Vertical flanged check valve. Flanged check valve. Dimensions and parameters
In a lift check valve, the shut-off element is a lift spool. Under the influence of water pressure, the spool rises, allowing flow to pass through. When the pressure drops, the spool moves down onto the seat, preventing the flow from flowing back. Such valves are installed only on horizontal sections of pipelines. Required condition– vertical location of the valve axis.
Valves are divided into four groups according to the method of fastening:
- Welding mount: check valve attached to the pipeline by welding. Used when working in aggressive environments.
- Flange mounting: The check valve is connected to the pipeline through sealed flanges.
- Coupling connection: the valve is attached to the pipeline through a threaded coupling. It is used in systems not large diameter.
- Wafer mounting: the check valve does not have its own mounting unit. Clamped between pipeline flanges. Used in areas with limited dimensions.
Lift check valves that have a protective mesh at the inlet and are designed to be installed at the beginning of the suction pipeline are called foot valves.
Advantages of lift check valves:
- simplicity of design;
- reliable tightness;
- possibility of repair without dismantling the entire valve.
Disadvantages of lift check valves:
- high hydraulic resistance;
- the possibility of the valve jamming in the guide part of the cover when using the valve in systems with a contaminated working environment;
Ball check valves
In a ball check valve, the ball element serves as the valve. A spring is used as a pressing element, pressing the ball to the seat. Such valves are usually manufactured for small diameter pipelines and are used as household plumbing equipment. The ball check valve is inferior to the spring disc valve in terms of dimensions.
Check valves, operating principle:
In this design, the locking element is a spool - a “flap”. The axis of rotation of the “flap” is located above the passage hole. Under the influence of pressure, the “flap” reclines and does not interfere with the passage of water. When the pressure drops below the permissible value, the spool falls and slams the passage channel. In large-diameter check valves, the spool strongly impacts the seat, which leads to rapid failure of the structure. At further exploitation this provokes the occurrence of water hammer when the check valve is activated. Therefore, rotary check valves are divided into two groups: Simple – valves with a diameter of up to 400 mm. They are used in systems where shock phenomena cannot seriously affect the operation of the hydraulic system and the valve itself. Stressless - valves with devices that provide smooth and soft landing spool onto the seat. Advantage rotary valves is the ability to provide work in systems large sizes and low sensitivity to environmental pollution.
A flange check valve is a type of safety valve pipeline fittings. It differs from other modifications in the type of connection (flange). Refers to types of fittings direct action With automatic control– passes the flow working environment in one direction. When the direction is changed to the opposite, the valve automatically closes the flow area. For this purpose, the force from the gravity of the shutter, from the spring, from the lever-load mechanism is used.
Using flanged valves
The placement of check valves prevents the occurrence of emergency situations in pipeline systems in case of emergency pressure drop. Flanged check valves are installed on pressure sections of pipelines (according to the number of pumps connected in parallel), on pipelines after the meter (flow meter), in complex systems heating, water supply, other working environment in areas requiring movement in only one direction (fill valves closed systems; valves in front of the cleaning filters).
Advantages
The flange design slightly increases the size of the connecting size. This feature is compensated by the ease of installation, maintainability of the valve, unpretentiousness in operation (no need for Maintenance). In addition, flanged check valves are reliable in operation and provide complete shutoff of the reverse flow of the working medium. It is possible to select a full bore valve design with a minimum of hydrodynamic losses.
Design Features
Flanged valves have a cast metal (usually cast iron) body. There are connecting flanges on both sides. Internal structure determined by the type of shutter mechanism used. The most common types of mechanisms are: lifting, ball, disk, rotary.
Installation of flanged valves
All types of flanged check valves are installed in the pipeline taking into account the direction of forward flow. In valves with a lift-off mechanism, the normal closed position of the valve is maintained by a spring. When flow moves under the valve, the valve opens. Such a valve is mounted on vertical, inclined, and horizontal sections.
Ball valves use a locking element in the form of a metal ball. In the absence of flow or in the opposite direction, the ball, under its weight, blocks the passage hole. Installation of such a flanged valve is carried out with the ball chamber oriented upwards.
A check valve is protective fittings, which is installed on the pipeline. The main task of the part is to prevent the reverse flow of the substance in the event that the pump turns off or fails, or the pipeline breaks. Simply put, a valve is a safety device that activates automatically.
What is special about a check valve?
An element such as a check valve protects pipelines, equipment and the pumps themselves during emergency situation. At the same time, the valve is used to combine the activities of several pumps into one line. The main task of the valve in this case is to protect devices from excessive pressure.
The mechanism of action of the device is simple. If there is no flow of the working medium, the flap is in the closed position under the influence of its own weight. If the working medium moves through the pipeline, then the seat opens under its weight. But as soon as the substance changes direction, the flap returns to its original position.
All check valves are divided into two categories:
- check valves - made of steel and cast iron. The main areas of application are water supply and heating systems, water distribution and pumping stations. There are rotary, lifting, spring, coupling and reverse;
- check valves - the valve is made in the shape of a disk.
Return products are most often installed on horizontal sections of pipelines.
Five benefits of safety valves:
- simplicity of structure - makes it possible to easily and quickly maintain and repair parts;
- small stroke - to completely block the passage, only 0.25 Dу is required;
- compact dimensions and low weight;
- additional regulatory functions;
- the ability to operate the pipeline at high operating pressures and significant pressure drops.
Any pipeline is designed to transport a working medium in a given direction. The direction is determined in advance and should not be reversed, as this can lead to undesirable consequences, including failure of the entire system.
To prevent this possibility, various technical devices, among which the flanged check valve is most widespread.
Like all check valves, a flanged valve is designed to block the transported medium (mainly liquid), if for one reason or another it begins to move in the opposite direction.
If return flow in heating pipes is not particularly considered dangerous phenomenon, then it is unacceptable to allow its formation in oil pipelines, sewers or water supply systems. In these systems, the use of shut-off valves is an indispensable condition operation.
Another dangerous factor that the check valve is designed to combat is water hammer. These are sharp changes in the operating pressure level, provoking the passage of a shock wave along the entire length of the pipeline. Such a wave, when repeated many times, can have a destructive effect on the weak points of the structure.
Each valve in this case acts as a kind of bulkhead, dividing the pipeline into independent sectors isolated from each other. If a shock wave originates in one of the sections, it will not be able to leave its boundaries.
Advantages and disadvantages of the device
To the main advantages of inverse flanged valves can be attributed:
- Relatively small dimensions, allowing the devices to be successfully operated on almost any section of pipelines.
- Ability to work with almost all types of working environments, even heavily contaminated ones.
- Effective work on main pipelines, which usually have large diameters.
Such devices are not without some disadvantages. Although check valves flange type provide protection against water hammer; they themselves, in some way, are the cause of their occurrence. The fact is that at the moment of sudden closure of the valves, areas of high pressure inevitably arise in the liquid medium.
