Alberta Special Oilwell Boiler Practice Test 2026 – Complete Exam Prep

Two shutoff safety valves are placed in series on the fuel train to provide redundant, reliable isolation of the fuel supply. In normal operation only when both valves are opened can fuel flow occur; during shutdown both shut, giving two independent barriers to fuel flow. If a valve were to leak or fail in the open position, the other valve can still close and stop the fuel, ensuring a safe shutdown. A single valve wouldn’t give redundancy, two in parallel could still allow fuel to flow if one valve sticks open, and three in series is more than required for standard safety isolation.