90 degree elbow on second stage

[tbone1004]

@Akimbo obviously it was correct, but so is the fact that there is a pressure drop associated with a longer length hose. My issue with him saying it is he makes it sound like it is an actual issue to be aware of, no different than those that refused to use 7' hoses 20+ years ago in cave diving. Until someone puts it on an ANSTI and shows how bad it is, I'm going to still sit in the camp that it isn't something you are going to find to be an issue in any sort of recreational diving environment. 1000ft in a hardhat is well outside the bounds of this discussion, though it should be noted that the KM helmets do have multiple bends on the regulator feed hoses, and they also sell elbows for the regulators, so if it's good enough for them, I'd say it's good enough for recreational use. If you feel otherwise, please prove it

 

[Akimbo]

I'd say it's good enough for recreational use. If you feel otherwise, please prove it

John's caution was not limited to recreational (130'/40M, low-moderate work loads, on air/Nitrox). In any case, the burden of proof is with anyone making statements recommending field modifications that aren't authorized by the manufacturer.

Nobody has suggested that regulator elbows are unsafe across the board, only that there are undetermined limits and to use appropriate caution.

 

[Carl_F]

The calculator provided is for incompressible fluid flow and not applicable to compressible flow (air.) However, the overall concepts are correct (more fittings, more turning, more length, the higher the pressure drop.) And I believe tbone is correct in that the overall pressure drop introduced by the extra fitting is not significant. Based on my engineering knowledge, not specific to scuba regulators but just based on the hydraulics, the majority of pressure drop (measured by WoB) appears to take place in the 2nd stage, not the hose or attached fittings (unless an overly narrow ID fitting is used.)

And I would expect that KB and hard hat operations take into account the increased density of the delivered gas and the impact of hose length, ID, and fittings pressure drop to ensure the pressure delivered at the 2nd stage is sufficient to manage the WoB. At those densities, the pressure drop becomes more and more significant. Does hardhat diving at the 1000 ft depths even use a 2nd stage regulator device?

 

[bamafan]

I have heard a few people say they could tell a difference between the cheap swivels vs the fixed angle swivels. I have the welded Kirby Morgan ones and could not tell a difference in breathing between them and the old CA swivels I previously used. There is a big difference in the diameter of the ID hole. Now breathing just through the 2 swivels while sitting on my couch I can definitely tell a difference but diving I never tried to swap from one to the other. Some buddies swear there is a difference. I don't really think it would be much though.

 

[Flotsam]

Thanks for the responses! You're right Tbone, the orings are in there, just a bit hard to see. I missed it when I checked before. The elbow is mostly because the reg feels like it wants to pull out of my mouth, and after a really long, shallow dive, it's a real pill. I went to a Deep 6 reg servicing clinic, and it was suggested routing my hose through the bottom port on my reg might help, and it has! The hose goes down my side and kind of loops back up under my arm, staying close to my body. I had already bought the 90 degree elbow, so I'll go ahead and put it on, see if it helps any more. Or I would, if USPS would just deliver the narrow wrench I need to remove my second stage...which has been out for delivery for 2 days

My next gear order will probably include a full-length mouthpiece like the Seacure, because the short mouthpiece is also irritating after a long dive...

 

[tbone1004]

Thanks for the responses! You're right Tbone, the orings are in there, just a bit hard to see. I missed it when I checked before. The elbow is mostly because the reg feels like it wants to pull out of my mouth, and after a really long, shallow dive, it's a real pill. I went to a Deep 6 reg servicing clinic, and it was suggested routing my hose through the bottom port on my reg might help, and it has! The hose goes down my side and kind of loops back up under my arm, staying close to my body. I had already bought the 90 degree elbow, so I'll go ahead and put it on, see if it helps any more. Or I would, if USPS would just deliver the narrow wrench I need to remove my second stage...which has been out for delivery for 2 days

My next gear order will probably include a full-length mouthpiece like the Seacure, because the short mouthpiece is also irritating after a long dive...

try the Aqualung or Apeks comfobites first, I MUCH prefer them to Seacures and I suffer from pretty bad TMJ.

 

[Akimbo]

I suffer from pretty bad TMJ.

Yikes. I had my first and only bout of TMJ last year for some unknown reason. My cheeks felt like I lost a fist fight and I broke the roots on two molars. Who would have thunk? My condolences.

 

[tbone1004]

Yikes. I had my first and only bout of TMJ last year for some unknown reason. My cheeks felt like I lost a fist fight and I broke the roots on two molars. Who would have thunk? My condolences.

bagpipes was what did me in for that unfortunately. After about 3 hours, my jaw gets a bit out of line and clicks for 5-10 minutes after the dive if I'm not using a comfo-bite.

 

[tursiops]

Ahhh, personal preferences.
I'm OK with ComfoBites, prefer SeaCures.
I'm very happy with the 90-deg swivel on my primary rec reg, and on my SM regs. If there is a WOB increase, I do not notice it. I suspect there are many thousands in use without issues.

 

[Doc]

Never mind, I figured it out!!

Don't ever choke on ScubaBoard, you'll get Heimliched to death.