Shut-off valves - what is it? Device, application

The term "shut-off valve" means devices that control the flow strength of some medium. Most often, the elements of the stop valves are present on the pipelines. Next, we'll figure out what types of valves are divided, what it is and where it is applied.

Shut-off valves on pipelines serve to control the flow of liquids or gases. It is able to regulate the flow in the pipeline systems from a minimum supply reduction to a complete stop.

Some types of this equipment:

• Cast iron gate valves;
• Control valves;
• Cranes;
• Disc closures.

Application area

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

Device

All locking devices have a similar design. This is a closed sealed enclosure in which the valve assembly is located. In the case most often there are two (in some cases more) end, by means of which it is tightly attached to the pipeline. The purpose of the locking unit is the sealed separation of the pipeline system into parts. In its composition there is a saddle and a locking organ, constantly touching the sealing surfaces.

Cranes

Cranes serve 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, such as ball and cork. In accordance with the method of sealing, they are gland and tension.

Connection of the crane to the pipeline takes place by means of a flange, a coupling or by welding to it. Gas pipelines use gas couplings. The material for them is cast iron. To ensure the connection of the pipeline to the crane, a threaded coupling is required. Gas valves are designed to operate at a pressure of 0.1 MPa and a temperature of up to 50 ° C.

Higher loads can withstand stuffing box cranes. They serve oil pipelines and water pipes, their main parts are made of cast iron. At the same time, the 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 of up to 100 ° C.

The smallest sizes are ball valves. This equipment is famous for its high quality of work, which predetermined its use in large diameter pipelines. They are made of cast iron, and the O-rings consist of PTFE-4. Operating parameters of ball valves correspond to the characteristics of gland box cranes.

With the help of flanges, flanged steel cranes are connected to the pipelines. If the crane is large, it is supplied with a worm gear. To adjust the flow in such a crane is a flywheel. This equipment is used for gas pipelines operating in the temperature range from -40 ° C to +70 ° C. Similar cranes are mounted only vertically. The control can be either remote or via a flywheel.

Shut-off valves

Valves play a crucial role in a large number of regulators of pipeline networks. This is the most common stop valves. What it is, you can see in the picture.

These are parts that have a shutter that looks like a plate of a cone or flat shape that moves parallel to the axis of the sealing surface of the body saddle back and forth or along an arc.

The valve is a kind of valve, the movement of the gate 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 by 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, the working medium of which are air, steam or water. A threaded coupling is used for connection to the pipe. To fill the stuffing box is used asbestos packing AP-31 - a cord of woven asbestos threads with antifriction impregnation.

In water pipes with a water temperature of less than 50 ° C, shutoff valves are installed. This equipment can work in any position. This water comes under the spool. The body of the device is cast-iron, the gaskets are made of paronit, the sealing ring is made of leather, and the stuffing box is made of asbestos.

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

Dampers

The flaps are designed for use on large diameter pipelines. They are installed in air conditioning and ventilation systems at low pressures and low requirements for tightness.

Depending on the number of plates used, the flaps are single and multi-leaved. For liquid media, the flaps are not practically used, since they can not sufficiently ensure the integrity of the passage overlap. For gases, throttle valves are used quite often. This is facilitated by the simplicity and reliability of the structure. The purpose of throttle valves is to regulate and switch off the flow.

In addition to simple devices and controls, they have a relatively low price and low weight. It is possible to equip the flaps with a hydraulic drive, pneumatic drive or an electric drive.

On the pipes transporting water, waferless flaps are put at a pressure of 1.0 MPa. The seal is carried out by means of a rubber ring installed in the groove of the disc. The body of the product consists of cast iron, and the swivel shaft is made of steel.

The dampers, controlled by means of an electric drive, are mounted electrically with the drive upwards. In this case, the drive shaft is positioned vertically. Dampers that are manually operated can be installed in any position.

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

The diameter of the reinforcement using such an electric drive is from 200 to 1200 mm. Their power reaches 5 kW. The time taken by the shutter to open or close is about one and a half minutes.

Shutters

A rotary disc shutter is necessary in order to regulate the pressure and flow rate of the medium. The working 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.

The rotary disk shutter belongs to the shut-off valve. Being in the closed position, it gives an opportunity to achieve tightness. The advantage of the shutter is its small construction length and height. The product is used in heating, water supply and food industry.

Latches

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

Gate valve is a representative of a stop valve, which has a gate in the form of a wedge, disk or sheet that moves along the sealing rings of the body saddle. The medium flow is perpendicular to the gate. The diameter of the sealing rings may be less than the diameter of the pipe, and may be equal to it. In the first case, the valves are called narrowed, in the second - gateways.

In accordance with the shape of the gate bolts are divided into parallel and wedge.

These products are used on process lines and main pipelines. The spindle in the valves can be non-sliding or retractable. To close or open the passage, the spindle has to do a lot of revs. Therefore, these valves are equipped with an electric drive for remote control. Wedge latches have a non-movable spindle of cast iron. Their pressure is 0.25 MPa. The diameter of the reinforcement is from 800 to 2000 mm, the mass reaches 14 tons.

Advantages of gate valves:

• It is not necessary to overcome the pressure of the working medium during the movement of the working member;
• Direct fluid flow, allowing to minimize resistance in the open state;
• Symmetry of construction.

Disadvantages of valves:

• Strong friction when moving the valve body;
• A large construction height due to the fact that the rod must be pulled out at least two pipe diameters;
• High wear of the bolt in the intermediate position.

The valves are connected to the pipe by means of flanges. Most of the details are cast iron. The gasket material is paronite, the stuffing box packing is asbestos.

Pipelines transporting fuel gas with a temperature regime up to 100 ° C, use double-disk wedge gate valves. They have a non-sliding spindle and working pressure of 0.6 MPa. Only manual control is provided.

Similar two-disc latches, but with a sliding spindle are put on pipelines with coke oven gas. They are designed to operate at a pressure of 1.8 MPa and a temperature of 200 ° C.

On oil pipelines and oil lines welded wedge gate valves from steel are established. In their design, a sliding spindle and branch pipes are used. The maximum medium temperature for these valves is 250 ° C. The material of all parts of the valve is carbon steel.

Aggressive environments

Locking devices that work under the influence of aggressive media are selected depending on the characteristics of the medium. The calculation takes the life, tightness, reliability and other parameters that shut-off valves have. What is it - locking equipment for aggressive environments?

Gates are used in aggressive environments most often. In such products, the saddle and spool are reliably interfaced, which avoids friction. The knots of the glands were replaced by bellows knots. The disadvantage of such a valve is increased hydraulic friction.

In liquid media, couplings made of brass 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 ambient temperatures up to 350 ° C. Flanged porcelain valves have a body made of porcelain.

Repairs

Faults in pipeline valves are fraught with many problems for operating enterprises. Often they are not able to block the section of the network that was affected by the accident. It is no coincidence that repair of the stop valves, made on time, helps the company avoid large expenses in the future.

Causes of breakdowns

We will become acquainted with the most common causes of breakage of valves. The number of causes causing damage to the valves, includes debris that gets inside the pipeline during installation. It settles on the sealing rings, cuts through the grooves, which break the tightness. To prevent this, you can thoroughly rinse the backbone networks before starting their operation. Damaged latches are repaired in special workshops, which are equipped with lapping machines. They remove the damaged layer from the O-rings, returning them the same properties.

After the repair and tightening of the bolts, before the valve is installed, the valve passes the hydraulic bench test under pressure. If the tests are successful, an acceptance certificate is issued.

Manufacturers

In Russia, shut-off and shut-off valves are manufactured by many enterprises. The industry is constantly growing. One of the leaders of the industry is also a factory of stop valves from Chelyabinsk. The products of the plant Lenpromarmatura from St. Petersburg, ZAO Gidrogaz from Voronezh, LLC of the Murom Pipe Valve Plant are also popular.

Price list

Valve fittings, 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 in the market of Russia and Europe.