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

    1240 rpm

    its on the coltri website here http://www.coltrisub.it/COMPRESSORS/.../MCH5/mch5.htm
    Last edited by trdscfjc; 03-30-2015, 05:47 PM.

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

      Just a few points for clarification:
      1. The internal parts for the MCH13 and the MCH5 are mostly the same ... bearings, rods, pistons, cylinders, etc.
      2. MCH13 and the MCH16 are both three cylinder, three stage compressors and are rated for continuous duty up to 5000 PSI.
      3. The MCH6 is a four stage compressor rated for intermittent duty up to 4800 PSI.
      4. Intermittent/continuous duty has nothing to do with the number of cylinders. It is a rating of the bearings and sump size.
      5. Compressors that run slower and/or cooler will last a LOT longer as long as the proper lubrication is used
      6. There really aren't any U.S. dealers for the MCH5 CNG machine straight out of the box from Italy since they haven't jumped through hoops for whatever restrictions are imposed by the Feds/States.


      Hope that helps.
      Ray Contreras
      CompressorStuff.com

      Comment


      • 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.
        Originally posted by BritCNGUser View Post
        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?
        Don't you have a new warranty compressor? And why are you not installing it?

        Comment


        • 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.
          Originally posted by rcontrera View Post
          Just a few points for clarification:
          1. The internal parts for the MCH13 and the MCH5 are mostly the same ... bearings, rods, pistons, cylinders, etc.
          2. MCH13 and the MCH16 are both three cylinder, three stage compressors and are rated for continuous duty up to 5000 PSI.
          3. The MCH6 is a four stage compressor rated for intermittent duty up to 4800 PSI.
          4. Intermittent/continuous duty has nothing to do with the number of cylinders. It is a rating of the bearings and sump size.
          5. Compressors that run slower and/or cooler will last a LOT longer as long as the proper lubrication is used
          6. There really aren't any U.S. dealers for the MCH5 CNG machine straight out of the box from Italy since they haven't jumped through hoops for whatever restrictions are imposed by the Feds/States.


          Hope that helps.
          Three stage vs four stage makes no difference to coltri, for duty cycle, just every other major compressor manufacturer.just what does coltri know that no one else has learned in the last 150 years.

          Comment


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

            Originally posted by flatracker View Post
            Three stage vs four stage makes no difference to coltri, for duty cycle, just every other major compressor manufacturer.just what does coltri know that no one else has learned in the last 150 years.
            Well, not quite right. Some other makers that have three stage continuous duty compressors are Bauer, Mako, Ingersol Rand and many others.

            Like I said, it isn't the number of cylinders that determines the duty. It is the ratings of the bearings/crank. In order to make the smaller portable compressors cheaper and lighter to carry, the manufacturers thin down the crank shaft and use lighter weight bearings. So, while these compressors CAN pump to 4800 PSI, they can't hold that pressure for a long time.
            Ray Contreras
            CompressorStuff.com

            Comment


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

              Britcnguser writes,
              "Only I'm not sure I know what speed I am supposed to be seeing and at what pressures anyway.
              My mch-13 runs approx 95 psi on the first stage, approx 600 psi on the second stage. These measurements come from $20 Wika liquid filled gauges that are presumably accurate for identifying changes in operating parameters but doubtful they are precisely calibrated.
              I haven't calculated the exact rpm based on motor speed and pulley size but my unit was sold as a max air 90. I am a little concerned that max air may be running the compressor at a higher speed than coltri designed it for as they rate it at 10.8 scfm and Coltri rates it at 7.5 cfm.
              I do know that I get .5 cfm blowby with my variable frequency drive set at 60hz (full motor speed) and the blowby flowmeter stays virtually unchanged if I drop the vfd down to 20hz. 1st and 2nd stage pressures remain unchanged as I vary the speed. The only thing that seems to affect the pressure is the pressure the stage upstream is pumping at. With a priority/backpressure valve installed on my output the compressor always runs at a constant pressure on the third stage hence the lack of pressure variation in my case.

