My portables

[Jimmer]

Great report, I look forward to installment 2 of the Walter Kidde Files Interesting to think that they had the ability to machine inconel to a tenth back then. I'm an engineer and machinist, and I used to work in a machine shop that did a lot of "hard turning" on stainless, inconel, M2, Titanium, and we'd struggle with our best CNC lathe to hit half a thousandth consistently. CNC surface grinder was the only way.

 

[pescador775]

Hey, Jimmer, wow, sounds like you know your stuff. About the tenth accuracy, it could be that Kidde machinists only were shooting for two or three tenths and then depended on select fit and running in to take care of the discrepancies. I guess the final turns were done with polishing media, slurries or pastes. Probably art as much as knowledge. A new piston and barrel is a very snug fit. I mean, the piston won't fall out even if shaken a bit.

 

[Jimmer]

So there are no rings or any other seal between the barrel and the piston? Strictly a tolerance fit? So how hard is it to actually find service parts for these units? The more I learn about them the more interesting they become. Realistically how high pressure can these units pump and be reliable for the long term?

 

[pescador775]

Stages 2,3 and 4 use floating pistons. The second stage piston has four iron rings and an oil control ring. Pistons 3 and 4 are interference fit, metal to metal somewhat similar to the Bauer 3rd stage but the Kidde has closer fit and brilliant finish. The early Kidde second stage employed a floating piston with two teflon rings. Over several hundred hours, these rings would eventually crack and need replacement. (Fortunately, a machine shop can make these if necessary). Again, second generation Kiddes have a different piston and the rings last a long time, thousands of hours. The second stage piston is also graphite coated and this wears with use but doesn't seem to cause problems. One of the consequences of using iron rings is dust. The first and second stages produce a small amount of ring dust. When the new compressors with this different second stage came into use there were instances of the filter, which is located in the air line between stages 3 and 4, becoming clogged prematurely. This problem was rare in the old Kidde but a real nuisance in the new machines. The factory promulgated a retrofit. The filter was replaced with an adapter. At this point, all new compressors came with this stainless steel adapter which replaced the filter. The Kidde does not incorporate interstage separators. Thus, dust, water and oil are carried through to the final stage. Over time, the fourth stage will show signs of wear and need to be replaced. This will occur at a minimum of 2000 hours if the correct oil is used. This oil is Mobil JET II.

The barrels are made of steel. If the compressor is run and left to sit a long time, accumulated water in the 3rd and 4th stages will cause a small amount of rust in the barrel. This may cause the inconel chrome alloy piston to stick in the barrel. The piston must be removed by striking with a drift followed by the barrel being abraded lightly with fine emory cloth. It only takes a minute to do this and is part of the inspection process of a surplus compressor. Rust formation is avoidable simply by running the compressor under no load for 15 sec which will blow out the water.

There is a dive shop in the LA area which maintained a large bank with a Kidde compressor. After three years, the Kidde was replaced due to business expansion. The compressor was still in good, operating condition when removed from service. What was surprising to me, the compressor was used to pump NITROX and was lubed with Anderol 500. (that is a matter of interest to people like me only, I suspect, LOL).

 

[pescador775]

I see there were more questions: Kidde rates the compressor @ 3000 psi continuous duty.There is little doubt that they can meet that. A friend rebuilt some of these for the paintball market. He proof tested each unit to 8000 psi and recommended them for 4500 intermittant. At 4500 psi, the compression ratio of the Kidde fourth stage is 3.7 and at the same pressure the compression ratio of a Bauer Capitano third stage is 6.0. Moreover, the fan of the Kidde turns at 3 times the speed of the big Bauer and 1.4 X that of the small Bauers like the Oceanus. Heat in the stages and in the block vary with these numbers as well as volumetric rate of delivery. Oil temp tracks these values also. However, one thing to mention here; the Kidde does not use a sump. Oil is stored in a tank which is mounted directly in the air stream. However, the one pint capacity is less than some of the Bauers for example. The Oceanus, in particular, absolutely needs the larger, 1 liter tank. My feeling is that the Kidde oil should be drained more frequently but I have never found the oil in that tank to be more than luke warm. Max safe oil temp is 170 deg before break down begins. The Kidde tank doesn't come close to that.

