English 简体中文

Welcome to Alliance Industry Limited !　

Search
Latest news 
Home >> Know-How >> Valve Positioner Failure
Valve Positioner Failure
Source: | Author:Alliance | Published time: 2020-01-20 | 3232 Views | Share:
The ordinary positioner uses the principle of mechanical force balance, and the nozzle baffle technology, and the following types of faults exist:

1. Due to the principle of mechanical force balance, there are many moving parts, which are easily affected by temperature and vibration, causing fluctuations in the control valve.

2. Nozzle baffle technology is used, because the nozzle hole is small, it is easy to be blocked by dust or dirty air source, so the positioner cannot work normally.

3. Using the principle of force balance, the elastic coefficient of the spring will change in harsh scenes, which will cause the non-linearity of the control valve and reduce the control quality.

4. The intelligent positioner is composed of microprocessor (CPU), A / D, D / A converter and other components. Its working principle is completely different from ordinary positioners. The comparison between the given value and the actual value is purely an electric signa, it is no longer a force balance.Therefore, the disadvantage of the force balance of the conventional positioner can be overcome. However, when used in emergency parking lots, such as emergency shut-off valves, emergency vent valves, etc., these valves need to be stationary at a certain position. Only when an emergency occurs, they need to be reliably operated. Staying at a certain position for a long time is easy Dangerous situation where small signal does not work due to runaway electrical converter.In addition, since the position sensing potentiometer for the valve works in the field, the resistance value is liable to change, causing the small signal to not operate and the large signal to be fully open. Therefore, in order to ensure the reliability and availability of smart positioners, they must be tested frequently.