Underground gas ball valve: design and operational features

Timely isolation of the pipeline section where the accident occurred is needed to quickly fix the problem. In such situations, you can not hesitate. Do you agree? Using a ball gas valve for an underground installation, you can quickly and flawlessly shut off the medium transported through the gas pipeline.

Proper installation and proper use of the ball valve will help to increase its service life and ensure high-quality and safe operation of the gas supplying system. We will tell you all about the design of this type of shutoff valves. We will analyze what the principle of its work is based on.

Features and purpose of ball valves

The oil, chemical or gas industry cannot be imagined without shutoff valves. Stop valves manufactured using modern high-tech equipment will ensure the safety of the entire system.

Locking gas pipeline fittings - This is a mandatory structural element. These devices are used both for external gas pipelines and for internal systems.

The purpose of ball gas valves is quite large:

• equipping complex systems through which aggressive and non-aggressive environments pass;
• use in pipelines located in inaccessible places;
• efficient operation in case of nominal pressure up to 16 MPa, etc.

When using ball gas valves, there is no need to create an inspection well and enclosing structure.

If you need to dismantle any product, just some of the nozzles are cut off. In this case, the shutter must be in the open position so as not to damage the locking ball. The design of the crane is not intended to control the flow of the pumped medium.

During any repair work on gas pipelines, the ball valve shutter must be open so that the structure does not break completely

If it is required to install a restriction device on buried highways, then ball gas valves are most often used, driven by an electric motor, gearbox or pneumatic cylinders. If the design has hydraulic or pneumatic actuators, they can be controlled using external sources or a transported medium.

To do this, holes are made in the body of the gas valve through which the drive is strapped. To prevent the structure from breaking, the spindle extension is protected by a sheath in the form of a vertical tube.

Moreover, this tube is attached to the upper part of the valve body by a flange method. Most often, shut-off valves are installed directly where the gas equipment is located.

A gas ball valve can only be mounted on a section of a gas pipeline after preliminary cleaning of the inside of the pipe and adjacent sections

At the same time, an individual valve is mounted for each gas consumption source, which ensures the sealing of a particular pipe. You can also install one additional valve with a ball valve at the inlet, which is responsible for the complete cessation of gas supply. Such installation meets all the necessary safety system requirements.

Gas ball valves provide two-way gas movement in the pipeline. Such devices can be mounted on gas pipes any diameter. They can be used on trunk networks, used in the operation of storage facilities and in the transportation of natural gas over long distances, etc.

Pros of using a ball valve

The ball valve intended for underground installation is a device that is necessary to shut off the gas flow in pressure pipelines laid in trenches.

These devices are used in both industrial and domestic conditions. Gas valves provide fast and complete shutdown of the flow of the working medium. Their wide distribution is due to reliability, durability, strength and relatively low cost.

If the gas valve breaks, then in the event of an emergency, the pipeline cannot be closed to isolate the damaged branch. It will not work and prevent the spread of gas

Ball valves are made of heavy-duty materials, resistant to corrosion, inert to aggressive environments. Alloys are used in the production, without any problems and deformations, transferring all kinds of mechanical damage.

Products have high wear resistance regardless of operating conditions. Ball gas valves are able to maintain their technological properties for thousands (or more) cycles without malfunctions.

In this case, the temperature of the moving and the environment can be almost any. Empirically, it was found that ball gas valves are able to withstand temperatures from -60 to +80 degrees. Most gas taps can last much longer than the manufacturer stated.

Ball valves are simple in design, so they do not require constant repair and maintenance, unlike complex systems

The constipation of the ball gas valve is made in a spherical shape and has an opening through which gas passes through the pipes. The diameter of the hole is selected in accordance with the dimensions of the pipeline. Adjustment of the throughput of the line is ensured by the possibility of turning the locking mechanism around its axis.

In the working position, the lock is perpendicular to the pipeline, and it can be easily closed with your hands by performing a slight turn of the handle. When rotated 90 degrees, the side with the through hole changes to a solid surface.

With a smaller turn, the pipe will be partially blocked. But manufacturers do not recommend leaving the structure in a half-open state, as this contributes to increased abrasive wear of the device.

In intermediate positions, due to the excessively fast flow velocity of the pumped fluid, the seat rings can be completely damaged or partially deformed. This can lead to serious damage to the crane, its repair or replacement in the future.

The body of the product is highly tight. The use of metals and special alloys in the construction helps to reduce the weight of the structure. Such valves for gas pipelines can be safely installed in hard to reach places.

In the event of any breakdown, the gas ball valve can be easily repaired by improvised means without damaging the rest of the system

The use of high-quality gas valves with ball valves is beneficial from an economic point of view. These devices have a huge margin of safety and can fully function without the need for replacement for many years.

