The heating circuits are equipped with a non-return valve for heating. The element is used in the system when connecting a second boiler, underfloor heating branch, water heater or automatic make-up device. The type of shut-off valves is used to prevent the reverse flow of the energy carrier and protect against water hammer.
Purpose of the check valve for heating
The counter current of the coolant occurs under various circumstances: when the circulation pump stops or errors in the system design. Reverse movement of water is observed in the case of uneven cooling of sections of the heating main, with a breakthrough of a pipe or joint. Sometimes the reason is the unequal pressure in the sections of the pipeline.
A non-return valve is provided in the system to prevent damage to the boiler and other elements of the line due to the flow of water in the opposite direction. The mechanism passes the energy carrier in one direction and blocks movement in the other. The device is used in municipal heat supply and pipelines, it is installed in the heating circuits of a private house and a multi-storey sector.
Some types are designed to work in certain circumstances, for example, when entering a boiler room, shockless and impact valves are used. With a small pipe diameter (up to 400 mm), water hammer does not harm the system. In large lines, dampers are installed against sharp shocks. Such reverse devices cut into horizontal sections of pipelines.
Varieties of check valves
There are valves installed using couplings and flanges. Some require special fittings, welding. Coupling mechanisms are threaded, easy to connect, such a unit is used on disc valves. Couplings are used to install fittings in an apartment or your own house.
Backlocking valves differ in design, operating conditions and purpose.
There are shutter devices:
- petal;
- disc type;
- ball varieties.
Flange structures have additional parts with mounting holes and are connected to the line elements using bolts and nuts. The connection is robust and is used in large-diameter pipelines. Flanged devices are placed between the edges of the pipes, they are light and small in size. Welded valves are installed when the circuit is set with polypropylene pipes.
Petal
A thin steel plate serves as a breech block and is mounted on a hinged structure to provide a movable position.
The petal check valve for heating is available in two types:
- swivel or single-leaf;
- bivalve.
In the first variety, there is one plate that revolves around the center line. The sash rises when the coolant moves in a given direction. The through hole is closed by a lowered part on a spring during reverse flow. Double-leaf devices are equipped with two locking plates fixed on the central axis and located in the opening passage.
Petal species have advantages:
- some valves do not have springs, these types are used in natural gravitational systems (gravity);
- devices are inexpensive.
The negative sides are that the bivalve type impedes the flow of liquid, therefore it is used only in high-pressure lines.
Disc type products
The shutter is made in the form of a disc made of metal or plastic. The element shuts off the fluid flow if the energy carrier changes direction. The disc is mounted on a spring, which is in a compressed position during forward movement. A change in direction leads to a straightening of the part and a change in the position of the locking disc. The design has a seal for a tight fit of the shutter, such a part completely eliminates leakage.
The advantages of disc valves for home heating schemes:
- small dimensions and low weight allow the use of mechanisms on contours of small diameter;
- the device does not require periodic technical inspection and repair;
- the device has a low price.
The disadvantage is the impossibility of repairing the poppet valve, so replacement is required. The mechanism creates resistance to flow and is not used in geothermal pump applications. Salt sediment is deposited on the disc, the device stops working.
When closed, a standard heating clapper valve creates a water hammer in the system. Disc valves with a soft closing mechanism have been developed, which have a higher cost.
Ball valves
The shutter mechanism is made in the form of a ball made of aluminum or other metals. The element is covered with rubber for a longer service life. The ball rises when the water flow moves in the correct direction and is located at the top of the valve. The energy carrier does not flow in the opposite direction, since the element goes down and blocks the hole.
Ball Valves Advantages:
- the structure works reliably, since the structure does not provide for rubbing and moving parts;
- there is a cover at the top of the mechanism for inspection or repair;
- the device does not create water hammer in the system when the ball moves.
The disadvantages include a large diameter, due to which ball valves are used in highways of significant diameters, and connection to household heating networks is not always appropriate.
Advantages and disadvantages
The check valve has advantages and disadvantages common to all types of devices. The riser will not receive a hot stream if cold liquid is flowing there. This prolongs the performance of the system elements, which are designed for a certain temperature. The devices are easy to install and do not generate noise when the liquid passes through. Check valves solve the problem only in a specific area; for other circuits, additional control devices are installed.
Some mechanisms allow the occurrence of water hammer when the flow passes the working unit, but this feature of the valve harms only the system with a large diameter. The valves become contaminated from the water flow if the system is operated with an energy carrier without propylene glycol or other additives. In this case, the disc or plate may jam in the open or closed position.
Installation and setup rules
The valve must be installed in the direction of the main current, for this there is an arrow on the body. The joints are sealed with paronite, but the gasket is placed so that the inner diameter of the passage device does not decrease. The condition is important to prevent water hammer in the pipeline network.
The device is installed so that other elements of the line do not affect its operation.The pipe section with the valve can be supported by a metal frame to prevent vibrations or other influences. A screen is placed in front of the passage mechanism for coarse cleaning from solid impurities.
Connection diagram options
The connection versions of the devices depend on the type of system and the type of valve. Devices are installed on each circuit in a closed circuit, but circulation pumps are always installed. In a single-circuit pipeline, the non-return valve can be omitted.
In multi-circuit systems, a shut-off valve for the reverse flow must be installed, since when the pump is turned off, the energy carrier moves along a small branch. The mechanism is also mounted in a line with an indirect heating water heater, especially if there is no separate pump.
Shut-off valves are installed in highways with a bypass, when the system is rebuilt from gravitational current to forced one. On the section of the make-up pipeline, the valve is installed to prevent liquid from being thrown back into the water supply.
