Special spring safety valve. Safety valve. Disadvantages of Lever Relief Valves

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

Purpose and principle of operation

The main function that a check valve for water performs is that it protects the water supply system from critical parameters of the flow of 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.

Installing a check valve on water allows you to protect the plumbing system from the listed negative phenomena. In addition, the water check valve prevents the consequences that water hammer causes. The use of check valves in pipeline systems makes it possible to make their work more efficient, as well as to ensure the correct functioning of the pumping equipment that such systems are equipped with.

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 depresses the spring, with which this element is held closed.
• After compressing the spring and opening the locking element, 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, the spring mechanism of the valve returns the shut-off element to the closed state.

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

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

• operating, trial and nominal closing pressure;
• landing part diameter;
• conditional throughput;
• tightness class.

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

For equipping water supply systems household purpose check valves are used spring type, the nominal bore diameter is in the range of 15–50 mm. Despite their compact size, such devices demonstrate high throughput, ensure the reliability of pipeline operation, low level noise and vibration in the piping system on which they are installed.

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

Design features

One of the most common materials from which the body part of the water return valves is made is brass. Choice this material not accidental: this alloy demonstrates an exceptionally high resistance to chemically aggressive substances, which can be in the water transported through the 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 is also exposed to negative factors during their operation, is often protected with a special coating applied by the galvanic method.

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

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

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

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

• The flow of water entering the check valve at the required pressure acts on the spool and depresses the spring.
• When the spring is compressed, the spool moves along the stem, opening the orifice and allowing fluid to flow freely through the device.
• When the pressure of the water flow in the pipeline on which the check valve is located, or in cases where such a flow begins to move in the wrong direction, the spring returns the spool to its seat by closing the opening of the device.

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

Main types

Having figured out how the check valve installed in the plumbing system works, you should also understand how to choose it correctly. On the modern market there are different kinds check valve devices, the design, material of manufacture and the scheme of operation of which can vary significantly.

The valve body of this type consists of two cylindrical elements connected to each other by means of a thread. The locking mechanism includes a plastic stem, 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 provided by a spring. Between themselves, the constituent elements of the body are connected using a sealing gasket.

Distinctive features of this type of shutters 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 valve devices of any other type.

Many of those who decide to do the installation of the pipeline system on their own often have the question of why a check valve is needed, equipped with drainage and air vent systems. The use of check valves of this type (especially for equipping pipelines through which hot working media are transported) makes it possible to simplify the installation process and Maintenance such systems, increase their reliability, reduce the total hydraulic pressure, reduce the number of field connections.

On the valve body of this type, which can even be seen in the photo, there are two nozzles, one of which is used to mount the air vent, and the second serves as a drainage element. Branch pipe for the air vent, on inner surface which is threaded, is located on the body of the device above the spool chamber (its receiving part). Such a pipe is needed to bleed air from the pipeline system, for which a Mayevsky crane is additionally used. The purpose of the branch 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 a horizontal non-return valve is installed, its air outlet can be used to mount a pressure gauge. If you put the combined check valve vertically on the pipeline, then its drainage pipe can be used to drain the water accumulated after such a device, and the air vent pipe can be used to remove air plugs from that part of the pipeline that is located before the check valve. That is why, when deciding how to install a check valve combined type, you should clearly understand what functions such a shutter should perform.

Check valves, the body of which is made of polypropylene, even if you look at the photos of such devices, outwardly very much resemble oblique bends. These types of check valves, for the 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 gates of this type is necessary to accommodate the elements of the locking mechanism in it, which facilitates the maintenance of such a device. Thanks to this constructive solution, it is not difficult to carry out maintenance and repair of this type of check valve - 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.

Other types of non-return valves can be installed in pipeline systems designed for transporting water.

• The flap check valve is equipped with a special locking element - a spring-loaded petal. A big disadvantage of this type of shutters is that when they are triggered, significant shock loads are created. This negatively affects the technical condition of the gate device itself, and can also cause a hydraulic shock in the pipeline system.
• Double-leaf type check valve devices are compact in size and light in weight.
• The lifting coupling check valve includes a spool freely moving along the vertical axis as a locking element. The operation of the locking mechanism can be based on the 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 in vertical sections of the system. Meanwhile, the gravity valve is characterized by simple structure, while showing high reliability during operation.
• There are check valves, the locking element of which 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 a piping system needs an expensive valve is more complex design, you should first get to know technical specifications such a device and compare them with the parameters of the pipeline system. The main purpose of the check valve, as mentioned above, is to pass water through the pipeline in the right direction and prevent the flow of liquid from moving in reverse side. In this regard, the check valve for water should be selected 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, it should also be borne in mind that a check valve can be installed different ways. Flanged and wafer type check valves are installed on pipes of large diameter, and sleeve valves are installed on pipes of small diameter. The welded method of installing check valves is mainly used when mounting on polypropylene and metal-plastic pipes.

