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300 or 3000 psi Sch 80 pipe?

topic posted Thu, May 7, 2009 - 1:28 PM by  Mark
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Hi all, I'm in process of designing & ordering parts for my first flame effect device, and wanted a little clarification. I saw a couple posts commenting that full tank pressure may reach upto 600psi under certain conditions, but normally is limited to the 300psi max. That being said, is the 300psi rated sch 80 steel pipe sufficient to meet BM's flame effect safety requirements (or do we want the 3000psi stuff?)

Also, Grainger lists some of their 300psi stuff as malleable iron (vs the 3000psi stuff as forged steel.) Is iron sufficient if it meets the 300psi rating?
posted by:
Mark
SF Bay Area
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  • Re: 300 or 3000 psi Sch 80 pipe?

    Thu, May 7, 2009 - 7:59 PM
    Assuming you're talking about propane in the vapor state, the pressure will be directly dependent upon the temperature. There are different charts available, but here's one:
    www.engineeringtoolbox.com/prop....html
    You can see that the vapor pressure ranges from 0 PSI at the freezing point of propane (-44 degrees F) to 204 PSI at 110 degrees. Schedule 80 steel pipe rated for 300 PSI should suffice. 300 PSI or greater malleable iron pipe and fittings should be fine, too.

    A potential pressure problem comes from fuel in liquid form. Unlike the gas state, liquids hardly compress at all, so warmed liquids can build up huge pressures quickly if there's no expansion room. That's why new propane tanks come fitted with valves that have overfill protection devices (OPD) built in, preventing the tank from being filled more than 80% capacity.

    You could have a excessively large pressure build-up, say, if your tank tipped over and liquid propane was diverted into your device designed to use vapor only. Or you could have a pressure problem if fire or heat warmed your fuel.

    There are lots of safety standards described in the NFPA 160 manual for Flame Effects Before an Audience, and a copy of the document (the most recent 2006 edition) can be purchased online from nfpa.org.

    Does your flame effect device design use rubber hoses? Those must also be rated appropriately for pressure, and furthermore must be rated for propane. A cheap air hose, for example, might corrode from the inside out, so it looks ok but is doomed to fail at the worst possible moment. Also, screw-type hose clamps are forbidden because they can leak or cut into the hose, so all hoses must be use professionally swaged or crimped fittings on the ends.

    Another safety requirement that shouldn't be overlooked is your emergency plan. You should be well-versed with a sequence of steps you would take in the event of 1) a small propane leak, 2) a large propane leak, 3) a small unexpected fire, and 4) a large unexpected fire. Any inspector or Authority Having Jurisdiction (AHJ) will hopefully quiz you on your emergency plan.

    If you have the opportunity, there are occasional workshops on flame effects offered in the S.F. bay area at the Crucible, by the Interpretive Arson collective, and by the Flaming Lotus Girls. (The FLGs just recently hosted a 2-day workshop last weekend, in fact.) These can provide a great setting to get the required theory and practice to construct and operate a flame effects device safely. I'd encourage you to attend one of these workshops if you can, or track down an instructor to review your design prior to construction.

    Be safe!
    • Re: 300 or 3000 psi Sch 80 pipe?

      Fri, May 8, 2009 - 12:00 AM
      We require sch 80 on propane flame effects. In the past the Performance Safety Team has been a little lax on this during inspections, but over the last three years or so we have tightened that up. We are now also checking hoses to make certain they are rated for propane. NO hose clamps. The fittings need to be crimped. Shawns' post is completely accurate. The PST also does not allow soldered fittings as propane gets hot enough to melt solder.
      • Re: 300 or 3000 psi Sch 80 pipe?

        Fri, May 8, 2009 - 10:05 AM
        Thank you both. I appreciate your feedback and pointers. I'm still in the planning phase, and resources such as this tribe are absolutely indispensible for doing things safely.
        • Re: 300 or 3000 psi Sch 80 pipe?

          Fri, May 8, 2009 - 4:29 PM
          Another strong suggestion: keep your documentation neatly together in a "flame effects plan" binder, ready to show an inspector. Include your design drawings, operating procedures, emergency plans, manufacturer specs for plumbing and electrical parts, and MSDS sheets for fuel and other chemicals. This is supporting evidence that you've done your homework and have considered relevant engineering and safety issues.

          Here's a copy of a MSDS (Material Safety Data Sheet) for odorized propane:
          www.amerigas.com/pdfs/safe_eng.pdf

          shawn.
      • Re: 300 or 3000 psi Sch 80 pipe?

        Fri, September 25, 2009 - 5:12 PM
        so would this be acceptable?
        www.grainger.com/Grainger/items/6KC73

        it's schedule 40 but meets the PSI ratings (at least according to Grainger)
        • Re: 300 or 3000 psi Sch 80 pipe?

          Sat, September 26, 2009 - 2:53 PM
          The Grainger listing for this steel nipple assortment seems to have a discrepancy. Although it does indicate 300 PSI in the description at the top, in the "Tech Specs" section it says only WOG 150 PSI @ 150 degrees F, which concerns me. One of those numbers is a typo.

          I'd be inclined to choose a few different lengths and put together my own assortment of Schedule 80 nipples, double-checking their 300 PSI WOG ratings. The Schedule 80 pipe typically comes from Mexico these days, the 40 from China, and if you compare the two side-by-side you can definitely see the difference in wall thickness.
        • Re: 300 or 3000 psi Sch 80 pipe?

          Wed, September 30, 2009 - 8:51 PM
          > so would this be acceptable?

          No, it's not, at least in something I was building....

          There are two reasons to use thicker wall pipe:

          1) increased internal pressure
          2) consequences of failure

          In this case, the manufacturer states that the pipe is capable of handling 300 psi gas.... but we're still talking about schedule 40 pipe, and the very thin walls that remain after threading worry me, esp. in an environment involving possible unanticipated mechanical loads and severe consequences of failure

          In my 19' steam launch, I use schedule 80 pipe for all boiler connections because they can get tweaked if someone or something is thrown against the pipe, and because the consequences of failure include severe (possibly fatal) burns and/or possible loss of the boat...

          Buy what you need - it's there in a couple of days: www.mcmaster.com/#iron-and...pe/=3v4se3


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