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

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

    As stated earlier (from Carl from L&M) the weak link on the mch5 is the 2nd stage wrist pin.
    Don't know about you guys but I am going to replace the second stage wrist pin and bearing every 2000 hours from now on

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

      Originally posted by BritCNGUser View Post
      The piston is by Gandini, as are the original fitment rings. See: http://www.gandini-industria.it/www/...at_articoli=PC

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

      I remain philosophical...
      i think the above video may be a MCH-10


      the pressure on the 1st and 2nd stage seem high (for a MCH-5), according to ray the MCH-5 1st stage should be 55psi the second stage should be 550psi


      these are the pressures i am reading, and according to ray are spot on for what they are supposed to be.

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

        Originally posted by jthomson View Post
        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.
        J,

        Taking your machine's temperature at each head is a very easy and inexpensive way to help monitor machine health. On our commercial units we do exactly as you suggest - we keep a log of oil pressures, stage pressures and temperatures. we can usually spot a stage 'going down' before it actually fails using these observations. Your comment about temps varying because of the different pressures however is not accurate. a properly operating compressor will be advancing pressure in roughly equal multiples from one stage to the next, and it is this AMOUNT of compression that creates the heat, not the overall pressure. For example, you will create a whole lot more heat going from 5 psi to 500 psi than you would going from 3,000 psi to 3100 psi. So if the stages are doing equal work - which they should be - then the temps are going to be close.

        I completely agree that the coltri is the best deal going right now for home fueling. I've seen some guys get amazing usage from these machines. Good Luck!

        Keith Iaia
        Revolution CNG
        805-238-0624

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

          Keith or ray, can we get confirmation on wether that video is a mch5 or 10? I think it's a 10

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

            I don't want to hijack our man trdscfjc's thread although the bloke may forgive me, my issues look much the same, so we'll feed off each other. I have been following thsi so intently...
            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?
            I see 2.5 bar and 24bar at stages one and two which if I convert to imperial we get about 36psi & 350psi respectively whereas Coltri quote all should see 50psi (3.5bar) and 500psi (35 bar) I am filling to max out at Euro standard of 200 bar (2900 psi) Whatever I see it is way behind that Youtube clip.

            Are you or Joe running a priority valve?
            No, Ray mentioned this in another thread. I think it sounds like something we need. Pretty please, coould you point me in the right direction for one?? I suspect it would have saved my second stage barrel. It was at 800 hours that I started keeping a proper log of pressure-up times and I wish I had done it sooner. A bit 'After tha horse has bolted' and my first tip for a Coltri owner. And I should have got temperatures back then to compare with now too. Now I find myself in the dark. In my case I have changed almost everything, and with all the ring-sets changed, one 2nd stage piston and barrel too, and all 3 x valves-sets, I'm not sure I have anyhtign much left!? I've clearly messed something up. I have been doing very frequent oil changes with Anderol 755 (which is what Coltri supply as Coltri 750) and did my valves and rings before the service interval. All to no avail.

            So waving a pyrometer at this I take it I should be looking for a hotter spot than the rest. Or should I be looking for a colder spot? And having found it is the hot/cold spot a symptom of the problem and the source, or an indication of a problem downstream?

            Mystified is what i am...
            Last edited by BritCNGUser; 03-17-2015, 06:42 AM.

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

              my thoughts are get someone with a coltri that is running right to take head and cylinder temp and stage pressure readings and post them here for base line reference.

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

                Agreed. However I don't think aside from Coltri I know where to get precise info. Temperatrues would have to be measured at say five minutes from cold etc.

                I started a thread doing nearly that with pressure-up times, unfortunatly with mine a hybrid of 1 x coelescing filter and 2 x Coltri towers all away for ex-factory my times become irrelevant to anyone else, so could not really add mine. It could be called inexperience. I should have been far more systematic at each fitment, doing temps and times then. Thus at each tweak there would be a datum rather than the present mess both me and our man
                trdscfjc are in. I shall put ti down to pioneering
                Last edited by BritCNGUser; 03-17-2015, 09:05 AM.

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

                  I think that a stable temp after a few hours would tell more than temp rise from cold.

