# air compressor question



## ship (Jan 23, 2010)

So I have a 4gal. DeWalt air compressor on a shelf in my garage, it's attached by hose to a 10gal. Tool Shop air tank on a shelf one shelf higher. I still draw air line directly out of the DeWalt compressor, the second fitting on it is used to feed the other tank. The extra capacity helps and as long as I clean the filter and change the oil a few times a year on the compressor. I'm sure its fine in feeding the extra tank and running a bit longer to do so, the extra tank just reduces the frequency of having to re-charge. Had it running this way for about three years now w/o problems. That extra tank is really useful and someting we used to do at another shop on a slightly larger scale.

(This given only this year I noted the air filter and while I'll get a new one for its first time, I did blew it off and changed the orientation away from the blackened as installed side.)

Main question is about water/moisture. 
When I drain the tank I do get quite a bit of moisture out of the normal DeWalt tank, more so still I think than normal given the added capacity would add to overall moisture. Given the angle of the valve on the DeWalt, it dosn't drain completely and I don't always drain it every night. Given this when I was changing the oil last night and tited the compressor so as to get out the rest of the water, the last of it was rusty. I added some air tool oil to the compressor tank and pessurized it in the hopes of treating any rust for now. 

What do I do with the main DeWalt tank to treat any rust in the tank better? I don't really want to buy a new compressor until I move and have room for a bigger unit which will be a few years. Obviously draining it more (nightly) of course but given the angle of the drain valve doesn't let all the water out. Given the angle of the drain, it's not really feasible even with leaving the drain open at night to get all the water out short of taking the compressor off the shelf and tilting it every night. Would me draining the tank every night, given the added capacity allow given the not from the bottom drain, leaving it open at night be sufficient to get the water out otherwise? 
Very compact unit so its also not really possible to add a dryer between compressor and main tank. Or is there on the D55155 compressor a dryer that I should have serviced? Been about three years now.

Second question is about the Tool Shop air tank. Its fittings are at the top and there is no drain valve. Have not shaken it to see if there is water present, but given its elevation above the main compressor, is this sufficient to keep water out? I wouldn't think that given the in/out nature of this storage tank, it possible to add a dryer to it.

Could that blackened filter be the cause of the extra moisture? Changing the filter solve the problem? Overall, scrap these and buy a larger capacity compressor sooner than later given almost daily use for a few hours a night and constant usage on weekends? Other options and how do I best treat the rusting I see if at all?


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## last125eagle (Jan 23, 2010)

your usage on the compressor in itself seems to warrant you going to a nice belt driven unit. The noise savings alone are worth it.

What sort of tools are you running off the compressor set up.

The second tank will have moisture. As the air cools it will deposit it there. My friend compressor 120 gallon, we run an air dryer.

Having the larger tank to fill is not a bad thing unless you are constantly filling the tank due to a large demand like from a sander or grinder. It does make the compressor run a little longer and as you said less frequently. The manufacturers use the same motor and compressor setup on many models. A small increase in capacity wont hurt it to much. 4 to 14 is a but of a jump but again if you fill it up once a night instead of multiple bursts that is better for the compressor and if the motor has enough cooling and a long enough duty cycle you are fine. 

Rust is a vile enemy of compressors. They never ever seem to get the drain in the right spot. I have to tip our little unit at the theater, 4 gallon like yours, to get the last of the stuff out of it. I have heard of people coating the inside of the tank. etc etc. Either way the rust wins out eventually. Best thing to do is check your tank for water and fatigue. It is essentially a giant hand gernade waiting to go off. ( worst case) or a nice projectial for a partial rupture. ( think when you knocked hte end off a co2 thing to see how it would fly)


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## jwl868 (Jan 23, 2010)

ship

I can't add much else that the previous post didn't cover. I agree that you'll find water in the second tank. Each time the tank is filled with hot water-saturated air, it will then cool and moisture will condense.

