Safety Philosophy
At Acaysia, safety is not a feature—it's the foundation of everything we build. Our safety architecture is guided by three core principles:
1. Never Compromise Safety for Performance
Acaysia will always choose the safe action over the optimal action. Performance improvements are only pursued within verified safe operating envelopes.
2. Fail Safe, Not Fail Operational
When in doubt, Acaysia returns control to proven traditional systems. We design for safe failure modes, not continued operation under uncertainty.
3. Operator Always Has Final Authority
Human operators can override Acaysia at any time. The system provides recommendations and automation, but never removes human agency.
Defense in Depth
Acaysia implements multiple independent layers of protection. If any single layer fails, subsequent layers prevent unsafe conditions.
Layer 1: Process Design
Inherently safer process conditions and equipment limits
Layer 2: Basic Process Control (BPCS)
Traditional PID loops maintain normal operation
Layer 3: Acaysia Optimization
Advanced control within verified safe envelope
Layer 4: Acaysia Safety Monitor
Independent watchdog validates all outputs
Layer 5: Safety Instrumented System (SIS)
Independent hardware-based emergency shutdown
Failsafe Mechanisms
Automatic Fallback to PID
In any anomalous condition, Acaysia automatically transfers control to traditional PID controllers. This "bumpless transfer" ensures continuous process operation.
Fallback Triggers
| Condition | Detection Method | Response Time |
|---|---|---|
| Communication loss | Heartbeat timeout | < 500ms |
| Model prediction error | Residual monitoring | < 1 second |
| Control output anomaly | Rate-of-change limits | Immediate |
| Process variable out of range | Boundary monitoring | Immediate |
| Operator request | Manual override | Immediate |
Watchdog Timer
The Acaysia edge device includes a hardware watchdog timer. If the control software fails to reset the timer within the configured interval (default: 1 second), the hardware automatically:
- Disconnects Acaysia outputs from the process
- Signals the PLC to resume direct control
- Logs the event for post-incident analysis
- Alerts operators via configured notification channels
Output Clamping
All Acaysia outputs are bounded by configurable limits:
# Output constraints configuration
outputs:
reactor_temperature_sp:
min: 50.0 # Minimum setpoint (°C)
max: 180.0 # Maximum setpoint (°C)
rate_limit: 5.0 # Max change per minute (°C/min)
coolant_valve:
min: 0.0 # Fully closed
max: 100.0 # Fully open
rate_limit: 20.0 # Max change per second (%/s)Runtime Monitoring
Model Confidence Tracking
Acaysia continuously monitors the accuracy of its internal models by comparing predictions to actual process measurements. When confidence drops below threshold, the system:
- Widens safety margins on control actions
- Increases reliance on traditional control
- Flags the situation for operator review
- Triggers model retraining if appropriate
Anomaly Detection
Multiple anomaly detection methods run in parallel:
Statistical Process Control
Traditional SPC charts monitor process variables for out-of-control conditions using CUSUM and EWMA algorithms.
Physics-Based Consistency
Mass and energy balance checks verify that sensor readings are physically consistent with each other.
ML Anomaly Detection
Autoencoder neural networks identify subtle patterns that may indicate equipment degradation or process drift.
Audit Logging
Every control action is logged with full context:
- Timestamp (synchronized to plant time server)
- Current process state
- Model predictions
- Control action taken
- Confidence level
- Active constraints
Logs are stored locally and can be exported to plant historians for long-term retention.
Safety System Integration
Independence from SIS
Acaysia is architecturally separate from the Safety Instrumented System (SIS):
- No shared hardware or software components
- No ability to modify SIS logic or setpoints
- SIS can operate correctly even if Acaysia completely fails
SIS Status Monitoring
Acaysia reads (but never writes) SIS status information to:
- Detect when process is approaching safety limits
- Proactively adjust control to avoid SIS activation
- Recognize post-trip conditions and assist with safe restart
Operator Interface Integration
Acaysia integrates with existing HMI/SCADA systems to provide:
- Clear indication of Acaysia mode (Shadow/Advisory/Closed-Loop)
- Easy one-click override to return to manual control
- Alarm integration following ISA-18.2 standards
- Trend displays showing Acaysia recommendations vs. actual control
Standards Compliance
IEC 61511 / ISA 84
Acaysia is designed to operate within process plants that comply with IEC 61511 (functional safety for process industries). Key considerations:
- Acaysia operates in the BPCS layer, not the SIS layer
- Does not claim any Safety Integrity Level (SIL) rating
- Relies on independent SIS for safety-critical functions
ISA/IEC 62443
Acaysia follows industrial cybersecurity best practices:
- Secure-by-design architecture
- Encrypted communications (TLS 1.3)
- Role-based access control
- Regular security updates and patching
See our ISA/IEC 62443 Compliance Guide for detailed information.
Industry-Specific Standards
| Industry | Relevant Standards | Acaysia Compliance |
|---|---|---|
| Pharmaceutical | 21 CFR Part 11 | Audit trails, electronic signatures |
| Oil & Gas | API RP 556 | Instrumentation best practices |
| Chemical | OSHA PSM | Management of Change support |
Safety Validation
Factory Acceptance Testing (FAT)
Before deployment, every Acaysia system undergoes comprehensive FAT including:
- Simulated fault injection testing
- Communication failure scenarios
- Boundary condition testing
- Failover timing verification
Site Acceptance Testing (SAT)
On-site testing validates integration with plant systems:
- End-to-end communication verification
- Manual override functionality
- Alarm system integration
- Watchdog timer operation
Ongoing Validation
Safety systems require continuous validation:
- Automated daily self-tests
- Quarterly manual failover drills
- Annual comprehensive safety review
- Model accuracy validation against process data