90 degree elbow on second stage

[tbone1004]

@Akimbo there is a welded elbow, similar to the one that started this thread, but I believe it is on their FFM's not helmets, sorry. They also use 90's on the KMACS 5 system on both the inlet and outlet sides. They are CE approved on the FFM's, which again, means that even with them, they are less than 3j/l at a 62.5rmv on air at 50m. Higher consumption, and higher gas density than is ever seen in recreational diving.

They look like this

 

[Akimbo]

I believe it is on their FFM's not helmets,

OK, that makes sense. For everyone reading this here's the description:

Hi Flow Air Inlet Swivel
The high flow swivel allows the regulator hose to move freely and align with the mask without put-ting stress on the hose coupling. It uses standard SCUBA threads for incoming breathing air. The Inlet Swivel is CE approved for the M-48 with CE approved regulators. The Inlet Swivel is provided with masks that are sold with a Kirby Morgan®second stage regulator.
Part # 305-017​

Here's a link, it is under the Accessories Tab
M-48 MOD-1 | Kirby Morgan

Amron has them: Kirby Morgan 305-017 Hi Flow Air Inlet Swivel

 

[tbone1004]

@Akimbo ding ding. so what we don't have is the actual ansti curves on the FFM and the swivel, but we know that the mask passes both with and without the elbow. Same with Poseidon and Apeks since they sell CE approved kits with elbows on them.
So if you are OK with the CE requirements for regulators, which are beyond the actual limits of what divers will really breathe, does the turbulence/pressure drop/increased effective hose length of the elbows matter? I say not at all and I sure as hell can't tell the difference between regs with swivels/elbows/long/short hoses regardless of what I'm doing

 

[Akimbo]

... I say not at all and I sure as hell can't tell the difference between regs with swivels/elbows/long/short hoses regardless of what I'm doing

​

You keep saying that you can't tell the difference and that is the part that is irrelevant and misleading for everyone reading. People are NOT sensitive enough to detect excessive respiratory stress that contributes to a host of medical problems and is panic-inducing.

The reason that NEDU built the breathing machine was because the test diver's couldn't tell the difference and it only showed up on diver performance stress tests. As I understand it, the breathing resistance increases dramatically at the top of the inhalation curve. Jumps at the peak of the inhalation cycle apparently is the worst time for the biomechanics of the lungs. Yes, CE is a good start but is the least demanding standard. Lots of regulators on the market do great under CE tests and poorly on USN tests, which is only one atmosphere deeper. It doesn't take much to screw up the delicate balance that changes great regulator and a stinker.

So if you are OK with the CE requirements for regulators, which are beyond the actual limits of what divers will really breathe, does the turbulence/pressure drop/increased effective hose length of the elbows matter?

Yes, it can matter a lot in the wrong combination of parts, depths, gases, and divers. I only harp on this issue because of direct personal experience screwing up making field mods that seemed benign. Fortunately nobody died but luck was with us that day.

 

[tbone1004]

@Akimbo people are not, and the tests of "real people" situations show very little change as a function of depth. When the problems arise is when the gas density and breathing frequency increases. Any test deeper than 165 to me doesn't matter because no one dives on deep air anymore. Any RMV over the 62.5 doesn't matter to me because it isn't relevant to real divers.
The USN was doing a bunch of deep air dives when those test standards came out, they are also using guys in their 20's in peak physical fitness that are capable of far higher levels of exertion than us mere mortals. If you look at the breathing curves, they are pretty flat at the 40rmv rate which is very much elevated and all well under the 0.14 target

 

[John C. Ratliff]

@John C. Ratliff I do not, nor have I ever sold scuba gear, so I have no interest in that and unsure where you thought that came about

I will say that Kirby Morgan uses and sells 90* elbows on their hard hats, many of the most extreme cave and technical divers use them on their regulators and have for many many years with no ill effect.

They have also passed CE testing which means they can't have significant effect on the regulator and are sold by various manufacturers as parts of standard kits that have passed CE testing *62.5RMV at 50m with WoB not to exceed 3.0j/l*, if it passes those tests, it's good enough for me

tbone1004,

in all your posts, you have a subheader stating: "Deep Sea Supply- Innovative Backplates, Wings, Harnesses and accessories" That, to me, meant that you are selling these items; it gives that impression, plus your emphatic emphasis on their not having any problems.

