Isolation valves - what is it? Device, application

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

The concept of "shut-off valves" refers to devices that control the force of the flow of a certain medium. Most often, elements of valves are present on pipelines. Next, we will figure out what types of valves are divided into, what it is and where it is used.

Isolation valves on pipelines are used to control the flow of liquids or gases. It is able to regulate the flow in pipeline systems from a minimal decrease in flow to a complete stop.

Some of this equipment:

• cast iron valves;
• control valves;
• faucets;
• butterfly valves.

Scope of application

All of these products are widely used in engineering systems and can be manufactured for both general technical applications and for work in special conditions. If the valve is used only to completely shut off the flow, then shut-off and adjustable fittings (valves and taps) can not only shut off the flow, but also regulate its intensity.

Device

All locking devices have a similarconstruction. This is a closed hermetic case, in which the stop valve assembly is located. The body most often has 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 seat and a shut-off element that are constantly in contact along 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 faucet diameter can be from 1 to 3 inches. The most common types of valves are ball and plug. According to the sealing method, they are gland and tension.

The connection of the valve with the pipeline occurs with the help of a flange, coupling or by welding to it. Gas coupling valves are used on gas pipelines. The material for them is cast iron. To ensure the connection of the pipeline to the tap, a threaded coupling is required. Gas cocks are designed to operate under pressure conditions of 0.1 MPa and temperatures up to 50 °C.

Greater loads can be handled by stuffed box valves. They serve oil and water pipelines, their main parts are made of cast iron. In this case, the cast-iron gland is stuffed with rubber or hemp. Such valves are capable of operating at pressures up to 1 MPa and withstand temperatures up to 100 °C.

The smallest sizes are ball valves. This equipment is renownedhigh quality of work, which predetermined its use in pipelines of large diameter. They are made of cast iron, and the sealing rings are made of fluoroplast-4. The performance parameters of ball valves are the same as those of glanded socket valves.

Flanged steel cranes are attached to pipelines with the help of flanges. If the crane is large, it is equipped with a worm gear. A flywheel is used to regulate the flow in such a faucet. This equipment is used on gas pipelines operating in the temperature range from -40 °C to +70 °C. Such cranes are mounted only vertically. Control can be either remote or by means of a flywheel.

Shutoff valves

Valves play a critical role in many pipeline regulators. This is the most common stop valve. What it is can be seen in the picture.

These are parts that have a cone-shaped or flat-shaped plate-shaped valve that moves parallel to the axis of the sealing surface of the body seat, reciprocating 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. They are adjusted manually using a flywheel or remotely using an electric drive.

The strength of the seal is ensured by rings made of leather, rubber or PTFE-4. Shut-off valvesare used in pipelines, the working medium of which is air, steam or water. A threaded coupling is used to connect to the pipe. Asbestos packing AP-31 is used to fill the stuffing box - a cord made of woven asbestos threads with anti-friction impregnation.

In water pipes with a water temperature of less than 50 ° C, shut-off valves are installed. This equipment is able to work in any position. In this case, water enters under the spool. The body of the device is cast iron, the gaskets are paronite, the o-ring is made of leather, and the gland packing is asbestos.

In pipelines for transporting air or water, the medium is heated to a temperature of +45 °C. In such engineering networks, it is permissible to use an electromagnetic drive in shutoff valves. It is designed to operate at temperatures up to +50 °C. It should be directed upwards. The body of the device is cast iron. In this case, the spool and cover are made of steel. Such a valve is controlled both manually and remotely.

Dampers

The valves 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, dampers are single and multi-leaf. For liquid media, dampers are practically not used, since they cannot adequately ensure the tightness of the passage overlap. For gases, throttle valves are used quite often. This is facilitated by the simplicity and reliability of the design. Purposethrottle valves - regulation and shutdown of flow.

Besides a simple device and control, they have a relatively low price and light weight. It is possible to equip dampers with a hydraulic drive, pneumatic drive or electric drive.

On pipes transporting water, flangeless dampers with a pressure of 1.0 MPa are installed. Sealing occurs by means of a rubber ring installed in the groove of the disc. The body of the product is made of cast iron, and the rotary shaft is made of steel.

Motor operated dampers are mounted with the motor upwards. In this case, the drive shaft is located vertically. Flaps that are manually operated can be installed in any position.

The dampers are connected to the pipeline by means of flanges. Another connection method is welding. The working pressure of dampers is 1 MPa. They can be controlled by electric drive.

