Start of the coal grinder!
Thread Content
Why is it that during the startup of the coal grinder, the motor is started first and allowed to run for a while before the pneumatic clutch is engaged? Can’t it be started directly?
My understanding is that for medium-speed roller mills, it is necessary to let them run idle first, and then load them after the coal feeder starts feeding coal; this ensures a smooth start-up of the mill and prevents increased vibration due to an overly thin layer of coal.
No, it can cause overload during motor startup and lead to burnout
A question: What is a pneumatic clutch? Do medium-speed grinders also have pneumatic clutches?
A form of protection, similar to how a car’s clutch works, to prevent excessive current flow and similar issues
All large-scale equipment requires a process of starting up, gradually reaching stability, and then feeding materials in – this process is essential in order to protect both the safety of the equipment and that of the entire installation! Moreover, during the startup process, the technicians also need to test the magnitude of the instantaneous current. Have you seen a rural mill grinding flour? (If you don’t believe it, go and see.) Experienced operators wait until the mill is running at full speed before adding the wheat; this is generally the procedure followed. I think it works on the same principle as a coal grinder! This post was last edited by GSP on 2009-2-6 09:29 ]
First, it should run at idle speed; you need to be prepared, as there is a lot of noise when it’s running at idle
Protective effect. It works on the same principle as a car’s clutch.
Prevent the motor from being damaged due to excessive starting current.
The motor of the coal grinder is a high-voltage unit; to prevent voltage fluctuations in the power grid during startup, it is necessary to start it with a reduced load.
It seems that the grinder cannot run idle; first, the motor is started, usually a synchronous motor. Once the motor is running, the clutch is activated to start the grinder. It cannot be started, mainly to prevent excessive starting current from damaging the motor.
Actually, it’s the same principle as starting a pump – rotating the pump before starting it is basic common sense.
To protect the motor – it’s high-voltage and has sliding bearings; something that weighs dozens of tons definitely needs some form of protection.
If the motor isn’t started first and runs idle, it will burn out
First, avoid impacting the power grid (direct startup is fine as long as the grid capacity is sufficient). Secondly, it protects the motor by preventing excessive starting current (an instantaneous high current does not cause much damage).
One more thing to add: the Arto coal mills used in our facility operate with direct startup, and they work very well.
A small amount of base coal is used, along with direct startup at low load to reduce vibration.
A mill, including its own weight, the mill rods, water, and coal slurry, can weigh at least 300 tons. The normal operating power of such a mill is over 500 KW, with even higher instantaneous startup power. If started directly, this could not only damage the motor and cause fluctuations in the power grid but, most importantly, it might also harm the mill’s large rotating components. Therefore, we need to use a pneumatic clutch, and after the mill starts up, there should also be a gradual acceleration process.
It primarily serves to protect the main motor from overload during startup. During the engagement of the clutch, there is a time required for the air bag to inflate; as the pressure in the air bag increases, the clutch plates come together, thereby increasing the starting torque and thus protecting the motor. ok
It primarily serves to protect the main motor from overload during startup. During the engagement of the clutch, there is a time required for the air bag to inflate; as the pressure in the air bag increases, the clutch plates come together, thereby increasing the starting torque and thus protecting the motor. ok