Instrumentation Questions

Gas Turbine Start Interlocks Quiz – 25 Advanced MCQs for Engineers

Sundareswaran Iyalunaidu
By Sundareswaran Iyalunaidu

Gas turbine start interlocks are essential for safe and reliable turbine operation in both power generating and industrial processes. These interlocks serve as safeguards, ensuring each vital subsystem is in the positive state. They check lubricant oil, hydraulic pressure, the position of the IGV, purge conditions, fuel readiness, and vibration health. Only then does the unit move from permissive checks to the firing sequence. These systems are designed to prevent catastrophic breakdowns, misfires, and abnormal speeds.

In actual industrial settings, the initiation of permissible actions needs to be consistent with the original equipment manufacturer’s (OEM) logic, the guidelines provided by the application programming interface (API), and the safety protocols unique to each plant. This question tests your grasp of high-integrity start sequences, dynamic shutdown conditions, and the intricate field situations that senior engineers often encounter. 

Gas Turbine Start Interlocks – 25 Advanced MCQs With Answers

Gas Turbine Start Interlocks

Gas Turbine Start Interlocks Quiz – 25 Advanced MCQs for Engineers

Gas turbine start interlocks serve a crucial function: they ensure every essential system is primed before the turbine can even think about cranking up. This includes checking lubrication oil pressure, hydraulic control, purge airflow, IGV positioning, vibration monitoring, and fuel delivery. Only when all these elements are confirmed as ready does the system allow the crank and ignition sequence to begin. These measures are in place to avoid misfires, heat shocks, and mechanical breakdowns. This exam tests your skill in understanding complex permissives, interlocks, and shutdown logic as they apply to turbine start sequences at actual plants.

1 / 26

A turbine start is blocked due to “Servo Oil Temperature Low.” Why is this critical?

2 / 26

“Vibration System Not OK” blocks start. What condition typically triggers it?

3 / 26

Turbine trips during firing on “Flame-Out.” Most probable root cause?

4 / 26

“Auto Purge Valve Not Closed” prevents start. Which condition causes this?

5 / 26

Turbine fails on “Fuel Stop Ratio Valve Mismatch.” What is the best explanation?

6 / 26

“Bearing Metal Temperature High” appears but start continues. Why is it not a start interlock?

7 / 26

Fuel gas compressor trips, but turbine remains in purge. Why?

8 / 26

“Trip Oil Pressure Low” forces an immediate shutdown. What does this interlock protect?

9 / 26

Turbine does not proceed to acceleration after ignition. Most likely reason?

10 / 26

“Compressor Discharge Pressure Low for Firing” appears during crank. Common cause?

11 / 26

The turbine refuses to start because “Emergency Stop Loop Not Healthy.” Which situation fits?

12 / 26

“Exhaust Temperature Spread High” aborts startup post-ignition. Probable cause?

13 / 26

A unit fails to complete purge due to “Airflow Low.” What explains this condition?

14 / 26

“Fuel Forwarding Not Ready” blocks ignition. Most likely cause?

15 / 26

IGV fails to reach the commanded pre-start position. Which subsystem is directly implicated?

16 / 26

The unit trips on “Differential Vibration High” during crank. Probable root cause?

17 / 26

“Vent Fan Not Running” blocks purge. What hazard does this interlock mitigate?

18 / 26

“Vent Fan Not Running” blocks purge. What hazard does this interlock mitigate?

19 / 26

The turbine aborts start because the turning gear does not disengage. Probable cause?

20 / 26

Turbine overspeed test cannot initiate. Which permissive is primarily required?

21 / 26

A turbine enters firing but aborts immediately on “Ignition Failure.” What condition is most realistic?

22 / 26

Fuel gas valve fails to move to “Purge Position.” What interlock usually stops it?

23 / 26

The turbine does not advance to ignition because the flame detector permissive is false. Which scenario explains this?

24 / 26

During crank, the unit trips on “Hydraulic Pressure Low.” Which failure is most probable?

25 / 26

A gas turbine fails to enter purge mode. Which interlock most commonly inhibits the purge sequence?

26 / 26

During a turbine start attempt, the Lube Oil Pressure Low permissive remains false. Which condition most likely prevents the start?

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The average score is 60%

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