Hi Guys,
I've tried to stick with my blog as a single point of information on this issue, as things have changed/will change as more is learned. As others have mentioned, Miflex have been in contact with and this hoses concerned will be returned to them for inspection.
I did manage, finally, to get hold of the regulator hoses used in the incident (they weren't mine). As you can see on the blog with the LPI hose.... stamped 'MFX'. That is not inconsistent with older-type Miflex hoses. For a few years, Miflex have been laser-etching their hoses. There is no dispute that the hoses aren't new...
However, the stamped markings does lead to the possibility, however remote, that they could be fakes. Miflex will need to confirm the hoses are/are not of their manufacture in due course. It is for this reason that I've avoided publicly stating the hoses are Miflex.... and at the time I first wrote the article I didn't have access to the hoses to see the markings... then I had the LPI hose (but not the reg hoses).
I have no agenda to persecute any manufacturer over this issue. To date, I have been impressed with Miflex's response and strong safety-minded attitude in dealing with my article.
My primary concern when writing the article was to simply warn the diving community about the risk of nylon-braided hose inner lining failure. Since then, the issue becomes clearer and more specific advice should result.
Firstly, there is the issue of hose age. Hoses
should have a lifespan. That should come from the manufacturer, not the industry. That happens already with some other scuba or industrial components, so it could with hoses also.
I would note that I was told that these hoses were "3-4 years in use". We need to note that "in-use" differs from the 'date of manufacture'. It is possible that hoses could sit on a suppliers' shelf for years - so do check the manufacture date on hoses. I'd propose that the lifespan of a hose should stem from it's date of manufacture, not it's time in use. But, that would depend ultimately on the physical/chemical mechanism that was deteriorating the hoses.
I was told verbally that the hoses came as a batch "from Italy".
Since publishing the original article, I've heard numerous stories of divers/technicians experiencing the same problem (and deterioration). I cannot confirm or deny those stories. I've only seen one report accompanied by photos.... which showed an identical problem (plastic debris) to what I observed. That person is also returning the regulators to Miflex for study.
I've heard lots of theories on what made the hoses deteriorate;
a. Use with enriched air - unlikely given that these hoses were in-use for technical back-gas (in which high O2 is not a prevalent gas of choice).
b. UV damage - the regulators were stored inside. The outer cover showed no signs of fading or other damage.
c. Contamination with cleaning fluids - impossible to deny, as I wasn't present during servicing/maintenance of the hoses... but I am not aware of strong cleaning fluids being used in contact with the hoses at all.
d. Polymorphic Crystallization - seems the most likely, given storage in hot, tropical environment and regular immersion in cooler waters / cooling effect of compressed air flow through the hoses at significant depths. This chemical process causes materials to become more brittle (and progressively higher 'melting' point). The type of deterioration and fragments observed coming from the regulator inner lining seem quite 'brittle' in nature.
I am not a scientist, but I guess proper analysis will be available to determine exactly what process caused the issue. Polymorphic crystallization should be measurable in terms of melting point variance against other samples (
a chemist will probably tell me there is already a formal test to prove/deny this process....)
My current concern is that the outer layers of these regulators are "too good" at containing inner-hose failure. That prevents a sudden, explosive loss of pressure and gas. However, excellent performance in containing an inner-hose failure has also potentially led to an unpredictable, immediate loss of gas through hose/regulator blockage.
"Lesser" hoses (
i.e. rubber) would probably have shown external evidence of inner-layer breach... either through observable gas leak or 'bulging'. They would (
should...) consequently be changed long before inner layer materials could totally detach, transit along the hose and congest air-flow...
As long as the outer braid is intact, the liner should hold the pressure easy...
Which may be a distinct problem, given the issue of internal lining deterioration causing hose blockage and gas supply cessation.
Until now.... and having studied the hoses extensively.... there are
no observable signs of inner-lining degradation. There
are, however, the
symptoms of increased breathing workload and/or reduced gas flow (
i.e. in LPI action). To notice those symptoms would require certain sensitivity to the performance of regulators/LPI flow over a period of time.
Do not dismiss those symptoms without checking the hoses as a possible culprit. I know, personally, that previously I'd be decreasing the venturi... then tweaking IP settings if breathing workload increased. Now I know to check hose integrity also.
Perhaps someone could suggest some non-destructive testing that divers could do to confirm hose inner-lining integrity?
I can only think of this:
1. Remove the hose/s and manually blow through them. Notice if effort of blowing is higher than 'usual' (compare against a new hose). Also note if any foreign matter is ejected from the hose on blowing.
*I will be updating my blog article as new details/facts become available over time. I am avoiding doing updates on every social media where this incident/issue is being discussed (not just here on Scubaboard) for reasons of accuracy and 'canon'.
Nylon-Braided Regulator Hose Diving Emergency
