Standard heating system includes many elements. Each of them performs its own task, as a result of which the structure works smoothly and smoothly. One of these elements is a non-return valve for heating, which controls the flow of the coolant.
We will introduce all the types of check valves used in the organization of heating circuits today. In the article presented by us, their design features are described in detail, the technical characteristics are given. Independent masters we will find installation guides and valuable tips.
The content of the article:
- Why do we need a check valve?
Types of check valve
- Disc-type fixtures
- Ball check valves
- Petal version of the shutter
- Lifting equipment
- Selection rules for locking device
- Variants of working connection diagrams
- Nuances of competent installation
- Conclusions and useful video on the topic
Why do we need a check valve?
During operation, hydraulic pressure appears inside the heating system, which may be unequal in different parts of it. The reasons for this phenomenon are very different.
Most often it is uneven cooling of the coolant, errors in the design and assembly of the system or its breakthrough. The result is always the same: the direction of the main fluid flow changes, and it turns in the opposite direction.
This is fraught with very serious consequences up to the exit of the boiler, and even the entire system, from the system, which will require further significant repair costs.
For this reason, experts strongly recommend to put a check valve. The device is capable of passing liquid only in one direction. When a reverse flow appears, the locking mechanism is activated, and the hole becomes impassable for the heat carrier.
Thus, the device is able to control the flow of fluid, passing it only in one direction.
The principle of the check valve is very simple. It passes the heat transfer fluid in a given direction and blocks the path when it tries to move in the opposite direction.
For normal operation of the system, it is necessary that the device does not create additional pressure, and freely letting people move to the radiators. heat carrier. Therefore, it is extremely important to correctly select the product.
Types of check valve
Despite the fact that all devices of this type perform one task, they have structural and, therefore, operational differences. Let us consider in more detail each of these species.
A distinctive feature of the product is the presence of a butterfly valve. This is a plastic or metal element whose dimensions allow it to completely block the flow of coolant if it begins to move in the opposite direction.
The disk connects to a steel spring. With direct movement of fluid, it is in a compressed state. When changing the direction, it straightens and shifts the disk from its place, thus blocking the pipe.
The valve design also includes a gasket, which allows the bolt mechanism to sit as tightly as possible on the seat. Therefore, in serviceable devices leakage is excluded.
Disk devices are widely used in the arrangement of domestic heating systems, since they have significant advantages:
- Compactness. The dimensions of the products and their weight is small, which makes it possible to install them on any system.
- Regular maintenance is not required.
- The cost of the device is low.
Of the significant shortcomings worth noting unsuitable for repair. Therefore, the failed valves are immediately replaced with new ones.
A significant disadvantage of disk devices is a significant hydraulic resistance. The diagram clearly shows how it arises. Fluids have to overcome the obstacle in the form of a locking disc
And one more minus - significant hydraulic resistance created by the device. For some systems, for example, with geothermal heat pump, it can be critical. Over time, the valve is covered with a layer of mineral deposits, which leads to device breakage.
Standard disc valves during closure create some shock loads. This does not affect their performance and technical condition, but a hydraulic shock occurs in the system. What is undesirable for her.
Disk devices with the additional mechanism allowing to close an opening most smoothly are deprived of this shortcoming. Their cost is higher than that of standard analogues.
Ball check valves
A metal ball is used as a shutter in devices of this type. It is made from aluminum, steel and other metals. To extend the life of the item is covered with a layer of rubber.
Such a shutter operates as follows: when the coolant moves through the device in the right direction, it raises the ball, which moves into the upper valve compartment.
The ball valve has a minimal hydraulic resistance, therefore it is widely used in a variety of heating systems. Another plus is a long service life.
As soon as the direction of motion changes or the flow stops, the ball immediately descends and closes the tube. Thus, the movement of fluid in the opposite direction becomes impossible.
The advantages of these valves include:
- reliability - the design does not include rubbing or moving systems, which significantly reduces the possibility of breakage and allows you to work in any position;
- maintainability - the upper part of the valve body is equipped with a removable cap, which provides easy access to the inside of the structure;
- low hydraulic resistance.
Considering the shortcomings, it is worth noting a rather large working diameter. For this reason, it is impossible to use them in domestic pipelines of small sections.
Ball valves are capricious during installation, due to structural features. When mounted horizontally, they must be placed with the lid up, otherwise the shutter will not be able to rise to let the water flow through. Based on the same considerations, in a vertical installation, it is necessary to strictly ensure that the liquid moves strictly upwards.
