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Miflex LP Hose - interior disintegration

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  • Miflex LP Hose - interior disintegration

    Citez de-aici:

    "I have an Apeks DS4 and ATX 50 second stages with Miflex LP hoses (7’ and 24”). I had been diving for the previous 4 days with no issues regarding the regulator. On the first dive of the fifth day I entered the water, dropped to the bottom, adjusted the strobes on the camera and headed to the wall in search of subjects. I saw a Hawksbill turtle below (85’) and descended to take some shots as it swam south along the wall. While keeping pace with the turtle I took a deep breath and air flow dropped as if someone put a hand over your mouth. I tried a second time with the same results. I changed to the backup which worked properly. I ascended to the top of the wall, checked to make sure the valve was open all of the way, and that all of the controls on the second stage were properly set. Everything checked out OK so I switched back to my primary. With normal breathing it functioned fine. However, when I would take a quick deep breath the same thing happened and air flow was restricted.

    I got back home and took the regulator to the repair tech. When he disconnected the LP hose from the primary second stage there were numerous chunks of an off white substance (photo 1) plugging up the seat crown in the valve spindle (photos 2 & 3). The Miflex hose under the bolt snap was soft and spongy and not firm as the rest of the hose. We cut through the hose at that point (photo 4) and discovered that the entire diameter of the hose, at that location, was disintegrating (photos 5& 6) and flowing down stream and collecting at the valve spindle restricting the flow of breathing gas.

    I just checked the wife’s regulator and discovered a soft spot about an inch down from the swedge fitting at the first stage but she never experienced any issues at this time but I am still checking it out.

    Hoses purchased in 2008 and used with air, nitrox and Trimix."

  • #2
    Saga continua:


    Although my wife did not experience any issues of gas delivery her Miflex LP long hose showed external signs of a possible problem located approximately 1 inch from the swedge at the first stage end (photo 1).

    When I disconnected the LP hose fitting from the second stage I discovered numerous chunks of an off white substance at the inlet valve (photo 2) and a chunk in the end of the LP hose itself (photo 3).

    Photo 4 is a picture of some of the chunks that I was able to remove from the second stage inlet.

    I also checked her back up regulator even though an inspection of the 24 inch Miflex LP hose did not show any deformities. When I separated the second stage from the LP hose a white chunk was found in the inlet valve (photo 5 and 6).

    I will be heading back to my LDS to have the Tech get all of the pieces of the collapsed hose out of the second stage."
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    Last edited by whitecrowro; 17-04-13, 20:12.


    • #3
      While most of our subscribers are members of DAN, and therefore, receive their magazine, Alert Diver, we think it's important to call attention to a recent story (winter 2017 edition) that points out a potential problem with the lightweight, flexible hoses that have replaced the old, standard, rubber-covered regulator hoses. They are so flexible, they can be tied in knots!

      DAN has reported a regulator failure that was caused by this type of hose becoming restricted in such a way that for the diver, it seemed as if he was out of air; however, the tank was not empty. The inside of the braided hose had become blocked with a polymorphic crystallization related to the molecular structure of the internal tube -- a phenomenon associated with cyclical heating and cooling.

      It seems that the sun may heat up the hose, and when the tank valve is opened, the flow of depressurized air then cools it rapidly. This happens before every dive, causing tiny crystals to form and accumulate over time. As they grow, these crystals can either block the hose or migrate into the second-stage, resulting in a significant failure.

      The incidence of failure is quite small. However, because this occurs internally, it is not visible to a diver looking at the hose, so the deteriorated internal surfaces go unnoticed. That means divers should periodically examine these hoses by squeezing them every inch or so along their length to assess whether they exhibit the same degree of flexibility. Any change in resistance would be a sign of an impending problem.

      If you're diving in hot tropical climates, you need to know that DAN believes these hoses have a limited functional life, because the internal surfaces appear to be prone to this crystallization in hot weather. If you notice any gas-flow restriction, cease using your regulator.

      To better understand the phenomenon, DAN wants more information. If you observe this degradation in your regular hose, please contact DAN, preferably with pictures showing the condition of the hose.


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