Vintage Aerotecnica Coltri MCH-6

[rcontrera]

I f you are going to be filling beyond 2250, I suggest a new gauge and fill yoke as both of yours are designed for 2250 psi.

Oh, and an air sample only really tells you the quality of the air at the time you sampled. Anything can happen to make bad air as soon as you start up again after sampling. So, it is really only a test for you to evaluate the function of your filter system.

 

[W W Meixner]

I f you are going to be filling beyond 2250, I suggest a new gauge and fill yoke as both of yours are designed for 2250 psi.

Oh, and an air sample only really tells you the quality of the air at the time you sampled. Anything can happen to make bad air as soon as you start up again after sampling. So, it is really only a test for you to evaluate the function of your filter system.

Ray...

Industry standard due diligence is defendable...where doing nothing could be deemed careless disregard and negligence...

Who said...Buying a compressor to save on the cost of air...is like buying a farm to save on the cost of milk...

May suggest following ones own advice...

W.W...

 

[SurfLung]

I f you are going to be filling beyond 2250, I suggest a new gauge and fill yoke as both of yours are designed for 2250 psi.

Oh, and an air sample only really tells you the quality of the air at the time you sampled. Anything can happen to make bad air as soon as you start up again after sampling. So, it is really only a test for you to evaluate the function of your filter system.

Thanks for your comments Ray. I should have explained I'm a Vintage Equipment Diver and most of my tanks are Twin 38s at 1800 psi working pressure. I do have another fill whip that's modern and built for higher pressures. That's the one I've been using until the BPR fitting broke. My little Aero has an over pressure valve that starts releasing air at 2800-2900 psi and that's fine with me. I have gone that high with the other whip and modern aluminum tanks... That's how I know where it lets go.

With Regard to Air Purity Testing, I agree with Ray's reasoning. It is easy to take WW's point of view... Afterall who would argue AGAINST air purity testing. But you can detect in Ray's comments someone who has alot of practical, hands on knowledge of actual air sampling conditions and actual practical value of testing. He's not advising against testing. He's merely commenting that it doesn't guarantee that your air is good.

Now WW... I believe your approach on this is more of a litigious concern than one arrived at through experience. The reason I say this is your comment about pumping your own air to save money. Anyone who owns a compressor will know it's mainly for convenience. The actual cost of time and materials is usually more than store bought fills. There's certainly a place for legal concerns. But you can have a wall full of air purity certificates and still get sued. I don't fill Scuba tanks for a business but why would you assume that I don't care about the quality of air I pump for my own breathing safety? You don't think I know about Carbon Monoxide? Here's what an experienced compressor operator does to avoid carbon monoxide:
1. Place the air intake upwind of the compressor and away from possible sources of CO... Like not next to a filling station or highway. You can't smell or taste CO but if you smell engine exhaust, you can bet CO is there too. So don't suck air from contaminated spaces.
2. Don't over heat your compressor as this has a potential to diesel (ignite) the lubricating oil and produce CO.
3. Use a modern compressor oil with a high flash point so its not likely to diesel.
4. Use an efficient moisture accumulator, drains, and monitored filtration (like blue test strip equipped 13X Molecular Sieve)
5. Use a modern Back Pressure Regulator (BPR) or Pressure Maintainance Valve (PMV) to keep the filtration system above 1800 psi... Which squeezes approximately 97% of the moisture and vaporized oil to a drainable state. This assures the efficiency of your filtration system.
6. 13X Sieve is for remaining moisture and vaporized oil. You can monitor it often by checking the blue test strip.
7. The rest of the filtration is this: Hopcalite converts any CO to less harmful CO2. And finally activated Charcoal removes tastes and smells.

From a practical standpoint, I can control what air goes into my compressor and I can make sure its not over heating. I can see condensed moisture and oil when I open the drains. And I can check the blue filtration test strip regularly to make sure my filters have plenty of capacity left.This is what tells me my air should be good. But I can't argue against testing a sample to see if all of this is actually working... So I'm in agreement with Ray and WW on that and will get it done.

Finally, to illustrate what can happen with Carbon Monoxide poisoning, and to promote vintage equipment diving, I recommend watching Episode 36/Season I of Sea Hunt. Its the Lord Cristobal Story...