The diameter of the fittings using such an electric drive is from 200-1200 mm. Their power reaches 5 kW. The time it takes for the damper to open or close is approximately one and a half minutes.

Shutters

The butterfly valve is necessary in order to regulate the pressure and flow of the medium. The working medium for the valve is water and gas. They operate at a pressure of 1.6 MPa and temperatures from -15 °C to 200 °C.

The butterfly valve belongs to shutoff and control valves. Being in the closed position, it makes it possible to achieve tightness. Shutter advantageis its small building length and height. The product is used in heating systems, water supply and food industry.

Valves

In engineering networks, other valves are also installed. What is a "valve" - one of the types of pipeline fittings?

Gate valve - a representative of shut-off valves, having a wedge-shaped, disk or leaf-shaped valve that moves along the sealing rings of the body seat. The flow of the medium in this case is perpendicular to the stroke of the shutter. The diameter of the sealing rings may be less than the diameter of the pipe, or may be equal to it. In the first case, the gate valves are called narrowed, in the second - through.

According to the shape of the gate valves are divided into parallel and wedge.

These products are used on production lines and main pipelines. The stem in gate valves can be non-rising or retractable. To close or open the passage, the spindle has to make a lot of turns. Therefore, such valves are equipped with an electric drive for remote control. Wedge gate valves have a non-rising cast iron stem. Their pressure is 0.25 MPa. Rebar diameter - from 800 to 2000 mm, weight reaches 14 tons.

Valve Benefits:

• it is not required to overcome the pressure of the working medium when moving the working body;
• direct fluid flow to minimize open resistance;
• symmetric design.

Disadvantages of valves:

• strong friction when movinggate valve;
• large construction height due to the fact that the stem must extend at least two pipe diameters;
• high bolt wear in intermediate position.

The valves are attached to the pipe with flanges. Most of the parts are cast iron. Gasket material - paronite, gland packing - asbestos.

Pipelines transporting fuel gas with temperatures up to 100 °C use double-disc cast iron wedge gate valves. They have a non-rising spindle and a working pressure of 0.6 MPa. Provide only manual control.

Similar double-disc gate valves, but with a rising spindle, are placed on pipelines with coke oven gas. They are designed to operate at a pressure of 1.8 MPa and a temperature of 200 °C.

Welded steel wedge gate valves are installed on oil and oil pipelines. Their design uses a retractable spindle and nozzles. The maximum medium temperature for these valves is 250 °C. All valve parts are made of carbon steel.

Corrosive environments

Locking devices that operate under the influence of aggressive environments are selected depending on the characteristics of the environment. The calculation takes into account the service life, tightness, reliability and other parameters that the valves have. What is it - locking equipment for aggressive environments?

Valves are used in aggressive environments most often. In such products, the seat and spool are securely mated, which avoidsfriction. The bellows assemblies have replaced the stuffing box assemblies. The disadvantage of such a valve is the increased hydraulic friction.

In liquid media, brass coupling valves are used, designed for a working pressure of 1.6 MPa. Such a valve is connected to the pipeline by means of a threaded coupling.

In steam pipelines at a pressure of 1 MPa and temperatures below 50 ° C, a brass sealing 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 medium temperatures up to 350 °C. Flanged porcelain valves have a body made of porcelain.

Repair

Failures in pipeline fittings are fraught with many problems for operating enterprises. Often they are not able to block the section of the network that has undergone an accident. It is no coincidence that the repair of shut-off valves, done on time, helps the company to avoid large expenses in the future.

Causes of breakdowns

Let's get acquainted with the most common causes of valve failures. Among the causes of valve failures is debris that enters the pipeline during installation. It settles on the o-rings, cuts grooves there that violate the tightness. This can be prevented by thoroughly flushing the main networks before they are put into operation. Broken valves are repaired in special workshops, which are equipped with lapping machines. They remove the damaged layer from the o-rings,returning them to their former properties.

After the repair and tightening of the bolts, before the installation of the valves, the valve is subjected to hydraulic bench tests under pressure. If the tests are completed successfully, an acceptance certificate is issued.

Manufacturers

In Russia, shut-off and control valves are manufactured by many enterprises. The industry is constantly growing. One of the industry leaders is the Also shutoff valve plant from Chelyabinsk. The products of the Lenpromarmatura plant from St. Petersburg, ZAO Gidrogaz from Voronezh, OOO Murom Pipeline Valve Plant are also popular.

Prices

Stop valves, the price of which can range from 20 to several tens of thousands of rubles, depending on the diameter, purpose and material of the products, are widely offered on the Russian and European markets.