MCH6 Filter lifetime

[oxyhacker]

Lawrence Factor gives the efficiency of mechanical separators as being between 80% for a simple hole-in-tube style to 90-95% for one using a sintered element, up to 99% for the latest, top-of-the-line LF product. I believe Coltri still uses the hole-in-tube method. So the situation may be even worse than you describe.

Think about it, assuming water separator can remove 99% of water. At 45C final air temperature, one empty 80CF tank will need easy 2,000 liters of air. At 45C, water content is 65.65 x 2 = 131 grams or cc. 99% removed by water separators, you still have 1.31 grams of water. That 1.31 grams of water per tank will soak your 25 grams MS in no time.

BTW, in the absence of a PMV, if the whip has a needle valve on it it is possible to get the same effect by simply manipulating the needle valve to maintain the desired backpressure. It's actually much easier than it sounds, and doesn't require constant fiddling.

 

[h90]

H90,

No PMV ? Holy Cow !!!

25 grams is too little and surely never 10 hours life at 30C ambient.

Here is how Bauer calculate the filter life and this is assumed the PMV is set at 2,000 psi or 136 BAR:

Volume of air which can be processed:
Va [m3] = 0,2 x mMS [g] / (X [g/m3] / p [bar]) = 0,2 x p [bar] x mMS [g] / X [g/m3]


So for your Coltri MCH6 with 25 grams, its like :
{ 0.2 x 207BAR x 25 gram } / 65.62 = 15.77 cubic meter or 15,772 liters

If your compressor is an 80L per minute model, so its 15,7770 / 80 = 197 minutes

0.2 its the water holding capacity of molecular sieve
207 BAR is tank pressure of 3,000 psi
25 grams is what you said your filter capacity for the molecular sieve

65.62 is the water content in grams for 1,000 liter of air at 100% humidty at 45 Celcius. It is always a 100% humidity when the compressor compressed the air. Always add 15C above ambient as final temperature at final water separator or filter housing if the filter housing is a combo of water separator and filter housing.


Final Temp at filter Housing >> Water Content in grams per 1000 liters of air

40.0C >>>>>>>>>>>>>>>>> 51.21
41.0C >>>>>>>>>>>>>>>>> 53.83
42.0C >>>>>>>>>>>>>>>>> 56.57
43.0C >>>>>>>>>>>>>>>>> 59.43
44.0C >>>>>>>>>>>>>>>>> 62.41
45.0C >>>>>>>>>>>>>>>>> 65.52
46.0C >>>>>>>>>>>>>>>>> 68.75

Molecular sieve only adsorb water 20% of its own weight. Some say 23% but 20% is better because the air need to be very dry to pass proper air standard. So your 25 grams of MS can only adsorb 5 grams of water or 100 drops. This is why water separators and PMV is soooooooooooo important.


PMV is important because it allows the air to be kept at 136BAR ( assumed 136 BAR setting ) constant in the filter housing before releasing it to the tank. Many Americans called PMV as Back Pressure Valve. LF call it Priority Valve, all the same thing.
Not only PMV allows the media which is the dryer aka molecular sieve and the poison adsorber which is the activated carbon to have more contact time with air aka dwell time, it also allows simple physics to work. Increase in pressure, the air hold more water. So by allowing 136 BAR pressure built up in small filter housing, the water separator facility at the filter housing ( assumed it is a combo filter+water separator ) can remove more water from the air due to the higher pressure.

Without a PMV, to reach 136BAR for a 80CF tank at 80 liters per minute, it will take approx 17.8 minutes. In these 17.8 minutes, your filter media would be very wet fast. If a filter housing is say 1 liter volume, to reach 136 BAR at 80 liters per minute it only need like 102 seconds and only 136 liters of air in it. So, one can remove water from air efficiently since the filter housing is always at high pressure. I don't thing anyone knows how efficient the mechanical water separator is to the exact percentage but some said its like 98-99% efficieny of water removal capability. The way Bauer calculate its filter life, it seems they use approx 99.4% as water separator ( two water separators ) water removal efficiency

Think about it, assuming water separator can remove 99% of water. At 45C final air temperature, one empty 80CF tank will need easy 2,000 liters of air. At 45C, water content is 65.65 x 2 = 131 grams or cc. 99% removed by water separators, you still have 1.31 grams of water. That 1.31 grams of water per tank will soak your 25 grams MS in no time.

Do you know what Bauer P21 filter of 68 grams MS reccomends at 45C final temperature, its only 4.xx hours at 200 liter perminute at 200 BAR or 20 tanks of 80CF empty.


Now, depending on your filler whip/hose design, without a PMV and without some sort of shut down valve at the filler Yoke, when you change tanks and have to remove the air from the hose, you may end up removing air from the entire filter housing. I am not familiar with Coltri. In a Bauer filer whip, it has a special valve which remove only the air at the yoke and not the hose. Less than 50cc of air at 1 BAR or at the most 10 liters of air at 200 BAR. Also Bauer always has a PMV at the output of all their filter housing. I am not suprised Craig was stunned that in this day and age, a compressor manufacturer can be so cheapo by not providing a PMV which is only like US$75 or so for American type PMV on a near US$3,000 compressor

Again about this PMV thingy.
If a PMV is set properly and installed, the life of the filter housing will be longer, because it will be 140-207-140 BAR pressure cycle. If there is no PMV and a user get to cycle the filter housing 0-207-0 BAR for every tank change, the filter housing which is a pressure vessel will be much shorter lived. If I see Bauer pressure vessel life, typically it can be reduced by 60%+ if 0-207-0 BAR is the pressure cycle, compared to 140-207-140 BAR pressure cycle.

