K14 Elevated CO2

[Agro]

MCH-6 Icon with the 1,800psi PMV and no they don't leak

Yes they do

 

[Agro]

Coltri MCH-6 iterations have been successfully used by a lot of divers over many years and they will disagree with all your angst against Coltri.

I was one of those users. Unfortunately. 4 of 4 Coltis failed within 50 hours. No I ddi not use it "successfully". Not at all. It took a lot of money out of my pocket.

 

[CG43]

Thanks to all who responded to my post # 61 page 7,
especially Thanks A Lot for the link to Bauer general compressor instructions.

The low number of cycles of the Bauer combifilter really surprised me.
I have some experience with pressure vessels from my work as an engineer.
My large tank was a 12 m long heating condenser for a power plant with power/heat coupling.
Despite its 12m length, it had to be able to run 12 cycles per day, which it did.
My medium tank was used for high pressure sterlization of medicines with 5000 bar (73500 psi)
and a cycle time of less than 10 min.
Building a 350 bar filter tank with a high number of cycles is not a big problem.
The Bauer P41and P61 (manual page 45 Fig.29) separator also has a cycle count of 85000
at delta P of 350 bar (5145 psi). At least that's the number I expected for the combifilter.

Then I measured the aluminum separator and filter container of my 44 year old Mohnsam compressor:
Da = 65 mm , t = 7 mm which leads to a tension of 140 N/mm^2 at 300 bar .
I had not expected that much , for aluminum and a high number of cycles this not low .
If I now assume that Bauer also calculates in a similar way then you would do well to stick to their recommendations.
If I have written something else, or that has aroused a different impression, shame on me.

 

[iain/hsm]

Every new compressor I know has at least one separator between stages. Unless Coltri of course.

1. My guess is that the Coltri design engineer has been instructed to reduce cost and has designed the interstage cooling heat exchangers and the cooling coils to run the gas hotter and increase the gas velocity so that that flow faster so they don't strictly need to fit an interstage separator as nothing is condensing out into them and that this has been done to achieve a big valve cost saving.
A similar idea to achieve cost saving could be incorporated also by omitting the BPR regulator. Although It's not the best of engineering principle but it's one heck of a huge cost saving for the sales profit and marketing departments.

Further by not fitting an expensive pressure vessel interstage separator and its expensive additional components and likewise omit the expensive BPR regulator on the MCH-6 and I-Con
You achieve a very cheap build with a massive profit margin you can share with the dive shops and they will sing its praise to the ignorant punter who buys this junk.

Good design doesn't help because it contrasts sharply with the required sales and marketing requirement of making a cheap compressor with bags of profit to share with the retail shops and scuba diving distributors paint ball shops etc and the like.

2. Now the main advantage / reason for not fitting these parts is simply to make a cheaper build and make more money for the folk selling them without loosing manufacturing profit margins in fitting these items is I hope both clear to all and evident. Further why fit them and be more expensive when you can offer them as an optional extra. Its a marketing win win profit all round box of fun.

3. In addition the stupidly small diameter and short stack length filter tower together coupled with a cheaper less effective industrial molecular sieve chemical and the accepted poor short filter chemical life has one hidden advantage.

And answers in part the OP's original question regarding C02 retention (accumulation due to adsorption) and the reason I joined this thread in the first place albeit my mistake for answering the posts backward.

4. Co2 Wash out

Inadvertently a poor filter design coupled with a high "wash out" effect from the lack of a BPR does help in the desorbing of any high C02 concentrations adsorbed in a dry parts of the filter chemical matrix. Change the filters more often make more money for the shops and the numpty buying this junk is as happy as a pig in a blanket.

In addition by changing the oil more often you also have less contamination to measure. Discarding the evidence so to speak.

Further if the compressed air interstage coming off the 1st and 2nd stage is so hot and the cooling fan and housing designed are so poor that nothing that much of the water vapour will condense out from water vapour to into water condensate into the cooling coils to the separators so the question is why bother fitting a separator and adding cost. The folk who sell you this need the profit I accept .

The problem is all the hangers on retailers making it also

Consider this Coltri don't sell you a compressor they make it for the benefit and profit of the scuba shops the importers and the in country distributors they sell them to.
The dive shop you buy it from or retail on line folk also needs to make money and its a very popular product due to the massive profit they make on your purchase dime and dollar.

Now the dive shop also require to milk money out of your further
akin to the parts for life stunt with some regulators so Coltri supply them a more made for profit item than supply a properly designed item such as in the short life throw away cartridges and expensive Oil that requires frequent change. However it appears end user are happy with a 13 hours filter life with no separator and no BPR then great its a win win to those who sell Coltri. The Rabbits Foot of luck and the lucky charm to those too ignorant to know the difference

So as far as Coltri is concerned there is no reason to provide long life filters and oil. But to be fair Coltri have little or no choice but to design a compressor package to create plenty of money to the retail folk for frequent sales in filters and oil.

Note the popularity is beginning to backfire and the new Coltri larger units are getting near and nearer to the Bauer units in design. As dive shops by and large are not as ignorant as the retail market customer for Coltri. Some may disagree as always feel free.

 

[iain/hsm]

The low number of cycles of the Bauer combifilter really surprised me.
I have some experience with pressure vessels from my work as an engineer.

CG43 There is a background to this as with everything else I guess and its the detail that is important.

The above filter is a combination filter/separator its both a water/oil separator in the lower end of the column tower combined with an upper chemical filter element. Frankly Its a compromised design in an attempt to cheapen manufacturing costs. One filter tower doing two jobs, that of separation of water oil condensate and adsorbing of residual water vapour. To address first just the application problems I will detail the filter metallic design in a following post

1. Problem 1. Any and all water condensate left over in time and when the filter tower is idle then any water droplets left over in the lower section will be adsorbed by the upper chemical reducing filter life for no advantage in use. Resulting in a shortened filter chemical life.

2. Problem 2. Further this collection of water and oil over the time the compressor is lying idle develops a stinking smelly stagnant mess.

3. Problem 3. At the lower part of the chemical tower the water adsorbed into the chemical matrix becomes again over time idle a super saturated clump mass into the molecular sieve.

4. Problem 4. This saturate clumps mass becomes over time similar to that of a used cat litter a solid mass of junk

5. Problem 5. Bauer use a particular molecular sieve that has a carcinogenic warning to dispose of safely (when used) in landfill

6. Problem 6. Eventually this inert carcinogenic mass is in fact the binder that creates the molecular sieve "ball" eventually this mass becomes a solid clump mass.

7. Problem 7. When restarting the compressor after a lay off this new solid mass at the lower end of the chemical tower is disrupted up into the dry chemical compartment at some force leaving a residual mess akin to a design that of our British services use for a Wall Breaching Cannon known in the trade as Harvey Wall Bangers

8. Problen 8. Those tempted to use 3rd party plastic cartridges will need a brush and shovel at some point, The reason for which will become apparent sooner or later. Again others may disagree once again feel free