Spring safety valve. Safety spring valves - all about the design and installation. Magnetic spring safety valves, operating principle

A check valve is an element of a pipeline system that allows for the movement of the working medium in only one direction. Its use is mandatory for autonomous pumping stations and other equipment that may fail when the fluid flow moves in the opposite direction.

A spring check valve is one of the types of shut-off elements. It belongs to the category of direct-acting valves and is activated automatically by the energy of the working environment, which prevents equipment failure in the event of a power outage or other malfunctions.

Design features

The spring valve is structurally composed of three elements:

1. A body usually made of brass and equipped with elements for fastening to the pipeline (coupling, thread). The body is also made of steel, cast iron and polypropylene. The choice of material is determined by the parameters of the working environment and the diameter of the pipeline.
2. The working element, which represents a movable spool, includes two plates with a special sealed gasket between them and a rod.
3. An actuator representing a spring located between the work element plates and the seat. Provides automatic shutoff of fluid flow when pressure decreases or changes its direction. The minimum pressure of the working medium at which the valve automatically opens depends on the stiffness of the spring.

Advantages of spring check valves:

• Possibility of installation in any position;
• simplicity of design;
• versatility.

At the same time, the valve is sensitive to contaminants in the water, which lead to wear of the sealing plates, so it is advisable to install a filter in front of it. It is also recommended to mount the valve easily accessible places to simplify its maintenance and replacement.

It is advisable to install the valve in vertical position so that the blocking force of the spring coincides with the force of gravity. For correct installation it is necessary to focus on the arrow marked on the valve body, which shows the direction of flow of the working medium through.

Scope of application

Spring check valves are widely used in systems autonomous water supply, intra-house networks apartment buildings. They are installed on the suction lines of pumps, before DHW water heaters, boilers, water meters and other equipment.

The safety valve is protective device, which prevents the backflow of the substance through the pipeline and releases its excess into the area low pressure or atmosphere. This is an indispensable device, as it allows you to save pumps, equipment and the pipeline itself in case of emergency situations.

What types of safety valves are there?

The design of the device is as simple as possible: a locking element and a setpoint that provides power voltage to it. The locking element, in turn, consists of a bolt and a seat.

There are several types of valve:

• spring safety valve - the pressure of the working substance is opposed by the force of a compressed spring. The amount of pressure is determined by the compression force, and the range of possible valve settings is determined by the elasticity of the part;
• lever - the working substance is restrained using a lever mechanism. Size, pressure and overall range of action are determined by the weight of the load and the length of the lever;
• low-lift - the bolt rises only 0.05 of the seat diameter. The opening mechanism is proportional. Such devices are distinguished by their low throughput, low cost and simple structure;
• full-lift - the bolt rises to the height of the seat diameter or a little more. The mechanism is two-position. Typically installed on pipelines carrying steam or compressed air. It is distinguished by its ability to pass a large amount of working substance and its higher cost.

What are the advantages of safety devices?

• the most simple structure - guarantees ease and speed of repair and replacement of worn parts;
• small size and light weight;
• wide price range, which allows you to purchase the product at the most favorable price.

The safety valve allows the pipeline to function efficiently under conditions of high pressure and sudden pressure changes.

With pressure above the specified level. The valve must also ensure that the release of the medium ceases when the operating pressure is restored. The safety valve is a fitting direct action, operating directly from the working medium, along with most designs of protective fittings and direct-acting pressure regulators.

Dangerous overpressure can arise in the system both as a result of third-party factors (improper operation of equipment, heat transfer from third-party sources, incorrectly assembled thermo-mechanical circuit, etc.), and as a result of internal physical processes caused by some initial event not provided for by normal exploitation. PC are installed wherever this can happen, that is, on almost any equipment, but they are especially important in the field of operation of industrial and household pressure vessels.

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Operating principle

When the safety valve is closed, a force from working pressure in the protected system, tending to open the valve and the force from the set pointer, preventing the opening. With the occurrence of disturbances in the system, causing an increase in pressure above the operating pressure, the magnitude of the force pressing the spool against the seat decreases. At the moment when this force becomes equal to zero, equilibrium occurs between the active forces from the influence of pressure in the system and the setpoint on the sensitive element of the valve. The shut-off element begins to open, if the pressure in the system does not stop increasing, the working medium is discharged through the valve.

