The Reason For Coolant
Coolant is very important to plasma, it prevents the electrode and nozzle from melting due to the high temperature of the plasma arc. Some units can use air to cool these consumables but those are the smaller units cutting below 100 amps. When cutting at higher amps you have to have coolant to keep the torch from overheating; coolant will carry away the heat.
Inside the torch body, the electrode is a big heat source. The plasma arc attaches to the face of the electrode, so a lot of power is passing through a small metal part. To keep it from melting, cooling fluid circulates against the back side of the electrode.
The torch cools as the coolant becomes warmer than it was when it entered the torch at the beginning. The coolant is pumped around and around in a closed circuit, and as it keeps getting warmer it can no longer cool the torch, so the coolant is pumped, under high pressure, back to the coolant reservoir. It is important for this flow rate to be maintained so the consumables and the torch will not overheat, and also for keeping the coolant temperature low. Insufficient flow will overheat the torch and cause it to burn up.
What Coolant Should Be Used?
Every manufacturer has its own coolant and there are a number of different types of plasma coolant available. There are several after-market brands of coolant on the market as well. They all use either ethylene glycol or propylene glycol mixed with distilled water as the main ingredients. Most mixtures range from 25 to 50% glycol (75 to 50% water), although there is at least one coolant that has no glycol at all.
If your shop ever gets down to sub-zero temperatures, but your plasma coolant only protects down to +12º F, it’s not going to end well. The damage caused by a hard freeze will put a machine completely out of commission, and require replacing a lot of hoses, fittings, and expensive plasma control components. That’s why it is highly important to avoid freezing.
Glycol additives offer freeze protection anywhere from +12º F to as low as -35º F. The higher the glycol content, the lower the freezing temperature. But the glycol additive also has an adverse effect, it reduces cooling efficiency, which shortens consumable life. Take caution if using a coolant not rated for the plasma unit you're using; it can damage the unit if it jells up.
It mostly depends on the working environment in your shop. Here is what you have to know before you decide which coolant to use. Distilled or deionized water is the best coolant when it comes to conducting heat away from the electrode and discharging it through a radiator. And the better you cool the electrode, the longer it will last. Coolant can have a huge impact on consumable life, so changing from a much higher percentage to a much lower percentage of glycol in the coolant can increase consumable life by more than 30%. However, distilled or deionized waters will freeze pretty easily on their own. Based on your environment, using a mixture of distilled or deionized water and glycol content with enough protection against freezing temperatures is the optimal way to keep your equipment protected and functioning properly.