Selection principles and maintenance introductionss
一. Selection
A. Selection importance
Regulator is self-control system actuators, its application quality direct responsed in system control quality. As process control terminal components, people have newer understanding to its importance, compared with the past. Good or bad regulator application, except the product itself quality, whether user is correct installation, operation and maintenance, correct calculation, selection is very important. Due to the calculation and selection fault, cause system start and stop at times, and some even are unable to use, so to users and system design personnel should know the valve on-site importance, it is necessary to pay more attention to the regulator selection.
B. Selection principles
1. according to the process conditions, choosing appropriate structure form and material.
2. according to the technics object's characteristic, choose regulator flow characteristics.
3. according to the craft operating parameters, selecting the appropriate regulator diameter.
4. according to the process requirement and select the desired auxiliary devices.
5. rational selecting actuators. Actuator response speed should be able to meet the process.
To control the stroke time requirements: the selected regulator actuators can be sufficient valve stroke and process to leak amount level requirements. In some occasions, if selecting pressure regulator (including venting valve), should consider the actual probable pressure differential to proper amplifier, which requires actuators can provide larger force. Otherwise, when the process occurs abnormality, the actual pressure difference before and after regulator is bigger, will happen can not close or can not open danger.
二. Annex
In the producing process, control system puts forward all kinds of special requirements to valves, therefore, regulator must equip with various accessory device (hereinafter referred to as attachment) to meet the needs of the production process. Regulator accessories include:
1. valve positioning is applied to improve regulator adjusting properties operating characteristics, achieve correct positioning.
2. valve position switch display valve upper and lower limit work position.
3. Pneumatic protect position valve when regulator air source breaks down, leaving valve in starting position before air source fault occurred.
4. solenoid valve realize gas circuit electromagnetic switch, ensure valve in the wanted safe opening position when power failure.
5. The handwheel when the control system controller is fault, can switch to manually mode to operate valve.
6. pneumatic actuator makes actuators movement speed up and reduce transmission time.
7. air filtration pressure is applied to purification origin, adjust air pressure.
8. gasholder ensures when air source is fault, make no spring cylinder piston actuators can put the control valve acting to safe position. Its size depends on the size of the cylinder, valve actuation time requirements and valve working conditions, etc.
In short, annex role regarding function is to make the regulator more perfect and more reasonable and more complete.
