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Designing an effective custom expansion joint for a GTX (Gas Turbine Exhaust) application requires strict attention to a number of unique engineering problems. Typically installed in the vital space between the turbine duct and exhaust duct, a GTX expansion joint represents a single point of failure – if the joint fails, the plant ceases to operate as the turbine must be shut down. Therefore, when FlexCom engineers are tasked to design a custom expansion joint for a gas turbine exhaust system, we expect to face certain challenges common to most gas turbine applications, but unique compared to other industrial facilities.
Heat stress poses an intense issue to gas turbines, since the thermal state of a GTX system fluctuates severely during the course of turbine operation – particularly as the turbine starts. A gas turbine initiates from a cold state to extreme heat very quickly, subjecting an expansion joint installed on the exhaust outlet flanges to thermal shock. If the joint is not adequately protected against these rapid shifts in thermal stress, the heat will damage the joint and ultimately cause it to fail.
In addition to heat, vibrations and mechanical movement add significant stresses to an operating GTX expansion joint. As turbines and connected ductwork assemblies increase in size, power and temperature output, so too do they produce greater levels of duct movement and overall metallic vibrations.
The turbulent flow of exhaust gas through the joint additionally increases vibration – as well as “flutter”, rapid shifts in gas pressure that can damage an unprotected fabric joint. These mechanical stresses can cause significant damage to an inadequately designed joint in a relatively short amount of time.
For hot-to-hot configurations (one in which both flanges must operate at the exhaust gas temperature), we also recommend including an accumulation pillow in the custom joint design. A pillow will reduce the overall temperature of the joint, as well as limit vibration transmission to the turbine outlet flange and help absorb ductwork movement stresses in these very high temperature environments.
Custom design of a gas turbine exhaust (GTX) expansion joint requires a special level of engineering precision, as well as specialized expertise in compensating for the extreme stresses present in this type of exhaust ductwork. Don’t risk your gas turbine operation on a lesser quality product – call FlexCom offices today and let us show you how our custom designs deliver superior performance.