Air system upgrade? 10 HP Quincy to 15?

For my home shop, I made a "manifold" sort of using pipe at T's & ball valves. I can connect multiple air compressors and tanks to my shop air and still quickly disconnect for portability. I'm working on a much smaller scale than you, 1.5 HP to 3 HP compressors instead of 10 & 15 HP, but the idea should still work.

If you did something like that, you could connect both compressors to your air lines and decide which one you should sell. Find a bargain compressor, connect to your system, try it out, decide what you want to sell and what to keep. Have something that needs extra air, add a compressor temporarily. Someone comes to buy a compressor that you have been "testing", shut off valve, drain, disconnect, unplug & load. Buyer can see it run before purchase.

Do you have 460 3 phase?

RogerN

Bigger is better :)

Sandblasting on the other hand is a bit of a mess and will produce a fair amount of somewhat hazardous waste to dispose of once you have your good silica-free blast media mixed with all the unknown crud like lead paint, military CARC paint and other nasty stuff.

Thanks. I am still thinking about it. Your idea is not a bad one. I just do not want projects for the sake of projects.

If you have multiple compressors then when one craps out you can just use the 'spare' until the 'main' is either fixed or replaced. It's a lot better than being out of operation, or having to scramble to get your compressor back on line.

I suspect that if you do the trick where the standby is set to switch off at a lower pressure than the main turns on that, if you have water-in-the- oil problems you can swap your "main" for your "standby" compressor every week or so -- that'll get the one that's been sitting thoroughly warm on a regular basis, and drive out the water.

I'll now stand by and let some real compressor expert say if my wild-ass guess has merit, or needs shooting down...

You're not at that point yet, but if your operation is big enough to have more than one building it is nice to have a compressor in each. My Dad's company used to have a 5HP in one building and a 10HP in the other; not only did this save on head losses between the buildings, but in the event that one or the other _did_ crap out the two systems could be tied together while the sick compressor was dealt with.

The larger compressor will cost for a new conduit run and lots extra while running.

I'd probably sell the larger compressor and install an extra tank or two on the 10hp for when you need the extra air for blasting. With valves, they could be out of the picture until you blast.

Also consider investing in some of Tawm's rotary brushes and cleaning the thicker rust off projects prior to blasting, which would limit the air you needed. It's sometimes quicker that way, anyway.

What are Illinoise' laws about blasting, Ig? You might need a filtered cabinet and lead abatement certification to do it. It's getting to be an overregulated world, damnit...

Makes sense.

I would definitely use a filtered cabinet.

Take the 15 hp motor off. Store it for replacement at a later date. Install a gas/diesel engine in it's place. Set it up so it provides air for your blast boot. Then only run it as needed. Blasting takes a LOT of air flow. If you want some jobs that are not real difficult but pay pretty good, visit a few auto restoration type shops and see where the closest walnut shell/baking soda/plastic media blaster is and what their prices run. I know the closest outfit to me gets around 1,500 to blast a complete body shell. (takes 8-12 hours on smaller cars)

quote: OK, this is growing out of a discussion about reserve tank filling.

Right now I have a 10 HP Quincy compressor with a 80 gallon tank. Looks similar to:

I just acquired a 15 HP compressor at auction. Here it is:

I also have some extra tanks such as:

If you are thinking of bead blasting, hook up both compressors and keep the tank size medium to small. I've spent many an hour bead blasting small stainless steel tanks that were part of one of our products at work, to clean up the welds and give them a uniform matte finish, and there is no such thing as too much air. We started with a 7.5 hp compressor and standard blast gun in a cabinet, and two 60 gallon tanks in parallel. Single stage 7.5 hp compressor, shuts off at 120 psi, let it shut off and pull the trigger on the gun to start drawing down the tanks. Compressor kicks on at 90 psi and would come on after a few minutes (less than 5), compressor would run continuously and hold about 80 psi until I let off to give it a rest - it would be stinky hot in 20 minutes and the apparent air density falling off judging by the quality of the finish I would get on the SS. Twiddle thumbs for 10 minutes, and go again. I hate waiting. Added a pressure regulator to the blast gun set to 70 psi or so per glass bead mfg suggestion, more uniform finish, compressor happier but still needed a rest every 30+ minutes. At this point it was taking 50-60 minutes per little tank to get one done. Our fabricator scrounged a 5 hp compressor, single stage, from an auction, and plumbed that in parallel. Wow, what a difference. Actually went up one nozzle size on the gun, air must have been cooler because surface finish was better even though the pressure gauge read the same, and I could finish a tank in 35-40 minutes with the compressor actually cycling sometimes if I let off the trigger for a minute. We don't have an aftercooler, just the tanks and a 50-70 foot run of 1" copper pipe to the blast cabinet. Anyway, life was great whenever I had to fill in and do the blasting, and then it was decided to "dedicate" the second compressor to the machine shop and our air system was cut into two parts, so I lost the extra capacity and it was back to the bad old days. Finally drove me to redesign the product with a custom extruded PVC tank so no more blasting :-).