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

                    20150317_093215.jpg

                    Got the pin from L.F. sourced the bearing locally for 6.50$....nuvair wanted 55$

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

                      Originally posted by BritCNGUser View Post
                      I don't want to hijack our man trdscfjc's thread although the bloke may forgive me, my issues look much the same, so we'll feed off each other. I have been following thsi so intently...


                      I see 2.5 bar and 24bar at stages one and two which if I convert to imperial we get about 36psi & 350psi respectively whereas Coltri quote all should see 50psi (3.5bar) and 500psi (35 bar) I am filling to max out at Euro standard of 200 bar (2900 psi) Whatever I see it is way behind that Youtube clip.
                      IIRC, in one of your posts long ago , you were dealing with issues of obtaining sufficient gas supply pressure from the gas utility company and a " pulse tank ? " in the machine gas supply. Is all that resolved ?

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

                        Second stage wrist pin/ bearing and rings replaced, still getting 1.5 cfm above 3000 psi....The Mystery remains...

                        Going to replace 1st stage rings tonight, that's the only thing left
                        Last edited by trdscfjc; 03-17-2015, 12:13 PM.

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

                          I hope it is the first stage rings for your sanity on this.

                          I would think you could identify which stage was generating blowby if you maintained a constant 60 psi output and measured gas flow, next maintain a constant 550 psi output and measure gas flow and then chart gas flow as it increases up to 3600psi.

                          If you get minimal blowby at 60 psi output pressure then I would say the first stage rings are fine, if you get minimal blowby at 550psi output then I would say the second stage rings are fine as well.

                          If you monitor pressue at each stage with output pressure beween 3000 and 3600 psi it should tell you if any of the valves are leaking by observing higher or lower than normal operating pressure on stages one and two.


                          Originally posted by trdscfjc View Post
                          Second stage wrist pin/ bearing and rings replaced, still getting 1.5 cfm above 3000 psi....The Mystery remains...

                          Going to replace 1st stage rings tonight, that's the only thing left
                          Britcng,
                          I am not convinced that adding output filters will reduce your output. Do you percieve them to be highly restrictive. I get the impression the use of a priority valve would cause as much or more restriction as any filter. If you compressor is capable of pumping up to 5000 psi I don't think the filter should slow it down at 3000 psi.

                          I would look on any scuba compressor site (like Ray's) for an example of a priority valve.

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

                            trdscfjc You were lucky to get that pin so quickly and cheaply. Once you have the 1st stage done you'll be cuaght up with me. I wish you luck. Thank you fo rhte piccy. I will try to locate that brand here, for one of those for my parts stash. (I am learning tis is better to have stock for these bits than hang about waiting) I'm going to be using it anyway.

                            Lakewood, I hear where you coming from, I have a low first stage and it could just be that it's as simple as the utility supply regulator giving-up and not firing as much as it did when I first installed the Coltri. That would explain the low first stage readings which in turn drag down the rest. I put the gauges on to diagnose this issue so I have never seen what the pressures would have been reading had I fitted them from new. If I had one real bitch about the Coltri it is the cost-cutting on lack of gauges. It causes so much greif yet must keep the Coltri parts dept busy...

                            or am I being a tad cynical?

                            Now in the UK our supplies run thru' a 10 m3/h meter (about 6cfm) which is double what a MCH5 will pull, so capacity excepting an MCH10 should be OK. I did find the Coltri would knock out the pilot lights on my 'old skool' boiler at switch off if the boiler was sitting off demand and my room and water stats were not calling to heat, this was solved by a pulse/ballast tank. So I don't think I have a supply issue per se, but the regulator may be stuck and not opening as it should. I should looksee at thsi next.
                            Last edited by BritCNGUser; 03-17-2015, 03:26 PM.

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

                              I think that what you are calling a priority valve is a back pressure regulator if so it will also reduce oil consumption by keeping head pressure on the piston to hold oil down the davey has no oil rings on the forth stage just back pressure.

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

                                Search ebay for a Dwyer Magnehelic pressure gauge. They are about $25 and will allow you to easily measure the line pressure in your gas supply while the compressor is running. You will know right away if you are below your target inlet pressure. I use a 0 to 50" of water column gauge on my gas line. My gas supply is set at 42 inches. It drops to about 38 while drawing approx 5cfm.
                                Last edited by karl; 03-17-2015, 04:08 PM.

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