Newsflash! Low Pressure Hose Deterioration

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 ([email protected]), 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.

Posted in Dive Safety Tips

6 Comments

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Andy - June 16th, 2016 at 6:13am

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 18th, 2016 at 6:28am

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?

John Clark - January 27th, 2017 at 4:16pm

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.

Lloyd Borrett - April 20th, 2018 at 4:53am

The DAN Alert Diver article titled 'Air Hoses: A Closer Look' has triggered some inquiries regarding material used in the construction of double braided flex hoses. We supply Miflex hoses and they ARE NOT constructed with an inner lining of Polyester-TPU. That material can undergo changes, called hydrolysis, which cause the rapid failure of the hose especially in hot and humid conditions.

Miflex branded hoses are constructed with an inner lining of Polyether-TPU. Some other braided flex hoses are constructed with an inner lining of High Syntactic Polyvinyl Chloride. Regardless, neither Polyether-TPU or HS-PVC is Polyester-TPU. In our long 10 year history with all the double braided Miflex hoses we've sold, we've never seen anything we think could be the hydrolysis problem described in the DAN Alert Diver article.

Miflex hoses are the real deal and we believe safer with longer life than rubber hoses. They are manufactured in Italy with more than thirty individual performance and safety automated tests. All Miflex hoses are designed to meet CE EN250 standards and are Nitrox Ready. But make sure you buy high quality, Miflex hoses, not cheap brand flexible braided hoses made from inferior materials.

DAN Medical Team - April 24th, 2018 at 11:36am

DAN does not promote or demote specific manufacturers' products. Our intention is to point out the fundamental reasons for failure and then to advise the diver as to what measures to take to remain safe.

Miflex themselves state that a 5-year or 500 dive count is what the diver should understand as the life span of the hose; of course assuming that there is no abrasion or other mechanical damage. This is their recommendation.

Miflex do indeed use poly-ether PU: this we determined when we found early onset degradation in hoses containing a poly-ester PU liner. They confirmed this although they also informed us that up to 2008, they had some doubts about the quality of the liner materials they used. After this date, they enhanced their quality control to make sure that the material used was indeed the poly-ether version.

Lastly, Miflex cooperated fully with our investigation and in fact both approved of the articles as well as being grateful for our publishing them.