Expansion joints for gas-fired power plants
Gas-fired power plants are widely used, especially during peak or unscheduled demand, as they can be turned on and off within minutes.
The many starts and stops along with high temperatures, pressure and velocity, puts additional stress on the the duct and pipe systems. The increase in production demands the installation of highly engineered expansion joints to compensate for these stresses.
The gas turbine compresses air and mixes it with fuel. The fuel, usually natural gas, is burned and the combusted gas expands through the turbine blades turning the gas turbine rotor. The gas turbine is coupled to and drives an electrical generator which produces electricity.
After passing through the turbine, the hot gas passes to the gas turbine exhaust. In a single cycle power plant, the process would end here and the exhaust gas is discharged through the exhaust stack into the atmosphere.
In a combined cycle power plant, the heat from the exhaust gas is used the produce steam by feeding it into a Heat Recovery Steam Generator (HRSG). The HRSG takes the highly purified water flows in tubes and the hot gases to produce steam .The steam is then used to rotate the steam turbine and coupled generator to produce Electricity. The hot gases leave the HRSG at around 140 ºC / 284 ºF and are discharged into the atmosphere.
Expansion joints in a general gas-fired power plant system