If you choose the right check valve and the way it is installed, such a device will not only serve long time, but also ensure the correct operation of the entire pipeline system.

How to install correctly

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

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

If you are interested in check valves that can be installed both vertically and horizontally, choose not gravity, but spring models. You can find out in which direction the water flow should move through the valve using a special arrow printed on the body of the device. When installing sleeve-type check valves, be sure to use FUM tape for good sealing. In addition, one should not forget that check valves need regular maintenance, so they must be installed in accessible places in the pipeline.

When installing a non-return valve on the suction line submersible pump care should be taken to ensure that a coarse filter is installed in front of such a device, which will prevent it from getting into inner part devices to mechanical impurities contained in underground water. As such a filter, a perforated or mesh cage can also be used, in which a check valve is placed at the inlet end of the suction line of the submersible pump.

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 shut-off device.

How to make a check valve yourself

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

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

• tee with internal thread, which will perform the function of the body;
• threaded socket outer surface- a homemade check valve seat;
• 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;
• steel threaded plug, which will act as a stop for the spring;
• a standard set of locksmith tools and a FUM sealing tape.
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The safety valve is a pipe fitting that protects high pressure equipment and pipelines from mechanical damage and various kinds of destruction as a result of the occurrence emergencies. This is achieved by venting excess liquid, gas or vapor from the system, as well as vessels in which excessive pressure is formed. In addition, this valve prevents the discharge of the working medium when the nominal pressure is restored.

A safety valve is a mechanism that operates in direct contact with the working medium, together with other structures that perform the function of protective fittings, including pressure regulators.

The main types of valves and their purpose

All safety products may differ from each other in a number of parameters, depending on design features, namely:

1. Closing valve type:
   • proportional;
   • on-off.
2. According to the lifting height of the closing body:
   • low-lift;
   • medium-lift;
   • full-lift.
3. Depending on the type of load on the spool:
   • spring;
   • lever;
   • lever-spring;
   • magnetic spring.

Also, safety valves may differ in the nature of their work and be direct or indirect acting devices. The former are considered classic safety mechanisms, while the latter belong to the class of impulse devices. The most commonly used modification in the industry is the spring type angular safety choke.

High pressure (or rather, its excess) can occur in the system due to different reasons caused by physical internal processes or other external factors, such as, for example:

A non-return valve is an element of a pipeline system that provides for the movement of the working medium in only one direction. Its use is mandatory for autonomous pumping stations and other equipment that can fail if the fluid flow moves in the opposite direction.

Check valve spring - one of the varieties of locking elements. It belongs to the category of direct acting valves and operates automatically from the energy of the working environment, which prevents equipment failure in the event of a power outage and other malfunctions.

Design features

The spring valve structurally consists of three elements:

1. The 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, the diameter of the pipeline.
2. The working element, which is a movable spool, includes two plates with a special sealed gasket between them and a stem.
3. An executive body representing a spring located between the plates of the working element and the seat. Provides automatic shutoff of the fluid flow when the pressure drops 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 mounting in any position;
• simplicity of design;
• versatility.

At the same time, the valve is sensitive to impurities 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 in easily accessible places to simplify its maintenance and replacement.

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

Scope of application

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

Safety valves- a type of pipeline fittings designed to protect the heating system from excessive pressure. The safety valve is a direct acting valve, i.e. valves operating directly under the control of the working medium itself (as well as direct-acting pressure regulators).

Safety valve classification:

By the nature of the rise of the closing body:

• valves of proportional action (used on incompressible media);
• two-position valves;

According to the lifting height of the closing body:

• low-lift (lifting height of the locking element (spool, plate) does not exceed 1/20 of the saddle diameter);
• medium-lift (plate lifting height from 1/20 to ¼ of the saddle diameter);
• full-lift (lift height is 1/4 of the saddle diameter or more);

By type of load on the spool:

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

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 also called valves. proportional action. These valves are mainly used for liquids where a large capacity is not required. In full-lift valves, the opening occurs in one step, therefore they are also called valves two-position action. These valves are highly efficient and are used for both liquid and gaseous media.

Lever (lever-weight) safety valves, principle of operation:

The principle of operation of a lever-weight safety valve is to counteract the force on the spool from the pressure of the working medium - the force from the load transmitted through the lever to the valve stem. The basis of the mechanism of this type of valve is a lever and a load suspended from it. The operation of the device depends on the weight of the load and its location on the lever. The more weight and the farther on the lever it is, the more high pressure valve is activated. Lever valves are adjusted to the opening pressure by moving the weight on the lever (possibly changing the weight of the weight). Levers are also used to manually purge the valve. Lever valves must not be used on mobile heating devices.

