Field instrument measurement parameters are generally divided into four parameters: temperature, pressure, flow, and liquid level.
According to the different measurement parameters, different field instrument failures are analyzed.
1. First of all, before analyzing on-site instrument failures, it is necessary to have a thorough understanding of the production process, production process conditions and conditions of the relevant instrument systems, understand the instrument system design scheme, design intent, instrument system structure, characteristics, performance, and parameter requirements.
2. Before analyzing and inspecting the failure of the on-site instrument system, it is necessary to understand the production load and the changes in the parameters of the raw materials from the field operators, check the record curve of the faulty instrument, and conduct a comprehensive analysis to determine the cause of the instrument failure.
3． If the instrument's recording curve is a dead line (a line that has not changed at all is called a dead line), or the recording curve originally fluctuated, it now suddenly becomes a straight line; the fault is likely to be in the instrument system. Because the current recording instruments are mostly DCS computer systems, the sensitivity is very high, and changes in parameters can be reflected very sensitively. At this time, you can artificially change the process parameters to see the curve changes. If it does not change, it is basically determined that there is a problem with the instrument system; if there is a normal change, it is basically determined that there is no major problem with the instrument system.
4． When changing the process parameters, it is found that the recording curve suddenly changes or jumps to the maximum or minimum, and the fault at this time is often in the instrument system.
5． Before the fault occurred, the instrument recording curve always behaved normally. After the fluctuation occurred, the recording curve became irregular or made the system difficult to control, even the manual operation could not be controlled. At this time, the fault may be caused by the process operating system.
6. When the DCS display instrument is found to be abnormal, you can go to the site to check the indication value of the same intuitive instrument . If they are very different, it is likely that the instrument system is malfunctioning.
In short, when analyzing the cause of field instrument failure, special attention should be paid to the characteristics of the control object and the control valve, which may be the cause of the field instrument system failure. Therefore, we must comprehensively consider and analyze from two aspects of the field instrument system and process operating system, and check the reason.