WRT parts; few and far between. Unless a bunch of these units become available again I wouldn't recommend anyone follow this path.

 

[Jimmer]

Thanks for all the info Pesky. I'd like to get a little 3.5 CFM compressor someday when the funds allow. Since you don't recommend people to go down that path due to problems finding parts, what do you recommend for a small compressor that can push 4500 if needed?

 

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

Great report, I look forward to installment 2 of the Walter Kidde Files Interesting to think that they had the ability to machine inconel to a tenth back then. I'm an engineer and machinist, and I used to work in a machine shop that did a lot of "hard turning" on stainless, inconel, M2, Titanium, and we'd struggle with our best CNC lathe to hit half a thousandth consistently. CNC surface grinder was the only way.

Hi Jimmer,

Have seeing you talking about CNC surface grinder, in actually I had one time of experience to facing this tough inconel material, that was in the past I been bought one 4 cfm 4 stage 4th generation of kidde, but unfortunately when it all setup already and start to testing it but it just would not go to reached it's rating 3000 psi, finally I found the problem is caused by the third stage piston and cylinder both with some scraped, and in order to save this unit, I had looking for some way to recover it, finally, I got a larger one third stage piston which come from one broken of 3.5 cfm 3 stage Kidde together with the original damage cylinder and I sent them to a machine works who specialized in ""centerless grinding service by using "centerless grinding machines"" to matching both of the piston and cylinder, and finally it's work ( this unit I been using it for arround one year before I sold it out ) but the machine works owner have complained it to me about he never been saw such tough material and doing the piston grinding job he just lost a pair of grind wheel.

The above is one of my previously owns 4 cfm 4 stage kidde story.

Peter

 

[pescador775]

Jimmer, it's the wild west out there. Look for something on the resale market like EBay or Craigs list. The Utilus 10, Junior, Coltri, Alkin, etc can push 4500. The paintball trade has really made this competitive and a gold mine for compressor manufacturers. Also, Homeland Security has been making funds available to local authorities and the fire depts have been replacing some perfectly good (big) compressors with new. In the early 90's it was possible to pick up a Utilus 10 for $1200. I found one in the local trading post for that amount. My buddy bought it and used it for several years to PP fill tanks with NITROX. Ebay is crawling with crooks. I think right now, one of those phony ads for a Bauer is bidding up around a thousand bucks and climbing. Be careful out there.
Pesky

 

[shil]

Pesky,

Did this unit also serve in Boeing 707 s ? I seem to recall reading about that somewhere ? I may have that document somewhere in my files.

- Theoriticaly musing, could a interstage separator be piped in the somewhere in the Kidde pumping circuit, so that most of the water, (iron dust which you mention in your post ) be purged out ? If so where would you put it. Naturally it would be something you made out of a hydraulic cylinder /acumulator, , and have to fix to the frame somewhere outboard.

-When my unit was working the oil would get diluted by water way before it was time to change it, forcing a change. and maybe a late discard of the watermixed oil would have contributed to premature wear and tear in unit ?

-What was that black coating on the first stage piston, ? you had mentioned about it somewhere .

- and that shop down under, (got not reply from them ) supplying Kiddes, where does it source it's units ? maybe parts can be obtained by/from them.

Shil

 

[pescador775]

Hi, Shil; yes, a separator could be rigged. It could go in the airline where the filter is located. Remove the filter. Remove the pipe fitting from the head and install a 1/8 NPT (male) to AN-4 flare (male). Note that this is the same AN-4 elbow fitting used in other stages.The air line should have AN-4 female ends. Run the return line back to the third stage exhaust tube using a male/male adapter. The air hose would have to be rated for about 1500 psi.

The black coating is graphite. I don't know about parts availability from Dependable Distributors in Adelaide. Actually, they don't make the units but the mfgr is located in Adelaide, also.

Water in the oil would indicate quite a bit of blowby. Normally, this is vented somewhere and doesn't show up in the oil until a lot of hours are clocked.

Yes, the Boeing had a Kidde installed. Air Force One, in fact.