Due to improper operation, temperature changes and pressure surges in the operation of autonomous heating systems may fail. Negative consequences in such situations are critical: starting with the breakdown of individual components, ending with the destruction of buildings and a serious threat to life.
The safety valve in the heating system will help to eliminate the dangerous risks. What is he and what is his principle of action? We will consider these questions in our article. We also analyze the types of such valves and indicate the main differences between them, consider the rules installation in the heating system and give recommendations on the selection and setting of safety fittings.
The content of the article:
- What is a safety valve for?
Varieties of devices and principle of operation
- Classification # 1 - by clamping mechanism
- Classification # 2 - according to the lift height
- Classification # 3 - by speed of operation
- Features three-way emergency valves
- Tips for choosing the best model
- Rules of installation and configuration
- Conclusions and useful video on the topic
What is a safety valve for?
Heating systems are filled with water, the temperature of which is about 15 degrees. Circulating in a closed loop, the coolant heats up, significantly increasing in volume. At this time, the pressure exerted on the inner surface of the pipes and the instruments installed in the system significantly increases.
Exceeding the permissible rate, in most cases more than 3.5 bar, turns around:
- leakage at the joining of parts of the pipeline;
- damage or rupture of connecting elements and pipes made of polymers;
- the explosion of the boiler tank;
- short circuit electrical equipment in the boiler room.
The highest risk of emergencies is characteristic of solid fuel boilers, in which it is difficult to regulate the power of heat transfer.
The performance of electrical and gas equipment is quickly adjusted from starting to maximum performance and vice versa. Often present in them safety automatics, disabling work items with excessive temperature rises.
The intensity of burning wood, coal and other types of fuel in a solid fuel boiler is adjusted by opening / closing the valve. In this case, the force of heat release does not change immediately, but gradually. Due to the inertia of the heat source, the heat transfer fluid can be very hot.
Together with a pressure gauge and an air vent that removes air from the system, a safety valve is often included in the safety group.
When the firewood in the chamber is well warmed up, bringing the water in the network to the required temperature, the access of air is blocked and the active flame begins to fade.
However, in a hot state, the firebox continues to emit accumulated heat. Reaching 90-95 degrees, the coolant boils and starts the inevitable intense evaporation. As a result, a sharp pressure jump is triggered.
It is in such circumstances that the safety valve is activated. When the boundary parameter of pressure is reached, it opens the valve, freeing the way out for the steam that has formed. After the values stabilize, the valve closes automatically and goes back to sleep.
Its installation is mandatory not only for solid fuel, but also for steam boilers, as well as furnaces equipped with a water circuit. Many modifications of heating equipment are equipped with these devices at the production stage. Often this valve is one of the elements security groups. Usually, the device is cut directly into the heat exchanger or installed in the pipeline near the boiler.
Varieties of devices and principle of operation
The design of the drain valve consists of two essential components: a gate part consisting of a saddle and a bolt, and a force actuator. There are several types of equipment that have their own characteristics. They are classified according to certain characteristics.
Classification # 1 - by clamping mechanism
In the heating systems of private houses, apartments and industrial installations of small capacity, preference is given to the spring type of product.
The main working element of the device is a spring. It supports the membrane that covers the saddle. A washer is placed on the rod connected to the handle, against which the upper part of the spring rests. The position of the washer and the clamping effect on the membrane is regulated by the handle
The device has a simple and reliable structure, compact dimensions, the possibility of combining with other elements of the security unit, an affordable price. The compression force of the spring mechanism depends on the pressure parameter at which the valve is activated. On the setting range affects the elasticity of the spring itself.
The principle of operation of the spring fuse is as follows:
- the flow of the device affects the flow of water;
- heat carrier movement is limited by spring force;
- critical pressure exceeds the force of compression, raising the spool rod up;
- fluid is sent to the outlet;
- the internal volume of water stabilizes;
- the spring closes the bolt, returning it to its original position.
The body of the springy device is made of high-quality high-strength brass using technologies and methods of hot stamping. Steel is used in spring production. The membrane, seals and handle are made of polymers.
Some brands produce equipment with factory settings already installed. Also in the range there are models that are customizable at the place of installation during the commissioning period.
