Question: Why is it necessary to turn the chiller shaft by hand after it stops operating until the temperature drops to normal levels?
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Today I heard the technicians discussing that after a chiller (driven by a turbine) is shut down, it is necessary to use a turning gear to rotate it until the temperature drops to room temperature. Why is this done? Should the turbine be brought to room temperature or the compressor? How often should I check the tire pressure after parking? What parameters are related to the interlock of the turntable? Speed, temperature? An expert who is aware of this could please provide an answer. Thank you.
Reply to 1# Fengmaniu: In short, once the turbine stops, the temperature inside the cylinder inevitably drops, and the rate of temperature decrease varies between the upper and lower cylinders. Therefore, it is necessary to use a turning gear, primarily to prevent bending or deformation of the turbine rotor due to uneven temperature distribution on its upper and lower surfaces. For turbine barring, it is generally required to perform continuous barring for 6-8 hours; this can be changed to intermittent barring of 5 minutes each time for 4-6 hours every 30 minutes. It can also be adjusted to 2 hours of barring per session, or 4 hours of barring per session, with a total of 24 hours in total.
It is mainly to prevent, during the cooling process, uneven cooling rates of various components of the chiller, which could lead to temperature differences among these components and thus cause deformation.
It is mainly to prevent thermal deformation of the components caused by uneven temperatures.
The purpose of rotating the shaft is to ensure that, throughout the shutdown and cooling process of the compression unit, the upper and lower parts of the rotor reach similar temperatures, thereby minimizing deformation caused by differences in temperature between these two parts. Since the rotational speeds of industrial turbine compressors are very high, exceeding 10,000 rpm, bending deformation of the rotor can exacerbate the vibration in the turbine compressor or cause it to stop operating. It is mainly used to cool the rotor in the turbine room. The turning of the shaft is done manually; it is not interlocked with the speed, but there is an interlock between the shaft turning operation and the pressure of the oil used for this purpose.