Special spring loaded safety valve. Safety spring valves - everything about design and installation

With pressure in excess of the set pressure. The valve must also ensure that the discharge of the medium is stopped when the operating pressure is restored. The safety valve is an armature direct action operating directly from the working medium, along with most designs of protective valves and direct-acting pressure regulators.

Dangerous overpressure can arise in the system as a result of third-party factors (improper operation of equipment, heat transfer from third-party sources, improperly assembled thermomechanical 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 domestic pressure vessels.

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Why safety valve in the hot water supply system

Safety valve design (stereo anaglyph)

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Operating principle

When the safety valve is closed, force is exerted on its sensing element by working pressure in the protected system, tending to open the valve and the force from the setpoint, preventing the opening. With the emergence of disturbances in the system, causing an increase in pressure above the working pressure, the value of the force of pressing the spool to the seat decreases. At the moment when this force becomes equal to zero, an equilibrium of active forces occurs from the effect of pressure in the system and the actuator 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 dumped through the valve.

With a decrease in pressure in the protected system caused by the discharge of the medium, disturbing influences disappear. The shut-off element of the valve is closed under the action of the force from the adjuster.

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 the tightness of the shut-off element after operation, a force is required that is much greater than that which was sufficient to maintain the tightness of the valve before opening. This is explained by the need to overcome the adhesion force of the molecules of the medium passing through the gap between the sealing surfaces of the valve spool and the seat during landing, to displace this medium. Also, a decrease in pressure is facilitated by the delay in closing the shut-off element, associated with the impact on it of dynamic forces from the passing flow of the medium, and the presence of friction forces that require additional effort to close it completely.

Safety valve classification

By the principle of action

• direct acting valves - these are usually the devices they mean when the phrase is used safety valve, they open directly under the action of the pressure of the working medium;
• indirect valves - valves controlled by using an external source of pressure or electricity, the common name for such devices is impulse safety devices;

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

• low lift
• mid-rise
• full lifting

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

Differences in designs

Safety valves usually have an angle body, but they can also have a straight-through, regardless of this, the valves are installed vertically so that when the stem is closed, it goes down.

Most relief valves are made with one seat in the body, but there are designs with two seats in parallel.

Low-lift safety valves are those in which the lift height of the locking element (spool, disc) does not exceed 1/20 of the seat diameter, full-lift valves are valves whose lift height is 1/4 of the seat diameter or more. There are also 1/20 to 1/4 poppet lift valves, commonly referred to as mid-lift valves. 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. These valves are used, as a rule, for liquids when a large throughput... In full-lift valves, the opening occurs immediately to the full stroke of the disc, therefore they are called valves two-position action... These valves are highly efficient and are used for both liquid and gaseous media.

The biggest differences in safety valve designs are in the type of load applied to the spool.

Spring loaded 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 setting limits of the response pressure by completing with different springs. Many valves are made with a special mechanism (lever, fungus, etc.) for manual blowing for control valve purging. This is done in order to check the functionality of the valve, since during operation, various problems e.g. 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 purging can be very dangerous, therefore, for such valves, the possibility of manual purging is not provided and is even prohibited.

Most often, the springs are exposed to the working medium, which is discharged from the pipeline or container when triggered; special spring coatings are used to protect against mildly aggressive media. These valves do not have a stem seal. In cases of work with aggressive media in chemical and some other installations, the spring is isolated from the working medium by means of a seal on the stem with a stuffing box, bellows or elastic diaphragm. The bellows seal is also used in cases where the leakage of the medium into the atmosphere is not allowed, for example, at a nuclear power plant.

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. The adjustment of such valves to the opening pressure is made by fixing a weight of a certain mass on the lever arm. The levers are also used to manually purge the valve. Such devices must not be used on mobile vessels.