Good luck maintaining your baby Coltri.

IYA

Well the Coltri sells at 1500 Euro (approx. 2000 USD) in Europe. I bought a PMV. I first set it to 100 bar, now to 120 and when it compressor is well run in I set it to 150 bar.
When filling I had the aircondition running and could get the temperature down to estimate 28 degree but relative dry air and filling 2Tanks 15 liter 300 bar gave me approx. 0.1-0.15 liter water from the separator. Beside the built in fan I let an additional fan blow which helps a little. Estimate temperature of the separator outside 35-45 degree (specially at 200-300 bar range everything get warm).
Later I'll add an additional small filter. There is enough place to almost double the air filter diameter, don't know why they didn't do that.
For me amazing is that they didn't add a heat sensor, which shut down the motor when the compressor overheats (or when there is low oil and it overheats). That cost nothing but adds a lot safety.
In general it looks very retro, like a 1960s design with some nice painting...

 

[oxyhacker]

If you mention it to Coltri they will tell you most of their customers are more interested in a compact, lightweight machine, than long filter life. I don't believe this myself - I think if people realized how marginal the current filter is they would demand something better. Increasing the diameter of the housing just a little would double the media capacity, which would be a major improvement. One of the irritating things about filter cartridges is the small ones all seem to cost about the same, whether they are the little Coltri, which is good for 1800 cf or the "short" 1 lb. Mako-style cartridge (which has become pretty much become the standard cartrige for generic housings) which is good for 12,000. Around here they both cost about $35.

Oh, here is a chart from LF I haven't seem before.

Later I'll add an additional small filter. There is enough place to almost double the air filter diameter, don't know why they didn't do that..

 

[h90]

If you mention it to Coltri they will tell you most of their customers are more interested in a compact, lightweight machine, than long filter life. I don't believe this myself - I think if people realized how marginal the current filter is they would demand something better. Increasing the diameter of the housing just a little would double the media capacity, which would be a major improvement. One of the irritating things about filter cartridges is the small ones all seem to cost about the same, whether they are the little Coltri, which is good for 1800 cf or the "short" 1 lb. Mako-style cartridge (which has become pretty much become the standard cartrige for generic housings) which is good for 12,000. Around here they both cost about $35.

Oh, here is a chart from LF I haven't seem before.

Well, both from the space and weight it wouldn't really make any difference if they increase the filter size and add a PMV. They could even call it "Air+" and charge 200 USD more for it. The same price might be because the material in the filter costs almost nothing. I just bought 1 kg Molecular Sieve and 500 Gramm Activated Carbon and paid a 20 USD for it.
Thanks for the chart, it looks good. It is about 1/2 to 1/3 of the recommendation from Coltri.

 

[rjack321]

I think if people realized how marginal the current filter is they would demand something better.

I actually reported Alkins to the US consumer product safety commission for so blatently lying about their W31 compressor's filter capacity (its about the same size as the Coltri with a similarly 3x inflated rating). I got a form letter back and it wasn't pursued.

I use the stock filter as a "prefilter" and have a 12,000cf LF as a "backup". I have taken the compressor on the road with just a triplex filter in the supplied cartridge. But I only used it maybe 3 hours in 60F weather so I was confident it was still filtering well.

 

[h90]

I actually reported Alkins to the US consumer product safety commission for so blatently lying about their W31 compressor's filter capacity (its about the same size as the Coltri with a similarly 3x inflated rating). I got a form letter back and it wasn't pursued.

I use the stock filter as a "prefilter" and have a 12,000cf LF as a "backup". I have taken the compressor on the road with just a triplex filter in the supplied cartridge. But I only used it maybe 3 hours in 60F weather so I was confident it was still filtering well.

You are right. Usual customer might trust what the guide book tells. I would have trust it, if I wouldn't had to wait 3 month for it and spent my time waiting on reading about it. By the way guys thanks a lot for all the help and informations so far.

 

[oxyhacker]

If you are fearless, and creative, and good with your hands, there is a $50 Parker hydraulic accumulator on ebay similar to the one some of us have made into media stacks for our compressors. Item 2730522.

To use it on as a filter you have to clean it, make adaptors to go from the AN (aviation) threads on the accumulator, and make preforated plates, one spring loaded, to hold the media. See:
Untitled Document

I hope to find somewhere on and old filter which I can add, but that will need a while....

 

[h90]

If you are fearless, and creative, and good with your hands, there is a $50 Parker hydraulic accumulator on ebay similar to the one some of us have made into media stacks for our compressors. Item 2730522.

To use it on as a filter you have to clean it, make adaptors to go from the AN (aviation) threads on the accumulator, and make preforated plates, one spring loaded, to hold the media. See:
Untitled Document

I thought of buying this: Bristol Channel Diving: Personal Filter & Cartridge Assembly
putting it between my Filter and PMV should be good enough, I hope.

 

[Peter_C]

I thought of buying this: Bristol Channel Diving: Personal Filter & Cartridge Assembly
putting it between my Filter and PMV should be good enough, I hope.

Ummm...NO!

Try more like this one. I got lucky and paid $35 for it
Purification Chamber

Once in a while someone on The Deco Stop or here sells filter towers.

 

[h90]

Ummm...NO!

Try more like this one. I got lucky and paid $35 for it
Purification Chamber

Once in a while someone on The Deco Stop or here sells filter towers.

Well that's a bit of an overkill for my small amount of tanks and small compressor