Buying a compressor

[rjack321]

The smaller coltri's (among others) are not rated for continuous service.

My Alkins is continuous rated and seems to run quite cool. The only intercooler getting "hot" is the start of the 1st to 2nd stage cooler. While it gets pretty hot, the latter portions of that tube are fine.

I have some supplementary fans on it for summer use.

The primary is repackable and I have a jug of that media. I keep one spare secondary filter on my shelf at a time. They last me 6-9 months.

 

[pescador775]

What really ruins a compressor is low oil or not running them. When they sit the oil drains down over time and leaves upper parts un-protected from corrosion, and when you do start it up you have metal on metal wear. I run mine once a week for 1 hour during the low demand seasons. (Winter)

A Bauer can sit for years without damage as long as it is out of the weather and covered with a sheet. However, Bauer third and second stage (Junior) valves are encapsulated, therefore replaceable as a unit, and, moreover, subject to corrosion. I don't know why Bauer don't make them from inconel or stainless but that is the way it has been. Lately, the exhaust valves seem to last longer than before. Perhaps, they have been improved. Anyway, the point is that water laying in these valve capsules can corrode the springs, and the valve or valves will lock up tight. This problem can be put off indefinitely if the water is expelled by running the unit under no load. Just run it 15 sec with final filter drains open after the last tank is filled. That does the trick.

I understand that cartridges are time stamped but I don't know why. If the cartridge is in a sealed container it should last for many years. If this were not so, then the individual chemicals would be time stamped and they are not.

 

[rjack321]

I understand that cartridges are time stamped but I don't know why. If the cartridge is in a sealed container it should last for many years. If this were not so, then the individual chemicals would be time stamped and they are not.

So you buy more?

 

[rcontrera]

Neither the Bauer Junior nor the Coltri MCH6 are rated for continuous run. The reason is the small size of the oil sump, the bodies being made of aluminum allowing fast heat up and the size of the cooling fins on the heads. Alkin has been able to get away with saying theirs is continuous run since they started with a low pressure cast iron compressor body that has more of a sump than the other two. Additionally, since they have had to make different heads, they had room to put the large cooling fins.

Now, as far as having your compressor sit for a long time ... any time you will have it shut down for more than a couple of weeks, it is best to prepare it for storage. To do that, remove the inlet filter, open the drains wide and run the compressor to blow out any accumulated moisture. Then SLOWLY pour about a cap full (about a tablespoon) of oil directly into the air intake and let it run for about six to ten seconds and shut it off. That way you are lubricating the top end of the cylinders so the rings don't rust. Now, wipe down the filter housing, put the inlet filter back in and cover it up!

If you have been running it for a long time (say over the summer) and have not changed the oil before putting it to bed, you may want to do that...change the oil that is. Any moisture that has become emulsified in the sump will settle out over time and sit on the bottom plate causing corrosion in that one spot. Although minor, it is still best not to allow any corrosion to take hold in your air system.

 

[pescador775]

Neither the Bauer Junior nor the Coltri MCH6 are rated for continuous run. The reason is the small size of the oil sump, the bodies being made of aluminum allowing fast heat up and the size of the cooling fins on the heads. Alkin has been able to get away with saying theirs is continuous run since they started with a low pressure cast iron compressor body that has more of a sump than the other two. Additionally, since they have had to make different heads, they had room to put the large cooling fins.

Now, as far as having your compressor sit for a long time ... any time you will have it shut down for more than a couple of weeks, it is best to prepare it for storage. To do that, remove the inlet filter, open the drains wide and run the compressor to blow out any accumulated moisture. Then SLOWLY pour about a cap full (about a tablespoon) of oil directly into the air intake and let it run for about six to ten seconds and shut it off. That way you are lubricating the top end of the cylinders so the rings don't rust. Now, wipe down the filter housing, put the inlet filter back in and cover it up!

If you have been running it for a long time (say over the summer) and have not changed the oil before putting it to bed, you may want to do that...change the oil that is. Any moisture that has become emulsified in the sump will settle out over time and sit on the bottom plate causing corrosion in that one spot. Although minor, it is still best not to allow any corrosion to take hold in your air system.

I don't know where to start with this. The Alkin sump holds one pint of oil, a trifle more than that of the Junior at 330 cc. The Alkin is very heavy for a portable at 120 pounds. It has a cast iron block which harms heat dissipation (aluminum is far better). However, the sheer amount of metal and the large fins and coolers compensate. Moreover, the Alkin turns so slowly at 1200 rpm, and it delivers air so slowly (actual 3 cfm) that it can be operated continuously, so claimed by the mfgr.

Like the Alkin, the Bauer is a three stage which puts constraints on the performance. Moreover, it is lighter weight and turns at relatively fast 2600 rpm. Also, the output at 3.4 cfm is relatively high which produces more heat than the Alkin. That, combined with the small sump cause Bauer to exercise caution in recommending operational limits. It's sister, the Oceanus has higher output and a 1 quart sump. Its manufacturer claims continuous rating.

