The DCS (Distributed Control System) is composed of system software, hardware, operator panels, and field instruments. Any issue in any part of the system can lead to partial or complete failure of its functions, potentially causing a complete control system breakdown. In severe cases, this could result in production shutdowns, leading to significant financial losses.
In fact, many DCS failures stem from small, often overlooked daily details. By paying closer attention to these aspects during routine operations, a considerable number of failures can be prevented. So, what should you focus on? Recently, we carefully compiled relevant information, hoping to provide valuable guidance for everyone.
What are the main sources of DCS faults?
First, let’s look at the common causes of DCS failures.
**Human Error**
Although DCS technology is now quite mature, with high levels of modularity, the probability of hardware failure remains relatively low. Most issues are caused by human factors such as incorrect configuration or improper operation, which are quite common.
**Information Security**
Industrial control systems are no longer isolated environments. Cybersecurity threats are increasing, making it essential to protect DCS systems from potential attacks.
**Power Failure**
A power outage during system operation can severely impact the DCS. Poor connections, failure to activate backup power, inadequate circuit breaker capacity, mismatched loads, power line accidents, and damaged components can all lead to power issues. These include power interruptions, voltage fluctuations, overvoltage, undervoltage, etc. High voltage can damage boards, while low voltage may cause malfunctioning, alarm signals, or abnormal outputs. A sudden power loss can crash the entire DCS system.
**Electromagnetic Interference (EMI)**
DCS systems are often located near high-voltage equipment, creating a challenging electromagnetic environment. It is difficult to eliminate interference sources or improve the system's immunity to EMI.
**Poor Grounding**
Improper grounding can lead to signal instability or drift when the system is exposed to interference. In extreme cases, it may even damage the board.
**Temperature and Humidity Effects**
High or low temperatures, dryness, or humidity can significantly affect system performance. For example, every 10°C temperature change can reduce analog card accuracy by 0.1%. When humidity exceeds 65%, moisture can form on surfaces, reducing insulation and accelerating corrosion. Low humidity can make materials brittle and prone to cracking.
**Static Influence**
Insulating materials can accumulate static electricity, which may cause chip malfunctions due to electrostatic discharge. This type of damage is often hidden and hard to detect.
**Corrosion Effects**
Corrosive gases or sea breeze in coastal areas can severely damage DCS boards and computer components, leading to short circuits and hardware failure.
**Lightning Impact**
Lightning can cause ground potential rise, leading to discharges between the lightning protection grounding and the control system, potentially damaging the DCS.
**Other Hazards**
Dust and rodents can also cause serious damage to DCS equipment and wiring.
**How to Prevent Issues?**
First, proper engineering design and construction are crucial before installation. Measures like lightning protection, shielding, and grounding must be implemented early, as they are difficult to modify later. The design should use a single-point equipotential grounding method, and correct grounding techniques should be applied according to standards.
Second, address any issues found during application promptly. For EMI, cut off the transmission path between the source and the DCS. Use grid-type shielding in control rooms, install filters on signal cables, and ensure proper cable routing. Also, install SPD devices to prevent lightning surges.
Third, follow strict operational procedures. For static issues, wear anti-static wristbands when handling cards and store spare parts in anti-static bags.
Fourth, maintain daily DCS operations:
- Regularly check power supplies, perform redundancy tests, and inspect network connectors and terminal blocks.
- Monitor controller workloads, clean hard disks, and archive historical files.
- Install virus firewalls on gateway stations and keep OS patches up to date.
- Avoid making changes unless necessary.
- Document all system modifications and back up configuration data regularly.
- Ensure the control room has proper temperature, humidity, and dust levels. Clean components quarterly.
Fifth, implement preventive maintenance during system overhauls. Check power supplies, grounding, redundancy, and hardware. Perform regular cleaning, defragmentation, and system testing.
Finally, keep detailed logs and troubleshooting records.
**What to Do If a Problem Occurs?**
Even with strict prevention, faults can still occur. When a DCS failure happens, quickly diagnose and locate the problem. Follow these steps:
1. Analyze the symptoms thoroughly, ideally by observing them firsthand.
2. Determine under what conditions the fault occurred—during commissioning, operation, or maintenance.
3. Check if any recent changes were made to the system.
4. Look for fault indicators on the boards.
5. Use standard signal generators to test board functionality.
6. Replace suspected faulty boards using spares, if possible.
7. Determine if the issue is temporary or recurring.
8. Review operation logs and historical fault records for clues.
By following these steps, you can effectively identify and resolve DCS issues efficiently.
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