Introduction
Stuck when facing instrumentation faults? This article thoroughly explains the troubleshooting methods for temperature, flow, and pressure instruments!
As the "nervous system" of industrial production, automated instrumentation systems determine the stability and efficiency of production processes. They play a decisive role especially in the petrochemical industry, making the stability of automated instrumentation systems crucial for this sector. This also places requirements on the professional capabilities, fault diagnosis skills, and operational proficiency of instrumentation maintenance personnel—factors that are key to gaining the trust of process engineers and achieving close collaboration.
1. Fault Diagnosis Principles for Instrumentation
Due to the characteristics of petrochemical production, such as pipelined operations, process-oriented workflows, and full enclosure—coupled with the high level of automation in modern chemical enterprises—process operations are closely linked to measuring instruments. Process engineers rely on various process parameters displayed by measuring instruments (e.g., temperature, material flow rate, vessel pressure and liquid level, and raw material composition) to determine whether production is normal, whether product quality meets standards, and to adjust output (increase/decrease) or even shut down operations based on instrument readings.
Abnormal instrument indications (e.g., high/low readings, no change, or instability) stem from two possible factors:
Process-related factors: The instrument correctly reflects abnormal process conditions.
Instrument-related factors: A fault in a component of the instrument (or its measuring environment) causes the indicated process parameter to deviate from the actual value.
These two factors are often intertwined, making it difficult to immediately identify the root cause. To improve fault diagnosis capabilities, maintenance personnel must not only be familiar with instrument principles, structures, and performance characteristics but also understand every link in the measurement system. Additionally, knowledge of process flows, properties of process media, and characteristics of chemical equipment helps expand their troubleshooting perspective and facilitates fault analysis.
2. Flow Measurement Fault Diagnosis
2.1 Fault Phenomena
Abnormal flow indications (high/low readings, zero reading, or fluctuating readings).
Taking a differential pressure (DP) flow transmitter (e.g., orifice flowmeter) as an example:When troubleshooting, maintenance personnel should consult process engineers to understand: Conditions of the measured medium, pump status, and process flow. After gaining a detailed understanding of process startup conditions, follow the troubleshooting flowchart below for diagnosis and inspection.
2.2 Common Faults and Analysis of Flow Instrument Systems
Minimum flow indication: Typically caused by damaged measuring elements, short circuits/opens in wiring, blockage/leakage in the positive pressure chamber, low system pressure. For parameters involved in control, additionally inspect the controller, control valve, and solenoid valve.
Maximum flow indication:The primary cause is blockage or leakage in the negative pressure chamber’s impulse line system. Transmitter calibration issues are rarely the cause.
Fluctuating flow readings:
