Special considerations must be made for gas turbine enclosures in cold climates. If natural gas turbines experience extreme cold and icing situations, functionality could be impaired to the point of dropping power to thousands of people. In addition to anti-icing systems, which prevent ice from forming on the intake filter systems, operators should also have warm air systems that will keep the turbine generator enclosure warm while being ventilated for start up. Both of these features are essential for applications in cold weather.
Keeping the enclosures from freezing
From a ventilation standpoint, operating a combustion turbine generator in cold weather is not as straight-forward as it might seem. With the ambient temperatures being below freezing at times, special consideration for heating and ventilation has to be given to all the steps in the operational process from standby, to startup, to long term operation.
When in standby mode waiting for electrical demand and startup, explosion proof heaters are typically used to keep the inside of the turbine and generator enclosures at an acceptable temperature. Normally a turbine operator will want to keep the temperature around 50°F (10°C) inside the enclosure. The amount of heat required will depend on the temperature range at the location of the turbine generator and the insulation level of the enclosure.
Up until the time the turbine starts, the heating scenarios are fairly routine other than the need for explosion proof heaters. When it’s time to fire the turbine back up, heating and ventilating of the package become much more complicated.
First, the turbine and generator enclosures must be cleared with fresh air. This is done to purge the package from any possibility that natural gas or other fuel has leaked from the fuel system into the enclosure, which could potentially cause an explosion. However, the real issue becomes the need to maintain a temperature inside the enclosure above freezing during the ventilation purge cycle.
For instance, one operator we worked with needed to maintain a 45°F temperature inside the turbine enclosure or the turbine would not start. This operator was in a climate where temperatures would often reach -30°F in the winter and make the turbine unavailable for use. Eldridge developed a system for this customer with a combination of explosion proof heaters and a fresh air bypass system whereby the system would circulate a mixture of fresh air and recycled air and maintain a temperature above 45°F (7°C ) until we had enough fresh air change inside the enclosure to properly purge the spaces and safely start the turbine. We followed this ventilation philosophy until the turbine ran long enough to provide heat on its own without the use of heaters. Then, since the heat rejected from the turbine would provide an 80°F (27°C) delta temperature above the ambient temperature of the ventilation, operation would switch to normal ventilation and not include any recycled air.
Working with a ventilation expert
At Eldridge we strive to be good listeners and gain an understanding of how ventilation should work in concert with a customer’s needs whether they are in cold or hot climates. By listening well we are able to solve the most difficult ventilation and noise control problems in industry.
Stay tuned to our blog for future articles on critical application ventilation and noise control. In our next blog we will write about the considerations for ventilation of combustion turbine packages for warm climates.