Hi there. I'm out on the boat diving and the compressor Coltri MCH6 is acting up. I'm hoping to get some information on trouble shooting so maybe I can do something about it.
The issue is that it is only getting up to 190 bar and after I stop a lot of SMOKE comes out at the air intake for a few minutes. It's really like a compressor oil mist.
I imagine one of th check valves (those little metal plates) on each stage is not setting right and the pressure is sipping back. Or could it be something else?
Is it worth opening up and trying to sand the plates clean?
Any help is appreciated as I'm very far from any dive shop. Cheers!
I'm probably not the best person you want to hear on a forum post about the Coltri MCH 6 but as the Coltri fan boys and the Coltri rep are nowhere to be seen here goes.
I don't like the Coltri MCH 6 for breathing air scuba applications it's poorly designed for diving applications and better suited for the air gun and paint ball applications. Non the less:
You have a problem in both the symptom and in cause going on here. If the smoke as you put it is indeed oil mist and assuming that if it were smoke you would smell the burnt oil an acrid smell/taste at the back of your throat. The cause is hopefully just your air intake filter being saturated with oil cos you're running the pump on a yacht on a rolling deck. Or it's more in cause and that would be a 1st stage valve plate reed valve not seating back onto the 1st stage valve body plate.
An air intake filter and the 1st stage kit2-6-01-008/r should work out OK to kick off repairs so far.
Then take out your air intake filter element out of the filter can and smell the element for oil would also be useful task to do and also check its not soaking wet from either spray salt water or condensate rain etc. This will clog up the pleated paper element and bits of wet paper will break off and get under the 1st stage reed valve lifting it up and off the valve plate and causing the oil mist blow back and damaging all the other valves and pistons in the 2nd 3rd and 4th stages in the process. Make sure to make a judgement call by inspection that the paper hasn't dried out before you inspect it.
Now if you ever look at a proper HP compressors for breathing air on a boat you will find the inclusion angle is over 50 degrees compared to your allowable 5 degrees and the air intake element is alway a 7 micron polyester element in a properly designed marine compressor and never a dense paper pleated element.
Also note that the Marine Polyester elements don't degrade in damp or wet or marine conditions and cannot block or reduce the air intake air flow like these cheap Coltri paper ones do.
2. Also note that the Coltri MCH6 cannot be used for breathing purposes on an incline of more than 5 degrees and as such are not suitable running on a rolling deck with both pitch and roll considerations further depending on the orientation of the pump to the keel it could be OK in pitch but not roll or OK in roll but not pitch you can't have both.
3. You will also need a spare cylinder head cover gasket.
4. Check the 4mm ID 7mm OD PVC clear tube 1st stage head oiler is clean and clear
That about covers the air intake problem cause of the MCH6 on a yacht.
Damp or water blocks up the fine paper element and increases suction load this in turn reduces air intake flow and starves the upper cylinders and pistons of air. Then the compression ratio goes into orbit and the interstage heat increases exponentially interstage. The fan assisted cooling coils can't cope with this increased heat so the approach intake temperatures on the intake side of the remaining stages increase to the point of overheating the oil on the discharge side of the valve. You have no RTD on the Coltri MCH 6 to protect you from overheat and so the result is a burnt sticky discharge valve on each of the upper stages that on each stage starts to blow back air and you're left with in effect an overheated two and a bit stage compressor than a four stage. This is your effect that the compressor can't get much above the 3rd stage pressure hence your ever reducing discharge pressure as this problem continues.
Now there are other factors with the MCH-6 especially the problem with the crank attached pin 4th stage piston design and the con rod bearings going from an old design to a new design then back to an old design. When again all the other quality brands heck even the junk pumps from China and Turkey use a floating piston design.
More in depth detail in another post if I don't get in too much trouble from the Coltri fan boys for this one. Iain
