Air Compressors & Pneumatic Tools
Discussion on criteria for selecting the correct air compressor for home or industrial use. Covers tank size, pressure, pumps, motors and duty-cycles of compressors and reviews air consumption of typical mechanic's air tools. Alright, today on Repairs101 I'm going to address a request from a viewer that I got back in January, and well, it's June right now so I got to say I'm really sorry it took me this long to get to it. Alright , well today on Repairs101 we're at the shipyard, and we're going to talk about air compressors and pneumatic tools. There is a serious compressor. So here's a beautiful air compressor set up. That one's just permanently mounted in the back of this service truck. You can see that it says 30 gallons. So there's an engine mounted air compressor, direct-driven on the side of this fairly new Cummins diesel. Alright now, speaking of air compressors, here's a couple of "tow behind" air compressors made by the SULLAIR company. This bigger one over here delivers a 125 pounds of pressure and 425 cubic feet per minute -- which is quite an impressive amount of air. You'd use that for sandblasting equipment or jackhammers .When you go to choose an air compressor, what's funny is that the first thing that you'll see listed about it is the tank size -- which in reality is about the least important thing to do with the air compressor. What's really important is the pump size and the motor size. And the pump will be rated in cubic feet per minute. If you can't find the rating for how many cfm the air pump is going to make then it's safe to say that you're going to get 3 or 4 cfm for every hp. A lot of hobbyist machines, the hp has been exaggerated by marketing departments in order to sell more. If it's a 110 plug in then it's not going to be more than 2 hp, otherwise it will have a 220 volt hook-up. You know the pressure rating on it again is not that important, they should all make at least 90 to 110 PSI. Now if you need higher pressure than 90 to 110 you're going to have to look at a 2 stage air compressor. When you have a 2 stage compressor you might have as high as 175 PSI. So the duty cycle of your air compressor is one of the more important things that you can try and find out. The duty cycle is how long it's rated to keep running during use. So if you have a hobbyist air compressor that's duty cycle is 50% that means that 50% of the time you're using it that motor can be running safely and without overheating. If you exceed 50% of the time then you're in danger of wearing out your pump a lot faster than you had bargained for. Commercial duty air compressors, on the other hand, have duty cycles of 75% and even 100%. You don't even need a tank if you've got an air compressor with a 100% duty cycle. So if you're a hobbyist you know 50% duty cycle is probably all you need, but if you're running a shop and you've got a lot of guys perhaps you're going to want to look at something industrial with a 75 or even 100% duty cycle. A 5 hp compressor with a 100% duty cycle is going to make more air than a 7.5 hp compressor that only has a 75% duty cycle. If it is for commercial use you really should get as big a compressor as you can afford because you won't be sorry. Let's go open my file folder of owner's manuals and technical data. OK this is for... 3cfm then just to operate this little right angle grinder. And a right angle drill this time, again, 6 cfm. This little cut-off saw here 4 cfm. This is an air body-saw it's basically a pneumatic hacksaw, great for doing bodywork. 6 cfm for this one. Alright so this is an air hammer. It's rated at 90 PSI of course and 4.4 cfm. This pistol grip drill consumes 4 cfm again rated at 90 PSI. 3/8ths impact gun that's rated at 4 cfm. Another style 3/8ths pneumatic wrench again rated at 4 cfm. And 4 cfm for this one as well. As far as my personal impact tools go, this is my heavy hitter and again it only uses 4 cfm. 1 inch impact gun, you need a real good air supply to drive something like that. just a couple of drops of motor oil in the end of your tools. Might be 10w30 or 15-40 or 5-30. You know, whatever's around -- straight 30 weight oil. 20 bucks. 1 gallon tank with a little tiny compressor on the back. Perfect for -- you know, inflating bicycle tires or doing cleaning around the shop, that kind of work. You can't really power any tools with something like this. I put a quick connect fitting on the end. Quick connect like that so you connect it, there now it's already part of the system. Just pull back like that, snap it on, pull back and it comes off. Anyway, there are all kinds of different fitting ends that you might pick to go with your quick connector and I would recommend that you just look at the place where you work or what fittings came with the equipment you bought and just go with that. So don't forget to wear your safety glasses and please remember what I always say about power tools -- which is "use both hands and both eyes".