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

Solenoid valves

These devices use an electromagnetic drive, that is, they are not direct-acting valves. Electromagnets in them can provide additional pressing of the spool to the seat, in this case, when the trigger pressure is reached, according to the signal from the sensors, the electromagnet is turned off and only the spring opposes the pressure, the valve begins to work like a conventional spring valve. Also, the electromagnet can create an opening force, that is, oppose the spring and force the valve to open. There are valves in which the electromagnetic drive performs both additional pressing and opening force, in this case the spring serves as a safety net in case of termination

An obligatory element of equipping autonomous water supply systems in summer cottages and in country houses is a non-return valve. It is such a technical device, which can have a different design, that ensures the movement of the liquid 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 valve devices, check valves are triggered automatically, for which the energy of the working medium transported through the pipeline system is used.

Purpose and principle of operation

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

To protect the water supply system from the listed negative phenomena, it is possible to install a check valve on the water. In addition, the water check valve prevents the effects of water hammer. The use of check valves in piping systems allows them to work more efficiently, as well as to ensure the correct functioning of the 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 shut-off element and depress the spring, with the help of which this element is kept in a closed state.
• After the spring is compressed and the shut-off element is opened, the 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 starts to move in the wrong direction, the valve spring mechanism returns the shut-off element to the closed state.

By doing so, the non-return 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 are presented to such devices by manufacturers of pumping equipment. Technical parameters, according to which, in accordance with these requirements, a check valve for water is selected are:

• working, test and nominal closing pressure;
• seat diameter;
• conditional throughput;
• tightness class.

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

To equip water supply systems for domestic use, spring-type check valves are used, the nominal diameter is in the range of 15-50 mm. Despite their compact size, such devices demonstrate high throughput, ensure reliable operation of the pipeline, low noise and vibration levels in the pipeline system on which they are installed.

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

Design features

One of the most common materials from which the body part of water return valves is made is brass. Choice of this material not accidental: this alloy demonstrates extremely high resistance to the effects of chemically aggressive substances, which can be dissolved or suspended in the water transported through the pipeline. Such substances, in particular, include mineral salts, sulfur, oxygen, manganese, iron compounds, etc. The outer surface of the gates, which during their operation is also exposed to negative factors are often protected with a special electroplated coating.

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

So, if we talk about the structural elements of the spring check valve, then this device consists of:

• case of a composite type, the elements of which are connected to each other 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;
• a spring installed between the spool plates and the seating seat at the outlet of the orifice.

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

• The flow of water entering the check valve at the required pressure acts on the spool and depress the spring.
• When the spring is compressed, the spool moves along the stem, opening the orifice and allowing fluid flow to move 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 closing the through-hole of the device.

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

Main types

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

Valve body of this type consists of two cylindrical elements connected by means of a thread. The shut-off 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. The body components 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 to increase the volume of the spool chamber and, accordingly, the throughput of the check valve. The shut-off 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 decided to independently engage in the installation of the pipeline system often have a question about why a check valve equipped with a drainage and air vent system is needed. The use of this type of check valves (especially for equipping pipelines through which hot working media are transported) simplifies the installation process and Maintenance of such systems, to increase their reliability, to reduce the total hydraulic pressure, to reduce the number of mounting connections.

On the valve body of this type, which can be seen even in the photo, there are two nozzles, one of which is used for mounting the air vent, and the other acts as a drainage element. The branch pipe for the air vent, on the inner surface of which the thread is cut, is located on the body of the device above the spool chamber (its receiving part). Such a branch pipe is needed to bleed air from the pipeline system, for which a Mayevsky crane is additionally used. Purpose of the branch pipe, which is located on opposite side body - at the outlet of the valve, consists in draining 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 drain pipe can be used to drain the water accumulated after such a device, and the air vent pipe can be used to remove air locks from the part of the pipeline that is located before the check valve. That is why, when deciding how to install a check valve combined type, it should be clearly understood what functions such a shutter should perform.

Check valves, the body of which is made of polypropylene, even if you look at the photo 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. Thereby constructive decision 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 check valves can be installed in pipeline systems intended for transporting water.

