This document outlines the risks associated with common operations in the instrumentation field and provides detailed preventive measures to ensure operational safety and accuracy. It serves as a guide for engineers and technicians to mitigate risks in various instrumentation tasks.
1. Equipment Power Shutdown and Activation
Risks:
- Confusion between similar devices (e.g., A/B systems).
- Simultaneous or unintended operation of adjacent switches or fuses.
Preventive Measures:
- Ticket Approval:
Ensure proper documentation through an operational ticket system, specifying the exact system and device tag numbers. Devices with similar identifiers (e.g., “A/B systems”) must be clearly distinguished. - Double Verification:
- Always perform operations with two personnel.
- Double-check the target equipment for shutdown.
- Single Device Isolation:
- Verify that no other devices are connected to the switch or fuse being operated.
- Inspect for sticky or faulty components before operation to prevent unintended actions.
- Position Identification:
For a row of switches or visually similar components:- Confirm the circuit using tag numbers and wire labels.
- Ensure the correct alignment with the intended circuit.
2. Instrument Cable Disconnection and Reconnection
Risks:
- Process monitoring disruptions.
- Misidentification of devices during operations.
Preventive Measures:
- Process Monitoring Assurance:
- Obtain a work permit for any operation affecting process monitoring.
- Validate protective measures (e.g., interlock bypasses) with process personnel.
- Device Identification:
- Match tag numbers, descriptions, and locations precisely before operation.
- In complex systems (e.g., A/B/C devices), confirm via system readings or control room displays.
- Power Isolation for Powered Devices:
- For devices like solenoid valves and four-wire instruments, ensure they are powered down before operation. Never perform maintenance on live equipment.
3. Instrument Draining and Purging
Risks:
- Fluctuations in readings.
- Leakage of hazardous media, causing burns or poisoning.
Preventive Measures:
- Operational Necessity:
- Perform draining or purging only when necessary, with prior approval from the workshop.
- Personnel must be familiar with the properties of the medium and use appropriate protective equipment.
- Risk Mitigation:
- Double-check safeguards (e.g., interlock bypass) to prevent unintended actions or fluctuations in process values.
- Device Matching:
- Verify tag numbers and locations. If systems are complex, cross-check with control room readings.
4. System Downloads and Updates
Risks:
- System-wide instability or shutdown.
- Incorrect operations in similar systems (e.g., A/B systems).
Preventive Measures:
- Comprehensive Risk Assessment:
- Use a multi-layer approval process before downloading updates.
- Develop detailed operational plans to address potential risks.
- Double-Personnel Verification:
- Ensure two people (e.g., team leader and technician) are present to validate the operation.
- Detailed Records:
- Take photographs of changes in the system before initiating downloads and share them for group verification.
- Timing Considerations:
- Perform downloads during periods of high alertness (e.g., mid-shift). Avoid end-of-shift or pre-holiday periods to prevent errors caused by fatigue or inattention.
5. Measurement Point Forcing
Risks:
- Triggering unintended interlocks or alarms.
- Extended forcing durations leading to oversight.
Preventive Measures:
- Documentation:
- Log forced points clearly and precisely, including the system-confirmed tag numbers.
- Simulation and Testing:
- Collaborate with process personnel to simulate the expected forcing results before implementation.
- Confirm positions (e.g., source or intermediate variables) to ensure effectiveness.
- Routine Inspection:
- Maintain records of forced points and perform weekly reviews with process teams. Limit forcing duration to avoid accidental oversight.
6. Interlock Debugging
Risks:
- Overlooked or unintended actions causing system disruptions.
Preventive Measures:
- Approval and Coordination:
- Obtain a maintenance permit and involve process teams during debugging.
- Pre-review interlock logic to identify potential triggers and actions.
- Cross-Functional Synchronization:
- Conduct debugging collaboratively with DCS and process teams using a single interface to prevent communication delays or misunderstandings.
- Restricted Operations:
- DCS personnel should refrain from operating valves or pumps directly. Such operations must be handled by process teams.
7. Air Supply Shutoff and Restoration
Risks:
- Multiple valve movements due to shared air supply lines.
- Sudden changes in process conditions.
Preventive Measures:
- Systematic Checks:
- From the air supply source to valve connections, verify whether multiple valves are connected to a single air supply line.
- Controlled Operations:
- Perform air supply changes gradually, allowing time for process stabilization.
8. Interface Disconnection and Reconnection
Risks:
- Medium leakage or pressure hazards.
Preventive Measures:
- Pre-Work Inspections:
- Validate the correct interface and secure approval from process teams before operation.
- Controlled Execution:
- Depressurize and isolate connections before disconnecting.
- Avoid standing in line with potential leak paths.
Appendix:
- Example Ticket Template: Includes fields for system identifier, device tag numbers, personnel approvals, and risk mitigation steps.
- Regulatory References: Links to applicable industry standards and regulations.
- Case Studies: Analysis of past incidents with recommendations for future prevention.