my chinese compressor project
Hi
I bougth a chinese compressor last month on alibaba and I start to modding it. You will find it identical to the on from mrodair.
I have add a water-oil separator between LP cylinder and HP cylinder. I take the time to make a coil that come close to the motor fan. On the high pressure side , I add a big coal filter and a PMV . I have no trouble with the low pressure pumping oïl. I also run a iso 150 oïl like the chemlube 751.
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Because you miss the point that I allready have a refillable cartridge. It is all aluminium that why finding a way to avoid contact with the desiccant is a must , but if I use silica gel, it look to be non corosive so ok with aluminium, the only question I need to find the answer is does silica gel with active carbon and a PMV is enougth for pcp air rifle filtering. I m not going to use it for scuba diving.
Why not just buy the proper disposable filter cartidge… or buy a refillable one.
Or make one that contains the media and is sealed so the air has to go through the media.
Not that hard really….
What about silica gel?
It is non corosive. Should it br enougth efficient for pcp air rifle?
For scuba diving , desiccant should be better for removing humidity but it is corosive.
The sleeve has to be a very precise fit or air wil bypass the desicant media.
If you look carefully at the picture , you will see that I allready have a alluminium cartridge. I just need a sleeve to slip in to protect the alluminium, that why a pvc pipe look cleaver or a ss sleave if there is no probleme with the contact with the desiccant.
A tube wont cut it…. it needs to be encapsulated…. and it should have some sort of seal on one end so that the air has to go into the tube… rather than around it…
I don’t think it would be that hard to make a reusable repack able filter cartridge.
I live in Quebec Canada and I have acces to anything on the web ;p
if pvc pipe is good , i may give it a try. it sound like a good idea! once I find time , i will work on it!
So how about a pvc pipe with felt disc in the ends? Maybe tyvek bag of some sorts?
Oh ok I understand. Where are you located? Do you have access to eBay?
Yes I have read it for the acrylic tube but I don t know where I can find the good size and length!
That why I talk about the stainless pipe!
Guy suggest using a acrylic tube in the first paragraph daoust.
Interesting, but how should I avoid direct contac of desican with the alluminium? Maybe a stainless sleave?
If I can find a way to have no contact with the aluminium I will follow your tips
For the oil water separator, if they are run on the oposite side ( in become out and out become in) without the check valve, maybe the silica gel will work better? But I don t want to remove the check valve as I belive it help the engine alot! Less back pressure =Less work = less amp!
It will be on my improve list , next step will be the intake air filter with a custom brass head. Why brass , because this is what I have and also it is better for heat transfer.
To do list
Air filter
Custom brass head
25a overload reset button
PMV
Desican filter mix with active carbon
Done list
Power cable 12-2
Rocker switch 30 amp
Hours meter
Second water oil filter
Big filter tower
Non return valve
5/16 coil
Side panel remove
More fun modding it thant use it lol
Yes, I would replace 2/3 to 3/4 of the activated carbon with X13 molecular sieve. I’d encase all the filter material in an acrylic tube to minimize direct contact with the aluminum pressure wall. A felt pad to separate the desiccant from the activated carbon. Weigh my new “filter cartridge” and use until the mass goes up by no more than 18-20% of original mass of the molecular sieve. At that point the desiccant is nearing it max effective capacity that will keep RH% less than 30%. Look at the curve for desiccants below and see where it bends and starts to flatten. You want to stay away from the flat part because the RH% will climb fast for just a small amount of additional usage. For molecular sieve, 20% gain in mass is near top of curve’s bend. You want to stay below that point.
from https://www.sorbentsystems.com/desiccants_charts.html
I don’t think the minuscule amount of silica gel you can get in the water separators is adequate in volume. By the time you do the first bleed of each separator the desiccant in that separator is completely spent. It gets overwhelmed because the desiccant is at the wrong step in the water removal process. Each stage makes it possible for the next stage to either perform better or last longer. The later stages do removal that the prior stages cannot achieve.
1 Interstage separator: Removes water that can be condensed from pressurizing and cooling 1st stage output. Output RH is 100% for its temperature and pressure, but capacity is unlimited. (assuming you bleed the separator before condensed water gets to output)
2 Final separator: Removes water that can be condensed from pressurizing and cooling final stage output. Output RH is again 100%. It can’t make it lower than 100%. Capacity is unlimited.
3 Desiccant: Absorbs water vapor to drive RH% below 100%. Unlike separators, a desiccant can drive RH% below 100%. ideally. the desiccant drops RH% down to 40% or lower. However, desiccant capacity is very limited – only about 20% the desiccant mass of water can be absorbed. Desiccant is easily overwhelmed if mechanical water separation has not preceded the desiccant. Hence, the importance of the prior separators removing the bulk of the water. It makes no sense to put desiccant in front of separators. That would waste desiccant capacity absorbing water that could have been separated instead of absorbed.
Choice of desiccant material matters. If RH% target is lower than 40%, molecular sieve has a huge advantage of silica gel in absorbing capacity / gram of desiccant.
Direct contract of desiccant with metal pressure walls is avoided because the chemical processes include production of corrosive products. Corrosion of the pressure wall or threads is undesirable.
4 Activated Carbon: Adsorbs hydrocarbons from air if RH is 50% or lower. More effective if RH% is even lower. Limited capacity mean the compressor must not put tons of oil through the system. The water separators remove some of the oil, but a well functioning compressor should limit the amount of oil blow through. If RH% goes too high, activated carbon may release previously adsorbed hydrocarbons and you quickly foul your tank with water and oil that was once trapped in the filter. This is another reason to replace the desiccant media early enough (before reaching 20% mass increase)
5 PMV: Prevents air flow until pressure increases to where separators and desiccant are at highest efficiency. If filling a system from low pressure, the initial portions of air flowing through the compressor won’t undergo as complete mechanical separation. That loads the dessican with more water vapor to absorb. As pressure builds, the separators become more efficient. A PMV causes more of the filling cycle to be done at higher separator pressures so more water can be removed. Without a PMV, the gradual filling of a tank from low pressure also gradually alters the efficiency of the separation. A PMV simply forces things to be efficient from the get go. If topping off an already pressurized tank, a PMV is less necessary because the back pressure of the tank does the PMV’s job. Filling an air rifle reservoir doesn’t give you that back pressure effect due to the gun’s fill check valve.
PMV also balances mechanical load of the pistons.
Yes the big air filter is active carbon only 60g. I have 1 small desican beads in each oil-water separator. Is it good like that?
If it is not enought I can remove 40g of active carbon and replace by desican first step and active carbon 20g second step
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Looks at the graph at the 20% humidity level. Silica gel should work, but you can only use it until it increases in mass by about 10%. Above that, your humidity level is going to be too high. It’s the higher absorption capacity at lower humidity levels that gives molecular sieve an advantage. If you can reliably change out the silicon gel on a frequent basis, I think you would get away with it.You can weight your initial silicon gel and cartridge masses. Once the cartages gains a mass equal to 10% of the original silicon gel mass, is time to replace the silicon gel.
I would still want to isolate silica gel. There is still conversion of atmospheric CO2 to carbonic acid at the high pressure and moisture. Some o-ring grooves and o-rings should let you achieve a seal for your “cartridge”
Dmann111 has good cartridge based filtering price down to something proportionate to the compressor price. The Alpha shifts the price point considerably more.