Why can’t forced turning of the shaft be carried out during warm-up?
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This post was last edited by foam_ZPTK on 2018-2-3 23:05. Is it to prevent shaft seizure that turning the shaft is not required during the heating pump operation? How can shaft binding occur during cranking while the heat pump is running?
The main concern is uneven heating by the pump; there is a large temperature difference between the upper and lower parts of the pump, leading to different amounts of thermal expansion, which can easily cause the pump to seize.
During the heating pump operation, temperature differences occur, leading to abnormal expansion; if the original gap is too small, friction may arise~~~~
During the warm-up period, forced shaft rotation is not prohibited to avoid shaft seizure; rather, it is to prevent damage to the mechanical seal – that’s the key point! ! ! Because the material does not fully liquefy during heating, forcing the machine to operate will damage the mechanical seal. Only when manual cranking can turn the shaft is it known that the material has been completely liquefied; only then should the motor be started, which constitutes the startup procedure.
The material is not solid; it just has different viscosities
Forcing shaft rotation during the warm-up period is to prevent the medium from circulating too quickly and damaging the seals, I guess.
The pump is not forced to rotate during the warming process to prevent the rotor from getting stuck!
If the viscosity difference is significant, since the motor is selected based on the shaft power required at the viscosity level under operating conditions, if the material’s viscosity is not yet at that level due to low temperature, the motor will operate under overload and will not function, appearing as though it is stuck
Heat pumps are sensitive to uneven heating – some parts get hot while others remain cold, resulting in different amounts of thermal expansion, which can cause the rotor to get stuck
Turn the shaft only after the heat pump has been fully warmed up. At this point, the temperature inside is more uniform, and so is the thermal expansion. All high-temperature pumps are equipped with warm-up lines; the standby pump is in a heated state, allowing for immediate switch-over of the pump