With a decrease in pressure in the protected system caused by the release of the medium, disturbing influences disappear. The shut-off element of the valve closes under the influence of force from the setpoint.

The closing pressure in some cases turns out to be 10-15% lower than the operating pressure, this is due to the fact that to create a tightness of the shut-off valve after operation, a force is required that is significantly greater than that which was sufficient to maintain the tightness of the valve before opening. This is explained by the need to overcome, during landing, the adhesion force of the molecules of the medium passing through the gap between the sealing surfaces of the spool and the seat, to displace this medium. Also, the decrease in pressure is facilitated by the delay in closing the shut-off organ, associated with the impact on it of dynamic forces from the passing flow of the medium, and the presence of friction forces, requiring additional force for its complete closure.

Classification of safety valves

According to the operating principle

• direct acting valves - usually these are the devices that are meant when the phrase is used safety valve, they open directly under the influence of pressure from the working environment;
• valves indirect action- valves controlled by using an external source of pressure or electricity, the generally accepted name for such devices is pulse safety devices;

• proportional action valves (used on incompressible media)
• on/off valves

• low-lift
• mid-lift
• full lift

• cargo or lever-load
• spring
• lever-spring
• magnetic spring

Design Differences

Safety valves usually have an angular body, but they can also have a straight body; regardless of this, the valves are installed vertically so that the stem goes down when closing.

Most safety valves are manufactured with one seat in the body, but designs with two seats installed in parallel are also available.

Low-lifting are called safety valves valves in which the lifting height of the locking element (spool, plate) does not exceed 1/20 of the seat diameter; full-lift valves are valves in which the lifting height is 1/4 of the seat diameter or more. There are also valves with a poppet lift from 1/20 to 1/4, these are usually called mid-lift. In low-lift and medium-lift valves, the lift of the spool above the seat depends on the pressure of the medium, therefore they are conventionally called valves proportional action, although the rise is not proportional to the pressure of the working medium. Such valves are used, as a rule, for liquids when large throughput is not required. In full-lift valves, the opening occurs immediately at the full stroke of the disc, which is why they are called valves on/off action. Such valves are high-performance and are used for both liquid and gaseous media.

The greatest differences in safety valve designs lie in the type of load on the spool.

Spring valves

In them, the pressure of the medium on the spool is counteracted by the compression force of the spring. The same spring valve can be used for different response pressure settings by equipping it with different springs. Many valves are manufactured with a special mechanism (lever, fungus, etc.) for manual detonation for control purging of the valve. This is done to check the functionality of the valve, since during operation there may be problems various problems, for example, sticking, freezing, sticking of the spool to the seat. However, in some industries under conditions of aggressive and toxic environments, high temperatures and pressures, control blowing can be very dangerous, therefore, for such valves, the possibility of manual blowing is not provided and is even prohibited.

Most often, springs are exposed to the working environment, which is discharged from a pipeline or container when triggered; special spring coatings are used to protect them from mildly aggressive environments. There is no stem seal in such valves. In cases of working with aggressive media in chemical and some other installations, the spring is isolated from the working environment using a seal along the rod with a stuffing box, bellows or elastic membrane. Bellows seals are also used in cases where leakage of the medium into the atmosphere is not allowed, for example at nuclear power plants.

Lever-weight valves

In such valves, the force on the spool from the pressure of the working medium is counteracted by the force from the load, transmitted through the lever to the valve stem. Setting such valves to the opening pressure is done by fixing a load of a certain mass on the lever arm. Levers are also used to manually purge the valve. Such devices are prohibited from being used on mobile vessels.

