[PSUBS-MAILIST] Scuba Tank Purchase Questions

Thu Feb 20 15:56:26 EST 2020

Oop, just had lunch with my wonderful wife and she reminded me that during the tank change over during a boat dive in the Bahamas two weeks ago the O-ring on her tank failed on pressure-up.  The dive boat had plenty of tanks available to switch out so no problem. I subsequently removed the O-ring and noted that it had a slight tear but was not otherwise broken. The dive boat operator probably just replaces O-rings when necessary. So that's now one personal O-ring failure, two sub op O-ring failures, and one recreational dive boat O-ring failure. Not a lot, really.

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of T Novak via Personal_Submersibles
Sent: Thursday, February 20, 2020 12:11 PM
To: 'Personal Submersibles General Discussion' <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] Scuba Tank Purchase Questions

To be fair, in 40 years of scuba with a yoke regulator, including with my family of five divers,  I have only experienced one other O-ring failure on the tank valve.  I have also experienced two failed internal regulator O-rings and two failed regulator low pressure hoses.  In each case the tank valve regulator O-rings failed upon the initial pressurizing, not ever during a dive, which in the case of the tank valves allowed quick and easy replacement.  Careful inspection to ensure that the O-ring is properly seated and then slowly turning on the gas usually prevents failure unless the O-ring is getting old and inflexible.  In the case of the two low pressure hose failures, the first was about 10 years old and its replacement just one year old.  Late model yokes are rated to 5000psi and have a good reputation.

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Steve McQueen via Personal_Submersibles
Sent: Thursday, February 20, 2020 11:31 AM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> >
Subject: Re: [PSUBS-MAILIST] Scuba Tank Purchase Questions

Thanks. