IC3603A279B - Thermocouple Processor Unit

SPECIFICATIONS

Part No: IC3603A279B
Manufacturer: General Electric
Function: Thermocouple Processor Unit
Series: Mark I and II
Repair: 3-7 Day
Availability: In Stock
Country of Manufacturer: United States (USA)

Functional Description

IC3603A279B is a Thermocouple Processor Unit developed by GE. It is a part of Mark I and II control system. Thermocouples are temperature sensors that generate a voltage signal based on the temperature they measure. Receives these raw signals and processes them into usable data that can be monitored and interpreted by the turbine’s control system.

Temperature Loop – Ensuring Safe and Efficient Gas Turbine Operation

One of the most critical control loops in a gas turbine system is the temperature loop, which is designed to monitor and regulate the turbine’s temperature during start-up and continuous operation. The primary objective of this loop is to ensure that the gas turbine operates within safe thermal limits, thereby preventing damage to components and maintaining overall system integrity.

Use of Exhaust Temperature as a Control Parameter

Instead of directly measuring the turbine inlet temperature (TIT)—which, while important, presents practical challenges—the system uses exhaust temperature as the main parameter for temperature control. This approach is both technically and operationally advantageous for several reasons:

• Component limitations: Certain components of the turbine, such as the first-stage turbine buckets, inter-stage passages, and exhaust ducting, are highly sensitive to thermal stress. The exhaust duct, typically made from low-alloy steel, has strict temperature limits that must not be exceeded.
• Sensor durability and serviceability: Measuring exhaust temperature allows for more durable sensors that are easier to install, maintain, and replace. In contrast, sensors placed in hotter regions like the turbine inlet tend to degrade faster.
• Operational consistency: Exhaust temperature readings provide a reliable and representative snapshot of the turbine's thermal profile, allowing for consistent control.

By focusing on exhaust temperature, the system indirectly ensures that turbine inlet temperatures are also held within design limits, using predefined component gains and biasing within the control logic.

Accurate Sampling – The Twelve Even Area Criterion

• To achieve precise control, the system relies on accurate sampling of exhaust gas temperatures. Through extensive testing in both factory and field environments—and with the application of statistical analysis—GE developed a method known as the "twelve even area" criterion.
• This method involves sampling exhaust gases from twelve evenly spaced areas within the exhaust duct. This approach provides a highly accurate average temperature reading, with an average deviation from the mean of less than 5°F, even when there is a total spread of 50°F across the exhaust flow.
• In practice, the actual temperature spread observed in the exhaust duct is typically even less than 50°F, which underscores the precision and effectiveness of this sampling methodology.

WOC is happy to assist you with any of your GE requirements. Please contact us by phone or email for pricing and availability on any parts and repairs.

FREQUENTLY ASKED QUESTIONS

What is IC3603A279B?
It is a Thermocouple Processor Unit developed by GE.

How does the temperature loop ensure the turbine inlet temperature stays within safe limits?
While the system monitors exhaust temperature directly, it uses component gains and biases in the control logic to indirectly keep turbine inlet temperature within design specifications.

Why is accurate exhaust temperature sampling important?
Accurate sampling provides a true average temperature reading, which is essential for precise turbine control, efficient performance, and protection against overheating.

What happens if the turbine exceeds safe temperature limits?
Exceeding temperature limits can lead to serious damage to turbine components such as buckets, nozzles, and ducting, resulting in costly downtime and repairs. The temperature loop helps prevent this by dynamically adjusting fuel input and other variables.