The Dewalt owner's manual states to drain the tank after each use, and notes to tilt the tank so it drains. The manual even says to get the tank inspected routinely because of rust/corrosion over time. (The manual is on the Dewalt website.) (And it there is no dryer on the unit.)

For some shop-level articles about compressed air systems, see the Vanair website (Compressed Air Dryer | Desiccant | Refrigerated Air Dryer - Van Air Systems). They include a link to a DOE publication on compressed air systems:

Energy Technical Publications - Van Air Systems

See: Improving Compressed Air Systems - A Sourcebook for Industry



Joe


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## FatherMurphy (Jan 23, 2010)

If you're curious about the remaining thickness of the metal of the pressure tank, an ultrasound thickness tester is the best way to find out how much the rust has thinned the shell of the tank. If you know someone who works on boilers (HVAC mechanical contractors), you might be able to borrow one (they are rather pricey widgets). Most of the corrosion will be at the bottom (where the water always is, even after you've just drained it, and the worst of the loose sediment), but some pits may be higher up the sides, along the waterline. The manufacturer may have some guidelines on how much thickness may be lost before condemning a tank, or you could look into recalculating Maximum Allowable Working Pressure using the existing dimensions of your Unfired Vessel (the tank).

One benefit air compressors have over other pressure vessels is that the water that does get in, being condensed humidity, is relatively free of the impurities that liquid water often carries, so there's fewer chemicals in the mix attacking your tank.

There are some products out intended for de-rusting and coating gas tanks for motorcycles, etc., some of these might be appropriate for use in an air tank as well.

In a two-tank situation, the second, higher, tank could be kept dry simply by turning it so that the air piping was at the bottom, so that any moisture that condensed in the upper tank could dribble back down the plumbing into the lower tank. Pascal's Law isn't terribly concerned with equipment orientation, and you don't have any moving parts on an air tank to worry about.


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## MPowers (Jan 24, 2010)

Several things here, first, it takes a loooooong time for a tank to rust all the way through. If it does, it will not explode or shoot across the room, the first failure will be a small pinhole leak, that lasts for days or weeks, you would notice the hiss, later a whistle as the hole slowly grows larger, giving you plenty of time to deal with the situation. Second, the physics of the situation would not shoot the tank across the room even if a large hole were to occur instantly as if a bullet or other projectile were to puncture the tank. The reason is the pressure in a small portable compressor tank, usually about 125 psi for a portable compressor and about 150-175 for a stationary unit, is simply too low to do the job. The volume in the tank is too small to sustain a reaction that size. Think about it, if you take an air nozzle or blower used to blow dust and debris off of things and squeeze the lever all the way, does your hand shoot back across the room? If the hole was 1/2 inch in diameter, that is huge, there would only be 29 pounds of force if the tank pressure were 150 psi. 

Now, that said, the post that said turn the reserve tank upside down is absolutely correct. In fact a well designed air system is always slanted slightly to the tank or to a "drop leg" with a automatic drain at the lowest point. Valves along the way should tap off the top of the system pipe, rise up a few inches and then back down to the regulator/water trap. Put an automatic drain 
Search automatic drain - Grainger Industrial Supply 
on your tank and you will solve a major portion of your problem. 

As for my credentials to talk about pneumatics, I have been designing and engineering pneumatic systems and stage special FX for over 30 years, taught pneumatic design for stage use, beginning, and advanced, exhibited several of my FX pneumatic projects at the USITT Tech Expo. If you have additional questions about your air system, feel free to contact me directly. [email protected]

Michael Powers, Project Manager, ETCP Certified Rigger-Theatre
Central Lighting and Equipment, Inc. Des Moines Iowa


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## ship (Jan 25, 2010)

Thanks to all above, wasn't worried about exploding, more about needing to buy a new one before ready, though I should probably plan it for summer given my usage. Bigger on even given the 1.1/4" narrow crown, 1.5/8" finish, infrequent paint sprayer and frequent air nozzle which immediately almost requires a refill.

