When the plasma cutter is in operation, the consumables and the plasma torch itself can get extremely hot and the temperature can rise up to 20,000°F. So, cooling systems are required to cool down the plasma cutting system. The cooling system comprises water, coolant, a pump, cooling hoses and a heat exchanger.
The torch gets overheated as it works at very high temperatures and requires water cooling to keep the parts from overheating and burning. The copper electrode is most exposed to the heat and needs to be cooled the most.
Plasma Torch Coolant
The coolant used to cool the torch is a mixture of ethylene glycol or propylene and water. The water is de-ionised, as it does not have conductive ions that cause issues in the plasma cutter. Contaminants in the coolant can reduce the cooling efficiency and also the flow. It is a good idea to use an OEM coolant and check the conductivity of the coolant regularly.
In the plasma cutter, the motor and pump are connected directly and the pumps used are quite simple and sturdy. However, the carbon vanes in the pump can wear out due to friction and heat and the bearing may also wear out in the long run. This causes excess noise and heat which can finally lead to the failure of the pump.
The flow switch helps to prevent the plasma torch and the parts from failing if the flow of the coolant becomes too low.
The coolant is carried to and from the plasma torch by hoses known as cooling lines that also contain the power cables. The power cables are water-cooled to prevent the copper wires from getting heated up.
Many plasma cutting systems make use of particulate filters to remove the contaminants and debris from the coolant. The filter should be replaced if the coolant flow reduces in the cutting system. It is a good practice to change the filter once in a few months anyway.
Heat exchangers comprise a radiator and a fan in the case of plasma cutters and the airflow is directed via the radiator by the fans, thus removing the heat from the coolant. Some plasma cutters have refrigerated chillers for cooling.
Coolant reservoirs are plastic or metal tanks that contain the plasma torch coolant and temperature switches, float switches and level indicators are installed inside the tank to avoid overheating. The coolant reservoir must be checked and topped up every day to check that there is enough coolant always.
If the coolant level is very low, then the cooling effect will get reduced as air gets into the coolant stream. And if the system is interlocked, the system can shut down completely and if the system is not interlocked, the pump can get overheated and fail.
If the plasma cutter and the consumables become overheated regularly, in the long run, the plasma torch and the parts will wear out quickly and ultimately the plasma torch will fail. And, if the problem is left unattended, you may have to replace the entire plasma cutting system, the motor and the pump too which can be a very expensive proposition. This can also cause downtime. All these problems can be avoided if you undertake preventive maintenance of the plasma cutting system and troubleshoot immediately when any problem occurs.