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Newsflash! Low Pressure Hose Deterioration
by DAN Technical Team on June 2nd, 2016

DAN has learned of at least 8 or more recent cases of failure in regulators arising from the build-up of crystals in the second stage hose, where these are constructed using a polymer-braided structure. We intend to publish a more in depth account of this in the Alert Diver Magazine, written by Francois Burman, a professional engineer on the DAN staff, but this safety-related issue needs to be brought to the more urgent attention of both divers and diving equipment service providers. 
The following notice has been extracted from the full article:
  • ​All regulator hoses, including braided hoses, have a limited service-life – irrespective of the external appearance, or the reinforcement and protection provided by hose protectors or the braiding itself. Prior to 2010, the stated service life of 5 years or 500 dives for braided hoses appears to be inaccurate; failures have occurred in hoses with less than 4 years of in-service life. After this date, the manufacturers appear to have made satisfactory changes.
  • The inside lining of all hoses appears to be uniquely prone to degradation in the form of 'crystallisation’, especially in hot, tropical locations. This is a gradual process, reportedly especially active in the range of 27° - 32°C, but the disruption of gas-flow and regulator function is unpredictable and invisible to external inspection.
  •  Any sign of gas-flow restriction in the regulator assembly should prompt careful inspection of the regulator and the hose. If the regulator is not the cause, suspect the hose.
  • A physical examination including squeezing the hose every couple of inches to assess whether the hoses exhibits the same degree of flex should indicate if all is well. Any indication of a change in the resistance.
Please share this information with other divers and promote diving safety through the following advice:
  • Make all divers aware of this problem and the need for regular equipment servicing.
  • Practice emergency alternative gas source sharing procedures to ensure preparedness and appropriate action in the event of regulator failure as well as out-of-gas situations.
  • Be aware of what you buy - ensure that any hose purchased clearly shows information on the manufacturer, the production date and the standard used on the ends, and check that this information is consistent with the packaging.
​We invite all divers who experience this inner-hose degradation to please contact DAN (info@dansa.org), preferably with pictures showing the condition of the inner hose. This will enable us to capture as much real information as possible, so that we can learn more about this phenomenon. Any new findings, cautions or advice will be shared with the diving community. 


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4 Comments

Andy - June 15th, 2016 at 10:13 PM
Originally brought to light in 2015 (see link)... this issue has been reported by many scuba divers.

http://scubatechphilippines.com/scuba_blog/regulator-hose-diving-emergency/
Alex - July 17th, 2016 at 10:28 PM
Can anyone comment on the brand of hose, number of dives, diving air or EANx? Were these rental gear used every day or did they sit in someone's closet most of the time?


DAN Technical Team - July 19th, 2016 at 8:08 AM
The recent hose that failed, reported in late May 2016, was about 6 years old (2010). It had been used, regularly – about 200 dives for air-only, for the past 4 years. This was a personal-use item and was used in the Caribbean where the temperatures are most certainly tropical.

The hose was definitely a new generation flexible hose, with a blue outer braid and a white inner-braid. The tube appeared to be made of polyurethane but was rendered into nothing more than hard crystals for the entire length.

It is not appropriate to name the manufacturer as it is very hard to determine, from the hose-end markings, who actually made the hose. It does not appear to have been of Italian origin though, as the markings are not those used by the Italian producer.
John Clark - January 27th, 2017 at 8:16 AM
I had a complete shutdown of airflow in January 2015 at 140 ft with a braided hose. The hose was stamped 2008, used daily for about 4 years in Cozumel.
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