Want a 2" M' gun anyway and given it's like 20-30 staples at this point for the narrow crown gun and the tank has to re-charge, I know it's not sufficient for such a tool aleady.

Brilliant and thanks on the turn the tank up side down idea, was wondering about the moisture collection for the upper tank. Have to remove the carrying handle and perhaps legs for it to fit on the shelf but that's not a problem - air compressor main unit at times travels, tank stays home and don't need to transport.

So at this point I'm thinking this summer I'll bite the bullet and buy a bigger one, for now and or for who I might sell the old one to, given the above concepts in de-rusting gas tanks, this verses just oil for now in fighting rust, any advice on that MPowers?

Realizing I need to drain the tank every night, and while a drip would be good, not really feasable for this tank given the location of the drain... or perhaps, just a plywood shelving over my recycling bin, hole in it, some modification and parts added, perhaps worth looking into. Shelf is sized for the compressor on the other hand, huge modificaiton to lift it to help drain... Gee, should have read the manual before use - imagine that.

Suppose I'll have to start pulling it out at night or re-design it's area for storage some. Needed a project anyway, between projects for the home at the moment now that the wine rack is built and I'm waiting on budget for hinges and lumber for cabinet doors.

Thanks for the advice. Now to re-design and loose a bit more space in an already overfilled garage for a larger air compressor to plan for. Hmm.. perhaps in the condo roof ceiling.... truss roof as normal to shake and bake condo's pad for shake and insulate for noise perhaps with some spanning of the truss as a concept. Gotta see the single car garage to understand the every inch of space in it in use concept. Much easier before Wifie bought a bike that required re-design last year.

While I'm at it, perhaps I'll add a 220v circuit to it so as to run the new air compessor and a IR heater for winter. Ah' plans for the coming summer. Would rather buy a jointer (in finding room for it like I had to do so for the router table) or Biscuit joner but the bigger air compressor would be a good investment. Thanks.


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## TonkaToy (Feb 1, 2010)

Good day everyone! Something I heard of years ago but never tried was to add a bit of Prestone (antifreeze) into the tank, swoosh it around and let it drain. Any thoughts on this? Considering the anti rust properties of Prestone in your car radiator, I figure this wouldn't be bad...maybe even leave 3 to 4 oz always in the bottom of the tank to mix with any moisture. It should keep the tank from rusting. Anyone know why this would be a bad idea?


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## MPowers (Feb 1, 2010)

Re the anti-freeze. It won't hurt the tank but I can't say what it might do to hoses, regulators and tools down stream. The biggest issue is if you use the air for spraying. Try mixing a few drops into a small cup of paint and see if it affects the results. One more possibility is in the aerosol state, will people be breathing it? If so, check the MSDS and see what the results would be. Hope this helps.

IMHO, solve all your problems by inverting the upper tank and installing an auto drain in the bottom of the other.

Michael Powers,Project Manager, ETCP Certified Rigger-Theatre
Central Lighting & Equipment Inc., Des Moines, Iowa


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## FatherMurphy (Feb 1, 2010)

Regarding the anti-freeze in the tank, that might be a thought if you were going to store the tank for a while, but during general use, I think the anti-freeze would mix with the condensate water and compressor oil, and be drained out with the rest. All you'd be doing is adding more strange things to the fluid you need to dispose of. If you're going to store the tank for a while, just get it dried out and keep it dry, and you won't have any rust to begin with.

As for the potential energy inside a compressor tank, while it may not be capable of launching the entire unit through the air, there's more than enough power there to smack you between the eyes with a 1/4" pipe plug from across the room, not to mention drive nails into 2x4s. It's all in how the pressure is applied, and one would do well to keep in mind that any pressure vessel deserves respect. A rusted thin pipe nipple that gets a large wrench dropped on it, a pressure switch that sticks and doesn't turn off a compressor at the right psi, a hose that's been kinked too many times - there's more than one way for even a small compressor setup to make life a little too interesting.


