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Air pressure regulator + single stage regulator = 2 stage regulator?

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  • Air pressure regulator + single stage regulator = 2 stage regulator?

    If we attach an air pressure regulator to a single stage regulator (use it as an inline reg),
    do we get the flow stability of 2-stage regulator and avoid end of tank dump?



    They are not expensive. Most are small and light to ship.

    http://cgi.ebay.com/ws/eBayISAPI.dll...#ht_3573wt_782

    http://cgi.ebay.com/SMC-AR2060-02-1-...ht_2430wt_1008

  • #2
    No. It doesn't work like that. Matheson wrote a simple explanation about single and two stage regulators.

    TWO STAGE regulators reduce the source pressure down to the desired delivery pressure in two steps. Each stage consists of a spring, diaphragm, and control valve. The first stage reduces the inlet pressure to about three times the maximum working pressure. The final pressure reduction occurs in the second stage. The advantage of a dual stage regulator is its ability to deliver a constant pressure, even with a decrease in inlet pressure. For example, as a cylinder of gas is depleted, the cylinder pressure drops. Under these conditions, single stage regulators exhibit a “decaying inlet characteristic”; where the delivery pressure increases as a result of the decrease in inlet pressure. In a two stage regulator, the second stage compensates for this increase, providing a constant delivery pressure regardless of inlet pressure conditions. The dual stage regulator is recommended for applications where a continuous supply of gas is required; such as the gas supplied to analytical instruments where constant delivery pressure is critical.

    SINGLE STAGE regulators perform the same function as the two stage regulator using a single step reduction of source to outlet pressure. For this reason, the outlet pressure cannot be as accurately controlled as the source pressure decays. We highly recommend single stage regulators only be used in circumstances where the operator can monitor and adjust the regulator as needed or where the regulator is supplied a nearly constant source pressure.

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    • #3
      Sorry for bringing a thread back from the dead...

      The answer is YES, this will work... IF your inline / secondary regulator is designed for the pressure ranges you intend to work with, both inlet and delivery. This isn't hard since most single stage CO2 regulators will deliver pressure in the normal air-compressor range (0-150psi) that these inexpensive regulators are designed for. You would have problems if for example your primary regulator suddenly delivered 250psi, or if you wanted the secondary regulator to deliver a very low (1-2psi). The other downside is that these inexpensive regulators will not be as long-term reliable as the super-premium Victor / Concoa / Matheson / Harris / etc. regulators we're finding on ebay for cheap, and at current prices they aren't saving you any money either.

      An example from my own experience... To run a steady tap-water drip into my aquarium I bought a cheap ($20) regulator for an air compressor at Home Depot. Plumbed it in-line and it did reduce the water pressure which varied between 60-120psi but the delivery pressure was all over the map and not consistent enough for a steady drip. So I just bought another of the same cheap regulator and ran the outlet of the first to the inlet of the second. Presto! I've got a two-stage regulator that holds my drip water delivery pressure steady as a rock around 20psi which is perfect for the metering valve to handle.
      Last edited by Oreo; 05-28-2010, 12:13 PM.
      "Do, then talk about it.
      No do? No talk!!" - Tom Barr

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      • #4
        Hi,

        Thanks for your reply.

        The other downside is that these inexpensive regulators will not be as long-term reliable as the super-premium Victor / Concoa / Matheson / Harris / etc. regulators we're finding on ebay for cheap, and at current prices they aren't saving you any money either.
        There are some good quality air-regulators (SMC brand) that should last long.
        Someone here in Thailand has been using it. But unfortunately the one I bought
        was wrong model which I found out later that it always released some gas to atmosphere.

        Yes, that's true that those 2-stage regulators are very interesting. But shipping cost from USA to Asia
        has killed all the deals. Anyway, I can't blame them in this case, since they are very heavy.

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