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LDS vs The Burst Disk

Discussion in 'Tanks, Valves and Bands' started by viperwsu, Jan 11, 2019 at 2:07 PM.

  1. grf88

    grf88 Divemaster

    # of Dives: 1,000 - 2,499
    Location: Markham, Ontario
    I have just looked at a bunch of burst discs. They are either marked with two numbers showing both the service rating and the burst pressure or just one number showing the burst pressure so it would appear that these valves follow the convention of just showing the burst pressure. Do other valves such as the Thermo that just shows the burst pressure have a "buyer beware" notice?
  2. Bryan@Vintage Double Hose

    Bryan@Vintage Double Hose Instructor, Scuba

    Randy is as honest as the day is long and Piranha Mfg has a well deserved reputation for outstanding customer service.
    This is a mountain out of a molehill in my opinion.
  3. JackD342

    JackD342 Dive Shop

    # of Dives: 500 - 999
    Location: Highland Park, IL
    I guess my point wasn’t clear. The website listing says it has a burst disk installed. It does. So far so good.
    The listing does NOT say what the rating is for that installed disk, and it does NOT say what cylinder service pressure it is configured for.
    Plus, turns out the installed disk is at the least uncommon, and possibly even unknown in the market place where it was sold.
    This all leaves it up the the customer to sort out, with no forewarning. Big opportunity for improving the customer experience.
    So call Pirhana on Monday and figure it out.
    rjack321 likes this.
  4. viperwsu

    viperwsu Angel Fish

    # of Dives: 25 - 49
    Location: PNW
    Therein lies my problem. My LDS has a very good rep around my area, and Randy has a good rep on SB, and so far my experience agrees. So here I am kind of jammed in the middle.

    I'm "concerned" about the lack of parts, or published materials for that matter, but the issue that exploded was regarding filling it. I've gone back to get the valve, and my LDS is perfectly happy to hydro/viz the bottle with its old thermo valve. I'll just re-swap valves after and fill it from my back gas as I'd intended when I bought it - after all, 13cf will barely dent the 130cf I dive with. Saves me the cost of a $8 fill in a teeny bottle.
    txgoose likes this.
  5. rhwestfall

    rhwestfall Solo Diver

    # of Dives: 200 - 499
    Location: "La Grande Ile"
    Interesting, but unrelated - my LDS will fill a pony for free as a gesture of appreciation for safe diving practice.
    lv2dive, dead dog and abnfrog like this.
  6. txgoose

    txgoose Manta Ray

    # of Dives: 50 - 99
    Location: Houston
    Okay, that is just dang cool.
  7. KWS

    KWS ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: SE TEXAS
    I only remember vaguely but the burst disk is supposed to hold to something like 90% of test pressure so a al80 fould be a 5k disk that will hold to a min of 4500 psi.

    here is a chart i found and it looks like the 4250 may be for a lp tank with a + rating???? either way the nomber on the disk is teh burst info not eth wowrking pressure I do see4 on the valves a tag with the working pressure of the tank that the burst disk is for. so the out side of the valve is a number 3000 on it or 3442 etc.

    Type of Cylinder Service PRD
    Argon Bottles 2015 3360
    Low Pressure Steels 2400 4000
    Most Aluminums 3000 5000
    High Pressure Steels 3442 5250

    another math you may try is 9/5 working pressure is burst disk and it has to hold to 90% of that.

    so if yo had a 2400 tank it would 2400 *9 /5 * is about 4200 >>4300

    here is what i got on another site

    A burst disk consist of a thin copper disk held in place with a gasket and a vented plug. If the pressure inside the tanks rises to 140% of the working pressure, the disk ruptures, and the air escapes thought the vented plug. They are designed to rupture at pressures between 125% and 166%.

    The 1.66 jives with the disk equaling test pressure. on most cases.
  8. 2airishuman

    2airishuman Solo Diver

    # of Dives: 100 - 199
    Location: Greater Minnesota
    I think he is a great guy and does his best to represent what he sells fairly and accurately, and he has stood behind everything I've bought from him.

    The one-piece valve/regulator assemblies are unusual products, and there are widely varying attitudes about the importance of having the burst disc match the cylinder pressure or indeed of having burst discs at all. I believe they are important in the USA because unlike the situation in Europe most fill stations in the USA are capable of over-pressurizing cylinders in the event the operator makes a mistake.

    Anyway, it's a simple enough matter to install the correct burst disc.
  9. runsongas

    runsongas Loggerhead Turtle

    # of Dives: 200 - 499
    Location: California - Bay Area
    Not straightforward if the size is not 3/8 or 1/2 like 99% of burst assemblies on valves.
  10. guruboy

    guruboy Divemaster ScubaBoard Supporter

    Most new valves you buy now use 3/8” burst disk plugs now. So it should be very straight forward.

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