F-class Best Practices: FAST STARTS

Keep your steam turbine warm with electric blankets

A cold A10 steam turbine (ST) limited Faribault Energy Park’s ability to start-up in time to capture real-time market prices; plus, significant extra fuel was required to preheat the unit prior to ramping to target load. Starts after shutdowns of more than 24 hours required turbine warming; after a 48-hr shutdown, the plant was entering a cold-start phase requiring even more warming time. Goal was to minimize warming time while maintaining rotor stresses within allowable limits, and reducing startup fuel cost.

Plant personnel initiated a capital improvement project to install electric heating blankets under the ST insulation to maintain turbine shell temperature while offline on standby. Blankets were installed on the HP and IP turbines in 2010. Both turbines have multiple heating zones—each equipped with three redundant blankets, allowing for some failures without impacting zone temperature. Automation of zone controls is incorporated in the plant DCS. Note that the LP turbine section operates at a relatively low temperature and does not require continuous heating.

Installation of the electric blankets has eliminated cold starts altogether, and reduced warm-start times by nearly half. Hot-start times have been reduced by a small amount. Faster starts have saved fuel and increased the chances of being dispatched in real time.

Improved GT starts reduce gas consumption, satisfy dispatch requirements (link)

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