利用事件序列找出真正问题：PSB Industries 电气与控制工程经理谈历史运行数据诊断停机报警

Antoine Kabre, electrical & controls engineering manager at PSB Industries, shares how historical operating data can turn a shutdown alarm into a starting point for understanding equipment behaviour, identifying recurring problems, and preventing the next interruption.

When process equipment shuts down, the alarm on screen offers an obvious place to begin troubleshooting. But an alarm most often only identifies the condition that crossed a limit or caused the control system to take action. What it does not necessarily identify is the condition that started the problem.

A temperature can begin drifting several minutes before the alarm appears. Elsewhere in the sequence, a valve might fail to reach its commanded position or a motor could push the process outside its normal operating range. By the time the control system generates the alarm that catches the operator’s attention, the condition that started the problem can already be several steps in the past.

Treating the final alarm as though it were an isolated failure can send maintenance teams toward equipment that is responding exactly as designed, or have them attending to an issue that was just the final symptom of an underlying cause that will continue to cause problems. Finding the actual cause requires reconstructing what the system was doing before the alarm occurred, then determining how one abnormal condition produced the events that followed.

Read the sequence, not just the alarm

Consider a system that generates a motor related alarm, followed shortly by a process alarm and then several additional alarms as the normal operating sequence breaks down. Viewed individually on a human-machine interface, or HMI, those alarms can appear to represent several separate problems. Consider them as an interrelated sequence and the picture can change considerably.

When determining what initiated the problem, the first useful question is not simply which alarm appeared, but what changed first. What operating mode was active? Which step of the sequence was running? What outputs had the control system commanded, and did it receive the expected feedback? What were pressure, temperature, flow, or analyser readings doing immediately beforehand?

Timestamped alarm and event histories provide the chronology, while process data supplies the operating context. Together, they allow a team to determine whether an alarm represents an initiating event, a consequence of another failure, or simply the control system responding to conditions elsewhere in the process.

This approach also makes troubleshooting more efficient. If three alarms all trace back to the same failed component or abnormal process condition, treating them as three independent problems adds diagnostic work without addressing the source. The goal here should be to preserve enough relevant information to reconstruct equipment behaviour and understand the relationship between events.

Look for changes before they become trips

Historical operating data can do more than reconstruct a single shutdown. Comparing equipment behaviour across repeated operating cycles can reveal developing changes before they reach an alarm or trip condition.

In a temperature swing adsorption (TSA) system, for example, a regeneration cycle normally develops a recognisable heating and cooling profile. A temperature reading does not have to cross an alarm threshold for the profile to become useful diagnostically. If heating begins taking longer, cooling behaviour changes, or the temperature curve gradually departs from its historical pattern over several cycles, the change can justify investigation before the system reaches a shutdown condition.

Other variables offer similar clues. Slower or inconsistent valve feedback, sequence steps that take progressively longer to complete, and changes in pressure under otherwise similar operating conditions all mark departures from the unit’s established behaviour. In a deoxygenation system, shifts in heater response or in the relationship between inlet and outlet oxygen measurements provide additional evidence of how the process is changing over time.

Any one deviation can have an innocent explanation, so identifying repetition is more significant. When the same abnormal behaviour appears under comparable operating conditions, the pattern gives operators a stronger basis for asking whether a component is deteriorating, process conditions have changed, or the sequence is no longer behaving as expected. Trend data can therefore shift maintenance attention from the moment a limit is exceeded to the period in which equipment begins moving away from normal behaviour.

Preserve the evidence before changing the system

When it comes to alert systems, diagnostic value depends on keeping the evidence available long enough to examine it. When a unit trips unexpectedly, the natural response is to restore operation. Operators often acknowledge or reset alarms, restart the sequence, manually operate equipment, bypass a condition, or make another adjustment to get the process running again. Those actions can be necessary, but they also change the state of the system.

By the time technical support becomes involved, the equipment may be operating normally again and some of the information surrounding the original event may no longer be obvious. Troubleshooting can then turn into an exercise in reconstruction: What happened first? Which alarms appeared? Was anything operated manually? What did the process look like immediately before the trip?

A stronger diagnostic record captures the alarm and event history, accurate timestamps, operating mode, active sequence step, relevant process conditions, commanded outputs and feedback, and actions taken after the event. Historical collection can preserve much of that information automatically, reducing dependence on screenshots and an operator’s recollection during a stressful interruption.

This does not diminish the importance of operator observations. Someone standing beside the equipment can hear unusual sounds, see a mechanical condition that does not appear in the control data, or recognise another plant event occurring at the same time. The strongest root-cause investigation combines those physical observations with an objective record of what the control system saw.

Add equipment knowledge to the data 

A timeline can show what happened. Interpreting why it happened often requires understanding how the equipment was designed to behave. This is where OEM visibility can add another layer to troubleshooting, particularly for complex packaged process systems. PSB Industries designs and fabricates gas and liquid dehydration and purification systems, including TSA dryers, deoxygenation systems, and other engineered treatment packages. Because its engineers develop the equipment and its controls, they can interpret operating data against the intended sequence, permissives, alarm logic, and expected process response rather than examining the numbers without that design context.

PSB Industries has applied its expertise through a remote monitoring service that provides technical teams with access to operating trends, alarm histories, and system status. Instead of beginning a support call by asking site personnel to reconstruct an overnight trip from memory, the OEM can review the recorded sequence and determine where the investigation should begin.

An arrangement such as this also preserves an important division of responsibility. Plant operators remain responsible for operating the equipment and understand conditions across the facility; the OEM contributes specialised knowledge of the particular package. Remote visibility connects those two perspectives without transferring operating authority away from the site.

More importantly, the value of remote OEM visibility extends beyond faster response after a failure. Continuous access to historical behaviour can reveal gradual deterioration that would be difficult to recognise from individual alarms. A changing regeneration profile, for example, could prompt an inspection or consideration of desiccant condition during a planned outage rather than after performance falls out of specification and service is needed. PSB Industries’s monitoring service is structured around that broader approach, combining alarm monitoring and diagnostics with operating data review. 

Make every failure improve the next operating cycle

Finding the initiating condition solves the immediate diagnostic problem. The larger opportunity is around deciding what the finding should change. If repeated events point to a deteriorating component, maintenance can inspect or replace it during a planned outage. If the equipment repeatedly approaches a process limit, the operating conditions deserve closer examination. If different operators respond differently to the same event, the solution may involve clarifying a procedure or providing targeted training. When the problem lies in the controls, engineers can evaluate whether alarm logic, programming, or the HMI needs to change.

Historical event records enable better decision-making. Instead of reviewing a hypothetical failure during refresher training, operators can examine a real sequence from their own unit and trace how the process moved from normal operation to an abnormal condition.

It's important to keep watching after the corrective action. A replaced component, modified procedure, or control adjustment should produce a measurable change in equipment behaviour. If the troublesome pattern disappears, the data provides evidence that the intervention addressed the cause. If it remains, the investigation is not finished. This last observational step closes the diagnostic loop: identify the pattern, determine what produced it, make a targeted correction, and verify the result.

An alarm can tell an operator that the process has reached a condition requiring attention. The more consequential question is what the equipment was trying to tell them before that alarm ever appeared. Plants that preserve and examine that history gain something more valuable than a faster explanation of yesterday’s shutdown: the chance to recognise tomorrow’s problem while there is still time to mitigate it.