Coltri MCH 6 question/ advice appreciated

[Tony Pr]

@SurfLung Thanks for the advice. I have been running it a garage with little wind, but another fan is something I have been thinking about.

It was the old motor which could not handle the load. It got really hot and also slowed down when the pressure was starting to build up. There is no pressure switch on the compressor.

To give you an update, I purchased a new 3hp electric motor (my mother bought it to us from Australia in a suitcase - heavy) and fitted it up with the correct sized pulley, so it is doing the correct RPM now. It now fills tanks to 3000psi or 210 bar without any problems. That is the highest pressure I have taken it to, as that is all I need. Takes around 40 minutes from empty (11.1 litre tank). It should be a bit faster, I have checked for leaks with soapy water but I cannot see any. If anyone has any comparable data that would be appreciated. It is quite satisfying to watch it fill after it taking so long to get operational, but maybe thats just me. haha.

I have now filled three tanks with it successfully and will do some more after I go diving and empty my three this weekend. It seems that the better way to do it is to fill to around 2700psi, let the tank and compressor cool down and then top it up to around 3000 at the start of a run (and then fill another tank to 2700psi).

Next challenge is to clean it all up nicely and repack some filters. I did not want to spend heaps of time cleaning it up until I knew it was running well first. Now that it seems to be running well, does anyone have any advice on how to clean up the compressor body from a bit of surface rust? I was going to use baking soda mixed with a bit of water in a paste and scrub it down a bit. Any advice for the novice again would be appreciated. I read up on Surflung's process, but could not see how he cleaned it up so nicely.

I do have a couple of questions now that it has been running:

1. How often do you purge the water from the column and filter stack? I do it every 5 mins or so, but do not get much water out (and almost no water out of the filter stack). Can you wait longer like 7 mins? Running in about 28 degrees celcius (80 farenheight) ambient. Do you just purge until the water stops flowing out or let a bit of vapor out too?

2. How long should you give the compressor to cool down between fills? Can you wait 10 mins and then go again? Or more like an hour or two? It is not a big deal as i normally do one fill a day.

3. Do you have a specific order for purging water (and closing the valves on startup)? Does it matter?

4. How long do you other Coltri MCH 6 users take to fill an empty tank?

5. I have been looking at re-packing filters for this machine. Does anyone have any good videos/links to doing this process? I have access to 13X and Activated carbon and will need to change a filter soon (as well as the oil in the machine).

6. How do you clean up these compressors nicely?

Thanks again

 

[tbone1004]

1. purge as necessary. You can go longer than 5 minutes though. Try going for 10 and see. I usually purge for 5 seconds and it should be empty empty with no vapor. Bauers settings come stock at 6 seconds every 15 minutes as an FYI. I'd start at 10 minutes if you are particularly humid and that should be fine.

2. @rcontrera can speak better to this. I think there is a duty cycle on that pump, but I don't know what it is. Usually they're 2hrs on, 1hr off and it's mainly running at high pressure for long periods of time. I.e. if you are filling one al80 at a time, then it will probably go continuously with no hiccups. If you are filling HP doubles, that's a different discussion. I would probably go 2 tanks on, then half hour break, and an extra box fan blowing on it during the break will certainly help.

3. Auto drains will purge and close them all simultaneously, but I imagine you'd want to go LP->HP for closing them

4. It's a 3cfm ish pump, so time to fill doesn't really matter, it's CFM that does. 40 mins sounds really slow though, you likely have some check valve issues between stages.

5. can't comment, not familiar with that.

6. Steam! Steam cleaners are the bomb dot com, and make quick work out of degreasing and denastifying metal parts. Melts all the nasty's away and gets them spotless. They're also great multitaskers as they are a chemical free way to clean and sanitize/sterilize your floors, countertops, and bathrooms at home, and also the best way to clean cars and leather. Fabulous tools.

 

[rjack321]

4. It's a 3cfm ish pump, so time to fill doesn't really matter, it's CFM that does. 40 mins sounds really slow though, you likely have some check valve issues between stages.

The too frequent purging is drastically limiting his fill rate.
Normal purging is roughly every 15 mins. Even every 10mins is a bit short and will reduce the fill rate compared to the specified rate.

 

[SurfLung]

@SurfLung

I do have a couple of questions now that it has been running:

1. How often do you purge the water from the column and filter stack? I do it every 5 mins or so, but do not get much water out (and almost no water out of the filter stack). Can you wait longer like 7 mins? Running in about 28 degrees celcius (80 farenheight) ambient. Do you just purge until the water stops flowing out or let a bit of vapor out too?

2. How long should you give the compressor to cool down between fills? Can you wait 10 mins and then go again? Or more like an hour or two? It is not a big deal as i normally do one fill a day.

3. Do you have a specific order for purging water (and closing the valves on startup)? Does it matter?

4. How long do you other Coltri MCH 6 users take to fill an empty tank?

5. I have been looking at re-packing filters for this machine. Does anyone have any good videos/links to doing this process? I have access to 13X and Activated carbon and will need to change a filter soon (as well as the oil in the machine).