Valves are open and closed. In the first embodiment, the coolant is discharged into the atmosphere; in the second, it is discharged into the return pipeline.
Lever and cargo fuses are not as common. In private autonomous systems with a boiler, they are rarely mounted. Operation is concentrated in the industrial sector in large-scale industries, where the diameter of the pipelines is at least 200 mm.
The force on the rod in such mechanisms does not give a spring, and the load, hung on the lever. It moves along the length of the lever, adjusting the force with which the rod will be pressed against the saddle.
Lever-loading valve opens when the pressure of the medium from the bottom of the spool exceeds the values emanating from the lever. After that, the water goes through a special drain hole.
Adjustment of the lever-load fuses is performed by moving the thrust along the lever. In order to prevent its unauthorized or accidental change, the cargo is bolted, covered with a special casing and locked with a lock.
The response pressure, as well as the range of settings, is determined by the length of the lever and the mass of the load. Lever fuses are not inferior spring devices in terms of reliability, but they are more expensive. Devices are installed on flange fittings of pipes with a nominal diameter of 50 or more.
Classification # 2 - according to the lift height
In low-lift safety valves, the valve does not rise more than 0.05 times the diameter of the seat. The opening mechanism in such equipment is proportional.
It is characterized by low throughput and the most primitive design. Low-lifting equipment is used on vessels with a liquid medium.
Full-lifting devices are equipped with a two-position opening mechanism. They equip not only vessels with liquids, but also systems in which compressible media circulate (compressed air, steam, gas)
For full-lift appliances, lift the shutter higher. This means that their throughput is much better than the previous version, so they are able to dump larger volumes of excess coolant.
Classification # 3 - by speed of operation
The proportional safety valve shut-off valve opens gradually. As a rule, the magnitude of the opening is proportional to the increase in pressure exerted on the inner surface. Simultaneously with the rise of the mechanism, the volumes of the discharged coolant gradually increase.
The design of devices does not limit the possibility of their use in a compressible medium, but still they predominate in systems with water and other liquids.
The advantages of safety valves with proportional response speed are low cost, simplicity construction, lack of self-oscillations, batch opening at the level of values necessary to maintain specific operating parameters
A special feature of two-way valves is instantaneous operation with full opening after reaching the boundary pressure marks in the system, at which the fuse gate opens.
Experts recommend operating these devices in compressible media. Among their main drawbacks are the presence of characteristic self-oscillations of the shutter.
When installing a two-position valve in a heating system with a heat-transfer fluid, it should be taken into account that during an abrupt opening of the valve a large amount of water will be discharged.
Because of this, the pressure drops too quickly. The valve will instantly close and entail water hammer. Proportional devices do not cause such risks.
Features three-way emergency valves
We should also talk about a device that is not so well known to consumers - a three-way valve with a manual or electric switch. It is used in heating systems with low-temperature circuits.
The design of the fuses is equipped with three holes, one of which is the input, two - the weekend. Medium flows are controlled by a damper, made in the form of a ball or stem. The moving fluid is redistributed by rotations.
Three-way fuses are appropriate for condensing boilers and in cases where several different systems are operated from the same heating equipment.
Imagine a situation: the house has a heating scheme with a system of conventional radiators and a heated floor. Technical requirements for the operation of the second option provide for not too high coolant temperature.
The boiler heats the water at the same temperature for all systems. In such conditions, there is a need for a redistributing device, with the tasks of which a three-way valve is excellent.
He is responsible for the following functions:
- demarcation of areas;
- distribution of flux density by zones;
- facilitating the mixing of coolant from the main branches of the supply / return pipe for sending more cold water to the pipeline of a heated floor than to radiators.
In order not to exercise constant control over the temperature of the medium on its own, it is necessary to pay attention to valve models equipped with a servo actuator.
This device operates from a sensor installed in a low-temperature circuit. When the temperature changes, the locking mechanism works, opening or closing the flow of fluid from the return.
We talked in more detail about the variations of the three-way valve for heating and the criteria for its selection. in the next article.
