Compressor oil viscosity vs air temperature

[bobbyp10]

If you are running the same compressor in an environment that is 10 degrees Celcius, and then again in one that is 40 degrees, should you use a different viscosity compressor oil?

I run a Coltri-Sub MCH-6 in an area that is generally extremely hot, and often humid. Thus i change my cartridges very often (about 20 hours), Oil every 40 hours, air intake 80 hours.

I have always used an oil recommended and supplied by the company, in this case:
Coltri Oil CE 750, ISO VG 150/220

Is this oil compatable/adequate to use in cold as well as hot environments?

Is there a substitute of a higher viscosity (or at all) which would suit better?

 

[IyaDiver]

Hi Bobby,

Coltri website said the CE750 is synthetic and good for low temperature and year round operation.
Aerotecnica Coltri - Portable Compressors - SYNTHETIC COLTRI OIL CE 750

Bauer also reccomends that hot area of operation or cold one, its synthetic to be used. In fact all new Bauer use the synthetic. I am referring to German Bauer. I know Bauer stuff better than Coltri.


Your filter change interval, its very disturbing. Check if your unit filter capacity, is molecular sieve of 25 grams or not ? This MCH-6 manual did not state the capacity of the molecular sieve :
http://www.coltrisub.it/MAIN/MANUALS/PORTABLE_COMPRESSORS/mch6_manual_ALL.pdf

I have an older manual ( PPS slide version ) that said 50 hours filter life at 20 Celsius but the manual above from Coltri website stated 35 hours at 20C. The question is : Is that ambient and pre-calculated to have final water separator temperature higher by 10-15 celcius or that is the final water separator temperature ?

This filter life subject been beaten quite to death actually and please do spend sometime learning more about it because its about air quality produced.

The best way to find out is the weight of the molecular sieve on your MCH-6.
If it is only 25 grams ( new & dry ) , don't even expect 10 hours of filter life at ambient temperature of 30 Celsius and final water separator temp of say 40 Celsius at pumping rate 100 liters per minute.

Looking at a photo of the filter housing size of the MCH-6 , its surely smaller than a Bauer P21 ( P Zero in USA ) actual cartridge size. Unless yours has some bigger filter ?
P21 cartridge contain 68 grams of molecular sieve ( for non hopcalite cartridge ) and by Bauer calculation, its only 9 hours of filter life under the exact same operating conditions of what I described for your MCH-6..... to pass the breathing air standard by end of filter life.

This is the fact and math behind molecular sieve life :

01. Don't care about ambient humidity where your compressor is operating, it will be 100% humidity by the time air its compressed in your water separator.

02. Molecular Sieve can only adsorb water , 20% of its own weight.

03. Ambient temperature if "X", final water separator temperature will be X + 10 to 15 Celsius higher because compression produce heat and no basic air-cooled cooler can reduce the air any lower than ambient temperature.


04. Assuming water separator can remove 99.5% of water in air, that leaves 0.5% for the molecular sieve to adsorb.

At 40C final water separator temp and surely it is 100% humidity there due to pressure of nearly 120 BAR or so in there, the air will contain approx 50 grams or 50 cc per 1,000 liters of air. So per 60 minutes or 6,000 liters of air pumped thru the MCH-6, the total water content in that 6K liter of air will be 50 grams/cc x 6 = 300 grams of water.

Assuming the water separator can remove 99.5% of water in the air, there will be 0.5% of 300 grams of water getting into the molecuar sieve bed, which is 1.5 grams of water. As far as I know 99.5% efficiency of water removal from a water separator is on the HIGH side. Its OK, we are assuming a better technology of today.

Now we know that "IF" 25 gram of molecular sieve is the capacity on the MCH-6, that means only 20% of 25 grams is what it can handle before its service life expired, that is 5 grams of water only.

5 grams of water capacity divided by 1.5 grams of water produced = 3.33 hours of maximum filter life for the MCH6 based on 100 liters/minute air flow and 25 grams molecular sieve weight.

Now lets look at Bauer calculation on P21 ( P Zero ) filter cartridge life.
68 grams of molecular sieve = 20% x 68 grams = 13.6 gram of water adsorbtion capacity.
13.6 grams divided by 1.5 grams per hour of water into molecular sieve = 13.6 / 1.5 = 9.07hours of filter life. This is about right because for a 200 liter/minute Bauer, this filter life is given at 4.5 to 5 hours at 40-45 Celsius final water separator temperature.

Suprise that the life calculation is so stingy ? , I was too shocked at first but this is a fact unless you have a dew point meter to read air "wetness" down to -50 celsius in order to push filter life to its maximum and while maintaining decent air dryness as per accepted standard you want to follow.

Regards,
IYA

 

[rcontrera]

I have to agree that using the recommended oil is fine in almost every temperature.

However ... I, too, am concerned about your filter change interval. The cartridges are rated for 3000 cubic feet of air in the best conditions. You are pumping between 3100 and 4300 cubic feet through the chemicals (depending on which MCH6 you have). I suggest that you put a moisture eye on the outlet of your filter stack to get a better indication of when to change the cartridge.