To seal large-diameter seats, significant masses of weights on long levers are required, which can cause strong vibration of the device; in these cases, housings are used, inside of which the medium discharge cross-section is formed by two parallel seats, which are overlapped by two spools using two levers with weights. Thus, two parallel operating gates are mounted in one body, which makes it possible to reduce the mass of the load and the length of the levers, ensuring normal work valve

Magnetic spring valves

These devices use an electromagnetic drive, that is, they are not direct-acting valves. The electromagnets in them can provide additional pressing of the spool to the seat, in this case, when the response pressure is reached based on a signal from the sensors, the electromagnet is turned off and only the spring counteracts the pressure, the valve begins to operate like a regular spring one. Also, the electromagnet can create an opening force, that is, counteract the spring and force the valve to open. There are valves in which the electromagnetic drive provides both additional pressing and opening force, in this case the spring serves as a safety net in case of interruption

To reset overpressure into the atmosphere, spring safety valves are used, which are special pipeline fittings that ensure reliable protection pipeline from malfunctions and mechanical damage. The device is responsible for automatically discharging excess liquids, steam and gas from vessels and systems until the pressure is normalized.

Purpose of a spring valve

Dangerous excess pressure in the system occurs as a result of external and internal factors. An increase is caused by both incorrect assembly of thermal-mechanical circuits, which causes malfunctions in the functioning of equipment, heat entering the system from extraneous sources, and intra-system physical processes that are not provided for by standard operating conditions that periodically occur in the system.

Safety products are an essential part of any household or industrial system, working under pressure. Installation of safety mechanisms is carried out on pipelines in compressor stations, in autoclaves, in boiler rooms. Valves perform protective functions on pipelines through which not only gaseous but also liquid substances are transported.

Design and principle of operation of spring valves

The valve consists of a steel body, the lower fitting of which is used as a connecting element between it and the pipeline. If the pressure in the system increases, the medium is discharged through the side fitting. A spring adjusted depending on the pressure in the system ensures that the spool is pressed against the seat. The spring is adjusted using a special bushing, which is screwed into the top cover located on the body of the device. The cap located in the upper part is designed to protect the bushing from destruction as a result of mechanical stress. The presence of a special ear for sealing allows you to protect the system from outside interference.

For valves in which a spring acts as a balancing mechanism, the force of the working element is selected. If the parameters are selected correctly, in the normal state of the system the spool, which is responsible for releasing excess pressure from the pipeline, should be pressed against the seat. When performance increases to critical level depending on type spring device the spool moves up to a certain height.

The safety spring valve, which ensures timely pressure relief, is made of different materials:

• Carbon steel. Such devices are suitable for systems in which the pressure is in the range of 0.1-70 MPa.
• Stainless steel. Valves from of stainless steel designed for systems in which the pressure does not exceed 0.25-2.3 MPa.

Classification and characteristics of spring valves

The spring safety valve is available in three versions:

• Low lift devices suitable for gas and steam pipeline systems, the pressure in which does not exceed 0.6 MPa. The lifting height of such a valve does not reach more than 1/20 of the seat diameter
• Mid-lift devices, in which the lifting height of the spool is from 1/6 to 1/10 of the nozzle diameter.
• Full lift devices, in which the valve lift height reaches up to ¼ of the seat diameter.

There is a known classification of valves based on the method of opening them:

• Non-return spring valve. To control spring check valves, an indirect external pressure source is used. Reverse spring valves, which are called impulse safety devices, can operate through the influence of electricity.
• Straight valve. In devices direct type operating pressure The environment has a direct effect on the spool, which rises as the pressure increases.

Highlight valves open And closed type . In the case of using a direct type device, when the valve is opened, the medium is discharged directly into the atmosphere. Closed type valves remain completely sealed against environment, releasing pressure into a special pipeline.

Advantages

Highlight different kinds equipment that relieves excess pressure from the system, but spring safety valves are popular due to the presence of important advantages:

• Simplicity and reliability of design.
• Ease of setting operating parameters and ease of installation.
• Variety of sizes, types and designs.
• Installation of the safety product is possible in both horizontal and vertical positions.
• Relatively small overall dimensions.
• Large flow area.

The disadvantages of safety valves include the presence of restrictions on the lifting height of the spool, increased requirements to the quality of manufacture of the spring for safety valves, which may fail when operating in an aggressive environment or constant exposure high temperatures.

