Process control instrument fault analysis and treatment
1, the introduction
Instrument failures often occur in the process of chemical production. Due to the complexity of the fault phenomena in the process of detection and control, correct judgment and timely treatment of instrument failures in the production process are not only directly related to the safety and stability of chemical production, but also related to the quality and consumption of chemical products. It can also reflect the actual working ability and business level of instrument maintenance personnel, and it is also the key to whether instrument maintenance personnel can obtain the trust of process operators and cooperate closely with each other.
2, instrument fault judgment train of thought
Due to chemical production operation pipelining, streamline, fully enclosed and other characteristics, especially the modern chemical industry automation level is high, operation is closely related to the instrumentation, process engineering by detecting instrument display of various process parameters, such as reaction temperature, material flow, pressure and liquid level of container, the composition of raw materials such as judge whether the process is normal, Whether the quality of the product is qualified, according to the instrument instructions to increase or reduce production, or even stop.
The abnormal phenomenon of the instrument indication (indicating high, low, unchanged, unstable, etc.) contains two factors: one is the process factor, the instrument correctly reflects the process abnormal situation; The second is the instrument factor, due to the failure of a link of the instrument (measuring system), the process parameter indication is not consistent with the actual. These two factors are often confused, and it is difficult to tell immediately where the fault is. Instrument maintenance personnel to improve the fault judgment, in addition to the familiar with instrument working principle, structure, performance features, also need to be familiar with every part of the measurement system, at the same time, the technological process and characteristics of medium, should understand the characteristics of the chemical equipment which can help the instrument maintenance personnel development train of thought, help to analyze and judge fault phenomenon.
2.1 Fault Diagnosis for temperature Detection
Fault phenomena: The temperature indicator is abnormal, high or low, or changes slowly or even does not change.
A thermocouple is used as a measuring element for illustration. First of all, we should understand the process condition. We can ask the process personnel about the condition of the medium being measured and the installation position of the instrument, whether it is in the gas phase or the liquid phase or other process conditions. Because it is a fault in the normal production process and not a newly installed thermocouple, the factors such as reverse polarity connection of the thermocouple compensation wire and mismatch of the thermocouple and compensation wire can be excluded.
2.2 Traffic Detection Fault Diagnosis
Fault phenomenon: Flow indicator is abnormal, high or low, or indicates zero, indicates fluctuation.
Take differential pressure flow transmitter as an example (1151D). When dealing with the fault, the instrument maintenance personnel should know the fault condition and the process condition from the process operator, such as the condition of the measured medium, the machine pump and the process flow. Through a detailed understanding of the process driving situation.
2.3 Pressure Detection Fault Diagnosis
Fault phenomenon: the pressure indicator of a chemical container is abnormal, high or low, or zero or unchanged.
Take the electric pressure transmitter as an example (3051C). First of all, we should understand the measured medium is gas, liquid or steam, understand the process and simple process flow, according to the understanding of the process situation and instrument fault phenomenon to judge and deal with instrument failure.
2.4 Determining the Liquid Level Detection Fault
Fault phenomenon: Liquid level indication does not change, high or low, or no indication.
The differential pressure type liquid level transmitter is used as the detection instrument. First of all, we should understand the process status, process medium, the object of measurement is the distillation tower, the reaction kettle, or the tank (tank), the reactor. When measuring liquid level with differential pressure level gauge, glass level gauge is often configured at the same time. Process operators take the field glass level gauge as a reference to judge whether the measured value of differential pressure level transmitter is high or low, because the glass level gauge is more intuitive. And instrument maintenance personnel should judge and check according to the process condition and instrument fault phenomenon.
Contact Person: Ms. Gao