I have just written to Dive Gear Express, who do sell these 90-degree elbows, asking for any data they may have on the affect these items have on regulator performance. So far (just a few minutes), they have not responded.

So I did a bit more digging, and found this ScubaLab paper on "Backup Breathers." The lab they used was the Dive Lab at Panama City Beach, Florida. So I gave them a call, and talked to Mr. Mike Ward, Sr. He does the testing, and he has tested these 90-degree elbows. He said that in most cases, they are okay, but that he doesn't like the swivel ones. He has seen some swivel elbows come apart underwater, and said that this doesn't make a diver's day. He also said that the swivel soldiered together before it is chromed is better. When I asked about regulator performance, he said that in most cases, especially with people like cave divers who don't work hard at all, there is no problem. But at high work rates, and he cited greater than 62 liters/minute, there is turbulence which affects the regulator's performance. He said what I have been thinking, that any time there's a 90 degree turn, there will be turbulence generated. He said that the bigger the turn, the better for the air flow (again, this is basic flow dynamics, and was illustrated by the ACGIH figure I cited above). He also said that Kirby-Morgan and Excess Scuba make good quality 90-degree elbows.

Mike published on the Dive Lab website a paper on regulator performance. He wasn't sure whether these elbows were covered in that paper, but that it was a pretty good representation of how they test the regulators. Here is in part what this paper says:

...So how does this equate to a diver? Typically, the average t male open circuit scuba diver can swim along at a moderate work rate of 35-40 RMV for at least ve minutes. Military rebreather divers routinely swim long distances (1-2 miles) while maintaining 40-50 RMV. A scuba diver moving slowly taking in the scenery may take about 15-20 (bpm) and the breathing volume will average between 1.5 to 2.5 liters. For breathing simulator-testing purposes, if the breathing rate is 10 to 20 (bpm) a 2-liter tidal volume is normally used. For 25 bpm a tidal volume of 2.5 liters is normally used and for 30 bpm or greater, a tidal volume of 3.0 liters is normally used. Exactly how and why the actual volumes are used can vary according to the breathing characteristics being simulated. e ability to test over a wide range of volumes and rates allows the breathing simulator to identify the full capability of the equipment being tested...

...So now, we are back to what constitutes a great breathing regulator. It’s our opinion based on current regulator technology, the regulator should be capable of WOB under 2 J/L or less at 62.5 RMV down to the recreational depth limit of 130 fsw or the depth the user intends to use it to. For the “techi” people making deep air dives, it would be wise to use a regulator that is capable of below 2 J/L performance at 62.5 RMV to the maximum depth of the intended dive. Keep in mind regulator performance has gotten really good and this increase in performance makes diving safer and easier. Even a “hairy chested” deep sea diver in excellent condition diving to depths where WOB approaches 3 J/L leaves little reserve should things go side ways and heavy physical activity is encountered. Those diving into the ”outer limits” should go for the top performance regulators. In general, there is no excuse for the avid scuba diver not to have a good performing regulator, and not just one that squeaks in under the 3 Joule WOB limit. There are many good, inexpensive regulators capable of WOB performance under 2 J/L to depths of 130 FSW or deeper...
Ward, Mike, Sr., Regulator Performance
https://divelab.com/download/Regulator-Performance.pdf

What Mr. Ward says confirms my intuition that these 90-degree do affect performance under rather extreme conditions, but conditions that sport divers could encounter.

One of the problems I have with the way that you approach this is that the assumption is that these are good, and work well based simply upon other's experiences. But what is happening is that you are putting an unapproved accessory onto a piece of life support equipment, without first qualifying that accessory for that equipment. Normally, in industry, in order to modify a piece of equipment the accessory manufacturer first has to do the testing to show that his accessory is compatible with that equipment, and does not degrade the equipment's performance. Your approach, it seems to me, is backwards.

SeaRat

 

[tbone1004]

@John C. Ratliff that is a company that I endorse because they make high quality gear. I do not now, nor have I ever received any money from them, or any of the other companies in my signature. If you ask Tobin, I'm sure he will be more than happy to tell you that we have disagreements on several things about his gear and I do not believe they are perfect. Best value, yes, but not perfect.

