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look what I found lurking in my 3rd stage head (MCH5)

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  • #91
    Re: look what I found lurking in my 3rd stage head (MCH5)

    Wrist pin is always an area of very high stress and heat on compressors or engines. Splash lube may be adequate for lube, but does not carry much heat away like pressure lube does , IMO. The compromise of simplicity on a non pressure lube machine.

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    • #92
      Re: look what I found lurking in my 3rd stage head (MCH5)

      I have not read all posts on this thread and so apologize if what I'm about to say has already been covered. I've read enough to understand that we have a guy really diving into his little Coltri in an effort to recover performance. I've read about cylinders, rings, valves and wrist pins and I've read that stage pressures continue to be an issue.

      Has anyone brought up the value of a hand held pyrometer? Not having stage pressure gauges makes things tough, but a pyrometer can be your best pal in many cases. A valve that is not making normal temperature is also not making normal pressure, and the reason will always be either a faulty exhaust valve on the previous stage, or a faulty inlet valve on the cold stage. Unless of course, you have compression issues further down the cylinder such as a ring failure.

      I've spent a good bit of time goofing around with the coltri. They do not make the grade as a commercial duty machine but with proper upkeep I believe they can be a good light to medium duty machine. Good luck!

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      • #93
        Re: look what I found lurking in my 3rd stage head (MCH5)

        Originally posted by revolution cng systems View Post

        I've spent a good bit of time goofing around with the coltri. They do not make the grade as a commercial duty machine but with proper upkeep I believe they can be a good light to medium duty machine. Good luck!
        agreed, but compared to the other options available right now the MCH5 is a rockstar for home fueling

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        • #94
          Re: look what I found lurking in my 3rd stage head (MCH5)

          Using a pyrometer would be a great tool if you kept a temperature log of each stage on a regular basis, like when you change the oil. I would suspect that due to the pressures not being the same in each stage that the temperature would be different on each stage.

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          • #95
            Re: look what I found lurking in my 3rd stage head (MCH5)

            Originally posted by revolution cng systems View Post
            I have not read all posts on this thread and so apologize if what I'm about to say has already been covered. I've read enough to understand that we have a guy really diving into his little Coltri in an effort to recover performance. I've read about cylinders, rings, valves and wrist pins and I've read that stage pressures continue to be an issue.

            Has anyone brought up the value of a hand held pyrometer? Not having stage pressure gauges makes things tough, but a pyrometer can be your best pal in many cases. A valve that is not making normal temperature is also not making normal pressure, and the reason will always be either a faulty exhaust valve on the previous stage, or a faulty inlet valve on the cold stage. Unless of course, you have compression issues further down the cylinder such as a ring failure.

            I've spent a good bit of time goofing around with the coltri. They do not make the grade as a commercial duty machine but with proper upkeep I believe they can be a good light to medium duty machine. Good luck!
            Good statement, you can pick up an infrared tempter sensor fairly cheap. When I was operating stations I would log a daily record of interstage temps and pressures. You can see needed repairs before the become problems.

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            • #96
              Re: look what I found lurking in my 3rd stage head (MCH5)

              20150315_221507.jpg20150315_221205.jpg

              More pictures of the carnage, need some help identifying the brand name of this piston I assume it's a European manufacturer

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              • #97
                Re: look what I found lurking in my 3rd stage head (MCH5)

                Admittedly it is tough to see much on my pbone but I dont see what is wrong with the piston other than needing a new wrist pin.

                I encourage you to take the plunge and check out the big end bearings as well if you are this far into it. Is the bearing surface inside the con rod small end unblemished? You are into it far enough you might a few hundred dollars more will get you close to a complete rebuild.

                Karl

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                • #98
                  Re: look what I found lurking in my 3rd stage head (MCH5)

                  Originally posted by Lakewood90712 View Post
                  Wrist pin is always an area of very high stress and heat on compressors or engines. Splash lube may be adequate for lube, but does not carry much heat away like pressure lube does , IMO. The compromise of simplicity on a non pressure lube machine.
                  I'm not famliar with pressure lubed wrist pin bearings. Is there a nozzle that sprays it with a stream of oil from the crankcase or is there an oil passage running the length of the rod?

                  My bauer is supposed to be pressure lubricated but I didnt see any evidence of my second stage wrist pin having oil delivered under pressure when I put new rings in.

                  Karl

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                  • #99
                    Re: look what I found lurking in my 3rd stage head (MCH5)

                    I was just curious about the pistons origin...there is some scuffage on the piston where the wrist pin sits

                    I have not yet pulled the wrist pin bearing from the small end of the connecting rod so I'm not sure about the surface of this area yet

                    If you look at the second pic. you can see 2 holes on each side of the piston for oiling the wrist pin
                    Last edited by trdscfjc; 03-16-2015, 12:12 AM.

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                    • Re: look what I found lurking in my 3rd stage head (MCH5)

                      This is exactly what happened to me when I experienced my 3rd stage valve failure. The following pics are what was discovered when I took the crankcase down. I agree with Karl, remove the compressor and take er down. At the very least the metal shavings from your wrist pin need to be removed from the bottom of crankcase. If the wrist pin is that badly worn, you will more than likely have a worn 2nd stage sleeve on your crankshaft.
                      2nd stage sleeve damage.JPG

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                      • Re: look what I found lurking in my 3rd stage head (MCH5)

                        Originally posted by trdscfjc View Post
                        Here's another pic for Brit.
                        [ATTACH=CONFIG]4818[/ATTACH]
                        Got the pics, presently looking for tissues. Back in mo' after which you might get some sense out me....

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                        • Re: look what I found lurking in my 3rd stage head (MCH5)

                          The piston is by Gandini, as are the original fitment rings. See: http://www.gandini-industria.it/www/...at_articoli=PC Suspect it will be quicker to order form them direct but with courier costs to throw from Italy in their prices don't look too cheap. I was charged far less for my stuff from my usual supplier.

                          Now at 1300 hours and numerous Anderol cahnges, I too have low pressures on each stage, with my gauges fitted I see 2.5 bar and 24bar at stages one and two, this after replacing just about everything. I have chased my tale on this for ages. New 1st, 2nd and 3rd stage rings, (but I did not hone the bores or gap rings) valves on one, two and three. I found a scored 2nd stage bore at one point, so replaced bore and rings and Gandini piston. Bauer made 2nd and 3rd valves helped but still it is slow. Looking at the 1st stage pressure at 2.5 I thought I should do the reed/ vain valve and the rings. I did each one at a time to see first if it was the valve, and then if it was rings. Neither helped. My thinking was that the low 1st stage pressure was dragging down the 2nd, No change, still 2.5bar. I even have a gauge on my sump. I was reckoning to be putting my red-head on as a next job purely because I have one sitting there (don't ask). Perhaps the third stage inlet valve is dragging down the second??? Logic here has gone out of the window! I do have an infrared thermometer/ pyrometer jobby and it never occurred to me it could be useful here.

                          Unfortuately because I have no idea what the working temperatures should be I am not sure what it would be telling me. Pearls to swine and all that... I think I need a pro on this.

                          Mine has been like this for 150-200 hours but works so I live with it. And I do have the advantage over you all of having a complete new pump sitting there so I am kind of (happier) to tolerate it. Only thing I have not done apart from red-head is checked the mains gas supply pressure. So I feel for you. Mine presently goes through a fair bit of oil - gets caught in the extra coelescing filter I put in prior to the standard Coltri tower filter. I live with this too.

                          I am going to Google pyrometer and compressor faulting now.

                          I would definitely strip down that crankcase. It must be full of nasties.

                          These Coltri's are good bits of kit, ceratinly compared to anything else they are a dream ticket, the problem here is my inexperience.

                          I am seeing nothing close to these presssures
                          https://www.youtube.com/watch?v=f4QZXrgQ018

                          I remain philosophical...
                          Last edited by BritCNGUser; 03-16-2015, 08:40 AM.

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                          • Re: look what I found lurking in my 3rd stage head (MCH5)

                            I recall Ray Contreras being concerned about temperatures rising when a Coltri is installed in a cabinet. IIRC the more free air flow the better the compressor will hold up. It would be worth getting him to weigh in at this point as he seems to know coltri compressors more intimately than anyone on this forum.

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                            • Re: look what I found lurking in my 3rd stage head (MCH5)

                              Hi Brit,
                              You say,
                              " am seeing nothing close to these presssures
                              https://www.youtube.com/watch?v=f4QZXrgQ018"
                              It looks like the compressor in the video is running 80 psi on stage one, 600 on stage two and shutting off at 4000 on stage three.

                              What are your pressures?

                              My bauer three stage runs at 80, 550 shuts off at 3600 so the video seems quite normal in my experience.
                              I will check my MCH 13 today and note the pressures.

                              Are you or Joe running a priority valve? It is a backpressure maintaining valve that maintains a preset pressure on the third stage even if your tank is completely empty. In addition to allowing the floating piston to build pressure and stop clattering in a few seconds, my understanding is that the compressor has a "sweet spot" where the load is balanced on all three cylinders at a specific psi. At low pressures Stage two is doing most of the work and exerting most of the force on the crankshaft and at exceptionally high pressures the third stage is exerting the most force on the crankshaft. There is an ideal pressure where the compressor is experiencing equal loads from all cylinders and putting the least stress on the bearings. I always assumed this was why the priority valve on my MCH 13 is set at 3000psi. In other words, even if I am connected to an empty tank with the compressor running the priority valve maintains 3000 psi on the final stage. ie it won't let any gas exit the valve until it has 3000 psi behind it.

                              I would like to think this is the answer to bearing wear but my initial impression is it only impacts the crankshaft bearings.

                              The only thing I can see damaging the wrist pin bearings would be excessive pressure from a failed intake valve upstream or inadequate lubrication (heat related oil degradation)

                              Ultimately if these compressors need the wrist pin, big end con rod bearing replaced every 1500 hours it isn't that big a deal and they don't cost that much. It would be great if we could figure out an appropriate service interval before rod damage, or crank bearing sleeve damage occurs

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                              • Re: look what I found lurking in my 3rd stage head (MCH5)

                                This is what my wrist pin looked like when I had my issue. Also...these are the service intervals that were sent to me by Nuvair pertaining to the MCH5.
                                Wrist Pin.jpg
                                Attached Files

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