Valves are integral elements of any heating system (CO), regardless of the chosen scheme and configuration of the circuits. With the help of these simple devices, the heat supply parameters are adjusted, ensuring the safety and stability of the system. This publication will consider the main valves used in centralized and autonomous heating systems, their purpose, principle of operation and design features.
Criterias of choice
The number and parameters of valves required for a particular CO are selected at the stage of calculations and design. The main criteria that influence the choice of these elements are:
- Type, scheme and configuration of CO.
- Temperature conditions (nominal and maximum).
- Pressure in the system (working and maximum).
- Pipeline cross section and thread type.
- Type of heat carrier (water, brines, antifreezes).
The operation of these devices stabilizes CO, makes it efficient and safe. Anyone who is engaged in self-installation of a heating system in a dwelling needs to know the purpose and their principle of operation. All valves can be divided according to their purpose into three categories: safety, control and regulation group.
Everyone knows that any CO is an increased source of danger, since the coolant in the system is under pressure. And the higher the temperature, the higher the pressure (in closed CO). Next, consider the devices that are responsible for the safety of the CO
Safety
In most models of modern boilers, manufacturers provide a security system, the “key figure” of which is safety fittings included directly in the boiler heat exchanger or in its piping.
Purpose safety valve in the heating system is to prevent the increase in pressure in the system above the allowable, which can lead to: destruction of pipes and their connections; leaks; explosion of boiler equipment
The design of this kind of fittings is simple and unpretentious. The device consists of a brass body containing a spring-loaded locking membrane connected to a stem. The elasticity of the spring is the main factor that keeps the membrane in the locked position. The adjusting knob adjusts the compression force of the spring.
When the pressure on the membrane is higher than the set one, the spring is compressed, it opens and the pressure is released through the side hole. When the pressure in the system cannot overcome the elasticity of the spring, the membrane will take its original position.
Tip: Get a safety device with pressure adjustment from 1.5 to 3.5 bar. Most models of solid fuel boiler equipment fall into this range.
Air vent
Quite often, air pockets form in CO. As a rule, they appear for several reasons:
- boiling of the coolant;
- high air content in the coolant, which is automatically added directly from the water supply;
- As a result of air leakage through leaky connections.
The result of air pockets is uneven heating of radiators and oxidation of the internal surfaces of the metal elements of CO. The air release valve from the heating system is designed
to remove air from the system in automatic mode. 
Structurally, the air vent is a hollow cylinder made of non-ferrous metal, in which a float is located, connected by a lever to a needle valve, which, in the open position, connects the vent chamber to the atmosphere.
In working condition, the internal chamber of the device is filled with coolant, the float is raised, and the needle valve is closed. If air enters, which rises to the upper point of the device, the coolant cannot rise in the chamber to the nominal level, and therefore, the float is lowered, the device operates in the exhaust mode. After the air escapes, the coolant rises in the chamber of this type of fitting to the nominal level, and the float takes its regular place.
Back
In a gravity-flowing CO, there are conditions under which the coolant can change the direction of movement. This threatens to damage the heat generator heat exchanger due to overheating. The same can happen in rather complex COs with forced movement of the coolant, when water, through the bypass pipe of the pump unit, enters the boiler back. Mechanism of action check valve in the heating system quite simple: it passes the coolant only in one direction, blocking it when moving back.
There are several types of this kind of fittings, which are classified according to the design of the locking device:
- poppet;
- ball;
- petal;
- bivalve.
As the name implies, in the first type, a steel spring-loaded disk (plate) connected to the stem acts as a locking device. In a ball valve, a plastic ball acts as a shutter. Moving "in the right" direction, the coolant pushes the ball through the channel in the body or under the cover of the device. As soon as the circulation of water stops or the direction of its movement changes, the ball, under the influence of gravity, takes its original position and blocks the movement of the coolant.
In the petal, the locking device is a spring-loaded cover, which falls when the direction of water in CO changes under the influence of natural gravity. The double-leaf element is installed (as a rule) on pipes of large diameter. The principle of their work does not differ from the petal. Structurally, in such fittings, instead of one petal spring-loaded from above, two spring-loaded flaps are installed.
These devices are designed to adjust the temperature, pressure, as well as stabilize the operation of CO.
Balancing
Any CO requires hydraulic adjustment, in other words, balancing. It is carried out in various ways: with correctly selected pipe diameters, washers, with different flow sections, etc. balancing valve for heating system .
The purpose of this device is to supply the required volume of coolant and the amount of heat to each branch, circuit and radiator.
The valve is a conventional valve, but with two fittings installed in its brass body, which make it possible to connect measuring equipment (pressure gauges) or a capillary tube as part of an automatic pressure regulator.
The principle of operation of the balancing valve for the heating system is as follows: By turning the adjusting knob, it is necessary to achieve a strictly defined flow rate of the coolant. This is done by measuring the pressure at each fitting, after which, according to the diagram (usually attached by the manufacturer to the device), the number of turns of the adjusting knob is determined to achieve the desired water flow for each CO circuit. On circuits with up to 5 radiators, manual balancing regulators are installed. On branches with a large number of heating devices - automatic.
bypass
This is another CO element designed to equalize the pressure in the system. Principle of operation bypass valve of the heating system similar to the safety element, but there is one difference: if the safety element bleeds excess coolant from the system, then the bypass element returns it to the return line past the heating circuit.
The design of this device is also identical to the safety elements: a spring with adjustable elasticity, a shut-off membrane with a stem in a bronze case. The flywheel adjusts the pressure at which this device operates, the membrane opens the passage for the coolant. When the pressure in CO is stabilized, the membrane returns to its original place.
Three way
There is a practice to achieve a certain coolant temperature in various branches and circuits of CO by mixing or separating coolant flows. Three-way valve on the heating system plays the role of a device that regulates the temperature of the working fluid after the heat generator.
The design of mixing fittings is simple: there are three holes in the body of the device, two inlets and one outlet. Separating type devices have one input and two outputs.
The main control device of this element is a thermal head, inside of which there is a reservoir with liquid (bellows). When the remote sensor is heated, the liquid in it expands and enters the bellows. The volume of this reservoir increases and acts on the valve stem, which opens or closes the inlets for mixing or flow separation. In the separating types of this CO element, the same principle is used, but the stem does not open a passage for flows, but divides one flow into two.
Not only the thermostatic head can control the device. Manual devices are quite popular. The depth of pressing the rod is determined by the rotation of the control handle. Today, these devices with electric and servo drives are widely represented on the climate technology market.
Automatic make-up device
Due to various circumstances (natural evaporation, operation of the safety element, etc.), the volume of coolant in CO may decrease. The less coolant, the more air in the system, which inevitably disrupts the circulation of water in CO and overheats the boiler equipment. To prevent air from entering the system, it is necessary to replenish the amount of coolant in time. You can do this manually, or you can install heating system make-up valve
, thereby organizing automatic replenishment of CO with coolant.
The design of this kind of fittings practically does not differ from safety fittings, but the principle of operation is exactly the opposite: as long as there is the necessary pressure in the CO, which supports the membrane to the seat, the spring is in a compressed state. When the pressure drops below the minimum, the spring straightens and removes the membrane from the seat, allowing water from the supply tank or water supply to enter the CO. On fig. The construction of this device is shown below. 
As CO is filled, the pressure in it increases, the spring is compressed, and the membrane sits in the saddle on the body, blocking the recharge.
Important! Valve selection is a complex and important process that is best left to the professionals.