How to choose a spring valve?

When choosing a fuse, you should be based on several important principles, the consideration of which determines the uninterrupted operation of the system and the ability of the fuse to perform the necessary functions:

• Safety spring valves have smallest dimensions compared to other types of safety relief valves, so they should be chosen in cases where free space not enough.
• Features of the use of valves are associated with the presence of increased vibrations, which negatively affect performance characteristics device and can quickly render it unusable. For example, lever-load type devices are more susceptible to breakdowns due to exposure to vibrations due to the presence of a long lever with weight and hinges in the design. Therefore, for systems in which significant vibration impacts are observed, it is worth choosing a spring safety valve.
• Depending on the design features of the device, the spring may change the pressure force over time. This is due to the fact that the constant rise of the spool causes changes in the structure of the metal.

Installation nuances

Safety valve spring type installed at any point in the system that is exposed to high blood pressure and is in danger of getting mechanical damage. The device does not require a lot of free space, which is a significant advantage compared to other types of safety devices.

To avoid operational problems, do not install any shut-off valves. To reset gaseous medium special devices are installed or discharge occurs directly into the atmosphere. To alert personnel, a special whistle is mounted along with the spring valves, which is placed on the discharge pipe. When the valve is activated, a whistle will sound, indicating that the pressure in the system has increased and the valve has opened to release the medium.

Possible causes of safety valve failures

Safety valves are durable and reliable devices that provide constant protection of systems from overpressure. A direct or reverse spring valve fails for several reasons:

• The presence of increased vibrations;
• Constant exposure to an aggressive environment on the safety choke.
• Incorrect installation of safety spring throttle or valve.

In order to avoid accidents and malfunctions in the functioning of systems, safety valves undergo periodic checks for malfunctions. Valves are tested for strength and tightness before being put into operation. Periodic checks are also carried out to determine the tightness of sealing surfaces and gland connections.

At making the right choice safety devices taking into account system parameters, periodic inspections and timely troubleshooting, spring safety valves will ensure reliable operation of the system and trouble-free protection against overpressure for a long time.

A mandatory element of equipping autonomous water supply systems in dachas and country houses is a check valve. That's exactly what technical device, which can have different designs, ensures the movement of liquid through the pipeline in the required direction. Check valves installed in an autonomous water supply system reliably protect it from the consequences emergency situations. Relating to direct-acting valves, check valves operate automatically using the energy of the working medium transported through pipeline system.

Purpose and principle of operation

The main function that a water check valve performs is that it protects the water supply system from critical flow parameters of the liquid transported through the pipeline. Most common cause critical situations is to stop pumping unit, which can lead to a number of negative phenomena - draining water from the pipeline back into the well, spinning the pump impeller in the opposite direction and, accordingly, breakdown.

The installation allows you to protect the water supply system from the listed negative phenomena. check valve to the water. In addition, the water check valve prevents the consequences caused by water hammer. The use of check valves in pipeline systems makes their operation more efficient and also ensures correct functioning pumping equipment with which such systems are equipped.

The principle of operation of the check valve is quite simple and is as follows.

• The flow of water entering such a device under a certain pressure acts on the locking element and presses the spring, with the help of which this element is kept closed.
• After the spring is compressed and the shut-off element is opened, water begins to move freely through the check valve in the required direction.
• If the pressure level of the working fluid flow in the pipeline drops or the water begins to move in the wrong direction, spring mechanism valve returns the shut-off element to the closed state.

By acting in this way, the check valve prevents the formation of unwanted backflow in the piping system.

When choosing a valve model installed on a water supply system, it is important to know regulatory requirements, which manufacturers of pumping equipment require for such devices. Technical parameters, according to which a check valve for water is selected in accordance with these requirements, are:

• working, trial and nominal pressure closures;
• diameter of the landing part;
• conditional capacity;
• tightness class.

Information about how technical requirements The check valve for water must correspond, as a rule, contained in the documentation for the pumping equipment.

