Getting my First Reg - Need Advice

[cerich]

there are only so many materials that they can use for these things and there is only so much quality difference in standard tubing. This stuff is not rocket science. They take a standard tube, and put it in an overbraiding machine and braid over. They can choose some different material qualities especially for the braiding yarn, but the interior side is going to be standard tubing.

Miflex actually patented the inner tube material (Europe only, they failed to get patent in US, even though they did their best to try and assert they had to other brands selling non miflex braided hoses), it is the problem in my opinion. When the generics were made the miflex patent was looked at to get around it, thus in my opinion, better inner tube material choices were made

 

[tbone1004]

@cerich It's been a few years since I read the patent and I couldn't find it to re-read, but I my understanding was that they didn't develop a bespoke material for the inner liner, but it was more of a process patent on how to make the hoses. The inner material is PU for both companies. Could be wrong though, if you can find the patent, let me know and I'll dig through it again. My mind is in patent mode since I'm writing a couple this week

 

[DevonDiver]

Where do they commonly fail? After how many times in use? Root Cause?

The failure mentioned specifically to nylon braided hoses occurs with the inner layer of the hose.

It was first reported on my blog (see below) and was then taken up by DAN SA for investigation and study.

Nylon-Braided Regulator Hose Diving Emergency

Since publishing that report (which was disseminated widely on social media), I received numerous communications from divers / centres across the globe who, upon close inspection, found the same issue. The issue reached the attention of DAN, who instigated a study... which came to the same conclusions as I did (on my blog) about the need for close inspection and the need to attribute a lifespan to these hoses (2 years), regardless of use.

The root cause of the failure is Polymorphic Crystallization of the inner layer. This is a chemical degradation of plastics caused by temperature variation on the hose over time. The material becomes solid, then brittle and then crumbles.

You can't avoid temperature variation on the hoses when diving. So, it's not specific to one region or environment. Hoses tend to be stored in warmer temperatures, whether in a heated house (in cold climate) or room temperature (in the tropics). The hose is then cooled when you enter water and compressed air travels along it.

The issue specific to nylon braided hoses is that the degradation of the inner layer is effectively concealed by reinforced middle and outer hose layers. This allows the inner layer to completely crystallise, without obvious external sign, and restrict gas flow through the hose.

In the incident I observed, all the regulator hoses (2x IP reg hoses and 1x LP hose) had been bought as a batch, and all three had failed simultaneously. No failure was apparent at the surface or during initial descent, but gas flow ceased once 2.8ata was exceeded. It required an emergency gas donation (from myself), or it could easily have been a fatal incident

In contrast, rubber (2-layer) hoses would conspicuously bulge, and fail cursory inspection, as soon as any compromise to the inner layer occurred. Nylon braided hoses do not - they are engineered to 'not fail' if the inner layer is compromised. Miflex market the hoses based on this premise.

The reason why this failure is particularly insidious is because the nylon braided hose will still appear flawless on external inspection... and the restriction of gas flow may not be evident at surface breathing pressure. Gas supply may only become compromised as gas density increases at depth; as was the case in the incident I observed.

This isn't about 'cheap' hoses.... it's primarily about the higher quality hoses. These high quality hoses are the ones whose middle and outer layer unwittingly conceal the breakdown of the inner layer.

More photos of the same effect that were collated by DAN:

 

[Joneill]

The failure mentioned specifically to nylon braided hoses occurs with the inner layer of the hose.

It was first reported on my blog (see below) and was then taken up by DAN SA for investigation and study.

Nylon-Braided Regulator Hose Diving Emergency

Since publishing that report (which was disseminated widely on social media), I received numerous communications from divers / centres across the globe who, upon close inspection, found the same issue. The issue reached the attention of DAN, who instigated a study... which came to the same conclusions as I did (on my blog) about the need for close inspection and the need to attribute a lifespan to these hoses (2 years), regardless of use.

The root cause of the failure is Polymorphic Crystallization of the inner layer. This is a chemical degradation of plastics caused by temperature variation on the hose over time. The material becomes solid, then brittle and then crumbles.