 

[IyaDiver]

Hi Bob,

That is Ray the Coltri expert, he knows Coltri very well.
3,000 cubic feet x 28 = 84,000 liters of air under ideal condition
Less 65% = 29,400 liters ( hot ambient temp correction )
29,400 divided by 100 liters/minute = 294 minutes = 4.9 hours filter life, assumed very dry air

So, do adjust filter interval for proper air quality.

Safe Diving,
IYA

 

[bobbyp10]

Great. Thanks for all the info. All very helpful.

Until now i have been using the supplied Coltri manual as a guide for the filter replacment intervals. At 30 degrees they recommend 20 hourly changes. 40 degrees is 12 hours.
I also have been using the factory Coltri cartridges. They are full black with no indicators.
Recently i was given an X-Pendable, Lawrence Factor cartridge which i began using instead. It has the blue indicator tab on the side that turns beige when fully used.
I just pulled it out and had a look. The indicator tab shows that it is finished, full beige.
This cartridge has done 11 hours. Average temp would have been 30 - 35 Degrees.

So this discussion which started about oil (which now seems to be sorted as fine), has led to me learning something else extremely important. I will put a new cartridge in and check every half hour of use to see exactly how long it will last in these conditions.

Thanks very much for your all your input!

Ill post the cartridge time frame results upon completion.

Bob

 

[dryan]

hi all,i have a few questions to ask about my coltri sub mch6 comp and hope someone can help me out here. there is only 60 hours on it and i changed the filter and oil at 50 hour.the problem is i used some old tacky coltri oil and the air has a real bad smell from it.even when it has passed through the filter.i went divin with a few bubbies and they also noticed that the air tasted and smelled real bad. So i changed the oil for clean stuff, took out the filter and let the comp run for some time but the air is still stink.would puttin in a new filter in sort out the bad air problem or would it be more like strippin down the comp for a total clean of pistons ,rings,valves and pipes. hope someone can help. with regards dave ryan ireland.thanx

 

[rcontrera]

Changing oil away from the Coltri supplied stuff isn't going to do anything. You have a filtration problem.

My suggestion is to take the filler hose off the filter housing and wash the inside to get out any oil residue that may have been introduced. Then wash out the filter housing and inspect the inside walls. Make sure that any soap you happen to use to clean the oil get rinsed out thoroughly or you will be tasting it in your air.

It sounds like air is escaping past the o-ring on the outside top of your filter cartridge. make sure you are inserting the cartridge in the right direction. If the o-ring is near the bottom instead of near the top where it is supposed to be, it is upside down and air is bypassing the filter all together.

 

[dryan]

Thank you for the reply ray.As far as the filter goes it is in the correct way and the o ring is sealin good(i think).the filter when i took it out,the bottom felt pad was really yellow brown and the top was clean white but both ends smelt quite bad. is it normal to have a yellow residue on the spring at the bottom of the filter housing.also i ran the comp without any filter with the housing tube open and the air smells bad(like burnt oil. any more suggestions would be greatful.would a new filter sort me out.

 

[rcontrera]

You are going to get a bit of oil/water carryover from the separator and no matter which oil you use, it is going to smell. The air nozzle in the separator just sits a few inches off the bottom and if the collected moisture gets up to it you are definitely going to get a lot of carryover. You just need to blow down to reduce the collected gunk from heading towards the filter tower.

I suggest blowing down more often for shorter periods of time. I know the book says 15 minutes, but I am kind of anal about my air and will blow down every five minutes or so for just a few seconds until the air runs free of condensate.

It is quite normal for the inlet to get a buildup of oil/gunk over time. A good wash out every year or so should take care of that for you. Soap and water can be one of your compressor's best friends ... inside and out!

As for your filter smelling bad on the outlet end, the only way that can happen is if the chemicals aren't doing what they are intended to do or air is somehow bypassing that o-ring. Check the internal wall again and see if there is any gunk or debris or even any corrosion or damage to the wall that would interfere with the sealing of the o-ring.

 

[dryan]

hi ray,im havin problems with my compressor again,i have taken of the forth stage coolin tubes witch had a build up of old oil in it an cleaned it.also took apart both condnsa cylinders ,1 of cylinders,the 1 with the pressure guage it had alot of old smelly tacky oil build up on the walls,so i cleaned it out.put every thing back together with new filter and oil. i seemed to have clean air now comin from it(no oil smell).now i have just under 5 hours runnin time and the air is slowly startin to get smelly again.so i opened up the condsa cylinder and it had alot of emulsion in it.as in several t,spoons full.i have been blown of regular but the emulsion is just lodgin in the cylinder,so cleaned it again and put it back together and guess,smelly air again. the comp is a 2002year model with around 70hours and the oil im usin is coltri but it is also 2002,would oil that old have an effect on the air smell.maybe the piston rings and valves might need lookin at.hope you can help,thanx