Process Safety Beacon. Interlock Bypass: Training Guide and Quiz

The latest CCPS Process Safety Beacon is An Interlock bypass bites again at https://ccps.aiche.org/resources/process-safety-beacon/archives/2025/july/english.

We have created a Training Guide and Quiz based on this event.

Here are the quiz questions:

1. What was the cause of the 2017 refinery fire in the Netherlands?
A. Improper fuel mixture
B. Electrical malfunction
C. Bypassed low-flow safety interlock
D. Operator fell asleep

2. Why did the furnace tubes rupture?
A. A water leak caused steam explosion
B. Flow stopped but burners continued firing
C. External fire spread to the furnace
D. Overpressure due to valve failure

3. What safety feature was designed to shut off burner gas during low flow?
A. Flame detector
B. Manual reset switch
C. Low-flow interlock
D. High-temperature alarm

4. What did operators do instead of following the bypass management procedure?
A. Removed the interlock
B. Installed a backup control system
C. Extended the timer to 20 minutes
D. Used field-mounted bypass switches

5. What change did the company make after the accident?
A. Removed all interlocks
B. Installed explosion-proof equipment
C. Required supervisor keys for bypass switches
D. Increased pipe thickness

6. What is the purpose of a bypass timer?
A. To disable alarms during startup
B. To shut off burners automatically after startup
C. To automatically restore interlock after a short delay
D. To alert operators to evacuate the area

7. Which of the following is a recommended method to manage interlock bypasses?
A. Verbal approval only
B. Temporary Management of Change (MOC)
C. Removing the interlock permanently
D. Leaving systems in bypass indefinitely

8. During hazard reviews, what should be discussed regarding interlocks?
A. How to override them easily
B. Who is responsible for maintenance
C. Whether time limits are appropriate for bypasses
D. How much fuel they save

9. Where should systems in bypass be recorded?
A. In the unit logbook
B. In the operations budget
C. In the safety policy
D. On a bulletin board

10. Which previous Process Safety Beacon issues also address interlock bypass concerns?
A. April 2005, July 2011, December 2020
B. June 2003, June 2013, February 2019
C. March 2010, August 2012, May 2024
D. January 2001, September 2014, October 2018

The full training document and answers to the quiz are in the following file.