Moisture separator

[oxyhacker]

Sorry, I had assumed from the MCH6 that is was a Coltri, but it's an Aero Sub, and they use a two little canisters instead of one bigger one. Nothing like a photo to cut through the confusion. I seem to recall the cartridges may be even a bit shorter than the Coltri ones, a scary thought indeed.

Since you already have a decent larger cartridge, which will last longer, do a better job, and be cheaper to operate, I'd keep the two stock separators, and get rid of the two media stacks that the previous owner tried to turn into additional separators. You can probably sell them since people are always looking for filter stacks (or they could be turned into separators) or small filters to make portable travel filters out of. Though how practical this would be will depend on whether cartridges are available for it - I couldn't find anyone who lists them but LF may be able to come up with some.

If you still want to add drains to the other the cartridges, since they are all drilled on the side already, I wouldn' hesitate to add another hole, but it should be done right (right size tap drill, done in drill press or milling machine, not freehand, etc).

 

[David Iver]

Sorry, I had assumed from the MCH6 that is was a Coltri, but it's an Aero Sub, and they use a two little canisters instead of one bigger one. Nothing like a photo to cut through the confusion. I seem to recall the cartridges may be even a bit shorter than the Coltri ones, a scary thought indeed.

Since you already have a decent larger cartridge, which will last longer, do a better job, and be cheaper to operate, I'd keep the two stock separators, and get rid of the two media stacks that the previous owner tried to turn into additional separators. You can probably sell them since people are always looking for filter stacks (or they could be turned into separators) or small filters to make portable travel filters out of. Though how practical this would be will depend on whether cartridges are available for it - I couldn't find anyone who lists them but LF may be able to come up with some.

If you still want to add drains to the other the cartridges, since they are all drilled on the side already, I wouldn' hesitate to add another hole, but it should be done right (right size tap drill, done in drill press or milling machine, not freehand, etc).

So the first two with drains are the separators (one long and one short), and the other two (also one long and one short) are the filter stacks? There were no cartridges in any of them, but I had assumed that the small Coltri Sub filter cartridges would fit either the longer or the shorter of the vessels. What are the dimensions of the Coltri Sub cartridges?

 

[oxyhacker]

Sorry, no Coltri cartridge handy to measure. A call or email to Lawrence Factor should get the answere.

It seems unlikely that the Aero Sub could have two different sizes of media stacks, so one would assume that the two short ones are separators and the two long ones media, or vv. On the Coltri (whose stacks, BTW, look almost identical to yours) the short ones are separators and the long ones are media, and this would be the logical way since you don't need as much height for a separator.

You ought to be able to tell which is which by in what order the stacks were plumbed since a media stack will always be after the separator, never before. One would expect one separator on the second or maybe third stage, and the other after the final high pressure stage, with the two media stacks in series after it, but anything is possible.

So the first two with drains are the separators (one long and one short), and the other two (also one long and one short) are the filter stacks? There were no cartridges in any of them, but I had assumed that the small Coltri Sub filter cartridges would fit either the longer or the shorter of the vessels. What are the dimensions of the Coltri Sub cartridges?

 

[David Iver]

I finally managed to pull the separator apart, and it was full of marbles too! Isn't there supposed to be a coalescer element of some sort in there? Also, is there any difference between a separator and a coalescer? Or are they just different terms for the same appliance?

The marbles seemed to interfere with the perforated diptube(? not sure if that's what it is called in a separator) that extends up from the bottom cap, so I was thinking of using smaller glass beads (something like .25" diameter) instead of marbles. Would I be better off just purchasing an aftermarket separator instead? Any sources to find one that wouldn't break the bank? I've looked at new ones from Compressed Air Specialties and Nuvair, but the cost as much as a large filter tower. Looked on ebay too, but the only ones I could find are LP service.

 

[pescador775]

Everybody is looking for cheap stuff, particularly filters and coalescers. As a result, they are all expensive. Marbles are used because they will not induce galvanic currents and corrosion. I don't see anything wrong with that but a 2000 psi back pressure valve should be used. Also, the cans have to be drained from time to time, like every hour. The jet tube holes don't do anything unless they can work against a baffle; hence, the marbles, a trick used in equipment built in WWII. If you like, dump the marbles and replace with plastic scouring pads.

 

[David Iver]

Everybody is looking for cheap stuff, particularly filters and coalescers. As a result, they are all expensive. Marbles are used because they will not induce galvanic currents and corrosion. I don't see anything wrong with that but a 2000 psi back pressure valve should be used. Also, the cans have to be drained from time to time, like every hour. The jet tube holes don't do anything unless they can work against a baffle; hence, the marbles, a trick used in equipment built in WWII. If you like, dump the marbles and replace with plastic scouring pads.

I have a back pressure valve on order...should get here before I can get everything else assembled. I'd like to use the existing setup for moisture separation to keep the costs down and since I have a good final filter anyway. What do you think of the idea of using smaller diameter glass beads? My idea would be to get more of them in there. With the marbles and the small I.D. of the separator, it just can't hold that many. Plus, they get jammed next to the jet tube (now I know what it's called).

 

[rcontrera]

The idea behind some moisture separators is to just change direction of the air flow so many times that the water droplets are "flung" to the outside of the housing while others use a "bubble stone" like device to create a water collection point. Either way works. The Coltri standard separator for the little MCH6 is just a deflector in the way of the air inlet and that seems to work just fine.

Marbles force the air to take several different paths up the stack, changing direction and "knocking" the water droplets out of the air. As Pesky said, they are safe, cheap and easy to change out if they get gunked up. The only thing to be careful of is that you don't block the air flow through the chamber. I always just pack an empty filter cartridge with the marbles so that they stay where they are supposed to be.

Now ... as far as the AeroSub filter cartridges ... they are the same OD as the Coltri but two inches shorter. The original design was to have one tower with desiccant only and the other with half desiccant half activated carbon. I am pretty sure that LF still has generic filters for them ... but if you already have external filtration, then the little guys would be just a waste of money.

 

[pescador775]

About the idea of using small glass beads; I don't know, it would be an experiment which holds out the possibility of unintended consequences. Perhaps something will clog up or create too much of a barrier to air flow. As Ray said, the marbles deflect air and induce it to flow in circuitous paths. This causes changes in speed which affect the stability of saturated air causing it to lose part of its moisture load. Moreover, since water droplets do not form easily without collection points or surfaces (think dew) the increased surface area of many small spheres can itself force precipitation. Theoretically, very small glass beads might improve moisture separation and collection over the larger marbles. However, it might also create problems with flow or drainage.