View attachment 417108

You can't avoid temperature variation on the hoses when diving. So, it's not specific to one region or environment. Hoses tend to be stored in warmer temperatures, whether in a heated house (in cold climate) or room temperature (in the tropics). The hose is then cooled when you enter water and compressed air travels along it.

The issue specific to nylon braided hoses is that the degradation of the inner layer is effectively concealed by reinforced middle and outer hose layers. This allows the inner layer to completely crystallise, without obvious external sign, and restrict gas flow through the hose.

In the incident I observed, all the regulator hoses (2x IP reg hoses and 1x LP hose) had been bought as a batch, and all three had failed simultaneously. No failure was apparent at the surface or during initial descent, but gas flow ceased once 2.8ata was exceeded. It required an emergency gas donation (from myself), or it could easily have been a fatal incident

In contrast, rubber (2-layer) hoses would conspicuously bulge, and fail cursory inspection, as soon as any compromise to the inner layer occurred. Nylon braided hoses do not - they are engineered to 'not fail' if the inner layer is compromised. Miflex market the hoses based on this premise.

View attachment 417109

The reason why this failure is particularly insidious is because the nylon braided hose will still appear flawless on external inspection... and the restriction of gas flow may not be evident at surface breathing pressure. Gas supply may only become compromised as gas density increases at depth; as was the case in the incident I observed.

This isn't about 'cheap' hoses.... it's primarily about the higher quality hoses. These high quality hoses are the ones whose middle and outer layer unwittingly conceal the breakdown of the inner layer.

More photos of the same effect that were collated by DAN:
View attachment 417111

Do you think the same phenomena occurs in HP Miflex hoses and in the same timeframe? I have a 2.5 year old Miflex hose on my SPG. I'd imagine it's less of an issue than on a 2nd stage hose as it would just potentially show no pressure if it plugged, but I suppose there could be concern of crystals working back into the first stage?

 

[DevonDiver]

The regs causing the incident I assisted with were Miflex.

I doubt the issue of polymorphic crystallization is as critical with HP hoses.

I'm not sure what materials are used in Miflex HP hoses...and if they differ to the IP and LP hoses.

HP hose have a tiny bore anyway... and if they did get blocked, it'd be immediately apparent via the SPG. Plus, of course, loss of SPG data doesn't compare to the hazard of lost gas supply.

 

[ams511]

Do you think the same phenomena occurs in HP Miflex hoses and in the same timeframe? I have a 2.5 year old Miflex hose on my SPG. I'd imagine it's less of an issue than on a 2nd stage hose as it would just potentially show no pressure if it plugged, but I suppose there could be concern of crystals working back into the first stage?

I don't think the crystals would work their way back to the first stage but they certainly could wind up in the second stage, if the inner layer disintegrates fine enough. What I found amazing is that all three hoses failed simultaneously. Talk about built-in obsolescence.

 

[buddhasummer]

Sorry, if I've missed it or if it was mentioned in another thread but are all nylon braided hoses made using the same inner core? Or is this specific to Miflex? Cheers.

 

[Darghu]

Miflex replied in 08/2015
Miflex 2

Someone know if Miflex have made some fixes/new materials to prevent those issues?

A new made in 2017 will still have those issues?

Materials: All have Nylon according g to their website.

 

[DevonDiver]

Miflex replied in 08/2015...

I was in contact with Miflex at the time, and there was much suggestion that hose failures may have been due to improper maintenence.

I confirmed this wasn't the case... In 25 years diving, I'm unaware of anyone ever cleaning hoses internally using detergents.

I informed Miflex about the issue of polymorphic crystallization, but didn't get a reply on that matter.

When DAN SA took up the investigation, the issue of polymorphic crystallization was somewhat substantiated - and has featured in their warnings.

I'm unaware if/when Miflex accepted that as the issue and/or took corrective actions.

 

[Darghu]

In any case a hose have a 5years lifetime (start when that hose got made on factory) or less?