Stewart Warner/Kidde Compressor and moisture seperator questions (Home mixing)

[jtsmith]

I have decided to get setup to start filling my own tanks from home. This decision was in no way based on money...it's more of a hobby, convience thing. I have read all of the posts here and the oxy hackers companion(GREAT book!) and I have a basic knowledge of compressor's and filtering. I currently PP mix Nitrox and am interested in Premixing with a homemade stick. So far I have aquired a 3 tank bank with manifold and a Bauer BC-106 filter canister(15,000 cuft).

Left to go is the compressor (3-4CFM), moisture seperator, and BP valve.

On to the questions:

I have shopped around and I am thinking of the Stewart Warner or Kidde Military surplus compress refurbished from Protec Air fitted with an electric motor by me. Because the SW is a little quieter and parts or more readily available, I am leaning towards it. Has anyone used either of these compressors for Premixing? Any suggestions on which one is better?

I have deduced that dryer air is cleaner air. I was curious if anyone had considered making a loop or two of hose before the moisture seperator and submerging both the loops and the moisture seperator in water to keep them very cool. Wouldn't this cause a lot more water to condense in the hoses/seperator as well as cooling the air coming out?


Thanks!

Jason

 

[Stone]

Jason,

Welcome to the board!

I can't help with your questions, but I am interested in the answers. I am just starting to home brew, myself. I bought the Bauer Oceanus (4.9 scfm), and built an Oxyhacker "Stik". There are a few "lessons learned" that I might pass on if you are interested.

If we haven't met already, we probably have some dive buddies in common.

 

[omar]

You are right dryer air is cleaner. The oil particulate is typically combined with water vapor/droplets. The higher efficiency moisture separator, the more removal of the undesirable constituents. Running the high pressure line in a water bath would be the same as a water cooled aftercooler. This is a good thing. The cooler the air the less water vapor that it can hold. I would run the line in a manner where there was a gradient from upstream to downstream (horizontal coils) to help drain the water.

My compressor has about 6 feet of finned aftercooler line and is air cooled. This reduces the temperature significantly prior to the moisture separator and seems to work very well.

omar

 

[Larry M]

I also don't have the answers your looking for but am interested in the responses ... I mix my own Nitrox at home with a Bauer 9.2 cfm (K14) and use the Nitrox Membrane system from Undersea Breathing systems ...I did look into the Stick and blenderpanel options but decided that the Oxygen required was not practical were I live as well as safety concerns

 

[jtsmith]

Okay..now that the moisture question is over.....

Does anyone own a Stewart Waner or Kidde compressor??? I am just trying to get an idea of how they compare to each other and other small compressors.

If you own one of these please PM me!

 

[pp-1-3-5-7-9]

Okay..now that the moisture question is over.....

Does anyone own a Stewart Waner or Kidde compressor??? I am just trying to get an idea of how they compare to each other and other small compressors.

If you own one of these please PM me!

Even I prefered the Kidde one ( personally ideal is the Kidde " 4 stage one" , I supposed that it seems more solid then the Steward Wanner " 3 stage " one ), But from the spare parts resource concern then I would recommend the S.W., as I can see the Kidde were explosed more less and less then the S.W. in the surplus source market now. the above comment just for your reference.

Peter

 

[pescador775]

JT and all. Back in the day, I think I advised you privately that the Kidde should not be used for pumping brew. The reason had to do with the type of oil specified for the four stage, 4 cfm compressor. You see, unlike the slower turning compressors which require a heavy, 30 weight oil, like Bauer compressor oil or Anderol 500, the Kidde and Stewart Warner use a light viscosity oil. Some compressor manufacturers like Bauer say that their units can be fed NITROX up to 40% concentration but advise that "food grade" oil should be used. As far as I know, the food grade compressor oil which is readily available (from UBS) is only sold in 30 weight, OK for the Bauer and some others but too heavy for the Kidde or Stewart Warner. Don't misunderstand, the military pumps can be run with this heavy oil but I don't know how long they will last if run at max speed. The Kiddes seem to do OK on Bauer oil if run at 2500 rpm or thereabouts. Actually, there are several food grade compressor oils of the correct weight (10 W, ISO 32) in production but I don't know the availability or size quantities that can be purchased. Several brands can be Googled up without much effort. I suspect that the Stewart Warner 4 cfm could live happily on these type oils. Before the days of chemical filtrants, the SW's that were used for breathing air were fed medicinal grade mineral oil! However, there may be a problem with deposits building up in the Kidde if fed that kind of stuff. I don't know for sure. I do know that the current food grade oils are synthetic and have fairly high flash points but I don't know about coking control. If one wants to churn some brew through these pumps I believe it is a reasonable risk to go ahead and use a high quality 10W food grade oil in the machine, at max rpm.
Pesky

 

[pescador775]

Looking through my rather disorganized notes shows that I disassembled a Kidde 4 stage, 870 series which had been lubricated with 30W mineral oil. The crank seized up after about 120 hours. I examined an 890 series which had about 250 hours on Anderol 500 which is similar to Bauer oil. All the internals common to the four cylinders and oil tank showed unusual build up of gunk which was extremely hard to clean. The first stage valves were worn/warped.

The oils specified for these compressors are: aircraft use, MIL PRF 6085D (aircraft instrument oil). All other uses: MIL PRF 23699F (jet turbine oil), also know as JET II.

Although the food grade compressor oils do not contain the same extreme high pressure anti friction compounds as turbine oil, they do appear to be generally high quality, and the lighter grades produced for use in reciprocating compressors are probably safe for use in the Kidde and Stewart Warner.

 

[veggiedog]

I have an old Cornelius three stage, and it also uses a light oil. I purchase my oil from ProTec Air Systems, and it is a synthetic lubricant made by Ultrachem Inc. called Chemlube 201. I agree that it is a good idea to cool the air before it gets to the drier, and to have the line slope downwards into the drier to allow water that condenses in the line to drain into the drier. I suspect that if you cool the drier instead (immerse it in water) you might reduce the effectiveness of the desiccant. I use molecular sieves: not sure how they are affected by temperature (less than standard desiccants I suspect).

 

[pescador775]

Generally, condensers/filters/driers (driers are final filters containing dessicant only) are more efficient if kept cool. However, water cooling seems like a pretty drastic measure and is probably not necessary. Looking at the overall system, one tends to separate the components as to their specific function but these components have secondary roles as well. For instance, the condensators remove moisture but they also are part of the cooling system. Having a pair or more of these aluminum cans adds significantly to the heat dissipation and overall efficiency. On my Kidde portables/4cfm/gas I always install seperate condenser and final filter. I fix the back pressure valve to the condenser (rated up to two hours to drain). This causes a pressure rise in the condenser and noticeable heat build up and heat dissipation. The HP air squirts out of the condenser/BP valve with falling pressure and fast cooling as it enters the final filter (triplex type chemical filter). The air begins to warm up once again and exits the final filter at approx ambient temp.

Chemlube 201 is MIL L 6085A spec, aircraft instrument oil. The latest performance spec for this oil is 6085E. Ultrachem is a reputable mfgr of compressor oils.

My take is that their Omnilube 32/46, synthetic H-1 (food grade) oil is the right stuff for the Kidde and SW.

I realize how esoteric this subject is, but in the event that somebody has a homebuilt military compressor, it is likely that they are innovative, independent and self motivating. This type of person is more likely to attempt home brew through PP mixing or continuous flow blending. If blending is the plan it might be a good idea to purchase a quantity of this compressor oil.