This is especially true for well-known and trusted manufacturers of ball valves. At the same time, you can verify the quality of any crane by checking the certificates of conformity that confirm the quality of the products.

Typical ball valve design

Ball valves for underground installation of different brands have approximately the same structure. The design of the products is determined by their operational characteristics and purpose.

The standard gas valve for installation on underground pipelines consists of:

• sealed enclosure, most often made of brass or steel;
• a shut-off ball, which subsequently shuts off the gas supply (because of this element, the valve is called a ball valve);
• a saddle, which is responsible for ensuring that the locking ball does not move anywhere;
• a piece of connection pipe with a special thread, which is then welded to the pipeline;
• the throat portion necessary for the passage of the stem;
• elongated connecting rod;
• contraindications washers;
• parts responsible for the tightness of the structure (O-ring, spring, ring and flange made of soft and durable materials, for example, ethyl propylene rubber);
• handles made of strong material coated with polyvinyl chloride, due to which the entire product is controlled and the nut fixing it;
• stopper or limiter of the stroke of the handle.

In the production of component parts, alloyed and stainless steel is used, which has high anticorrosive properties. Elastic fluoroplastic is used to seal parts. Thanks to this polymer, the structure becomes water resistant.

Ftoroplast provides tightness of the coupling, quiet screwing and easy dismantling. This material is highly resistant to all kinds of aggressive environments, and its excess is quietly squeezed out when tightening the thread.

Fluorine plastic refers to fluorine-containing polymers (structural plastics), which are characterized by high heat resistance, chemical inertness, softness, fluidity and environmental safety

Due to the structural features, the closed position of the valve ensures complete sealing of the pipeline. The crane itself is small in size, which greatly simplifies its installation. During installation, both welded and threaded connections are acceptable.

In this case, the thread at the end of the pipe should not be longer than the thread of the valve, because otherwise, after tightening the threaded connection, the pipe end will abut the o-rings, leading to premature valve damage.

The gas ball valve can be installed together with the pipe in any position, which in the future can guarantee maximum ease of use and quick access to the problem area.

Underground crane body

The crane body is most often made of alloyed, carbon and stainless steel or brass. Brass products are more expensive than steel taps. But at the same time, both brass and steel are not subject to corrosion, due to which the service life of devices made from them increases several times.

The material from which the ball gas valve is made is indicated in the accompanying documentation for the product, which can be found when purchasing the design

Brass and alloy steel are characterized by a high level of ductility. However, they are not able to withstand strong and prolonged mechanical stress. For this reason, it is recommended to protect the locking mechanism from shock and friction.

The design of the body of the gas valve depends on the following factors:

• production method;
• internal development of a specific design office;
• the nature of the applicable standards (TU, GOST, OST or any European directives).

The most durable, able to hold any load is considered an all-metal non-separable case. First, it is machined on a machine, cast into a formwork due to centrifugal force, and then welded using additional parts.

Also, the crane body may consist of two vertical halves or three elements. A collapsible housing of 2-3 parts is more convenient for maintenance and can be used again after dismantling, but it is less tight.

More ball valve housings are divided into full bore and reduction valves. In the first case, the diameters of the valve and the pipeline completely coincide, due to which the minimum hydraulic resistance is ensured. In the second case, the couple is reduced by one size, so that the flow of labor can be controlled.

Regardless of the material from which the body of the ball gas valve is made, it must be covered with special protective agents against aggressive media. For these purposes, various chemicals are used.

The use of protective coatings allows the use of ball valves on any trunk networks with different temperature and barometric ranges

Firstly, it includes acrylic paint, characterized by electrical insulation properties. It protects products from induced and stray currents. Secondly, in order to provide the crane with anti-corrosion properties, it is coated with polymer coatings.

Thirdly, the body of the ball can be coated with epoxy-based coal paint. Such paint is characterized by high corrosion resistance and resistance to various mechanical damage. Fourth, to protect the reinforcement during its useless installation directly in the ground, a polyurethane foam coating is used.

Ball valve locking mechanism

When choosing a ball valve, special attention should be paid to its locking element - a ball or sphere. The ball should be smooth and shiny. Most often, the sphere is made of brass and covered with an expensive spraying of nickel and chromium.

Brass is an alloy based on copper and zinc, which has a beautiful color and lends itself well to pressure treatment, however, the material loses its anti-corrosion properties in the case of high temperature processing

Checking the quality of the locking sphere is quite easy. To do this, it can be checked with a magnet. If the magnet is attracted to the sphere, then this indicates that it is made of steel, which is intended for electrical use.

