Practical Welding Today - July/August 2010

the swirl ring is to channel the gas backward and pull the heat off the electrode.

You will see a number of things. Remember when I mentioned that the nozzle constricts the arc at the orifice? As that nozzle is used, the orifice gets larger and out-of-round. Even though it is cooled by the gas swirling down through it, it’s still very hot. Eventually the orifice widens and you lose that constricted arc. The kerf, which is the width of metal that you remove during the cut, gets wider and wider. In addition, your cut speed gets slower because you don’t have that concentrated arc. As a result, you don’t have as much heat concentrated it one place; it sort of fans out.

A lot of this is caused by a worn nozzle. If you look at the end of the nozzle and see that the orifice is exceptionally big or oval-shaped, then you know it’s time to change the nozzle.

As you use the electrode, the hafnium/ tungsten becomes molten and pieces of it start to blow out through the nozzle as you cut. It develops a pit at the front of the electrode. Once that pit depth is over 1⁄ 32, it’s time to change the consumable. If you don’t change out the electrode and instead run it to failure mode, which means it really won’t cut anymore, you’re actually burning through the copper now because the hafnium is gone. The arc looks like an ugly, green glow, if you can even cut at all. The whole top of the electrode will be burned off. You never want to get to that point because it introduces a tremendous amount of heat into that torch, which can cause a lot of damage.

We always recommend that you change the electrode and nozzle together. That way when you throw in a new set of consumables, you have the perfect orifice and the perfect pit depth every time. If you tend to just swap them out individually, you can compromise cut quality. You can put in a new electrode, but if your nozzle orifice is wider than it should be, you’ve given up some of the performance.

Nothing really deteriorates in the swirl
ring, although it can crack as a result of
being dropped or from the heating and
What are the visual signs that one of the five consumables is worn down or functioning improperly?

Remember to match plasma consumables with the application. Failing to do so will only shorten the life of the consumables and in some cases compromise desired cut quality.

cooling over time. Once it’s cracked, it can’t channel the gas the way it should, so it’s time to change it out. For every five to 10 sets of electrodes/nozzles, you should change the swirl ring.

With the retaining cap, look for cracks that would come from drops. Slag built up on the end of the shield can constrict the airflow coming off the shield. Make sure you avoid excessive buildup there.

dryers in air compressors are better than others. If oil or water is present in the line, it can be very detrimental to the consumables and the system. Not only do they result in poor cut quality, they also have a negative impact on consumables life.

It’s very important to replace consumables routinely, especially as you see that pit depth increase, the orifice widen, or slag build up on the shield. Besides replacing the consumables, you need to perform regular maintenance on the torch, such as replacing the torch leads when necessary. You should change the torch as needed as well. There’s no set time in which to do that, but when you start to see things like cracks in the torch’s body shell, or a cut into the torch lead’s jacket that exposes wires, you need to address them immediately.

There’s not a tremendous amount on a hand-held system to replace, but we do encounter damage resulting from water or oil in the air. Frequently hand-held plasma uses shop air (from a compressor), and some

What regular maintenance practices
should an operator perform
to ensure torch consumables
are up to par?

That’s tough as there’s really no right answer. First, we’re talking about hand-held systems, therefore every operator is different. Inexperienced operators may cut slowly, essentially burning through the consumables because they are introducing so much heat into the system. Also, material thickness has a tremendous amount to do with longevity. It takes a lot more energy to cut 1-in. material than it does thin-gauge material. As you cut thicker material, you have to increase your amperage. The more power or amperage you use, the shorter your consumable life will be.

In a hand-held system the consumables are air-cooled. If your torch lead leaks, is kinked, or whatever the case may be, then you’re not getting proper airflow to the torch. That means it’s running hotter than it should, and you’re getting shorter consumable life.

The core message is if you maintain your system, meaning you make sure your leads are in good condition, that you’re installing good consumables into the system, and