The four stage, all aluminum Coltri turns at 2600 rpm and produces 2.8 cfm. In theory, this low output, four stage machine should run cool and deserve to be continuous rated. However, the Coltri has a small sump and uses splash lubrication which puts limits on high rpm safety for the smaller structural components and bearings. Therefore, caution is advised for continuous running.

"Fogging" engines and compressors prior to storage is an old wives tale. Oil changes for these small compressors should be effected at 50 hours. Those are the facts and my interpretation. BTW, here is a worthwhile read, a breakdown on costs of operation written by one of the sharpest pencils around, long banned from SB, Genesis.

http://***************/cgi-scuba/akcs-www?post=9

I guess you'll have to type in scuba forum dot org. SB doesn't like this rival.


Pesky

 

[captain]

I don't know where to start with this. The Alkin sump holds one pint of oil, a trifle more than that of the Junior at 330 cc. The Alkin is very heavy for a portable at 120 pounds. It has a cast iron block which harms heat dissipation (aluminum is far better). However, the sheer amount of metal and the large fins and coolers compensate. Moreover, the Alkin turns so slowly at 1200 rpm, and it delivers air so slowly (actual 3 cfm) that it can be operated continuously, so claimed by the mfgr.

Like the Alkin, the Bauer is a three stage which puts constraints on the performance. Moreover, it is lighter weight and turns at relatively fast 2600 rpm. Also, the output at 3.4 cfm is relatively high which produces more heat than the Alkin. That, combined with the small sump cause Bauer to exercise caution in recommending operational limits. It's sister, the Oceanus has higher output and a 1 quart sump. Its manufacturer claims continuous rating.

The four stage, all aluminum Coltri turns at 2600 rpm and produces 2.8 cfm. In theory, this low output, four stage machine should run cool and deserve to be continuous rated. However, the Coltri has a small sump and uses splash lubrication which puts limits on high rpm safety for the smaller structural components and bearings. Therefore, caution is advised for continuous running.

"Fogging" engines and compressors prior to storage is an old wives tale. Oil changes for these small compressors should be effected at 50 hours. Those are the facts and my interpretation. BTW, here is a worthwhile read, a breakdown on costs of operation written by one of the sharpest pencils around, long banned from SB, Genesis.

http://***************/cgi-scuba/akcs-www?post=9

I guess you'll have to type in scuba forum dot org. SB doesn't like this rival.


Pesky

Carl had a world of knowledge, too bad he got banned, it's the board's loss.

 

[pescador775]

I made some errors (literati call these errata). About non-continuous rated portables; the Bauer Junior produces 3.0 cfm @ 2300 rpm, not 3.4 @ 2600; so, it jams the same as the slower speed Alkin and a tad more than the 2600 rpm Coltri. The Bauer Junior sump holds 360 cc, not "330", and it is splash lubricated.

The Oceanus produces 3.9 cfm @ 2300. It is pressure lubricated and the sump holds 1 liter, about. It is continuous rated.

I think that covers it. See link for Bauer Junior performance stats.

http://www.bauerpaintball.com/Products/playerSeriesJRIIPB_G.htm

PS: I don't know why they decided to publish the actual figures instead of the inflated numbers given to the SCUBA crowd. Maybe it is more hazardous to lie to paintballers? The PB version is the same engine and block, nothing different that I am aware of.

 

[rcontrera]

"Errata" is easy to understand for the Coltri machines as they have no set speed. In the MCH6, the speed ranges from 2240 RPM to 2800 RPM depending on the motor/engine supplied. I was at ColtriAmericas a couple of weeks ago for training and the single phase electric 115VAC compressor was spinning at about 2244 RPM and put out about 2.8 CFM while the gasoline engine, at full throttle ran it at 2815 and put out about 3.5 CFM or there abouts as it kept fluctuating as the engine hunted a bit under load.

And you are completely right ... they should be rated as continuous since I do have a dive shop (actually a wrecking yard with a dive department) that runs off one of the little electric with a two bottle cascade system. However the "official" word is to run for a while and let it cool down.

I am sure that you can get away with a LOT more than the compressor companies say you can if you pay attention and know what it is you are doing.

 

[Hoosier]

Based on my records (I record all activity), Alkin only put out about 2.8 CFM, not 3.2 CFM. I don't know how to measure RPM.

 

[rjack321]

I get ~3.1 cfm out of my Alkins. Definately not 3.5, but more than 2.8

With compressors this small, using the condensate drains seems to have a significant influence on your pumping rate. I use a timer set at 17 mins and vent just enough to see little moisture. Helps to be in a cool climate.

2 fans help keep them heads cool.