Prepare for gas turbine instrumentation interviews with essential questions and answers on vibration probes, interlocks, Master Trip SOV, and more. This article covers calibration, troubleshooting, and system testing for effective turbine management.
How do Vibration Probes Work, and What Critical Parameters do they Measure in Gas Turbines?
Vibration probes, such as proximity probes or accelerometers, measure the vibration displacement, velocity, or acceleration of rotating equipment like gas turbines. They detect changes in the distance between the probe tip and the rotating shaft or structure.
Key parameters include vibration amplitude, frequency, and phase, which help assess the condition of bearings, rotors, and other components.
Explain the Process of Calibrating and Installing a Vibration Probe on a Gas Turbine.
Calibration involves setting the correct gap between the probe and the shaft using a calibration fixture and reference voltage. Installation requires aligning the probe properly and securing it to avoid mechanical looseness. The signal is then verified to ensure it accurately reflects the machine’s vibration.
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What role does Proximity Probe Gap Adjustment Play in Accurate Vibration Monitoring?
Proper gap adjustment between the proximity probe and the shaft is crucial for accurate measurement. An incorrect gap can lead to erroneous readings, affecting data reliability. Correct adjustment ensures the probe operates within its designed linear range, providing accurate and repeatable measurements.
What are the Advantages of using Dual-Voting Vibration Protection Systems in Gas Turbines?
Dual-voting systems use two independent vibration measurements to prevent false trips and enhance system reliability. Both channels must agree on a high vibration condition before initiating a shutdown, reducing the risk of unnecessary turbine trips due to spurious signals.
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What are the Key Interlocks Involved in Gas Turbine Startup and Shutdown Sequences?
Key interlocks include fuel valve position, rotor speed, lubrication oil pressure, generator breaker status, and exhaust temperature. These interlocks ensure the turbine operates within safe parameters and that critical systems are functioning before allowing startup or during shutdown.
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How do you Test and Verify the Functionality of Interlock Systems in Gas Turbines?
Testing involves simulating conditions that trigger each interlock and observing the system’s response. This can be achieved using software simulations or physical manipulation of inputs. Verification includes ensuring that the correct actions are taken when interlocks are activated and that they reset appropriately.
Explain the Procedure for Troubleshooting a Failed Interlock in a Gas Turbine Control System.
Troubleshooting a failed interlock involves checking the sensor or input device for proper operation, verifying wiring and signal integrity, reviewing control system logic for errors, and testing the interlock under controlled conditions to identify and correct the issue.
What Safety Interlocks are Critical during the Gas Turbine Purge Cycle?
During the purge cycle, critical interlocks include fuel valve closure, exhaust damper position, and purge air flow rate. These interlocks ensure that residual gases are safely evacuated before ignition, reducing the risk of explosions.
How do you Implement Redundancy in Interlock Systems to Enhance Safety in Gas Turbine Operations?
Redundancy can be implemented by using multiple sensors or signals for critical parameters, dual-channel logic systems where two independent systems must agree before taking action, and fail-safe design principles where the system defaults to a safe state in case of a fault.
What role do Emergency Shutdown Systems (ESDs) play in Gas Turbine Safety, and How are they Tested?
ESDs are designed to quickly and safely shut down the gas turbine in case of critical faults, such as over-speed, fire, or loss of lubrication. Testing ESDs involves simulating fault conditions and verifying that the system responds correctly, shutting down the turbine and preventing damage or unsafe conditions.
How do you Troubleshoot Interlocks related to Over-Temperature Protection in Gas Turbines?
Troubleshooting involves checking temperature sensors for accuracy and calibration, verifying control system logic, ensuring cooling systems are functioning properly, and inspecting physical components(thermocouples) for signs of overheating or damage.
What are Common Issues with Interlock Logic in Gas Turbines, and How do you resolve them?
Common issues include incorrect logic configuration, timing mismatches, and sensor failures. Resolving these involves reviewing and correcting the logic, synchronizing interlock signals, and replacing or recalibrating faulty sensors.
Explain the Importance of Fail-Safe Design in Gas Turbine Interlock Systems.
