From the perspective of process operations, automatic control systems can significantly reduce manual intervention while enhancing safety and efficiency. Consequently, organizations generally strive to implement automatic control wherever possible. However, in practice, many installations fail to achieve the desired level of automation due to various constraints. Simply focusing on increasing the automation rate through performance assessments without addressing the root causes often leads to inefficiency and compromises safety. Below, I outline key reasons for the reluctance to adopt automatic control and propose practical solutions.
Key Challenges in Implementing Automatic Control
1. Conditional Constraints
Equipment Inactivity: Automatic control systems are redundant for idle or non-operational equipment.
Faulty Instruments or Actuators: Issues such as malfunctioning sensors or actuators prevent effective automation.
Without addressing these constraints, attempting to enforce automation leads to operational inconsistencies.
2. Errors in Implementation
Technical Errors: Mistakes in configuration, such as incorrect direct/reverse action or improper seamless switching, can cause significant disturbances when automatic control is activated. These errors often result in operators defaulting to manual control to maintain stability.
Operator Habituation: Over time, persistent technical errors discourage reliance on automation. This habitual reliance on manual operations can persist for years, even if automation is mandated.
3. Ineffective PID Parameters
Oscillation Issues: Poorly tuned PID parameters can cause process variable oscillations, which may propagate throughout the system. For instance, in liquid level control, maintaining a manual mode often demands constant operator attention. As a result, automation may be reluctantly adopted to mitigate persistent manual workload.
Inadequate Disturbance Rejection: Ineffective tuning can lead to insufficient disturbance handling, necessitating frequent manual intervention. Over time, operators may prefer manual operation, abandoning automation entirely.
4. Unrealistic Control Schemes
Mismatch with Operational Habits: Control schemes that fail to align with operators’ workflows or preferences are unlikely to gain acceptance. Modifying existing control schemes often faces resistance due to operational constraints or doubts about the technical viability of new solutions.
Complex Scenarios: Some processes, such as dual temperature setpoint control for distillation columns (e.g., overhead and bottom temperature), are inherently challenging to automate effectively.
Consequences of Inadequate Solutions
If these issues are not thoroughly addressed, superficial management practices focusing on automation rates can lead to formalism rather than actual improvements. Overemphasis on automation targets without sufficient empowerment and resources often results in counterproductive outcomes.
Practical Strategies for Improvement
1. Addressing Conditional Constraints
While removing constraints such as equipment faults or operational limitations is ideal, this often requires significant investment. Automation rates below 100% are not necessarily indicative of technical incompetence but rather reflect a balance between cost and benefit. Prioritizing high-value areas for automation can maximize returns.
2. Enhancing Engineer Competencies
Implementation Expertise: Engineers should be trained to follow standardized configuration workflows and handle complex control strategies. This ensures that automation is deployed correctly and effectively where conditions permit.
Problem Diagnosis: Empowering engineers to identify and address errors in implementation can prevent long-term reliance on manual operations.
3. Optimizing PID Parameters
Scientific Tuning Methods: Systematic PID tuning approaches can resolve most oscillation and stability issues. Engineers should treat operational inefficiencies and oscillations as problems to be solved rather than tolerated.
Institutional Support: Organizations should establish policies and provide tools to support engineers in mastering PID tuning techniques.
4. Adopting Advanced Control Techniques
Leveraging Operational Experience: Advanced control strategies can integrate accumulated operational knowledge to improve existing control schemes without altering the Distributed Control System (DCS) infrastructure. This provides flexibility for continuous improvement.
Revising Control Schemes: Where necessary, revisiting and revising control schemes within the DCS to align with process requirements can enhance automation effectiveness. However, this requires thorough technical validation and stakeholder buy-in.
Conclusion
The challenges associated with automatic control are multifaceted, ranging from technical limitations to organizational and cultural factors. Addressing these issues requires a combination of technical expertise, resource allocation, and strategic planning. While achieving complete automation may be impractical in certain scenarios, continuous efforts to optimize control strategies and empower personnel can significantly improve safety, efficiency, and operational performance.
As the saying goes, “Difficult as the task may be, success is inevitable with perseverance.” The road to effective automation is challenging but ultimately rewarding when approached methodically and collaboratively.