The ball valves will not function normally in low pressure pipelines either. Since the minimum value at which the sphere locking the passage opening rises is usually 25 bar.
Petal version of the shutter
The valve for this type of valve is a thin plate of steel. It is fixed on the design of the hinges, which provides it with the ability to move.
The double leaf flap check valve is very reliable, withstands great pressure. But at the same time it has a serious hydraulic resistance, since the rotary axis of the valves is located directly in the center of the bore
There are two types of petal devices. Single-leaf or swivel ones are equipped with one plate that can rotate around an axis.
When the coolant moves in a given direction, it lifts the flap, thereby opening the passage. When the flow direction changes, the plate is lowered. This can be done with or without a spring.
The butterfly valves are designed a little differently. They have two locking plates fixed on the rotary axis and located in the center of the bore.
The coolant moving along the heating circuit opens both flaps of the double flap check valve, and when the direction of its movement changes, the springs close the plates
The advantages of using these valves are the following:
- some models of gravity valves can operate without springs, which allows them to be used in gravity systems;
- relatively low cost devices.
Of the drawbacks, it is worth noting a rather high hydraulic resistance. This is especially true for double-leaf models - the rotary axis is located directly in the center of the bore hole, which is a significant obstacle for a moving fluid.
For this reason, butterfly valves are exclusively used in high pressure systems.
Lift valves are equipped with a spool that can freely move relative to a vertically located axis. At the opening there is a seat saddle where the spool is located.
When a fluid is supplied, the force of its pressure raises the shutter, and it moves along the axis, opening an opening for the movement of the coolant. As soon as the pressure of the flow weakens or it changes its direction, the spool will drop into the seat.
The lift check valve is installed only vertically. Otherwise, the pressure of the liquid coolant will not be enough to raise the locking mechanism
The advantages of these devices are:
- Reliability. The equipment has a fairly simple design, which allows it to operate with minimal risk of breakage.
- Low sensitivity to the quality of the coolant.
- The possibility of repair. For this purpose, a removable cover is located in the upper part of the instrument case.
Among the shortcomings it is necessary to note the limitations in the installation. Due to the design features, they can only be mounted in a strictly upright position.
Selection rules for locking device
Select a check valve intended for heating system- the event is responsible. If knowledge in this area is minimal, it is best to seek help from specialists. This ensures that the new heating system is operational and safe.
You need to know that regardless of their type, all check valves differ in the way they are connected to the pipeline.
Coupling check valves are very easy to install. However, the threaded connection can not withstand high pressure, so they have limitations in use
Coupling devices are equipped with a connecting threaded unit, which greatly facilitates their connection to the highway. Most often, such a unit is equipped with disc valves designed for installation in autonomous heating systems of the apartment or a private house. Their distinguishing feature is small diameter. Most often it is not more than DU-50.
Flange products are a structure assembled on the basis of a part having openings for fastenings. With the help of the latter, it connects to the main pipeline. The flange connection is much more durable than threaded.
For this reason, flanged valves are widely used in the construction of large-diameter lines. The most popular devices are ball type.
Wafer devices are designed for installation between two pipe flanges. They are lightweight and compact. Very often, in the interflange version, both types of petal-type valves are produced.
Commercially available check valves, which are installed by welding. This option can be used, for example, when arranging heating from polypropylene pipes.
Flanged check valves are securely fastened to the pipe. This connection withstands high pressure, which allows the use of devices in centralized highways.
Another important selection criterion is the material from which the device is made. It may be stainless steel. This option is considered optimal for highways with a diameter of less than 0.04 m.
The metal is practically not subject to corrosive processes, capable of withstanding a load of up to 10 atm. This allows the valve to operate in the system without a trouble and for a very long time, however, its cost is quite high. Lower price for brass valves. They are susceptible to corrosion, but this process is very slow, which significantly increases the service life.
However, their mechanical strength is much lower than that of stainless steel. Nevertheless, the load arising in the home network, they can withstand quite easily. The strongest valves are made of cast iron - they successfully cope with critical pressure values, have considerable dimensions and an impressive weight.
Due to the peculiarities of production, only body parts with a diameter greater than 40 mm can be made of cast iron. For this reason, they are rarely used for arranging autonomous heating systems.
It is desirable that not only the body, but also all the internal elements of the check valve are made of metal. Plastic usually has lower strength, which can lead to premature failure of parts
When choosing a check valve, one more rule should be remembered: its diameter should correspond exactly to the parameters of the bore. It is very important that the operating pressure of the system does not exceed the maximum allowable values for operation set by the manufacturer of the selected model.