Fail-safe design ensures that, in the event of a system failure, the turbine defaults to a safe state, such as shutting down or preventing startup. This minimizes the risk of accidents or equipment damage by prioritizing safety over continued operation.
What types of Gas Detection Systems are Commonly used in Gas Turbine Installations, and How go they Function?
Common gas detection systems include infrared sensors, catalytic bead sensors, and electrochemical sensors. These systems detect combustible or toxic gases by measuring changes in absorption, catalytic reaction, or chemical reaction, triggering alarms or shutdowns to prevent hazardous conditions.
How do you Calibrate and Maintain Gas Detection Sensors in Gas Turbine?
Calibration involves exposing the sensor to known concentrations of target gases and adjusting the sensor output to match expected values. Maintenance includes regular calibration, sensor cleaning, and replacing sensors that have reached the end of their operational life.
What Steps would you take to Troubleshoot a False Alarm from a Gas Detection System in a Gas Turbine?
Troubleshooting involves checking for environmental factors that could trigger the sensor, inspecting the sensor for contamination or damage, reviewing calibration records, and ensuring the control system interprets sensor signals correctly.
How does the governor control the speed of a gas turbine during startup and shutdown?
During startup, the governor gradually increases fuel flow to ramp up turbine speed smoothly, preventing sudden spikes. During shutdown, it reduces fuel flow to slow down the turbine, ensuring a controlled and safe stop.
What are the key parameters that a governor monitors to maintain stable turbine operation?
Key parameters include turbine speed, load, fuel flow rate, and temperature. The governor continuously monitors these parameters and adjusts fuel supply and turbine speed to maintain stability and performance.
How do you verify the Proper Operation of Combustion Burner Systems in Gas Turbines?
Verification involves checking fuel supply pressure and flow, inspecting burner nozzles for blockages or wear, ensuring igniters and flame detectors are functioning, and performing a test run to observe burner performance and flame stability.
What are the Common Issues in Gas Turbine Combustion Burner Systems, and How do you Troubleshoot them?
Common issues include poor fuel atomization, uneven flame distribution, burner fouling, and ignition failure. Troubleshooting involves inspecting fuel nozzles, checking fuel quality, verifying air-fuel ratios, and performing maintenance on igniters and flame detectors.
How the Control System Control the Air-Fuel Ratio in Gas Turbine Combustion Systems?
Monitoring is done using sensors that measure the concentration of oxygen and fuel in the combustion process. Control is achieved through automatic systems that adjust fuel and air flow rates to maintain the desired ratio for efficient combustion.
Explain the Process of Burner Tuning and its Impact on Gas Turbine Efficiency.
Burner tuning involves adjusting the air-fuel ratio and burner settings to achieve optimal combustion. Proper tuning improves efficiency, reduces emissions, and enhances turbine performance by ensuring complete and efficient fuel combustion.
What are the Critical Parameters Monitored by Flame Detectors in Gas Turbine Burners, and How do you test them?
Critical parameters include flame presence, intensity, and stability. Testing involves using diagnostic tools to simulate flame conditions and verifying that detectors respond accurately to different flame characteristics.
How do you address issues related to Burner Instability or Flameout in Gas Turbines?
Address issues by checking burner settings, fuel quality, and air supply. Inspect for blockages, leaks, or mechanical faults in the burner system. Perform diagnostic tests to identify the root cause and adjust settings or replace components as needed.
Describe the process for conducting a trip test on a gas turbine’s overspeed protection system.
The trip test involves simulating an overspeed condition to verify that the protection system activates correctly. This is done by gradually increasing turbine speed to the trip setpoint, observing the system’s response, and ensuring that the turbine shuts down or takes corrective action as designed.
How do you verify the functionality of a fuel trip interlock in a gas turbine control system?
Verification involves testing the fuel trip interlock by simulating a fault condition, such as a fuel supply issue. The system should respond by shutting off the fuel supply and stopping the turbine. The test ensures that the interlock functions correctly and activates in response to simulated faults.
What are the typical steps involved in testing the emergency shutdown (ESD) system of a gas turbine?
Testing the ESD system involves simulating emergency conditions such as high vibration, fire, or loss of lubrication. The system’s response is monitored to ensure it shuts down the turbine safely and performs any necessary actions to protect equipment and personnel.
