Field Device Parameter Write Approval for Active Loop Safety
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Solution Overview
Problem
In distributed control systems, independent access by asset management systems to field devices can lead to unintended changes in active control processes without the knowledge or approval of DCS operators, potentially causing operational hazards due to differing levels of situational awareness.
Innovation Solution
Implementing a security services module that intercepts write commands to field devices, requiring approval from DCS operators before executing parameter changes, especially for critical parameters, to ensure safe and controlled modifications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If asset management system has independent access to field devices, then device maintenance and health monitoring functions can be performed, but unintended changes to active control processes may occur without operator knowledge or approval
Solution Approach 1:
The patent introduces an intermediary approval mechanism between the asset management system and field devices. When the AMS attempts to write to a field device, the DCS intercepts the command and presents it to the operator for approval. This intermediary process ensures that maintenance functions can proceed while operator awareness and approval are obtained, resolving the contradiction between system versatility and process safety.
2Reliability
If write commands are intercepted for approval, then process safety is improved, but command execution time and system complexity increase
Solution Approach 1:
The system performs preliminary actions by notifying the operator in advance of the intercepted write command and awaiting approval before execution. This preliminary approval process ensures safety by giving the operator time to assess the command's impact on active control processes, while the automated interception and notification framework minimizes the time overhead compared to manual procedures.
3Loss of information
If security services module intercepts all write commands, then operator awareness is maximized, but system operation complexity and overhead increase
Solution Approach 1:
The security services module applies different levels of interception and approval requirements to different field devices and parameter types. Critical parameters and controlled fields require operator approval, while non-critical parameters may allow direct writes. This local differentiation maximizes operator awareness for important changes while reducing system complexity overhead for routine operations.
Data Source
AI summary
A system for preventing inadvertent or untimely parameter changes to an active online field device from a secondary system different from a distributed control system application providing control instructions to the field device, where the parameter changes may cause detrimental effects to a plant process or activity. A request for a parameter change from the secondary system may be intercepted before the request is received by a field device or a controller for evaluation by an operator of the distributed control system. The validation process may provide a plant operator with override authority to approve or deny a set of critical parameter changes to an active field device or other active plant device.