For equipping water supply systems household use use spring type check valves, diameter conditional passage falls within the range of 15–50 mm. Despite their compact size, such devices demonstrate high throughput, ensure reliable operation of the pipeline, low level noise and vibration in the pipeline system on which they are installed.

Another positive factor of using check valves in a water supply system is that they help reduce the pressure created by the water pump by 0.25–0.5 Atm. In this regard, a check valve for water allows you to reduce the load on both individual elements equipment of pipelines, and the entire water supply system as a whole.

Design features

One of the most common materials used to make the body of water return valves is brass. Choice of this material is not accidental: this alloy demonstrates exceptionally high resistance to chemically aggressive substances that may be present in water transported through a pipeline in a dissolved or suspended state. Such substances, in particular, include mineral salts, sulfur, oxygen, manganese, iron compounds, etc. The outer surface of the valves, which during their operation is also exposed to negative factors, is often protected with a special coating applied by the galvanic method.

The check valve device requires the presence of a spool, for the manufacture of which brass or durable plastic can also be used. The sealing gasket present in the check valve design can be rubber or silicone. For the manufacture of important element locking mechanism– springs – usually use stainless steel.

So, if we talk about structural elements spring check valve, then this device comprises:

• composite type housings, the elements of which are connected to each other by means of threads;
• a locking mechanism, the design of which includes two movable spool plates mounted on a special rod and a sealing gasket;
• a spring installed between the spool plates and the seat at the outlet of the through hole.

The principle of operation of a spring check valve is also quite simple.

• The flow of water entering the check valve under the required pressure acts on the spool and depresses the spring.
• When the spring is compressed, the spool moves along the rod, opening the passage hole and allowing the fluid flow to move freely through the device.
• When the pressure of the water flow in the pipeline on which the check valve is installed drops, or in cases when such flow begins to move in the wrong direction, the spring returns the spool to its seat, closing the throughput hole of the device.

Thus, the operation scheme of the check valve is quite simple, but nevertheless ensures high reliability of such devices and the efficiency of their use in pipeline systems.

Main types

Having understood how the check valve installed in plumbing system, you should also understand how to choose it correctly. On modern market Various types of check valve devices are offered, the design, material of manufacture and operation scheme of which can vary significantly.

Valve body of this type consists of two cylindrical elements connected to each other using threads. The locking mechanism includes a plastic rod, upper and lower spool plates. The position of the elements of the locking mechanism in the closed state, as well as their opening at the moment when the pressure of the water flow reaches the required level, is ensured by a spring. The component elements of the housing are connected to each other using a sealing gasket.

The distinctive features of this type of shutter are easy to see even in the photo. The brass body of such a valve in its middle part, where the spool chamber is located, has a spherical shape. Such design feature allows you to increase the volume of the spool chamber and, accordingly, the throughput of the check valve. The locking mechanism of this type of water valve, which is based on a brass spool, works on the same principle as in any other type of valve device.

Many of those who decide to independently install a pipeline system often have a question about why they need a check valve equipped with drainage and air vent systems. The use of check valves of this type (especially for equipping pipelines through which hot working fluids are transported) makes it possible to simplify the process of installation and maintenance of such systems, increase their reliability, reduce the total hydraulic pressure, and reduce the number of installation connections.

On the body of this type of valve, which can be seen even in the photo, there are two pipes, one of which is used for installing an air vent, and the second serves as a drainage element. The branch pipe for the air vent, on the inner surface of which is threaded, is located on the device body above the spool chamber (its receiving part). Such a pipe is needed to bleed air from the pipeline system, for which a Mayevsky valve is additionally used. The purpose of the pipe, which is located on the opposite side of the body - at the outlet of the valve, is to drain the liquid accumulated after the valve device from the system.

If you install a horizontal check valve, its air outlet pipe can be used to mount a pressure gauge. If you place a combined check valve on a pipeline vertically, then its drainage pipe can be used to drain water accumulated after such a device, and the air vent pipe can be used to remove it from the part of the pipeline that is located before the check valve. air jams. That is why, when deciding how to install a combined type check valve, you should clearly understand what functions such a valve should perform.

