How to correctly understand the regulation valve repair using the model? Correct understanding of the control valve maintenance and use, can effectively improve the use of performance of the control valve. This paper focuses analyzed regulating valve correct selection process, according to the importance of regulating valve, control valve selection principle regulating valve selection process configuration and control valve accessories four aspects summed up the experience of control valve selection and Notes , help to improve the selection level regulating valve employees understand the control valve selection knowledge, but limited to the author is limited, it is inevitable that many of the shortcomings and problems, criticism and welcome connoisseurs.
A control valve selection
A, the importance of the control valve selection
The regulating valve actuators in the automatic control system, the quality of its application direct response to adjust the quality of the system. As the terminal element in the process, the understanding of the importance of it has been updated over the past. Regulating valve applications, good or bad, In addition to the quality of their products, the user is correct installation, use, maintenance, correctly calculated, the selection is very important. Due to calculation mistakes of the selection, resulting in a system open to open the stop, and some can not even put into use in the importance of on-site for users and system designers should recognize that the valve control valve selection must attract enough attention.
B, control valve selection principles:
1, according to the process operating parameters, select the appropriate control valve caliber size;
2, according to the process conditions, select the appropriate structure and materials; copyright dedecms
3, according to the characteristics of the technological object, select the control valve flow characteristics;
4, in accordance with the requirements of the process, select the required assistive devices;
5, reasonable choice of the implementing agency, the thrust and speed of response of the implementing agencies should be able to meet the technical requirements.
C, control valve selection process
Selection process: determine the operating conditions (process parameters) - calculate the required initial the Cv value - determine valve size. Material, power and energy of the executing agency and control system requirements means of communication. And need to provide the following information will help you choose the most suitable for the existing working conditions regulating valve.
1, there is a need to control the type of fluid;
2, the temperature of the fluid;
3, the viscosity of the fluid;
4, fluid specific gravity;
5, the required flow capacity (maximum and minimum);
6, the valve inlet pressure (maximum and minimum);
7, the valve outlet pressure (maximum and minimum);
8, the normal flow of the strong state pressure drop;
9, turn off when the voltage drop;
10, the maximum allowable noise level;
11, the inlet and outlet pipe diameter and wall thickness
12, body material;
13 instrument signal (-20mA 0 ~ 10V, etc.);
14, valves caliber;
15, the valve body structure; weaving dreams, good weaver of dreams
16, the size requirements of the implementing agencies (driving torque is calculated based on the data in the valve selection from 1.2 to 1.5 times as the best configuration);
17, driving energy (electric, pneumatic, electro-hydraulic);
18, the other requirements of the process conditions (such as: whether explosion, etc.).
Second, the control valve must be fitted with various ancillary devices (referred to as the annex) to meet the needs of the production process, the control valve accessories, including:
1, the valve positioner is used to improve the characteristics of the regulating valve to adjust the performance to achieve the correct positioning;
2, the valve position switch valve on the working position and lower stroke;
3, pneumatic secure his position valve to keep the valve in the open position in the gas source before the failure occurs when the regulating valve of the gas source failure;
4, the solenoid valve to achieve the electromagnetic switching of the gas path, ensure that the valve during a power failure when the valve is in the desired the safety opening degree position;
5, the hand wheel when the control system controller failure can be switched to manual operation of the valve;
6, pneumatic Following the move allows the implementation of the agency's action accelerated, reducing transmission time;
7, the air filter a decompressor for purifying source, regulated pressure;
8, the gas tank to ensure that when the air supply fails, the the cylinder work without spring piston actuator control valve moves to the fail-safe position. Its size depends on the size of the cylinder, the valve actuation time requirements and working conditions of the valve.
In short, the role of attachment the regulating valve function is to make better, more reasonable, more complete.
With the rapid development of industrial automation and fieldbus technology, control valve as terminal elements of the control system, its reliability, reasonable, durability growing concern is reasonable, correct selection will improve your industrial control systems efficiency, production safety protection, energy conservation, and improve economic efficiency,
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