• The petal check valve is equipped with a special shut-off element - a spring-loaded petal. Big disadvantage gates of this type is that when they are triggered, significant shock loads are created. This negatively affects the technical condition of the shutter device itself, and can also cause a water hammer in the pipeline system.
• Double-leaf check valve devices are compact in size and light in weight.
• The lifting clutch check valve includes, as a shut-off element, a spool that freely moves along a vertical axis. 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 installation of such a device can only be performed on vertical sections systems. Meanwhile, the gravity valve is distinguished by its simple design, while demonstrating high reliability during operation.
• There are check valves, the closing element of which is a spring-loaded metal ball. The surface of such a ball can be additionally covered with a rubber layer.

When deciding which check valve is better and whether an expensive valve of a more complex design is needed in the pipeline system, you should first get acquainted with technical characteristics 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 desired direction and prevent the fluid flow from moving in the opposite direction. In this regard, a water check valve should be chosen based on the pressure under which the water flow moves in the pipeline. Naturally, it is imperative 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 you can install a check valve different ways... Flanged and flanged check valves are installed on pipes of significant diameter. wafer type, and on pipes of small diameter - coupling locking devices. The welded method of installing check valves is mainly used 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 serve long time, but will 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 newly 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, DHW cylinders 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 flow of water should move through the valve by looking at a special arrow on the body of the device. When installing clutch type check valves, for good sealing, be sure to use FUM tape. In addition, it should not be forgotten that check valves need regular maintenance, so 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 that a coarse filter is installed in front of such a device, which will not allow mechanical impurities contained in the groundwater to enter the interior of the device. A perforated or mesh cage can also be used as such a filter, in which a check valve is placed, installed at the inlet end of the suction line of a submersible pump.

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

How to make a check valve yourself

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

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

• tee with internal thread, which will perform the function of the body;
• a threaded sleeve on the outer surface - a saddle of a homemade check valve;
• stiff 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 spring stop;
• standard set locksmith tools and sealing FUM-tape.
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Check valve- an element of the pipeline system, providing 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 flows in the opposite direction.

Spring check valve - one of the types of shut-off elements. It belongs to the category of direct-acting valves and is triggered automatically from the energy of the working environment, which prevents equipment failure during a power outage and other malfunctions.

Design features

The spring-loaded valve is structurally composed of three elements:

1. The body is 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 medium, the diameter of the pipeline.
2. The working element, which is a movable spool, includes two discs with a special sealed gasket between them and a stem.
3. An actuator representing a spring located between the plates of the working element and the seat. Provides automatic shut-off of the fluid flow when the pressure decreases or changes in its direction. The stiffness of the spring determines the minimum pressure of the working medium at which the valve automatically opens.

Advantages of spring-loaded check valves:

• the ability to mount 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, therefore it is advisable to install a filter in front of it. It is also recommended to mount the valve in an easily accessible location to facilitate maintenance and replacement.

It is desirable to mount the valve in an upright position so that the locking force of the spring matches the force of gravity. For correct installation it is necessary to be guided by the arrow on the valve body, which shows the flow direction of the working medium.

Scope of application

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

Spring safety valve (gearbox)- type of pipeline fittings designed for automatic protection of equipment and pipelines from overpressure exceeding a predetermined value by dumping the excess of the working medium and ensuring the termination of the dump at the closing pressure and restoration of the working pressure.

Main assembly units and valve parts:

1 - body, 2 - seat, 3 - spool, 4 - cover, 5 - stem, 6 - nut, 7 - stud, 8 - spring, 9 - bellows (installed in bellows valves), 10 - locking screw, 11 - adjusting sleeve, 12 - guide sleeve, 13 - baffle, 14 - adjusting screw, 15 - cap, 16 - threaded flange.

Principle of operation. At normal operating pressure, the force of the compressed spring presses the spool against the seat (the port for the discharge of the working medium is closed). When the pressure rises above the set value, an oppositely directed force begins to act on the spool, which compresses the spring, and the spool rises, opening the passage for the discharge of the working medium. After the pressure before the valve has dropped to the closing pressure, the spool is again pressed against the seat by the spring, stopping the discharge of the medium.

Installation position - vertical, cap up.

Shutter tightness- class "B" GOST R 54808. At the request of the customer, it is possible to manufacture with other classes of tightness.

Possible valve designs:

• A sealed cap with a forced opening unit and without such a unit.
• Balancing bellows.
• Thermal protective partition.
• "Open" lid.
• Locking element preventing valve actuation.

