Structural characteristics of control valves
1.There are different types of Control valve, their application in different situations, therefore, should be based on the requirements of the production process technology control valve type of rational choice.
hydraulic circuit dual po check
2. Pneumatic control valve sub-class open air and gas off two. Air to open control valve closed when the fault condition,
hydraulic shuttle valve gas off control valve to open in fault state.
pilot check valve Composed of a number of auxiliary equipment can be used his position and valve or valves to control the self-locking, that is, failure to maintain control valve failure before the valve opening
3. Air and gas off the way open through positive, reaction type and is the implementing agency body, a combination of anti-body valve in the use of valve positioner, can also be achieved through the valve positioner
4. A variety of control valve structure is different, complement each other. From the control valve applications, the development directions are as follows:
a. a small executive body: You can reduce costs, improve circulation capacity.
b. sleeve guide: The guide sleeve is beneficial right, there is help to reduce friction and noise reduction benefit is conducive to the exchange of flow characteristics
c. Balanced Plug: To reduce the executing agency thrust or push torque, a balanced-type valve core is important, it is also the system dynamic performance has improved
d. Integration Plug and seat: In order to overcome the shortcomings of poor sealing valve seat, using the same material composition of an integrated valve core and valve seat within the piece, the leakage rate and the unbalanced force at the same time minimized.
e. Simple Flow: flow path simple, flow resistance decreases, not only can decrease pressure drop across valve, but also reduce costs.
f. Sealing and friction: sealing performance and tribological properties of the two contradictory aspects of the control valve design, not only to solve the sealing problem, friction and lifetime performance indicators must pay attention to, therefore, in recent years, packing and packing structure of letters to be attention, rotary-type control valve to be more widely used
g. noise reduction: Using a variety of ways to reduce noise, control valves, for example, use of noise reduction sleeve and valve core, using multi-stage spool, using noise-limiting plate, use of extensions, etc.
h. use of the same diameter and pipeline control valves and limit the ability of the valve within the flow of parts: help to reduce valve inlet pressure and exit flow rate, without having to install additional fittings such as different-diameter pipe will help reduce costs, by replacing the flow capacity of large Within the valve parts, scalable distribution capabilities, through the ability to use limited circulation valve diameter is too large pieces of corrected errors in the calculation
i. in the digital information age, will be more use of smart valve positioner or through a digital controller to achieve non-linear law, the compensation of nonlinear controlled object will be less choice of control valve flow characteristic to compensate for the controlled object Nonlinear
5. Valve piece of material varies with temperature, therefore, should be considered at different temperatures caused by thermal expansion effects, but also consider the high temperatures and changes in pressure levels should be considered the material corrosion resistance, anti-fatigue properties.
How to choose control valve
A, the importance of control valve selection
Regulating valve is self-control system, actuators, and its application quality direct response to the quality of the adjustment in the system. As a process control terminal components, the importance in it than in the past has been updated knowledge. Control valve applications, good or bad, in addition to the quality of the product itself, the user is installed correctly, use, maintenance, correct calculations, selection is very important. Selection of calculation errors, causing the system to open stop-open, and some can not even put into use, so for users and system designers should be aware of the importance of valves in the field, control valve selection must be taken seriously enough.
B, the principle of control valve selection
1, according to process conditions, selection of suitable structural forms and materials.
2, according to the technical characteristics of the object, select the control valve flow characteristics.
3, according to process operating parameters, select the appropriate aperture size control valves.
4, according to process requirements, select the required assistive devices.
5, selecting the implementing agency. The response speed of the implementing agencies should be able to meet the technical
To control the travel time requirements: the selected implementing agency should be able to control valves sounded very full schedule and process on the valve leakage volume level requirements. In some cases, such as the selection of pressure control valves (including the venting valves), pressure should be considered possible and practicable, appropriate amplification, which would require implementing agencies to provide a larger force. Otherwise, it may appear abnormal when the process occurs, the actual differential pressure control valve before and after the larger, will occur on or off without the risk of not open.
