Safety System Bypass and Override Procedure

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• Document control header (SOP SIS 001)
• Purpose, scope and references
• Safety, tools and prerequisites
• Numbered step by step procedure
• Acceptance criteria and records
• Approval block for sign off

1. Purpose

To make sure no safety function is left disabled without control, approval and compensating protection.

2. Scope

Bypasses of SIS functions, BPCS interlocks, fire and gas inputs and safety critical alarms.

3. References

• IEC 61511 operation and maintenance requirements
• Safety requirements specification
• Site permit and MOC procedures

4. Responsibilities

• Instrument technician: carries out the work and records results.
• Instrument engineer or supervisor: reviews and approves the records.
• Operations: grants the permit, isolates the process and returns the equipment to service.

5. Safety Precautions

• A bypassed safety function leaves the hazard unprotected: apply compensating measures before bypassing.
• Only authorised persons may apply or remove bypasses.
• Bypasses must be visible to operators at all times.

6. Tools and Equipment

• Bypass register
• Bypass request form or permit
• Cause and effect matrix

7. Prerequisites

• Reason for bypass defined (maintenance, testing, start up).
• Hazard and compensating measures assessed.

8. Procedure

8.1 Request and assess

1. Identify the function, hazard and reason.
2. Define compensating measures such as an operator watching a redundant reading.
3. Set the planned removal time.

8.2 Approve

1. Obtain approval at the level required (higher for SIS functions).
2. Enter the bypass in the register.

8.3 Apply

1. Apply the bypass with the control room; confirm it is indicated on the operator screen.
2. Put compensating measures in place.

8.4 Monitor

1. Review active bypasses every shift; overdue bypasses escalate.
2. Long term bypasses go through management of change.

8.5 Remove

1. Remove the bypass, confirm the function is healthy, and close the register entry.

9. Acceptance Criteria

• Every bypass approved, registered, visible and time limited.
• Compensating measures in place while active.
• Bypasses removed and recorded promptly.

10. Records

Related tools

This is a generic procedure. Adapt it to your site permit system, the manufacturer instructions and your quality system before use.

Frequently Asked Questions