Medium Pressure hose degradation

[N Bailey]

A recent post on a social media site for SCUBA service engineers indicated that a braided hose had degraded internally allowing particles of the plastic lining to block the inlet of the DV.
The hose appears to be an aftermarket fitment looking at the images on the site.
It is not known or stated where the hose was bought or how it had been used and stored.
If anyone has had a similar failing please advise me so I can other sectors of the industry aware.

[GLOC]

This is the thread that Nick was referring to

http://scubatechphilippines.com/scuba_blog/regulator-hose-diving-emergency/

From chatting with Andy, this is his comments/assumptions/hypothesis


It's pretty solid/crystallized... the guy who stripped the regs this morning says he'd seen it before. Cheap Taiwan /Chinese hoses... something... either solvent or plastic lining... is coming loose in the hoses and fouling gas flow.

The hoses were well used, but both failed at the same time. Neither gave gas at depth

It certainly looks like desiccant but will be interesting to see if there is any follow-up posted. Either way, if in doubt, bail and end the dive, then sort it out on the surface.

Regards

[nickb]

Either way, if in doubt, bail and end the dive, then sort it out on the surface.Sadly, this is one of those things that can creep-up on you and, if you don't know about gas densities and work of breathing, you may not realise what's going-on until you're in a world of hurt.

I had an issue with an Apeks second stage about 12 years ago. At 35m or so I came to the realisation that I was trying to suck air through a straw, but by that time I was already well into a CO2 hit. Nobody teaches you about that possibility on an open-circuit course (except possibly GUE?)

[Nickpicks]

Interesting that for 2 different hoses, it happened on the same dive - even if they were the same batch, I'd have expected the linings to deteriorate at different rates.

I wonder if they've cut the hose open to see whether it's actually the lining degrading - that would have been my next photo in the series.

[notdeadyet]

I imagine what's more likely is that the backup had failed previously and not been picked up at the surface/shallows then when with denser air at depth it became a problem when he switched.

[iain/hsm]

Interesting that for 2 different hoses, it happened on the same dive - even if they were the same batch, I'd have expected the linings to deteriorate at different rates.

I wonder if they've cut the hose open to see whether it's actually the lining degrading - that would have been my next photo in the series.

Cleaned at the same time by the same idiot with the same solvent cleaner. Nice table cloth mind. :shake:

And they still don't sell spares kits to the public ............ROFL Give me strength. Iain

[GLOC]

A follow-up:


MareNostrum.ws added 15 new photos from July to the album: Equipment Maintenance and Possible Implications (https://www.facebook.com/media/set/?set=a.10155777380600462.1073741828.221079165461&type=3).
Upon one of my last dives, I have realized a free-flowing short-hose regulator when we were doing an out-of- air drill. I cut the drill, went back to my longhose reg, closed the short-hose reg, purged it and reopened and we could complete the skill without further incident. Of course, this was the reason, I took the regulators apart in the first place.

Having a couple of days off, I started servicing then all of my regulators. I am a Scubapro Service Technician, but only service my own regulators so it is not that frequent that I use these skills. For that reason, I follow closely the service and maintenance procedures as outlined by Scubapro.

I could find in at least two second stages particles the maximum size of a grain of round rice (most were smaller) in yellow colour. By touch it felt like wax and could be squeezed. It also melts when heated with a flame. I also could find the very same particles in at least two first stages and therefore, rule out as possible cause the explanation that was given from Scuba Tech Philippines (https://www.facebook.com/ScubaTechPhilippines/photos/a.810115899000486.1073741840.201817833163632/1032789553399785/?type=3&theater)
My suggestion was that the lubricant that melted in the extreme heat we have here in Mexico (as well as in the Philippines) and when the regulators were brought into water and started work, the wax hardened that way. I also learnt later that this process is called Polymorphic Crystallization as nicely explained on the chocolate example in this article (https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/physprop.htm). I do not think it is defective or low quality material, but I will write to Scubapro in that matter as maybe they would like to revise there maintenance procedures and add a caution note.

