast iron. At the same time, the spool and cover are made of steel. Such a valve is controlled both manually and remotely.
Damper
The dampers are designed for use on large diameter pipelines. They are installed in air conditioning and ventilation systems at low pressures and low tightness requirements.
Depending on the number of plates used, the shutters are single and multi-leaf. For liquid media, dampers are practically not used, since they cannot sufficiently ensure the tightness of the passage passage. For gases, throttles are used quite often. This is facilitated by the simplicity and reliability of the design. The purpose of throttle valves is to control and shut off the flow.
In addition to simple device and control, they have a relatively low price and low weight. It is possible to equip the dampers with a hydraulic actuator, a pneumatic actuator or an electric actuator.
On pipes transporting water, flangeless valves with a pressure of 1.0 MPa are installed. Sealing occurs through a rubber ring mounted in the groove of the disc. The body of the product consists of cast iron, and the rotary shaft is made of steel.
The damper controlled by an electric actuator is mounted upward by an electric actuator. In this case, the drive shaft is vertical. Manually controlled dampers can be installed in any position.
The connection of the dampers with the pipeline takes place via flanges. Another method of joining is welding. The operating pressure of the valves is 1 MPa. They can be controlled using an electric drive.
The diameter of valves using such an electric actuator ranges from 200-1200 mm. Their power reaches 5 kW. The time that the shutter takes to open or close is approximately one and a half minutes.
Shutters
Rotary butterfly valve is necessary in order to regulate the pressure and flow rate of the medium. The operating medium for the shutter is water and gas. They operate at a pressure of 1.6 MPa and a temperature of -15 ° C to 200 ° C.
Butterfly valve belongs to shut-off and control valves. Being in the closed position, it makes it possible to achieve tightness. The advantage of the shutter is its small construction length and height. The product is used in heating systems, water supply and food industry.
Gate valves
In engineering networks, other shutoff valves are also installed. What is this "gate valve" - one of the types of pipeline valves?
Gate valve - representative of valves, having a valve in the form of a wedge, disk or sheet, which moves along the sealing rings of the body seat. The medium flow is perpendicular to the shutter movement. The diameter of the o-rings may be less than the diameter of the pipe, but may be equal to it. In the first case, the valves are called narrowed, in the second - passage.
In accordance with the shape of the shutter, the valves are divided into parallel and wedge.
These products are used on production lines and pipelines. The spindle in the valves can be non-extendable or extendable. To close or open the passage, the spindle has to do a lot of revolutions. Therefore, such valves are equipped with an electric actuator for remote control. Wedge gate valves have a non-retractable cast iron spindle. Their pressure is 0.25 MPa. The diameter of the reinforcement is from 800 to 2000 mm, the mass reaches 14 tons.
Gate Valve Advantages:
- it is not necessary to overcome the pressure of the working environment when moving the working body;
- direct flow of the medium, allowing to minimize resistance in the open state;
- symmetrical design.
Disadvantages of gate valves:
- strong friction when moving the valve body;
- high construction height due to the fact that the rod must extend at least two pipe diameters;
- high shutter wear in the intermediate position.
Gate valves are connected to the pipe using flanges. Most of the parts are cast iron. Gasket material - paronite, stuffing box packing - asbestos.
Pipelines transporting fuel gas with temperatures up to 100 ° C use cast-iron double-wedge gate valves. They have a non-extendable spindle and a working pressure of 0.6 MPa. Provide only manual control.
Similar double-disc valves, but with a retractable spindle, are placed on coke oven gas pipelines . They are designed to operate at a pressure of 1.8 MPa and a temperature of 200 ° C.
Welded wedge gate valves made of steel are installed on oil pipelines and oil pipelines. Their design uses a retractable spindle and nozzles. The maximum medium temperature for these valves is 250 ° C. The material for all valve parts is carbon steel.
Aggressive environments
Locking devices that work under aggressive environmental conditions are selected depending on the characteristics of the medium. The service life, tightness, reliability and other parameters that shutoff valves have are taken into account. What is it - locking equipment for aggressive environments?
Valves are used most often in aggressive environments. In such products, the saddle and spool reliably mate, which avoids friction. Bellows assemblies replaced the stuffing box assemblies. The disadvantage of this valve is increased hydraulic friction.
In liquid media, brass coupling valves are designed for a working pressure of 1.6 MPa. Such a valve is connected to the pipeline by means of a threaded sleeve.
In steam pipelines at a pressure of 1 MPa and temperatures below 50 ° C, a brass o-ring is used in the valves. A similar ring on the spool is made of rubber or leather.
Bellows valves made of corrosion-resistant steel are used at ambient temperatures up to 350 ° C. Porcelain flanged valves have a body made of porcelain.
Repairs
Failures of pipeline valves are fraught with many problems for operating enterprises. Often they are not able to block the part of the network that has suffered an accident. It is no coincidence that the repair of shut-off valves made on time helps the enterprise to avoid high costs in the future.
Causes of breakdowns
We will get acquainted with the most common causes of breakdowns of valves. Among the causes of damages to gate valves is debris that enters the pipeline during installation. He settles on the o-rings, cuts through the grooves there, violating the tightness. This can be prevented by thoroughly flushing the backbone networks before they begin to operate. Damaged valves are repaired in special workshops that are equipped with lapping machines. They remove the damaged layer from the o-rings, returning them to their previous properties.
After the repair and tightening of the bolts, before the shut-off valves are installed, the valve passes hydraulic bench tests under pressure. If the tests are completed successfully, an acceptance certificate is issued.
Manufacturers
In Russia, stop and adjustable valves are manufactured by many enterprises. The industry is constantly growing. One of the leaders in the industry is the stop valve factory Also from Chelyabinsk. Also popular are the products of the Lenpromarmatur plant from St. Petersburg, ZAO Hydrogas from Voronezh, LLC Murom Pipe Fittings Plant.
Prices
Shutoff valves, the price of which can be from 20 to several tens of thousands of rubles, depending on the diameter, purpose and material of the products, is widely offered on the Russian and European markets.