 

[W W Meixner]

Thanks for your comments Ray. I should have explained I'm a Vintage Equipment Diver and most of my tanks are Twin 38s at 1800 psi working pressure. I do have another fill whip that's modern and built for higher pressures. That's the one I've been using until the BPR fitting broke. My little Aero has an over pressure valve that starts releasing air at 2800-2900 psi and that's fine with me. I have gone that high with the other whip and modern aluminum tanks... That's how I know where it lets go.

With Regard to Air Purity Testing, I agree with Ray's reasoning. It is easy to take WW's point of view... Afterall who would argue AGAINST air purity testing. But you can detect in Ray's comments someone who has alot of practical, hands on knowledge of actual air sampling conditions and actual practical value of testing. He's not advising against testing. He's merely commenting that it doesn't guarantee that your air is good.

Now WW... I believe your approach on this is more of a litigious concern than one arrived at through experience. The reason I say this is your comment about pumping your own air to save money. Anyone who owns a compressor will know it's mainly for convenience. The actual cost of time and materials is usually more than store bought fills. There's certainly a place for legal concerns. But you can have a wall full of air purity certificates and still get sued. I don't fill Scuba tanks for a business but why would you assume that I don't care about the quality of air I pump for my own breathing safety? You don't think I know about Carbon Monoxide? Here's what an experienced compressor operator does to avoid carbon monoxide:
1. Place the air intake upwind of the compressor and away from possible sources of CO... Like not next to a filling station or highway. You can't smell or taste CO but if you smell engine exhaust, you can bet CO is there too. So don't suck air from contaminated spaces.
2. Don't over heat your compressor as this has a potential to diesel (ignite) the lubricating oil and produce CO.
3. Use a modern compressor oil with a high flash point so its not likely to diesel.
4. Use an efficient moisture accumulator, drains, and monitored filtration (like blue test strip equipped 13X Molecular Sieve)
5. Use a modern Back Pressure Regulator (BPR) or Pressure Maintainance Valve (PMV) to keep the filtration system above 1800 psi... Which squeezes approximately 97% of the moisture and vaporized oil to a drainable state. This assures the efficiency of your filtration system.
6. 13X Sieve is for remaining moisture and vaporized oil. You can monitor it often by checking the blue test strip.
7. The rest of the filtration is this: Hopcalite converts any CO to less harmful CO2. And finally activated Charcoal removes tastes and smells.

From a practical standpoint, I can control what air goes into my compressor and I can make sure its not over heating. I can see condensed moisture and oil when I open the drains. And I can check the blue filtration test strip regularly to make sure my filters have plenty of capacity left.This is what tells me my air should be good. But I can't argue against testing a sample to see if all of this is actually working... So I'm in agreement with Ray and WW on that and will get it done.

Finally, to illustrate what can happen with Carbon Monoxide poisoning, and to promote vintage equipment diving, I recommend watching Episode 36/Season I of Sea Hunt. Its the Lord Cristobal Story...

SL...

I maintain...you can verify purity as per industry standards...or you can choose not to...

You are correct that any verification is only a verification...at time of verification...but you're not verifying at all...

Far be it from me to be your clean air police...fill away...

W.W...

 

[SurfLung]

What Was Acceptable in the Past is Surprising...
- This little Aerotecnica Coltri MCH-6 is my second vintage compressor to restore to operating condition. The first one I did was a RIX SA3-E. And both of them were originally operated in a configuration that would shock modern compressor operators.
- The RIX has two moisture separator towers and no filters. It was sold as a "Sweet Air" compressor because it is oil-less... No oil sump. It uses self lubricating teflon rings instead of oil lubrication. And for this reason, it is believed incapable of carbon monoxide contamination. The manual shows the fill whip hooked up directly to the 3rd stage moisture tower... Filling tanks directly off the separator with no moisture absorbing filter media. The fill whip has a back pressure regulator which improves the efficiency of the moisture separator but a technician at RIX told me the BPR was mainly to build pressure rapidly to keep the floating piston of the third stage pressed against the piston rod to minimize hammering as the two parts settled against each other. Military divers are said to have filled their tanks directly this way without any moisture absorbing filter much less activated carbon or hopcalite. An addendum to the manual gives instructions for fire departments and others to add on a filtration system but can you imagine the rusty insides of tanks that were filled directly with just the separator towers?
- I acquired the Aerotecnica from a guy who was diving the great lakes with his friends back in the '80s. Two big glaring issues were apparent when I got it home. First, the air intake filter was mounted right on the compressor, within inches of the exhaust pipe of the Briggs and Stratton gas engine. So, these guys were relying on the wind to carry exhaust gases away from the intake. I couldn't believe this. But even today, the modern Coltri manual shows the MCH-6 operating with the intake filter right on the machine and advises to position the entire compressor somewhere that gives good ventilation. (They do now offer an accessory "remote" intake hose which is good news). The second shocker was when I opened the filter and found it was filled with nothing but activated charcoal. So here now was a configuration that could have contaminated the breathing air with not only Carbon Monoxide from the gas engine, but also moisture from the lack of moisture absorbing filter media.