Regards

[matt]

A recent post on a social media site for SCUBA service engineers indicated that a braided hose had degraded internally allowing particles of the plastic lining to block the inlet of the DV.
The hose appears to be an aftermarket fitment looking at the images on the site.
It is not known or stated where the hose was bought or how it had been used and stored.
If anyone has had a similar failing please advise me so I can other sectors of the industry aware.

Chap I was diving with today had this failure yesterday, with an original Miflex hose 2 years old. The pictures are off to Miflex.

His 2nd stage stopped working and his 100% O2 was inaccessible.

He was OC.

Matt.

[Paulo]

Chap I was diving with today had this failure yesterday, with an original Miflex hose 2 years old. The pictures are off to Miflex.

His 2nd stage stopped working and his 100% O2 was inaccessible.

He was OC.

Matt.

That is serious.


Looks like Graham was right to be sceptical :D

[notdeadyet]

Chap I was diving with today had this failure yesterday, with an original Miflex hose 2 years old. The pictures are off to Miflex.

His 2nd stage stopped working and his 100% O2 was inaccessible.

He was OC.

Matt.
Has there ever been any confirmation from Miflex as to whether or not they are oxygen service? Having particles blown down the line and hitting a stop sounds a good way to make an oxygen reg go bang.

[cathal]

If you buy a Miflex HP Hose and read the manufacturers booklet that comes with it it states that they are recommended for a max Eanx of 40% only. I contacted Miflex about this and they assured me that they can and are used with 100% O2 with no problems.

[notdeadyet]

If you buy a Miflex HP Hose and read the manufacturers booklet that comes with it it states that they are recommended for a max Eanx of 40% only. I contacted Miflex about this and they assured me that they can and are used with 100% O2 with no problems.

Can be used and certified for use are two separate things. Everyone uses their 40% max regs with high fo2's without a huge amount of heartache but accept they are using them for something they arent certified for with an inherent risk.

However, the idea of a hose degrading and firing pieces down a line full of oxygen or turning on an oxygen reg and having fast flowing gas hit a wad of stuff of uncertain origin... I'd want to know that gob of shite at the end isnt going to ignite.

[Dave1w]

I remember one of the reasons Kiss went for Miflex after the swagelok hoses was that they were told from the manufacturer that they were suitable for oxygen.




Sent from my iPhone using Tapatalk

[matt]

Has there ever been any confirmation from Miflex as to whether or not they are oxygen service? Having particles blown down the line and hitting a stop sounds a good way to make an oxygen reg go bang.

Don't they fit them to the JJ-CCR?

[Baron015]

Don't they fit them to the JJ-CCR?

LP hoses on the JJ are Miflex

HP hoses are still the heavy rubber ones

[GLOC]

Don't they fit them to the JJ-CCR?
They are. I think with the exception of the AP CCRs, a large number of CCRs are fitted with Miflex now (from discussions with Peter at TekCamp).

Regards

[matt]

LP hoses on the JJ are Miflex

HP hoses are still the heavy rubber ones


They are. I think with the exception of the AP CCRs, a large number of CCRs are fitted with Miflex now (from discussions with Peter at TekCamp).

Regards

So they must be OK for O2 service, you would have thought?

[Timw]

Cleaned at the same time by the same idiot with the same solvent cleaner. Nice table cloth mind. :shake:

And they still don't sell spares kits to the public ............ROFL Give me strength. Iain

Is this limited to braided hoses (any brand) or can it happen with standard rubber LP hoses?

Are the lumps bits of the lining or are they solidified lubricant as the OP suggests? I would have thought losing a piece of the inner lining the size of a grain of rice would make it more likely to burst than anything else.

[matt]

It's lining.

[iain/hsm]

Is this limited to braided hoses (any brand) or can it happen with standard rubber LP hoses?