The steel ball of a gas underground crane quickly rusts and cannot be used for a long time in a humid environment. In this case, the brass ball will not attract the magnet.

Gas cock handle

The convenience of its operation depends on the shape of the handle or handle of the ball valve. Most often, products with a handle in the shape of a butterfly (butterfly stroke) or lever come on sale.The lever is more functional, so if possible you should buy a gas tap with just such a handle.

The lever handle is especially convenient if the crane has not been used for a long time, and you need to make an effort to turn it. Gas taps are always available with green handles. Repainting them is not recommended.

Varieties of gas ball valves

In modern gas pipelines used gas taps The three most common types are classified by type of connection to pipes. It is threaded, flanged and welded. Threaded or coupling gas valves have a small diameter. Most often they are installed on gas pipelines for commercial premises, private houses and similar facilities.

Connection to the gas pipeline is carried out thanks to the thread. The threaded connection of the gas ball valve and the pipe cannot be tightened too much, because this may cause damage to the product body.

Flanged ball gas valves are used in large diameter gas pipelines because they are able to withstand strong pressure of the working medium.

Flanged taps are connected to pipelines in a flanged manner using bolts. Both threaded and flange products are collapsible. Those. they can be dismantled, transferred to another place and put again at another point in the pipeline.

Welded taps are connected to gas pipelines by welding. Those. they cannot be disconnected from the pipes without damaging the structure. Diameter of welded fittings varies from 10 to 70 mm. Welded gas taps are tight and reliable. They do not require regular maintenance, which is why they are very popular.

General operating rules

The basic rules for operating a gas valve are quite simple and predictable. The crane is closed by turning the handle 90 degrees clockwise, and opens by turning also 90 degrees, but already counterclockwise. If the handle is perpendicular to the axis of the crane, this indicates that it is closed. The parallel position of the handle means that the tap is open.

The working medium passing through this tap must not contain too rigid elements and solid impurities that can damage the polished surface of the shutter ball. If solid particles can still get into the ball valve, a strainer should be installed in front of the ball valve.

The ball valve itself needs to be periodically opened and closed so that it can later be easily turned in any direction.

Opening and closing the gas valve is only allowed for the handle made by the factory, and it is forbidden to extend it by any means

The ball valve must be operated using a standard handle. You do not need to use special levers for these purposes, which are able to lengthen this handle. Opening and closing the crane should be done as slowly as possible to avoid the occurrence of water hammer.

The pressure and temperature at the installation site of the ball valve should not be higher than the working pressure. For most designs, ball valves with the same temperature and pressure ratings are not allowed.

The ball valve requires periodic cleaning of rust and dust, as well as thread tightening. In accordance with the recommendations of manufacturers, this should be done once every six months.

When installing pipelines, a pipe fastening design is provided that excludes the possibility of external mechanical impact on the valve, taking into account axial, radial or torque loads.

Repair and maintenance of a ball valve under pressure is prohibited. For full operation, the required section of the pipeline should be cleaned first. During system cleaning, ball valves must be opened and closed several times.

How to identify a fake?

Before installing the gas valve, it is necessary to check its documentation of compliance with the specified pipeline and make sure that the device is not a fake. Fake gas fittings are quite common in the market. When buying a gas ball valve, you should be careful to distinguish the original product from the fake one. You can use some tips for this.

One of the main criteria for the quality of a ball gas valve is its price, because a product that meets all international and national standards cannot be cheap

To deceive buyers, sellers can fake accompanying documentation (certificates, declaration, product passport). Branded gas taps are somewhat more expensive, so this hype is common on the market.

The following signs also indicate a fake:

1. The uneven surface of the crane, on which microcracks and gaps are visible.
2. Blurred ball clearance.
3. Using silumin or zinc as the body material.

But to determine by eye the exact composition of the material used is extremely difficult. For this, numerous chemical analyzes are carried out. They cannot be made outside the laboratory in a limited period of time.

Therefore, when buying a ball valve, you should request a quality certificate for the product, a hygiene certificate or a declaration of conformity. In Russia, ball gas valves must comply with the requirements of GOST R 9544-2005 and GOST 21345-2005, 28343-89, 23941-2002. Also, certificates may contain references to other normative legal acts and quality standards.

Conclusions and useful video on the topic

The features of the choice of a gas ball valve for underground work are described in the video below:

Any gas pipeline must be equipped with a reliable locking mechanism, especially if the pipes are laid below the surface. The shutter is needed during an accident to isolate certain sections of the pipeline and to carry out repairs on the line in case of private breakdowns. It will protect against threatening situations and catastrophic consequences.

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