Check valves, the body of which is made of polypropylene, even if you look at the photos of such devices, look very similar to oblique bends. These types of check valves, for installation of which the polyfusion welding method is used, are installed on pipelines also made of polypropylene. An additional oblique outlet in the design of valves of this type is necessary to accommodate the elements of the locking mechanism, which makes it easier Maintenance such a device. Thereby constructive solution It is not difficult to carry out maintenance and repair of a check valve of this type - it is enough to remove the elements of the locking mechanism from its additional outlet without violating the integrity of the device body and the tightness of its installation in the pipeline system.

In pipeline systems designed to transport water, other types of check valves can be installed.

• The check valve is equipped with a special shut-off element - a spring-loaded petal. The big disadvantage of valves of this type is that when they operate, significant shock loads are created. This has a negative impact on technical condition the valve itself, and can also cause water hammer in the pipeline system.
• Double-leaf check valve devices are compact in size and light in weight.
• The lift-off coupling check valve includes a spool as a shut-off element, which moves freely along vertical axis. The operation of the locking mechanism can be based on gravitational principle when the spool returns to the closed state under the influence of its own weight. A spring can also be used for this purpose. If you decide to install a gravity check valve on the pipeline, keep in mind that such a device can only be installed on vertical sections of the system. Meanwhile, the gravity valve is characterized by a simple design, while demonstrating high reliability during operation.
• There are check valves whose closing element is a spring-loaded metal ball. The surface of such a ball can be additionally covered with a layer of rubber.

Deciding which check valve is best and whether an expensive valve is needed in the pipeline system is more complex design, you should first get to know technical characteristics such a device and compare them with the operating parameters of the pipeline system. The main purpose of the check valve, as mentioned above, is to pass water through the pipeline in the desired direction and prevent the liquid flow from moving in reverse side. In this regard, you should choose a check valve for water based on the pressure under which the water flow moves in the pipeline. Naturally, it is necessary to take into account the diameter of the pipes on which such a valve should be installed.

When installing the pipeline, you should also keep in mind that you can install a check valve different ways. On pipes of significant diameter, check valves of flange and wafer type are installed, and on pipes of small diameter, coupling valve devices are installed. Welding method installation of check valves is used mainly for installation on polypropylene and metal-plastic pipes.

If you choose the right check valve and the method of its installation, such a device will not only last long time, but will also ensure the correct operation of the entire pipeline system.

How to install correctly

Having understood the question of why a check valve is needed and its role in the pipeline system, you should also study the rules for installing it on an already operating or newly created pipeline. Such devices are mounted on various elements pipeline systems:

• on pipelines of autonomous and centralized water supply;
• on suction lines served by deep and surface pumps;
• in front of boilers, cylinders and water flow meters.

If you are interested in check valves that can be installed in both vertical and horizontal positions, choose spring models rather than gravity ones. You can find out in which direction the water flow should move through the valve by looking at the special arrow marked on the body of the device. When installing coupling-type check valves, be sure to use FUM tape for good sealing. In addition, we should not forget that check valves need regular maintenance, therefore they must be installed in accessible places in the pipeline.

When installing a check valve on the suction line submersible pump care should be taken to ensure that a filter is installed in front of such a device rough cleaning, which will not let you get into inner part devices for mechanical impurities contained in underground water. A perforated or mesh cage can also be used as such a filter, into which a check valve installed at the inlet end of the suction line of a submersible pump is placed.

When installing a check valve on an already operating pipeline, you must first disconnect the system from the water supply and only then install the shutter device.

How to make your own check valve

The simple design of the check valve allows you to make it yourself if necessary.

To solve this problem you will need following materials and tools:

• tee with internal thread, which will serve as a body;
• a coupling with a thread on the outer surface - the seat of a homemade check valve;
• rigid spring made of steel wire;
• a steel ball, the diameter of which should be slightly smaller than the diameter of the hole in the tee;
• a steel threaded plug that will serve as a stop for the spring;
• standard set metalworking tools and FUM sealing tape.
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