All HP flexible hose is made of two or three parts and most to a recognised standard.

1. The liner: retains the "fluid" it is not pressure resistant but the material is chosen to suit the "fluid" intended. Also called the core under press this core is designed to expand and has a low burst pressure in itself.

2. The pressure retaining band: For HP flexible hose its normally a Nylon Rayon or Kevlar woven fabric, the thickness or tensile strength of the material retains the inner core and affects the outside diameter OD of the tube
The greater the wraps or stronger the tensile strength of the weave the higher the burst pressure. This is not a pressure retaining part as the weave is porous to gas but as the inner core expands its this weave that then retains the expansion of the core and stops the inner core from expanding to bursting.

3. The outer jacket. This is normally a protective cover to protect the weave and again is designed to the required working conditions, non conductive, heavy duty, scuff resistant, oil and fuel resistant etc.

Miflex by contrast have only the core and the weave, they have no protective outer jackets and therefore any strand weave breakage weakens the hose and lowers the burst pressure as is so readily illustrated by many examples of failure.

Further Miflex is NOT made to any recognised standard in industry and would not be classed as suitable for a diving application.
The one exception that Miflex use to get under the radar so to speak is the scuba industry so called standard under the DEMA 105 or EN 250 standard

The EN 250 standard for IP and HP hose is frankly pathetic an utter joke.
and I'm happy to be quoted on this.

As for its use with rebreathers and oxygen. Just remember scuba gear under EN250 is still classed as sports equipment, the poor standard required only goes to prove the inadequacy incompetence and steer ignorance of the rebreather manufacturers that use it. And I would be happy to take on any clown that thinks otherwise.

By contrast your "standard "rubber hose is in fact built to a standard known as exceeding SAE 100R3 however please note the method of manufacture, the hose barb ends, insertion lubricant, cleaning procedure, inspection procedure all differ from the standard hose you may see on a search used for say hydraulic applications



Are the lumps bits of the lining or are they solidified lubricant as the OP suggests? I would have thought losing a piece of the inner lining the size of a grain of rice would make it more likely to burst than anything else.

Yes, no and no LOL

Yes, they are in all probability hardened cracked and crazed bits of deteriorating liner.
No, Solidified lubricant "waxing" is possible, I don't know their assembly procedure but unless they dip the ends in a bucket of grease before assembly like they do for hydraulic hose end.
No, The liner will only leak you have to remove some of the braid first to lower the burst point.

Hope it helped.

Iain Middlebrook

[WFO]

So they must be OK for O2 service, you would have thought?

Genuine miflex, or mysterious miscellaneous braided hose of an oriental persuasion.

[matt]

Genuine miflex, or mysterious miscellaneous braided hose of an oriental persuasion.

Miflex, genuine. Bought branded in Germany. It's a liability.

[bubbleless]

Isn't it strange the same weekend that we hear of some due in the Philippines has a problem with a non standard hose, filling up with bits, we have a diver who has a similar problem in the uk, who just happens to know someone on this forum.

Perhaps we should start with qualified facts like we abibe by with the incidents forum.

1, some due has posted a photo on facebook etc showing bits in the end of a 2nd stage hose, he hasnt identified what it is or the make/ brand of the hose.
2,another due diving on oc had a problem getting o2 out of a reg on a dive and it had a miflex hose on it.

That is as far as I can see the facts.

So should we all rush out and buy traditional hoses?? yes if you want.

As far as I know there was a problem with miflex hp hoses, they would fail at the crimp, since then there was some sort of redesign / shock absorber / hose protector no used.

I would have thought miflex would have to be made to some standard, buy Iain will know about that.

I don't know how long they have been making hoses for diving, but they have made alot.

Major Equipment manufacturers are using this type of braided hose.

It would be nice to find out what the Krud was.

Have I missesd something is it friday??