              Ultimately I prefer to run the compressor at a slow speed to keep temperatures and noise level down. I am not especially concerned with pumping rate as long as it does it in a reliable and predictable manner.
              Coltri specifies the mch 13 run at 1350 rpm and the mch-8 run at 900 rpm. They are both the same pump so I don't see any issue with running mine at reduced speed.

              If Ray Contreras doesn't often see bearing failures on his Coltri'ss I am guessing Maxair badged Coltri's like my own trash their bearings due to the increased volume Maxair sets them up for. I plan to calculate my compressor speed at my first opportunity.

              It seems like Britcnguser and Trdscfj both have blowby issues that are difficult to pin down. I have found the compressor inlet is very sensitive to changes in pressure and restriction and changes in those parameters have a profound effect on the blowby. Running a restrictive supply line or solenoid gas valve regardless of pressure can double my blowby to 1cfm.

              Anyone running an inlet filter would do themselves a favor if they added a blowby flowmeter and checked the blowby prior to installing the inlet filter and after installing. It doesn't seem logical to me but I find that even if you have a gauge showing the inlet pressure remains unchanged, adding additional elements to the supply plumbing will increase blowby.

              All I can speculate is that the pulses on the compressor inlet may act like a tuned exhaust on a two stroke or a tuned header on a four stroke and the volume and size of the supply piping may assist or obstruct the incoming gas in maintaining a steady flow.

              Flattracker,
              What compressor are you running? Do you have any measure of the blowby on yours?

              Karl

              Comment


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

                The MaxAir 90 is not an MCH13. It is actually supposed to be a MCH16. Yours is actually a MaxAir 50 if it is the MCH13.
                Ray Contreras
                CompressorStuff.com

                Comment


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

                  I am running a 20 year old cast iron relic, a bristol 4s7-70, they haven't even produced any of these in over 15 years. It is rated as a 5 cfm machine and mine will average 4.26 cfm on a 0 to 3600 3 hr fill so blow by is minimal, these are a duplex design so first and third stage a lubed from blow by. I average 1800 hrs a year and it just keeps pumping away.

                  Comment


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

                    shame that the beast compressors such as the Bristol, Davey and others that just keep going are not built anymore. the sign of a good compressor is that I use the overhead to move just the compressor.Good and heavy lots of metal.just my thoughts

                    Comment


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

                      Originally posted by rcontrera View Post
                      The MaxAir 90 is not an MCH13. It is actually supposed to be a MCH16. Yours is actually a MaxAir 50 if it is the MCH13.
                      that's interesting because the belt guard on mine clearly says maxair 90 but when I ordered piston rings from you for a MCH 16 they were too big for my unit and it became clear it was actually a MCH 13.

                      since I bought it used and have no knowledge of its prior history I will probably never figure it out.

                      thanks for clarifying.

                      Comment


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

                        Originally posted by cowboy View Post
                        shame that the beast compressors such as the Bristol, Davey and others that just keep going are not built anymore. the sign of a good compressor is that I use the overhead to move just the compressor.Good and heavy lots of metal.just my thoughts
                        agree completely, my shop compressor is an ancient saylor beall 750 that i bought used 38 years ago, gets annual oil changes and has worn out two baldor electric motors. Part of the problem in my view is 4 and 5 cfm 4000 psi compressors, their main market is scuba and those people want portability so here comes aluminum and three stages as opposed to cast iron and four stage.

                        Comment


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

                          Originally posted by karl View Post
                          Britcnguser writes,
                          "Only I'm not sure I know what speed I am supposed to be seeing and at what pressures anyway.
                          My mch-13 runs approx 95 psi on the first stage, approx 600 psi on the second stage. These measurements come from $20 Wika liquid filled gauges that are presumably accurate for identifying changes in operating parameters but doubtful they are precisely calibrated.
                          I haven't calculated the exact rpm based on motor speed and pulley size but my unit was sold as a max air 90. I am a little concerned that max air may be running the compressor at a higher speed than coltri designed it for as they rate it at 10.8 scfm and Coltri rates it at 7.5 cfm.
                          I do know that I get .5 cfm blowby with my variable frequency drive set at 60hz (full motor speed) and the blowby flowmeter stays virtually unchanged if I drop the vfd down to 20hz. 1st and 2nd stage pressures remain unchanged as I vary the speed. The only thing that seems to affect the pressure is the pressure the stage upstream is pumping at. With a priority/backpressure valve installed on my output the compressor always runs at a constant pressure on the third stage hence the lack of pressure variation in my case.

