Acceptable vs. non-acceptable consumable wear - swirl ring
Up next in our series on "Acceptable vs. non-acceptable consumable wear" is the swirl ring. The swirl ring's job is to control and swirl the plasma gas around the electrode and into the nozzle. This is done to control the arc attachment point on the electrode emitter, and the gas flow through the nozzle orifice in a way that delivers the best edge angularity. Controlling and swirling the plasma gas also creates a centrifugal effect that slings heavier un-ionized gas molecules to the edges of the nozzle orifice helping it to last longer.
In addition to all of the above, the swirl ring also ensures perfect alignment between the electrode emitter and the nozzle orifice and it electrically insulates the negatively charged electrode from the positive nozzle. Basically, the swirl ring is relied on for a lot of things. Without one, you would see much shorter life for all your consumables, and poor cut quality.
Hypertherm makes all its swirl rings out of volcanic lava which we precision machine then bake (as in an oven) to increase durability. You may wonder why we use volcanic lava. There are two reasons really, (1) it has very good electrical insulating properties, and (2) it can withstand a lot of heat, as you might expect from something that comes from a volcano.
The durability of the volcanic lava means swirl rings don't tend to wear out; however, they are fragile. Force one into your torch or drop it and it will chip or break as shown in the photo below. 
Besides a chipped or broken swirl ring, there are two more reasons swirl rings need to be replaced. The first is if it is cracked. Even small hairline cracks can impact gas flow. The second, has to do with the O-rings. Swirl rings have inside and outside O-rings that sometimes get torn, cut, or wind up with flat spots that prevent the formation of a tight seal.
Inspecting your swirl ring What all this means is that with careful use and clean hands, a swirl ring can last through 50 electrode / nozzle change-outs or more! Despite this, you still need to regularly inspect your swirl ring to make sure it is not compromised. Here's what you need to do:
1) Carefully check for cracks and chips. As explained above, even small cracks will impact gas flow.
2) Inspect the O-rings (especially the inside O-ring) for tears, cuts or flat spots.
3) Examine the metering and swirl holes for blockage. If you see any grease or debris, try to carefully clear out the hole. If you're successful the swirl ring can be re-used.
4) Ensure the swirl ring is not dirty or greasy. 
If all looks good during your inspection, then you can put the swirl ring back into the torch. A tip here is to add a tiny bit of lubricant to the outside O-rings. Put a small amount on your fingers, rub your fingers together, then lightly rub your fingers over the outside O-rings. As Jim Colt often tells people, "you aren't trying to pack a wheel bearing." The outside O-rings should look shiny, but you shouldn't see any lubricant. The lubricant will help you slide the swirl ring back into the torch and minimizes the chance of it meeting any resistance that could cause it to crack or chip.
What is your experience with swirl rings? Do you add a lubricant to the outside O-rings?