Valve and valve – reinforcement devices of the pipeline
The main difference of the valve from the valve, the analysis of design features of the design allows you to make the right choice of the reinforcement device when installing the pipeline.
Arrangement of valves
The gate valve is an armature device having a shutter in the form of a disk, sheet or wedge moving along the sealing rings of the housing perpendicular to the axis of flow of the medium.
Depending on the design, the latches can be pass-through and narrowed, having openings of sealing rings smaller than the diameter of the pipeline.
Depending on the geometry of the shutter, the valves are divided into parallel and wedge. Wedge gate valves are equipped with a wedge gate with sealing surfaces, which are located at an angle to each other. The shutter wedge can be a one-piece elastic, one-piece rigid or a compound two-disc.
Parallel valves are equipped with closures, the sealing surfaces of which are parallel to each other. This design can be single-disk (sliding) or double-disk.
The valves can be equipped with a retractable spindle (stem) and not a retractable (rotatable spindle). They differ in the design of the screw pair, due to which the bolt moves. Gate valves with a rotating spindle have a smaller building size.
Advantages and disadvantages of valves
The main advantage of the valves is that there is no overcoming of the medium pressure during the movement of the working element, which in turn is the force necessary to move the shutter. Of great importance is the direct flow of the fluid being transported and the small coefficient of resistance in the open state.
Thanks to the symmetry of the structure, it is possible to use valves for different directions of movement of the transported medium, and there are no extra assemblies and disassembly of the flange connections when it is necessary to change the direction of movement of the internal environment.
The main drawback of the design is that in the process of moving the valve body there is a strong friction. Gate valves have a large construction height due to the need to extend the rod.
When the valve is located in an intermediate position, the seats partially overlap the trays, the flow actively circulates the lower regions of the sealing annular surfaces, subjecting them to abrasive wear with solid inclusions of the working medium. Therefore, after operation in the partial shut-off mode, the valves are not provided with sufficient tightness when they are closed. This drawback is inherent in various types of reinforcement and limits the use of the valve as a regulating element. In addition, the regulating characteristics of the valves are unsatisfactory.
Application and operation of valves
Valves are used on pipelines with a diameter of more than 50 mm, where a smooth overlap of the cross-section is necessary to prevent a hydraulic shock.
They are also used in air conditioning and ventilation systems (as well as in furnace heating), an analogue of the sliding structure is a ventilation gate, which is a rectangular metal sheet that moves in the guides perpendicular to the axis of the duct.
Do not do without the valves and the installation of water and sewage systems, gas pipeline, as well as other industrial engineering systems. Many mistakenly believe that the valves are a variety of valves, but these are different devices that have structural differences that determine the features of operation.
Device and functions of valves
The valve is a valve, the gate of which is moved by means of a threaded pair. The constructions are made in threaded (mufty) version and for connection to pipe flanges.
Depending on the mutual arrangement of the outlet and inlet connecting pipes, the angular and passage valves are divided. The category of openings includes structures in which the axes of the output and inlet connecting pipes are parallel or coincident. The angle valve, in turn, is equipped with mutually perpendicular axes.
Depending on their purpose, they are divided into shut-off, safety, regulating, shut-off, bypass, respiratory, reverse.
The valve can be single-seat and two-seat. Single-seat valves, in turn, in the shape of the shutter are divided into needle and disk. A valve having manual control, in which the bolt moves by means of a threaded pair, is often referred to as a valve. There are regulating and shutoff valves. The purpose of the check valves is to completely shut off the flow of the medium, for this they are provided with a locking body.
Membrane valves are valve structures in which the flow of media is blocked by using an elastically deformable membrane (plastic, rubber). These systems are made of cast iron with an inner coating of corrosion-resistant materials (rubber, plastic, enamel).
Hose valve - the design of the valve, in which the overlap of the flow of the medium is realized due to the wear of the rubber hose inside the valve. Valves are used with both a one-sided and a bilateral hose strain.
The breathing valve is designed to discharge accumulated air or vapors and to prevent the formation of vacuum in the tanks during the "big" and "small" breathing. The concept of "big" breathing occurs when the flow and flow of fluid, "small" is caused by temperature fluctuations.
Thanks to the check valves, it is possible to prevent backflow of the medium. In the non-return valves, the closure organ is opened by a direct flow of the medium and is closed by a return flow. The lifting reverse design of the valve has a shutter that reciprocates. The structures, completed with a grid, are installed at the beginning of the suction pipeline. The rotary check valve is equipped with a shutter rotating around a horizontal axis that is located above the center of the valve seat.
Valve advantages and disadvantages
The main advantage of the valves is the absence of friction of the sealing surfaces when they close, since the bolt moves perpendicularly, which in turn reduces the risk of damage. The valve has a smaller height in comparison with the valve because the spindle travel is small and is not more than ¼ of the diameter of the pipeline. However, they have a greater construction length, since it is required to deploy the flow inside the shell.
The disadvantage of the valves is a large hydraulic resistance. It arises as a result of a change in the direction of the flow of the working medium. This change occurs twice inside the device case.
The valve differs in that it has limitations during operation and can be used only for a certain direction of movement of the working medium. The design is predetermined that the flow must leak under the plate and press on it from the saddle in the closed position. The opening of the valve provokes the separation of the plate from the saddle. If the valve is oriented in the opposite direction, then in the closed position the plate will be pressed against the seat, which will create considerable difficulties when opening. As a result, the disc may be disrupted from the stem and the valve outlet may be damaged.
The structural and functional difference between valve and valve
What is the difference between a valve and a gate valve? The difference is due to the design of their locking organs. In valves, the flow of gas or liquid is closed by means of a valve that is pressed against the seat in horizontal planes parallel to the flow, for this, a double bend of the gas or liquid flow is made at an angle of 90 °, but this increases the resistance.
In valves, the flow is blocked by a flap or cone, which is lowered perpendicular to the direction of flow.
With the correct design of the valve, there is no narrowing of the bores, in comparison with the input and output holes. In the case of gate valves, a number of options are possible. In most pipelines, all-wheel drive valves are installed, in which the diameter of the bore corresponds to the diameter of the pipeline, but often narrowed valves are used to reduce the torque, which makes it possible to reduce the wear of the sealing surfaces.
With high pressure or pipeline diameter of more than 300 mm, shutters are more effective. The valve has a simpler design, resulting in a lower cost. In addition, they are easier to rotate at high pressure, but at high pressures, an additional load on the structure is created by striving to squeeze the valve from the seat. In the valves, the resistance is completely absent, since they do not have bends.
Thanks to one-sided pressure, the flap is more closely adhered to the saddle, making bolts more reliable locking devices.
The blocking element of the valves can either completely block the flow of gas or liquid, or be completely open, the valves in turn can act as regulating elements.