Tips for choosing the best model
Before dwelling on specific safety equipment, it is imperative that you familiarize yourself in detail with the technical characteristics of the boiler plant.
The safety valve operation is negatively affected by freezing temperatures. Therefore, a sufficiently important characteristic for the device is the presence of frost protection.
Do not neglect the study of the manufacturer's instructions, in which all limit values are indicated.
Decisive role in choosing a device for heating have several criteria:
- Boiler performance.
- The maximum allowable pressure of the medium for the heating power of the heating equipment.
- The diameter of the safety valve.
It should be checked that the pressure regulator in the device has a range within which the parameters of a particular boiler are included. The response pressure must be 25-30% higher than the operating figure required for the stable operation of the system.
The higher the pressure performance, the less time the device must spend on actuation. The gap between the pressure at the start of the movement and the full opening of the shutter should be 15% for a nominal value less than 2.5 atm, 10% - for higher parameters
The diameter of the safety valve can not be less than the connector of the inlet pipe. Otherwise, a constant hydraulic resistance will prevent the fuse from fully performing immediate tasks.
The optimum material for manufacturing equipment is brass. It has a low coefficient of thermal expansion, which eliminates the destruction of the body from the effects of strong pressure.
The control unit is made of heat-resistant plastic materials that retain the desired rigidity even when in contact with boiling liquid.
Rules of installation and configuration
If you plan to install the safety valve yourself, you should prepare a set of tools in advance. The work can not do without adjustable wrenches and wrenches, a cross screwdriver, pliers, tape measures, silicone sealant.
Before you begin, you need to determine the place suitable for installation. It is recommended to install the safety valve on the supply pipe close to the boiler outlet. The optimal distance between the elements is 200-300 mm.
All compact household fuses are threaded. To achieve full tightness when winding, it is necessary to seal the pipe with tow or silicone. FUM tape is undesirable, as it does not always withstand critical heat
In the regulatory documentation, which is completed with each device, the installation process is usually painted step by step.
Some key installation rules are the same for all valve types:
- if the fuse is not mounted in the security group, a pressure gauge is placed next to it;
- in spring valves, the spring axis should have a strictly vertical position and be located under the device body;
- in the lever-cargo equipment the lever is placed horizontally;
- on the pipeline between the heating equipment and the fuse is not allowed to install check valves, cranes, latches, the circulation pulser;
- to prevent damage to the housing when the valve rotates, you need to be selected with a key from the side where the screwing is performed;
- drain pipe, the heat carrier in the sewer network or return pipe is connected to the outlet of the valve;
- the outlet is not supplied directly to the sewage system, but with the inclusion of a funnel or pit;
- in systems where fluid circulation occurs by natural patternThe safety valve is placed at the highest point.
The nominal diameter of the device is selected on the basis of the methods developed and approved by the State Technical Inspection. In addressing this issue, it is wiser to seek the help of professionals.
If this is not possible, you can try to use specialized online programs for the calculation.
To reduce hydraulic losses during medium pressure on the valve plate, installation of emergency equipment is performed with a slope to the boiler plant
The adjustment of the valve is influenced by the appearance of the pressure structure In the spring devices there is a cap. Spring compression is adjusted by rotating it. The adjustment accuracy of these products is high: +/- 0.2 atm.
In leverage devices, adjustments are made by increasing the mass or moving the load.
After 7-8 operations in the installed emergency device, the spring and the plate wear out, as a result of which the tightness may be broken. In this case, it is advisable to replace the valve with a new one.
Conclusions and useful video on the topic
How the safety valve consists of and what it consists of:
Emergency valve in the safety group:
Learn more about choosing and installing the optimal safety valve:
Safety valve - simple and reliable equipment that will protect the home from unforeseen emergencies that occur in heating systems. To do this, it is enough to choose a high-quality device with suitable parameters, and then perform its proper setup and installation.
Are you choosing a suitable safety valve for your heating system? Maybe you have questions, the answers to which you did not find in the above material? Ask them to our experts, leaving a comment below the article.
Or maybe you want to supplement the material with interesting facts and useful recommendations? Or share the experience of installing the valve into the system? Write your opinion about the need for such a protective device, share tips on choosing, based on personal experience.