Variants of working connection diagrams
Heating systems are distinguished by a great variety and the presence of a check valve is by no means all. Consider a few cases where its installation is necessary. First of all, a non-return valve must be installed on each of the individual circuits in a closed type circuit, provided that they are equipped circulating pumps.
Some craftsmen strongly recommend installing a spring-type non-return valve in front of the single inlet pipe in a single-circuit circulation pump. They motivate their advice so that pumping equipment can be protected from water hammer.
This is in no way true. First, the installation of a check valve in a single-circuit system is hardly justified. Secondly, it is always installed after the circulation pump, otherwise the use of the device loses all meaning.
If two or more boilers are included in the heating circuit, the occurrence of parasitic flows is inevitable. Therefore, the connection of the check valve is mandatory
For multiloop systems, the presence of a locking device of reverse action is vital. For example, when two boilers are used for heating, electric and solid fuel, or any other.
When one of the circulating pumps is turned off, the pressure in the pipeline will inevitably change and a so-called parasitic flow will appear, which will move in a small circle, which will cause trouble. Here it is impossible to do without valves.
A similar situation occurs when using indirect heating boiler. Especially if the equipment has a separate pump, if there is no buffer tank, hydraulic needle or distribution comb.
Here, too, there is a high probability of a parasitic flow, for the cutting off of which check valveused specifically for arranging a branch with a boiler.
Be sure to use valves and systems with bypass. Such schemes are usually used when modifying a scheme from gravitational circulation of a liquid to a forced one.
In this case, the valve is placed on bypass parallel to the circulating pumping equipment. It is assumed that the main mode of operation will be forced. But when you turn off the pump due to lack of electricity or breakdown, the system will automatically switch to natural circulation.
When arranging the bypass nodes for heating schemes the use of check valves is considered mandatory. The figure shows one of the possible options for connecting the bypass
This will happen as follows: the pump stops supplying the coolant, the actuator of the non-return valve stops testing pressure and closes.
Then the convection movement of the fluid along the main line resumes. This process will last until the pump runs. In addition, experts propose to put a check valve on the feed line. This is optional, but highly desirable, as it avoids the emptying of the heating system for a variety of reasons.
For example, the owner opened a tap on the make-up pipeline to increase system pressure. If, by an unpleasant coincidence, at that moment the water supply is blocked, the coolant simply squeezes out the remnants of cold water and goes into the pipeline. As a result, the heating system will be left without liquid, the pressure in it will fall sharply and the boiler will stop.
In the schemes described above, it is important to use properly selected valves. To cut off parasitic flows between adjacent circuits, it is advisable to install disc or flap devices. In this case, the hydraulic resistance will be lower in the latter case, which must be taken into account when choosing.
In heating systems with natural circulation of the coolant, the use of spring check valves is impractical. Only petal turning devices can be installed here.
For arranging the bypass assembly, it is preferable to choose a ball valve. This is due to the fact that it gives almost zero resistance. On the make-up pipeline, you can install a valve-type valve. This should be a model designed for a fairly high working pressure.
Thus, the check valve may not be installed in all heating systems. It is always used when arranging bypass of all types for boilers and radiators, as well as at branch points of pipelines.
Nuances of competent installation
In the process of installation of valves, one should strictly observe a few rules:
- The valve is installed strictly in the direction of the coolant current. In order to avoid an error, a marking in the form of an arrow indicating the working direction is necessarily present on the product body.
- Paronit gaskets can be used to seal the joints, provided that they do not reduce the diameter of the bore. Otherwise, the valve will exert more hydraulic pressure than planned.
- The device must be installed so that other elements of the heating system do not exert additional pressure on its body.
- It is highly desirable to put a coarse screen before the check valve. This will make it possible to prevent solid particles from getting into the locking mechanism, which, in turn, can lead to a violation of the tightness of the device in the closed state.
Another important point: before installation you need to once again make sure that the valve is selected correctly.
For example, for circuits with forced circulation, any type of device is suitable, and for gravity systems, only a rotary lobe without a spring. Since gravity moving by gravity can not cope with the resistance of the spring.
Conclusions and useful video on the topic
Video # 1. Where to use check valves:
Video # 2. How to choose the valves for gravity heating systems:
Video # 3. How to equip heating water with a check valve:
Check valve is a necessary element of complex heating systems. For circuits with one circuit, it is usually not needed, except for arranging the feed pipe. But if the system is complicated by the addition of a second boiler, boiler, or underfloor heating, the device is indispensable.
It is important to correctly select and install a check valve. This ensures trouble-free, long-term operation of the entire heating system.
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