Connection to the pipeline:

• flanged;
• for a lens extension (flange in accordance with GOST 9399);
• choke;
• tsapkovoe.

Valves with bellows.

The bellows is a mechanism that compensates for the action of the back pressure at the outlet of the valve. The bellows is designed to protect the valve spring from the harmful effects of an aggressive working environment at high or low temperatures. Bellows valves are made of steel grades 12Х18Н9ТЛ and 12Х18Н12МЗТЛ and are designed for working environments with temperatures from minus 60 ° C and below. Bellows valves designation: KPP4S, KPPS.

The design of the sealing surfaces and the connecting dimensions of the valve flanges are in accordance with GOST 12815-80, row 2, construction lengths are in accordance with GOST 16587-71.

Valves DN 25 PN 100 kgf / cm2 can be manufactured with choke ends for connection to the pipeline in accordance with GOST 2822-78, as well as with a flange connection in accordance with GOST 12815-80, row 2.

Safety valves with a nominal pressure of PN 250 kgf / cm2 and PN 320 kgf / cm2, like other models, are designed to protect equipment from unacceptable overpressure by automatically dumping excess working medium. They are used on equipment with liquid and gaseous working media that do not corrode body parts more than 0.1 mm.

Safety valves with stamped-welded body can be manufactured with individual face-to-face length (L and L1), height (H) and connecting dimensions flanges, which allows them to be used as substitutes for imported fittings without changing the already installed equipment and pipelines.

Calculation of the throughput of valves - according to GOST 12.2.085-2002.

Setting pressure, Рн- the highest excess pressure at the inlet to the safety valve, at which the gate is closed and the specified tightness of the gate is ensured.

Opening start pressure, Рн.о.(start pressure; set pressure) - excess pressure at the inlet to the safety valve, at which the force trying to open the valve is balanced by the forces holding the locking element on the seat. At the pressure of the beginning of the opening, the specified tightness in the valve gate is violated and the closing element begins to rise.

Pressure full opening, Rp.o.- excess pressure at the inlet to the safety valve, at which the valve travels and the maximum throughput is achieved.

Closing pressure, Рз(back-seating pressure) - excess pressure at the inlet to the safety valve, at which, after the working medium is released, the locking element is seated on the seat, ensuring the specified tightness of the valve. Valve closing pressure, Рз - not less than 0.8 Рн.

Back pressure- excessive pressure at the outlet of the valve (in particular, from the safety valve).

The back pressure is the sum of the static pressure in the exhaust system (in the case of closed system) and the pressure arising from its resistance during the flow of the working medium.

Mandatory minimum ordering information.

When ordering valves, you must fill out the questionnaire (Appendix B):

• product type, designation, type designation (according to the table of figures);
• nominal diameter of the inlet pipe, DN, mm;
• nominal pressure, PN, kgf / cm2;
• setting pressure (Рн, kgf / cm2) or the number of the spring (when specifying only the number of the spring, the valve is adjusted to the minimum value from the range of the specified spring);
• body material;
• the presence of a manual firing unit in the valve structure;
• the presence of a bellows in the valve design.

Example of designation when ordering a safety spring valve:

An example of designation when ordering a safety spring valve DN 50 PN 16 kgf / cm2 made of steel 12X18N9TL with a manual trigger, setting pressure - Рн = 16 kgf / cm2, KPP4R model according to TU 3742-005-64164940-2013:

Safety valve KPP4R 50-16 DN 50 PN 16 kgf / cm2, Рн = 16 kgf / cm2, 17nzh17nzh. When placing an order, the need to complete the valves with counterparts (counter flanges, gaskets, studs, nuts; for DN 25 PN 100 valves - nipples with union nuts and gaskets) is specially stipulated.

The safety valve is pipeline fittings that protects equipment and pipelines high pressure from mechanical damage and various kinds of destruction as a result of emergencies. This is achieved by releasing an excessive amount of 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 functions in direct contact with the working medium together with other structures that function as protective fittings, including pressure regulators.

The main types of valves and their purpose

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

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

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

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