The internal structure of the lever safety valve:

1.Inlet port; 2. Outlet; 3. valve seat; 4. Spool; 5. Cargo; 6. Lever.

For hermetically sealed saddles large diameters requires heavy weights on long arms, which can cause severe vibration of the device. In these circumstances, valves are used, inside which the medium discharge cross-section is formed by two saddles, which are blocked by two spools using two levers with weights (see for example: , ). The use of these two-lever valves with two gates, which allows to reduce the weight of the load and the length of the levers, ensuring the normal operation of the system.

Setting lever weight valve, as noted above, is carried out by moving the load along the lever. After the necessary pressure has been set, the load is fixed with bolts, covered protective cover and locks up. This is done to prevent unauthorized changes to the settings. Flanges are often used as cargo.

Features of lever-weight valves:

Lever valves - pipeline accessories, which was developed before the 40th year of the last century. This is an obsolete valve, purchased only to maintain boiler stations and similar facilities from the time of the Soviet public utilities.

A feature of the valve is the need to grind the working surfaces (spool and seat - a pressed bronze sealing ring) directly at the valve installation site. Lapping refers to the treatment of a bronze seat with abrasive materials to achieve tighter contact between the spool and seat. The spool in the valve body is not fixed and its working surfaces are easily damaged during transportation and loading. A valve without lapping will not seal.

Benefits of Lever Relief Valves:

• Simplicity of design;
• maintainability;
• Manual setting of valve actuation;

Disadvantages of Lever Relief Valves:

• The need to grind working surfaces;
• Small service life of the valve;
• Bulky design;

Spring loaded safety valves, working principle:

The principle of operation of a spring-loaded safety valve is to counteract the force of the spring - the force on the spool from the pressure of the working medium (coolant). The coolant exerts pressure on the spring, which is compressed. When the setting pressure is exceeded, the spool rises and the coolant is discharged through the outlet pipe. After the pressure in the system has decreased to the setting value, the valve closes and the coolant descent stops.

The internal structure of the spring-loaded safety valve:

1 - body; 2 - nozzles; 3 - lower adjusting sleeve; 4, 5 - locking screw; 6, 19, 25, 29 - gasket; 7 - upper adjusting sleeve; 8 - pillow; 9 - spool; 10 - guide sleeve; 11 - special nut; 12 - partition; 13 - cover; 14 - stock; 15 - spring; 16 - support washer; 17 - adjusting screw; 18 - locknut; 20 - cap; 21 - cam; 22 - guide sleeve; 23 - nut; 24 - plug; 25 - cam shaft; 27 - key; 28 - lever; 30 - ball.

The opening pressure of a spring-loaded safety valve is set by fitting the valve with various springs. Many valves are manufactured with a special mechanism (lever, fungus, etc.) for manual blasting for control blowing of the valve. This is done in order to check the operability of the valve, since various problems may arise during operation, for example, sticking, freezing of the spool to the seat. However, in industries using aggressive and toxic media, high temperatures and pressures, control purge can be very dangerous. Therefore, for spring valves used in such industries, the possibility of manual purge is not provided and is even prohibited.

When working with aggressive chemical media, the spring is isolated from the working medium by means of sealing along the rod with a stuffing box, bellows or an elastic membrane. The bellows seal is also used in cases where leakage of the medium into the atmosphere is not allowed, for example, at nuclear power plants. Maximum temperature working medium for safety spring valves up to +450°C, pressure up to 100 bar.

The relief relief valve opens before the set pressure is reached. The valve opens completely when the pressure exceeds the set pressure by 10-15% (depending on the model). The device closes completely only when the pressure is 10-20% less than the setting pressure, because the outgoing coolant creates additional dynamic pressure.

If the heating system functions stably, without failures and overpressure, the relief safety valve remains without "work" for a long period of time and may become clogged. Therefore, it is recommended to clean it periodically.

Benefits of Spring Valves :

• simple equipment design;
• small size and weight with large passage sections;
• possibility of installation in both vertical and horizontal positions;
• the possibility of obtaining high throughput.

Disadvantages of Spring Valves :

• a sharp increase in the force of the spring when it is compressed in the process of lifting the spool;
• the possibility of obtaining a hydraulic shock when the valve is closed;

Magnetic spring safety valves, working principle:

Magnetic spring safety valves use an electromagnetic actuator. The electromagnet provides additional pressing of the spool to the seat. When the set pressure is reached, the electromagnet is turned off and only the spring counteracts the pressure, and the valve starts to work like a conventional spring valve. Also, the electromagnet can create an opening force, that is, oppose the spring and forcibly open the valve. 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 a power outage. Solenoid spring valves are commonly used in complex impulse safety devices as pilot or impulse valves.