                          Ultimately I prefer to run the compressor at a slow speed to keep temperatures and noise level down. I am not especially concerned with pumping rate as long as it does it in a reliable and predictable manner.
                          Coltri specifies the mch 13 run at 1350 rpm and the mch-8 run at 900 rpm. They are both the same pump so I don't see any issue with running mine at reduced speed.

                          If Ray Contreras doesn't often see bearing failures on his Coltri'ss I am guessing Maxair badged Coltri's like my own trash their bearings due to the increased volume Maxair sets them up for. I plan to calculate my compressor speed at my first opportunity.

                          It seems like Britcnguser and Trdscfj both have blowby issues that are difficult to pin down. I have found the compressor inlet is very sensitive to changes in pressure and restriction and changes in those parameters have a profound effect on the blowby. Running a restrictive supply line or solenoid gas valve regardless of pressure can double my blowby to 1cfm.

                          Anyone running an inlet filter would do themselves a favor if they added a blowby flowmeter and checked the blowby prior to installing the inlet filter and after installing. It doesn't seem logical to me but I find that even if you have a gauge showing the inlet pressure remains unchanged, adding additional elements to the supply plumbing will increase blowby.

                          All I can speculate is that the pulses on the compressor inlet may act like a tuned exhaust on a two stroke or a tuned header on a four stroke and the volume and size of the supply piping may assist or obstruct the incoming gas in maintaining a steady flow.

                          Flattracker,
                          What compressor are you running? Do you have any measure of the blowby on yours?

                          Karl
                          I think the problems with these mch5's will probably come down to the fact they were developed for the european market and sold here as an afterthought, our cng vehicles over here have as a general rule much larger fuel tanks and 3600 psi as opposed to 3000 in europe. The higher pressures and the much longer run times is taking these compressors outside their operating envelope, they will stand it for awhile but 2,000 to 3,000 hrs seems to be the breaking point.

                          Comment


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

                            Originally posted by rcontrera View Post
                            Well, not quite right. Some other makers that have three stage continuous duty compressors are Bauer, Mako, Ingersol Rand and many others.

                            Like I said, it isn't the number of cylinders that determines the duty. It is the ratings of the bearings/crank. In order to make the smaller portable compressors cheaper and lighter to carry, the manufacturers thin down the crank shaft and use lighter weight bearings. So, while these compressors CAN pump to 4800 PSI, they can't hold that pressure for a long time.
                            Ray if you will look in coltri's own operation manual for the mch13 even the unit set at 3200psi is rated "non continuous pressure" at that pressure.

                            Comment


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

                              In previous posts I had a tech due to call. Now I have been let down a second time with a no-show. I now give this guy up as a bad-job, and so much for my earleir smugness - I can't get this guy to even turn-up! I have been holding off this day but I must put in the new pump. I have ordered a flow-meter and will install all in. Then (I hope) I will have a datum to work from. Doing that this w/e



                              1240 rpm

                              its on the coltri website here http://www.coltrisub.it/COMPRESSORS/.../MCH5/mch5.htm
                              Thanks for that, couldn't find it. Anyone know.... Is that the speed at no load or at working pressure? And if working pressure, which working pressure, 200bar or the US pressure?
                              Last edited by BritCNGUser; 04-02-2015, 07:27 PM.

                              Comment


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

                                Brit you have a typo in the url address for coltri use lit not it . Takes you to the mch5 online brochure and info. says 1240 rpm. I don't own one, but being run from an inverter, i'm 99 % sure the drive will run to the HZ. that will be that exact speed with or w/o load, unless you program it to run slower. I'm sure you could program the vfd to run slower , you will get reduced cfm.
                                Last edited by Lakewood90712; 04-01-2015, 04:42 PM.

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