 

[rcontrera]

The carbon filled cartridges were the European standard for years. They then went to all Molecular Sieve cartridges. I think they only started doing the tri-chem cartridges in the last few years. I had a bunch of them that we pulled out when we would get the container in from them. The carbon ones just got tossed while the MS ones were just sold off to paintball and air rifle shops at a discount.

 

[Couv]

What Was Acceptable in the Past is Surprising...

You're not kidding there. I worked in a LDS in the mid 1980ies. Our filter was an aluminum 64 with a hole drilled through the bottom. The hole was for an MS fitting that connected to the compressor line-out of the top was the line to the banks. Inside the "filter housing" was a sandwich of cotton tampons and activated charcoal. (I think we got the charcoal from an aquarium supply store.) It was quite an ordeal changing the sandwich.

Having said that, we never had any complaints about our air.

 

[rcontrera]

I bought a compressor system from a store that went out of business and took the filter to a compressor specialist and he asked if it went out because hi customers kept dying?

The filter stack consisted of a plain 4" pipe with flanges held on both ends by threaded rods. The nuts on both ends were rusted tight so it was difficult to even get them to budge. That told me that the owner rarely, if ever, changed the stuff inside out. When the compressor guy got it apart, it was full of Kotex and carbon and all was soggy and oily. I immediately bought a moisture separator and a filter housing. Back then, it was pack your own and a fairly new little company made fill your own plastic filter cartridges and they had a silly name ... Lawrence Factor.

One thing that still happens is that compressor operators still neglect their systems and, if customers don't get better air somewhere else to gauge by, nobody notices a slowly increasing stink level.

 

[SurfLung]

... Back then, it was pack your own and a fairly new little company made fill your own plastic filter cartridges and they had a silly name ... Lawrence Factor.

The SEE-THRU tubes and Blue Strips of Lawrence Factor add whole new level of efficiency to the maintenance of air quality. Previous to that, I think all anybody had to go by is how many hours of runtime or tanks to fill the instruction manual said was suitable before each filter change. This doesn't take into account changes in heat and humidity that might use up filters much faster. With these new Lawrence Factor filters, you can easily slip out the filter and just look at the test strip. No guessing... You can SEE when its time to change filters.

It must not have been that long ago that Coltri switched to the Clear Lawrence Factor filters. This 2013 video shows how easy it is to open and change the filter... But it shows the old style black filter tube and refers to it as the activate carbon filter. But you can see, if the Lawrence Factor clear filter is used, you can easily lift it enough to check the blue test strip. It only takes a few minutes to check the filter and to check the oil before every filling session.

 

[SurfLung]

Update Aero MCH-6
- I've done a few more upgrades to this little compressor and thought I'd share/record them here.
- First the drive belt. When my belt disintegrated, I took the remains to a local farm supply. They measured it and sent me home with what seemed to be the right size. I watched a Coltri video on how to replace the belt and it didn't show them loosening anything... Just leveraging the belt onto the pulleys. This proved to be a bit too tight and the belt wrecked itself again. I tried the next full size up and it slipped. I checked the engine mounting for adjustment but it seems to be maxed out in both directions. Finally, I found a half increment belt size online and that has seemed to work perfectly.
- 2nd the Belt Guard. This guard was vibrating quite a bit and had a crack started. I repaired the crack by sandwiching the screw hole between two washers and J-B Weld... Then I stuck a wood spacer between the bottom and the frame and zip tied the guard tight to it. No more vibration.
- 3rd the Condensation Drains - The original drains are more like bleed valves with small, hard to grip knobs. The seats are pointed but chewed up. Anyway, I got some nice Bauer style drains valves in 1/8 npt from Nuvair. The one under the belt guard was always hard to reach but now wouldn't fit because of the large knob. So, I put an extension on it. VERY slick and easy to reach. These new drains give an excellent seal and are easy to grip.

So now, this thing is running smooth as silk. I've got to go diving so I can fill some more tanks with it!