Thread: SCBA bottles

  1. #51
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    Quote Originally Posted by The nots so new FNG View Post
    Believe it or not - the torque spec is not a critical number. Its specified of course but the actual seal is done by an o-ring. The purpose of the torque is to ensure the o-ring has seated and will not come loose.
    It's little discrepancies like this that is exactly the reason you'll never see the manufacturers extend their liability/warranty beyond what they have control over.

    I'm betting that if there was a failure and the non-manufacturer certified person who installed the valve failed to torque the assembly properly, said manufacturer would walk away (more like run!). If the approved person failed to properly torque it? I'd guess they'd be unemployed. So depending on your perspective, it might very well be pretty damn critical.

    My limited understand of the torque spec is that it prevents over tightening which can crack the cylinder at the neck along with damaging the O-ring as was noted.

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    Quote Originally Posted by The nots so new FNG View Post

    The key to my point was that non-SCBA manufacturers are expected to service these valve/cylinder combinations during thier service life so the notion than only the manufacturer is capable of doing so is bunk.
    Who said non-SCBA manufacturers? I know I noted "manufacturer approved" or certified to conduct the work. This is the same with most consumer products

  3. #53
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    Quote Originally Posted by RFDACM02 View Post
    It's little discrepancies like this that is exactly the reason you'll never see the manufacturers extend their liability/warranty beyond what they have control over.

    I'm betting that if there was a failure and the non-manufacturer certified person who installed the valve failed to torque the assembly properly, said manufacturer would walk away (more like run!). If the approved person failed to properly torque it? I'd guess they'd be unemployed. So depending on your perspective, it might very well be pretty damn critical.

    My limited understand of the torque spec is that it prevents over tightening which can crack the cylinder at the neck along with damaging the O-ring as was noted.
    As an FYI - From Luxfer Cylinders guide.

    http://www.luxfercylinders.com/downl...scubaguide.pdf

    We recommend that all straight thread valves be installed in Luxfer high-pressure aluminum scuba cylinders with a torque recommended by the valve manufacturer for aluminum cylinders.
    Without a recommended torque from the valve manufacturer,we would recommend a torque of 50 lbf-ft, plus or minus 10 lbf-ft. All torquing should be done such that valve, valve components and cylinder are not damaged.
    Now for medical tanks with the CGA 870 valve:

    http://www.luxfercylinders.com/suppo...20060221.shtml

    .....
    Luxfer has extensive experience with new aluminum and composite cylinders, as well as new valves of the standard 870 post-type valve design for oxygen. For such new equipment, Luxfer recommends a torque value of 75 ft.-lbs. However, under certain circumstances described below, this torque value may not apply.
    ......
    Thus, Luxfer’s current recommended torque value of 75 ft.-lbs. applies only to the installation of a new standard brass, straight-threaded, nickel-coated 870 post-type valve with an approved o-ring into a new Luxfer oxygen cylinder. The o-ring makes a seal in a seat that Luxfer has machined into the cylinder opening. Since Luxfer seat dimensions may differ from those used by other aluminum cylinder manufacturers, Luxfer’s recommendations only apply to Luxfer cylinders. The o-ring material and size are critical for a leak-tight seal—not just any o-ring will work properly with a Luxfer cylinder. In fact, with valve types that use a metal o-ring, if the o-ring is installed incorrectly, gas will leak from the cylinder no matter what torque is applied.
    Basically - this is a cylinder manufacture who gives a baseline range for valves from other manufacturers - with a plus/minus 10 ft-lb range and then proceeds to give an exact value for a valve/tank combination they have and describe the ramifications for failing to adhere to it. The SCBA tanks luxfer makes out of Al have the 50ftlb ±10ftlb torque spec - or 40-60ftlb range and the 'non-critical' comment I have made above. Conversely, the 870 tanks have a specific 75ftlb requirement.

    Every tank and valve combination has this information on file with the DOT. A properly trained tech will have access to these references to know how to set the torque on the valves - especially since hydro testing requires valve removal.

    I still don't see how using a tank made to a spec but not by the same manufacturer as the SCBA can been seen to be dangerous.

  4. #54
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    Quote Originally Posted by The nots so new FNG View Post
    I still don't see how using a tank made to a spec but not by the same manufacturer as the SCBA can been seen to be dangerous.
    It is highly dangerous. It is dangerous to the bank accounts of MSN, Scott, Drager,...
    Could you Imagen the price war if you did not have to buy what is effect a proprietary tank?

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    I price war like that could put this country in deeper recession and fire departments would have more money, or be able to buy new tanks they couldn't before. Oh the same of it all. lol

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