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Diagnosis of Faulty Valves

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  • Diagnosis of Faulty Valves

    It was Flattracker in Joe's Lurking thread that wrote:

    If you have 175 psi shop air available you can often tap in between the stages with the compressor off and find a leaking valve in a hurry.

    Now he's a pro. This has set me thinking. I've now got a flowmeter / rotameter off my crankcase, and another sitting at the inlet to the first stage, all permanently plumbed-in, and gauges sitting on each stage of my Coltri. However, when a stage starts to drop, how can you definitely say if the rings for that stage are letting-go, or the inlet valve of the stage after it is going-down, or come to that, its own valve(s)?

    Also to quote 'revolution cng systems':

    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'd love a diagnosis flowchart for this, but I can dream...

    Again to quote Keith Iaia 'revolution cng systems':

    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.

    How would a pro approach this? Is it about keeping a log of temps and pressures too? But a pro is often thrown into a machine, with no logs, so how is it done then?

    Last edited by BritCNGUser; 06-15-2016, 05:21 PM.