[matt]

2,another due diving on oc had a problem getting o2 out of a reg on a dive and it had a miflex hose on it.

I'll as him for the pictures, and if he lets me have one then I will post it for you fact finding mission.

Fact is - diver with 100% O2 could not breath the O2 due to blockage in 2nd stage.

Matt.

[Timw]

Iain,
Out of interest, what material is the core of braided hoses normally made of and what solvents would cause it to degrade like that?
Cheers

[matt]

Just FYI, and speculation - the hose I have seen has never been cleaned from new, 2 years ago. The material at either end of the hose by the crimps has fallen apart. Speculation is some reaction with high PO2. No facts.

Matt.

[Paulo]

Just FYI, and speculation - the hose I have seen has never been cleaned from new, 2 years ago. The material at either end of the hose by the crimps has fallen apart. Speculation is some reaction with high PO2. No facts.

Matt.

Does anyone routinely clean out hoses? I know I do not

[matt]

Does anyone routinely clean out hoses? I know I do not

I never have. Not sure mom-and-pop would clean them when I had service. My unit (as a whole) has never had service.

Matt.

[ARJAYM]

I clean my hose ends annually when I service my regs. I put both ends of all hoses in the ultrasonic cleaner.

I expect if some are doing this with 'wrong' cleaning agent a problem could arise.

[iain/hsm]

Iain,
Out of interest, what material is the core of braided hoses normally made of and what solvents would cause it to degrade like that?
Cheers

The Miflex hose is nothing interesting material wise
The inner core is PU
The inner braiding is Polyethylene PET
The outer braiding is nylon

The yellow PET granules in the photo enclosed below may give some cause for concern, but the typical life expectancy for PU is only 4 to 5 years.

http://www.technologystudent.com/joints/pet1.html

http://www.azom.com/article.aspx?ArticleID=796

https://www.spilltech.com/wcsstore/SpillTechUSCatalogAssetStore/Attachment/documents/ccg/POLYURETHANE.pdf

http://healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2012/12059r-eng.php

http://www.consumeraffairs.govt.nz/pdf-library/product-recall-notices/Miflex-High-Pressure-Diving-Hose.pdf

By contrast a 30 year old nylon 6.6 core is only half way through its life expectancy, but its stiff by contrast. iain

[matt]

Snaps of genuine Miflex failure:

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/11221309_1665340003680671_3158733276997793126_o_zp s2apqkvnl.jpg

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/11722421_1665340203680651_9194273412586597836_o_zp sjvtls1eu.jpg

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/11754366_1665487580332580_96578825970293907_o_zps7 xnjddlw.jpg

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/11221754_1665489796999025_215149126197680006_o_zps jzmqaotd.jpg

[iain/hsm]

Snaps of genuine Miflex failure:

http://i1214.photobucket.com/albums/cc497/MatthewOutram/TDF/11221754_1665489796999025_215149126197680006_o_zps jzmqaotd.jpg



Nice post, thanks

Your photo clearly illustrated the (well known) problem using PU as a core material, flexible yes, but at a cost of premature breakdown and material failure.

and also an excellent illustration of the build cores:

On the far right the discoloured PU inner core nicely degrading as expected
Next in, the clear PET Polyethylene braiding, as the protective sheath
Then the outer nylon braiding each layer covering 97% of the wrap area.
The white the inner pressure retaining the black the outer sheath.

All perfectly acceptable under sports equipment EN250

But for divers, I think now the penny may be beginning to drop. Iain

[iain/hsm]

Interesting also the time scale considering the short 4 to 5 year life expectancy for PU and the insistence of the manufacturer
to keep insisting on EN250 as the standard,

For reference and background as this is a safety matter, Here below is the original January 2008 launch of the Mirflex and as yet my unanswered questions regarding the product suitability for diving. I guess now we know for sure. Iain


http://www.rebreatherworld.com/showthread.php?16742-Hello-from-Miflex-Hoses