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## ship (Feb 2, 2010)

Replaced the hose ends that are no longer sufficient and entire hose to the sub hose, Thanks by the way.

Hmm, will look into the anti-freeze.. My Coleman paint sprayer is out of commission at the moment due to O’rings going bad. Didn’t use it much anyway given how hard it was to clean. So other than spray on wood that would be sanded later, not a problem. More in use these days for the finish gun and narrow crown gun which don’t persay care about rust or anti-freeze. That said, my finish nail gun gasket no doubt is gone now and I need to replace it.

Been good of late, one more times at pressure in spraying off the dust from the winter heaters and I’ll drain the tank as opposed to leaving what’s left in it for the next days blowing out the heaters filters. All granted also that if I add chemicals to the tank, I won’t be blowing out any heaters any time soon.

Another night of given two circuits in the garage, half it has the big power tools and most of the lighting and is the 20A I ran, the other is the house garage 15A run to it which does the entertainment center, some ligthting and the air compressor. Added to each are two heaters, a large and small one to supplement it in warming it up faster. Constantly forget which heater is on when doing something and blowing a breaker - oops. Gas Washing Machine and Stove, thinking in the future when I buy a bigger air compressor it will be 220v and in the ceiling. This and supplemental to the heating already sent to the garage = classified as an office/workshop, I’ll run 220v to radiant heater in the coming year. Years ago when I ran the second circuit a 15A and 20A circuit was well enough for the garage, these days not enough. This especially after I bought more tools. Should have run more power when I was running the origional circuit. Didn’t follow the rule of doubling for one’s needs, this much less I never imagined I would have as many tools in need of power or thought about garage heating when I bought the place.


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## ship (Feb 20, 2010)

Bought a Coleman 20gal. vertical tank. Still planning to us the 10gal. add on tank with manifold and dryer/oiler. The Coleman tank should handle the added volume given the same motor is rated for a 26gal. tank.

Found it interesting that the new tank is 1.5HP for a 20 gal. compressor yet the DeWalt was 2.75 HP for only a 6gal. tank. New compressor isn't noticably longer in running and is even somewhat qieter. This much less runs less than even the added capacity tank. Good investment to have bought.

Now only a question of re-doing a 4x8x18" deep section of the garage wall... Given a one car garage full of every inch used, re-arrangement of it is a really good design challenge. Especially tonight with snowstorm... the car has to fit into the garage inspite of my toys.


Next step is replacing my road box. Too big for my needs now and might gain access to the water fitting in the garage once replace. Nice box, rigged to even fly out of the way. The next 48" to re-do in gaining more space.


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## erosing (Feb 20, 2010)

Ship, could you please post pictures of your shop/garage? You've talked about it so much and I must admit that I am incredibly curious to see it.


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## ship (Feb 20, 2010)

Arez said:


> Ship, could you please post pictures of your shop/garage? You've talked about it so much and I must admit that I am incredibly curious to see it.



One car garage with 1920's lighting in it and Wifie's bike as with various compressors, table saws, router tables, chop saws etc??? Can only imagine what form of pandimandomum Wifie's recent bike caused to the storage situation of my shop. This assuming a car can still be fit into it and mostly in the summer it don't. Chop saw table folds up and out of the way in clearing up like an important 12" of space. Very important in still getting the car in the garage yet still having a really accurate chop saw. Main work table at the center of the floor when car isn't there is fold up saw horses. Other work table for assembly is aways there and flame/pounding on it proof.. 


Will work on such a concept of photos given projects at work in the works still and I might just deliver the antiques to the shop and install them already at some point... kind of in the way. Lighting grid in the garage... na, it allows you to hang stuff from it which doesn't allow for the full usage of space. Good use of a small space perhaps in ideas. 

After done with it's next generation, phtos perhaps. For now, I love it in great space I prefer over even work to get stuff done.


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