DGX will not have the data that you have asked for and I doubt they or their supplier will foot the bill for testing. It is possible that if you ask Omniswivel they MAY have data on theirs, but again, I doubt it.

So the Dive Lab guys confirmed your suspicions but unfortunately don't have the data, but they also confirmed mine which is that at normal breathing rates, even elevated rates, the performance hit isn't really relevant because he did not say which depth it was performed at. Performance at 62.5rmv at 50m is not relevant to sport divers because no one anymore is stupid enough to go that deep on air and then start overly exerting themselves. You're going to have all sorts of problems that the elbow may not help, but you're going to have CO2 problems long before you overbreathe that thing. I'm sure at 62.5rmv at 30m it behaves just fine because the 30-40m range is where the curves start spiking up due to gas density

On the testing. The elbows come out of Taiwan with a couple exceptions, they are not bound by CE certification. Why on earth would they spend the money to get them tested on every regulator out there? You can't do it, literally not possible due to volume of regs. So you take the risk that we aren't retarded and don't do deep air high exertion dives, because again, we aren't morons, so I don't actually care what the reg does at 50m because I will be on helium with an equivalent gas density of 30m, and I'm also not dumb enough to let my RMV get that high, so what the reg does at 62.5RMV at 30m is what I really care about, and if it passes at 62.5/50m then so be it. We know that Apeks, Poseidon, and Kirby Morgan regulators pass CE with the elbows, so as long as you have a regulator that performs as well as those, putting an elbow on it is probably not an issue.

 

[northernone]

@John C. Ratliff that is a company that I endorse because they make high quality gear. I do not now, nor have I ever received any money from them, or any of the other companies in my signature. If you ask Tobin, I'm sure he will be more than happy to tell you that we have disagreements on several things about his gear and I do not believe they are perfect. Best value, yes, but not perfect.

Considering this pm material, say the word and I'll edit it. Would you be implying you receive no financial advantage in your relationship with the company's linked in your profile.

I mean: Do you pay full retail pricing when ordering from them just like anyone else who isn't advertising for them and recommending their products?

When discussing alterations to dive gear it's important to clarify if our financial interests or allegiances might be a factor in our recommendations to beginners.

I have 90 elbows in a few of my hoses. If I'm doing a rescue (a hobby diver trained activity) in rough conditions I am wanting to know if my equipment modifications are adding unquantified risks.

The fact many people use equipment in benign conditions and in leisurely manners doesn't mean a beginner might not get into trouble within "recreational depths" due to compromising equipment choices.

I've valued the discussion and data. Particularly from the military and commercial diving perspectives where safety is better researched compared to us hobby divers.

The feeling of trying to breathe through a straw with elevated co2 levels from an overbreathed regulator is a situation I do not want to contribute to recommending to anyone. If elbows are potentially a contributing factor, until there's testing showing it's inconsequential, I won't be recommending them on systems which were not designed for them.

I've seen a student breath an al80 empty in a pool in 11 minutes. Discarding reg performance in elevated RMV as irrelevant to beginner divers strikes me as dangerous.

If you'd like the clarification question at the top removed drop me a pm.

Cameron

 

[tbone1004]

@northernone Nothing to hide.
I do not pay full retail pricing from just about any manufacturer since I am an instructor, especially with an AAUS membership through the University.... Never tried from Huish/AUP, but can get key man from DUI, Santi, Aqualung, Scubapro, Poseidon, etc with no issues, just call up and ask. We/I am set up as a dealer through several of them, though incidentally not with the companies in my signature.
I think the only one I have to pay full price from right now is Huish, but I don't really buy anything from them and I'm sure if I called and asked the right questions I could. That is not abnormal for instructors or industry professionals in general, so it's not like I have any special privilege from them. The three companies listed in my signature are companies that I believe in because they are breaking the norms of the dive agency.
Deep Sea Supply changed my outlook on the ability to dive with a one-piece harness due to their long pattern backplates. They also haven't bent to the normal model of other manufacturers, have a great price point especially considering all manufacturing is done in LA, and when any random person can call up the owner of the company and get his advice on how to choose a piece of gear that speaks wonders. My hat is truly off to Tobin for everything that he does, and while we certainly butt heads, as recently as yesterday, I still believe in his company.
Cave Adventurers is just a great dive shop and I like to support Edd and his team
UWLD is similar to the DSS description and Bobby and I are friends personally
They have never asked me to link to their websites in their signatures and there is certainly no "agreement" in place with any of them, just companies that I believe in and want to support in whatever way I can.

