The timing for stopping the turbine barring gear
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After the main steam turbine is stopped, the turning gear is started. When is it appropriate to stop the turning gear, and what is the basis for this?
Siemens requirement: every 5 minutes during a shutdown of 1 hour or less； 1–3 hours: every 15 minutes; 3–8 hours: every 30 minutes ； 8–30 hours, once every hour. Once, the shaft needs to be rotated half a turn; the number of rotations required each time is determined by the number of teeth on the shaft’s turning gear. Typically, turbine manufacturers provide clear instructions. Now, all important turbines are equipped with barring pumps, which start automatically to rotate the rotor when its speed falls below 1 revolution per minute. Is that detailed enough? :)
Consider preventing bending of the main shaft by cooling it slowly; otherwise, the shaft will bend
Is continuous turning of the rotor better than intermittent turning for even cooling of the rotor and preventing shaft bending?
Modern turbines are equipped with automatic turning devices; when the rotor speed drops below 1 revolution, these devices automatically start up to rotate the rotor continuously； If the automatic start function is not available, the barring device should be manually started after the turbine rotor comes to a stop, that is, when its speed is 0. It should continue to operate until the turbine has cooled down, i.e., until the temperature of the rear cylinder of the turbine is below 50°C, at which point the barring device can be stopped. :lol
That makes it clear. Thank you so much!
Continuous turning is more effective, and that’s the case with automatic turning as well. Manual continuous turning of the shaft is not practical.