So anyway, no matter how big the tanks they will be down and the compressor running within a few minutes of pulling the trigger on the blast gun, and the bigger they are the longer to get them pumped up in the first place and back up when you let off the trigger, so keep the volume medium to low. When you are blasting it is all about the compressor hp since it will be running all the time. Whatever money you might realize by selling the smaller compressor you will more than pay in wages for the extra time to blast parts. Do put a pressure regulator/automatic draining water trap before the blast cabinet and be smart about sloping the lines and taking feed taps off the top. As someone else suggested, stage the on/off switches and alternate which one comes on first every so often. Build a room around the blast cabinet and vacuum often to try to contain the dust and grit, it will be almost as nasty as where you weld and grind.

----- Regards, Carl Ijames

I have a small SB cabinet that we use to blast small parts and rusty product. If it runs for more than a few seconds it has all three compressors running (combined 20hp) and still doesn't get enough air. I would want at least 25hp to supply a blaster and the rest of the shop.

What Tim says about the backup compressor is right on. I have a backup compressor that gets run maybe once a year, if that. It sits quietly behind a machine out of my way. But it has saved my butt a few times. Like when my main compressor threw a belt and I had to order a new one because there were none available on the island. And I had mistakenly ordered the wrong one as a spare so it wouldn't fit. Another time a bearing went out in the motor. A cheap enough part but not the kind of thing you keep around as a spare. Once again it was ordered in and my spare compressor kept the tool changer working. Eric

Can't help with technical question, but I'd like to point out that you seem to be laboring under the sunk cost fallacy. Sunk costs have no _rational_ bearing on current decisions. The only consideration should be the forward consequences. In your case, it doesn't matter what you paid for a compressor, only what you could sell it for. Consider the question to be "Should I sell it or should I use it?". I.e., if you use it, you will be giving up what you could sell it for. The question of how much to spend for it is past and irrelevant.

Bob

Sunk costs affect decisions when they can be deducted from the selling price on your income tax.

I have an MBA and I am aware of the sunk cost concept, but I do not think that this concept should be taken too far. Ignoring sunk costs leads to reckless behavior.

I have no idea what kind of potential operational profits you might have from using the big compressor - maybe they are big enough that the value of the compressor is incidental. Or not - after all you did consider the value of the compressor, using it's cost. Considering its value as what you would get from selling it wouldn't be "... tak[ing] it too far", I'd say.

I can't see that (but I don't have an MBA ). I _can_ see how focusing on sunk costs can be reckless.

Bob

Ah, so. They affect the _net_ current value. But you still start with the current value, adjust for taxes, transactional costs, etc. Bob

In the 1930's the Japanese Army justified their unauthorized territorial expansion in China to a skeptical government and population partly with the 'sunk cost' of previous casualties. jsw

Isn't this a funny world? PHDs asking if you want fries with that and MBAs making more money (and having more fun) in scrap than their college major could have given them. Har!

A lot of good, solid profitable businesses are utterly boring and unspectacular. For example, powder coating job shop, or renting street plates for construction projects. But they could make more money than high flying finance jobs.

Oh, sunk costs have a HUGE influence in political decisions. "Don't let our boys have died in vain" (e.g., Vietnam). "We've put so much into and we can't let that go to waste."

Not that we should have economists running things, but politicians should know more economics. Just knowing/using more logic would do it.

Bob