6. How do you clean up these compressors nicely?

Thanks again

Hey that's great news that a new motor solved so many of the problems. Some of your questions suggest that you may not have seen an operators manual. I got a lot of good information from the Coltri MCH-6 manual at Use and maintenance manuals - Coltri Compressors

1. As a general rule, I just try and remember to drain the water every 10 minutes. But you can use your own judgement. Atmospheric conditions will change how often you have to drain the moisture. In the winter, I fill tanks in my basement and it is so dry I condense very little water i the usual 10 minute cycle.BTW - You don't have to BLAST it out. If there's a pool forming in the condenser, just opening the valve enough to drain the liquid is enough. It'll drain down until its near empty and then it start venting air.

2. Cool down is also dependent on conditions. I think the manual says something about it.

3. The manual says drain the condensation tube first and then the filter tube.

4. Fill time. You mentioned changing your sprocket diameter (a.k.a. Pulley/Sheave). If you are running with the original sized sprocket, the manual has fill rates posted in a chart for various gas and electric configurations. My little 1980s MCH-6 runs at 2.8-3.0 actual cfm. That fills an 80 cf tank in about 25 minutes.

5. I would recommend going with pre-packed filters from Filtertech. Air Compressor Filters, Breathing Air Filter Cartridges The reason is because they are clear, see-thru tubes and they have a blue status strip. Instead of going by time of use, you can actually pop the top of the filter tube and check the blue strip. I think the manual has a chart for how long filters should last but, you should change filters when the blue strip turns pink regardless of the number of fills or time of use. I use the
X152412 filter.

6. My little Aerotech Coltri MCH-6 was actually in almost new condition. Hardly any rust. Just dirty. I used Dawn detergent and water. Then I used a carwash solution that was supposed to leave a wax coating. The... I spilled dirty oil all over it when I changed the oil. Geez.

 

[tbone1004]

The too frequent purging is drastically limiting his fill rate.
Normal purging is roughly every 15 mins. Even every 10mins is a bit short and will reduce the fill rate compared to the specified rate.

True, every 5 minutes at 5 seconds, over 40 minutes is 40 seconds per drain, I assume 80 seconds total on this pump? It's wasting around 3cf of potential volume from the pump, but if you are blowing the filters down to too low of a pressure, that could be fairly significant. My filters are roughly 8 liters of total volume. Every 100psi they lose during blowdown is almost 2 cubic feet of gas and they hold almost 80cf total at 4000psi which is not insignificant. Praise be to check valves and PMV's!

@SurfLung brings up a really good point. If you have manual valves, they only need to be open JUST enough to have the liquid/gas escape. The solenoid valves are full open or full closed, so they are less efficient, but no different than clearing your mask, you only need just enough to displace the liquid.
On the filters, he should probably figure out how to repack since Vanuatu isn't exactly near any convenient places to purchase stuff.... In general I agree that the prepacked ones are easier/nicer/better, but given the location restrictions I think we should stay on helping him repack

 

[rjack321]

@rcontrera can say for sure but I believe the mch6 purge rate is 10seconds every 15 minutes. If you do more than that the fill rate won't align with its specified rate.

 

[SurfLung]

...On the filters, he should probably figure out how to repack since Vanuatu isn't exactly near any convenient places to purchase stuff.... In general I agree that the prepacked ones are easier/nicer/better, but given the location restrictions I think we should stay on helping him repack

 

[SurfLung]

...On the filters, he should probably figure out how to repack since Vanuatu isn't exactly near any convenient places to purchase stuff.... In general I agree that the prepacked ones are easier/nicer/better, but given the location restrictions I think we should stay on helping him repack

Oh I forgot about the remoteness of Vanuatu. You might still get the benefits of Lawrence filters if you can at least get one and then repack it when the blue strip turns pink. I tried this and it works... Dumped out the used 13X and as soon as I put new 13X in, the pink strip turned to blue again. It requires modifying the bottom of the Lawrence Factor filter. A large snap ring makes a good "holder" to back the retainer screen that's already in the filter.

 

[SurfLung]

MCH-6 Charge Rates... SH vs EU
- The Coltri manual has charts for "SH" compressors and other charts for "EU" compressors. My little AeroTecnica Coltri MCH-6 has all its labeling in Spanish so I assume its an "EU" model with the motor running 3000 rpm and the pump 2350 rpm. The actual charging rate is about 3 cfm which agrees with the EU chart. But the "SH" models run the motor at 3600 rpm and pump at 2800 rpm to give a charging rate of 3.5 cfm. These rates are for the Honda gas engines. They also have charts for electric motors running 2800 to 3400 rpms and the fill rates on those run 3.2-3.5 cfm depending on the rpms.

 

[rjack321]

Oh I forgot about the remoteness of Vanuatu. You might still get the benefits of Lawrence filters if you can at least get one and then repack it when the blue strip turns pink. I tried this and it works... Dumped out the used 13X and as soon as I put new 13X in, the pink strip turned to blue again. It requires modifying the bottom of the Lawrence Factor filter. A large snap ring makes a good "holder" to back the retainer screen that's already in the filter.

Those strips turn pink at 40% humidity which is really "too wet" but...

If you really want to approach it this way you can regenerate those humidity indicators with a hair dryer and tweezers. A better humidity target more in line with actual breathing gas standards is to change out the filter at 20% RH.