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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)

    Originally posted by flatracker View Post
    ray i assume these 4500psi dive shop compressors are four stage as opposed to the mch5 three stage, air over cng should have no effect on rod load yet we are seeing multiple rod failures. one aspect i wonder about is the mch5 being enclosed in a cabinet and what effect that is having on lube temperatures.
    Actually, the MCH13 and MCH16 air compressors are the same blocks as the MCH5. I think the only real differences are the first stage valves, inlet filter and the air compressors don't have all the safety mechanisms you have on the MCH5. The rod failures are what has me baffled. Air is dealing with 4500 psi while CNG is 3300 or below. And rod failures in air usually only show up when the operators fail to change oil or use the wrong stuff (lots of garbage oil available in the diving industry).

    Cabinets do restrict cooling air flow so it is important to have plenty of cool air aimed at the box. Heat is the number one enemy for compressors.
    Ray Contreras
    CompressorStuff.com

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

      Ray do u know why the third stage valve is on top of the mch 5 and the 1st stage is on top of the mch13?

      As I mentioned Carl from L&M said that the mch5 has a weak 2nd stage wrist pin/bearing. This has proven true on both mine and Dave's compressor, is the second stage on the mch13/16 equally problematic? Are the wrist pins and bearings the same for the second stage for both the cng and dive compressors?
      Last edited by trdscfjc; 03-29-2015, 02:57 AM.

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

        Originally posted by rcontrera View Post
        Actually, the MCH13 and MCH16 air compressors are the same blocks as the MCH5. I think the only real differences are the first stage valves, inlet filter and the air compressors don't have all the safety mechanisms you have on the MCH5. The rod failures are what has me baffled. Air is dealing with 4500 psi while CNG is 3300 or below. And rod failures in air usually only show up when the operators fail to change oil or use the wrong stuff (lots of garbage oil available in the diving industry).

        Cabinets do restrict cooling air flow so it is important to have plenty of cool air aimed at the box. Heat is the number one enemy for compressors.
        The same compressor holds up better pumping air than it does pumping natural gas; There are two major differences: 1. The natural gas compressor is supercharged with one psi or so, unlike pumping air which charges stage one with only atmospheric pressure. Supercharging puts more of a load on everything, including the connecting rod bearings. 2. The natural gas has impurities, such as sulphur and mercaptan that is contaminating the oil.
        Last edited by hypermilinggx; 03-29-2015, 05:24 AM.

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

          Total sulfur in pipeline gas including the mercaptan is less than 17 parts per million.I know the oil analysis on my compressor oil after 250 hrs comes back at less than 75 parts per million

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

            If pipeline gas had the amount of sulphur some here think it does it would be illegal to burn it as a motor fuel and would plug a catalytic converter in a short amount of time.

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

              Originally posted by flatracker View Post
              Inquiring minds want to know, what did you find out????
              He hasn't logged in for several days. I hope he didn't decide to scrap it.

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

                Yes I would hate to hear he gave up, but if the tech put repair outside replacement cost?? Surely we will hear at some point. I wonder if the European manufacturer of these did not understand the duty cycle they would see over here often running 6 to 8 he's a day.

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

                  I've run mine for 12 hours a day on numerous occasions

                  I spoke with brit via Skype a few days ago he at the time the tech had not yet been by for repair/evaluation, i sent him a message, hopefully he logs in and let's us know what the verdict is.
                  Last edited by trdscfjc; 03-29-2015, 03:51 PM.

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

                    "I've run mine for 12 hours a day on numerous occasions"

                    I have no issues with coltri's quality but gven the recent challenges you are working through you arent necessarily the best testimonial .

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

                      Was meant as a statement of fact not so much as a testimonial

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

                        Any fueling appliance or compressor by nature of the task needs to be made for 100 % duty cycle/ continuous use.

                        Nothing to the contrary that I have seen from Coltri in MCH 5 data.

                        However , on the MCH 6 air compressor , Coltri specifically states it is for filling a single cylinder at a time and not for continuous use.

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

                          I think it is the duty cycle not the gas that is the problem. Jim Shelden that has been working with high pressure compressors longer than most of us have been alive says his experience is that pumping CNG compressor life is about double over pumping air due to the lack of water.

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

                            But he is talking about 4 stage continuous duty machines.

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

                              Originally posted by Lakewood90712 View Post
                              Any fueling appliance or compressor by nature of the task needs to be made for 100 % duty cycle/ continuous use.

                              Nothing to the contrary that I have seen from Coltri in MCH 5 data.

                              However , on the MCH 6 air compressor , Coltri specifically states it is for filling a single cylinder at a time and not for continuous use.
                              I don't know of any compressor manufacturer with the exception of coltri that classifies their 3 stage machines as continuous duty above 2500 psi.

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

                                I return. At this point I have nothing more to add. My 'tech' has messed me about already, due on Friday morn, he cancelled adn is now due tomorrow Tues. Already I have my doubts but hey-ho... we march on. I will report back. One line I have not tried is slow pump speed. I have a digital tachometer, you just point at a reflective bit of adhesive tape previously put on the item you want rpm measured from and it'll pick up the reflection. Only I'm not sure I know what speed I am supposed to be seeing and at what pressures anyway. I looked up the Coltri spec sheets and cant' see anything. Anyone?
                                Last edited by BritCNGUser; 03-30-2015, 04:12 PM.

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