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    What would make the temp go up on the 3rd and 4th stage. After running for 120 min the 3rd stage temp is 95c and pressure of 800psi this is on the output side before the cooler and used to be around 60-70c. Input temp to 3rd is 46c. 4th stage input after cooler is 53c and output 105c at 2200psi. Used to be 95c. 4th stage does not seem that high to me but 3rd stage temp has taken a big increase in temp. The output temp on the 3rd and 4th is about the same now. Compressor has about 200 hours on it and using clemlube 751. Open to all ideas.

    Ron

  • #2
    Make and model of compressor ?

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    • #3
      Have been told it's a coltri clone.

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      • #4
        This is the Chinese mch6 clone iirc.

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        • #5
          If this is a natural gas compressor, which I'm assuming it is I would say from what you told me that the 3rd stage discharge valve is out. I call stuff like this all the time at work and I can tell u from experience that typically the hotter valve cap is the one that is out. We usually verify this with ultrasonic and high frequency vibration traces

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          • #6
            Is this valve in the 3rd stage? There seem to be 2 valves, one at the top of piston of the 3rd stage and one at the input line at the 4th stage from the 3rd stage.

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            • #7
              You are really going to need to get to know what compressor you have and get yourself a manual with a parts breakdown. Every manufacturer has similar but different designs of valve placement and/or styles.
              Ray Contreras
              CompressorStuff.com

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              • #8
                Here is a picture of my compressor drawing CNG X100.pdf drawing CNG X100.pdf drawing CNG X100.pdf

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                • #9
                  It is a given that you are going to need to do valve maintenance periodically. It sounds like it is time for you to disassemble and inspect the third and fourth stage valves. You can likely clean them and lap the sealing surfaces using some 600 grit wet dry sandpaper on a piece of glass.. If you don't have spare valves now would be a good time for you to procure some.
                  It is not a question of "if" you need to renew/replace the valves, but "when".

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                  • #10
                    From your drawing, it looks like a knock off of the Coltri MCH6 compressor. And we have a 100 hour kit for it that includes the valves, springs, plates and gaskets for the 2nd, 3rd and 4th stages. At 500 hours, we also include the first stage valve plate and gaskets. But I don't suggest investing in a Coltri kit unless you know FOR SURE that the parts are exactly the same. It would better for you if you got the parts from your dealer. Like Karl already said, clean/lap your valves. Also REALLY inspect the springs as they will usually be the first thing to fail. And a piece of broken spring floating around in the system can do a TON of damage.
                    Ray Contreras
                    CompressorStuff.com

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                    • #11
                      Remove the 3rd stage head was not much carbon build-up but did have a lot of oil and crud on it( see picture. Lap the valves and reassemble, runs the same as before. Had a new piston for it and was going to install it but wrong size. Cylinder is 19mm piston is 20mm. Notice the gauge for stage 2 seems to varies about 150psi (needle of gauge bounces around) when compressor is running but has done this when it was new. Also after compressor shuts off and before I open valve the pressures on stages 2,3 and 4 stay up. The pressure for stage 1 goes to zero almost right away. Is this normal?
                      Last edited by janbo; 07-03-2016, 02:55 PM.

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                      • #12
                        From the valve photo, it looks like you definitely have a heat problem since it is all cooked/gunked like that. It can also mean you have an oil problem that allows cooking. Make sure you are using the right stuff and not something that somebody told you "is just like ..." As for the parts sizing, that can be a problem for you since this is a Chinese copy of the Coltri MCH6. Unfortunately you are going to be forced to deal with the Chinese on that. The gauge fluctuations are pretty normal since a piston pushes out and sucks in and that is what is being indicated. Most companies put silicone or glycerin filled gauges on there to slow the needle down. And pressure on the first stage will slowly bleed down normally on the MCH6 since the valves are carbon fiber. But, since we don't know what the Chinese are using for valves, it could just be normal.

                        Oh ... and on the PM I answered ... ignore that since I answered before coming here and refreshing my old man's memory.
                        Ray Contreras
                        CompressorStuff.com

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                        • #13
                          What is the size of the 3rd stage piston in a Coltri MCH-6?

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                          • #14
                            As of last year, Coltri shifted to only selling the 3rd stage as a kit ... piston, rings and cylinder. I am out of stock at this time so I can't measure one for you.
                            Ray Contreras
                            CompressorStuff.com

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