How do you address discrepancies observed during interlock trip testing and ensure corrective actions are effective?
Addressing discrepancies involves analyzing test results, identifying the root cause of the issue, and making necessary adjustments to the interlock system. This may include recalibrating sensors, revising control logic, or replacing faulty components. Follow-up testing ensures that corrective actions have resolved the issue and that the system functions as intended.
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What is the role of a Master Trip Solenoid Operated Valve (SOV) in a gas turbine control system?
The Master Trip SOV controls the fuel supply to the gas turbine. During normal operations, it regulates fuel flow based on system demands. During a trip or emergency, it rapidly closes to stop fuel flow, ensuring a safe and controlled shutdown of the turbine.
How does the Master Trip SOV ensure reliable operation during an emergency shutdown?
The Master Trip SOV ensures reliable operation by using a solenoid to rapidly and securely close the valve in response to an emergency signal. It is designed to be fail-safe, meaning it will close upon loss of power or signal, ensuring fuel is cut off even in the event of control system failures.
Explain the procedure for testing the Master Trip SOV during routine maintenance.
Testing involves simulating a trip condition to ensure the valve closes correctly. This includes activating the emergency signal, observing the valve’s response to ensure it shuts off the fuel supply, and verifying that the valve returns to its normal position when the signal is removed.
How is the Master Trip SOV integrated into the turbine’s control and safety systems?
The Master Trip SOV is integrated into the control system via electrical signals that trigger its operation during normal and emergency conditions. It is also part of the safety system, receiving trip signals from various sensors and interlocks to ensure it functions correctly in emergency situations.
How do you verify that the Master Trip SOV is functioning correctly during a trip test?
Verification involves simulating an emergency trip condition and observing the valve’s response. Ensure the valve closes completely, stops the fuel flow, and returns to its normal position when the test is concluded. Check the system’s feedback to confirm the trip was executed correctly.
Describe a scenario where the Master Trip SOV would activate and how it impacts turbine operation.
A scenario could be a high vibration condition or a critical fault detected by the control system. In such cases, the Master Trip SOV would receive a signal to close, shutting off the fuel supply and stopping the turbine to prevent damage or unsafe conditions.
What is a Gas Turbine?
A gas turbine is a thermodynamic machine that operates on the admission-compression-combustion-exhaust cycle. It converts chemical energy in fuel into mechanical energy, typically used for power generation or propulsion.
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How Many Stages are there in a Gas Turbine?
A typical gas turbine consists of three main stages: the compressor stage, the combustion stage, and the turbine stage.
What are the Main Components of a Gas Turbine?
The main components of a gas turbine engine are the compressor, the combustion chamber, and the turbine. The compressor draws in and compresses air, the combustion chamber ignites the fuel-air mixture, and the turbine extracts energy from the expanding gases to power the compressor.
How Many Stages are there in the Compressor?
The compressor in a gas turbine usually has around 17 stages.
What Type of Compressor is used in Gas Turbines?
Gas turbines use an axial flow compressor, which compresses air as it flows along the axis of the compressor.
How many Bleed Valves are there in the Compressor?
There are typically four bleed valves in the compressor.
At what stage of the Compressor is Air Extracted through Bleed Valves?
Air is extracted through bleed valves at the 11th stage of the compressor.
Why Is Air Bleeding required Through Bleed Valves?
Air bleeding is required to protect against pulsations during startup.
How do Spark Plugs Retract after Igniting Combustion Chambers?
After the turbine rotor reaches operating speed, the combustion chamber pressure causes the spark plugs to retract, removing their electrodes from the hot flame zone.
What Safety Measures should be Followed during the Operation and Maintenance of Gas Turbines?
Safety measures include thorough personnel training, regular equipment inspections, adherence to industry guidelines, wearing appropriate personal protective equipment, and implementing emergency shutdown procedures to ensure a safe working environment.
Explain the Concept of Combined Cycle Power Plants and their Advantages.
Combined cycle power plants integrate gas turbines and steam turbines to maximize energy output. This combination results in higher overall efficiency compared to standalone systems. Additionally, combined cycle plants offer lower environmental impact with reduced emissions.
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