None of those companies sell regulator swivels that I use. All of mine are Omniswivel branded because of the Poseidon adapters, and I do not like the elbows because I have seen a couple of them strip threads and split in half. The ball-swivel failures I have had happen were usually due to forgetting to put loc-tite on the screw that holds the thing together and it has never been catastrophic or non-repairable like the elbows. The KM elbows being soldered are much better, but I prefer the comfort of the ball swivels. Cave Adventurers does sell those, and while I recommend them, I certainly don't get anything out of it other than a hug from Stacy and if I've been a real good boy she'll cook ribs when we are down there....

Was said student experiencing any leaks/reg freeflows or any other divers breathing on their gear. I do not believe that a SAC rate of 4.5 can be maintained for 11 minutes. That is 30% above what the USN tests for an deems the equivalent of running up hill....

 

[northernone]

@northernone Nothing to hide.
I do not pay full retail pricing from just about any manufacturer since I am an instructor, especially with an AAUS membership through the University.... Never tried from Huish/AUP, but can get key man from DUI, Santi, Aqualung, Scubapro, Poseidon, etc with no issues, just call up and ask. We/I am set up as a dealer through several of them, though incidentally not with the companies in my signature.
I think the only one I have to pay full price from right now is Huish, but I don't really buy anything from them and I'm sure if I called and asked the right questions I could. That is not abnormal for instructors or industry professionals in general, so it's not like I have any special privilege from them. The three companies listed in my signature are companies that I believe in because they are breaking the norms of the dive agency.
Deep Sea Supply changed my outlook on the ability to dive with a one-piece harness due to their long pattern backplates. They also haven't bent to the normal model of other manufacturers, have a great price point especially considering all manufacturing is done in LA, and when any random person can call up the owner of the company and get his advice on how to choose a piece of gear that speaks wonders. My hat is truly off to Tobin for everything that he does, and while we certainly butt heads, as recently as yesterday, I still believe in his company.
Cave Adventurers is just a great dive shop and I like to support Edd and his team
UWLD is similar to the DSS description and Bobby and I are friends personally
They have never asked me to link to their websites in their signatures and there is certainly no "agreement" in place with any of them, just companies that I believe in and want to support in whatever way I can.

None of those companies sell regulator swivels that I use. All of mine are Omniswivel branded because of the Poseidon adapters, and I do not like the elbows because I have seen a couple of them strip threads and split in half. The ball-swivel failures I have had happen were usually due to forgetting to put loc-tite on the screw that holds the thing together and it has never been catastrophic or non-repairable like the elbows. The KM elbows being soldered are much better, but I prefer the comfort of the ball swivels. Cave Adventurers does sell those, and while I recommend them, I certainly don't get anything out of it other than a hug from Stacy and if I've been a real good boy she'll cook ribs when we are down there....

Was said student experiencing any leaks/reg freeflows or any other divers breathing on their gear. I do not believe that a SAC rate of 4.5 can be maintained for 11 minutes. That is 30% above what the USN tests for an deems the equivalent of running up hill....

Fair enough. And thank you.

His next tank lasted him 16 minutes. Not sure the math but quite confident in the fill and the time. Was one on one with him... He just breathed like a freighter. Not panicked, more anxiety. After a few weeks we made it to a scuba diver cert and he loves diving. His sac rate is still high but gave him a cave filled lp131 and his DM partner the same and they do just fine at 30ft until someone gets cold.

This discussion has me reevaluating my own equipment choices and more importantly for those I might influence. It's not the tec diving crowd often over breathing a regulator these days... And when there's a fatality it's difficult to know if reg inadequacy, co2 build up and clouded judgement played a part. (my own groundless speculation)

Those situations where regulator system performance matters are well beyond our normal lazy dives but can happen within recreational depths. Once in the water, most cave diving is fairly sedentary and a rational experienced person can control their breathing often. An inexperienced diver, not so much, again in a crisis situation.

Cheers,
Cameron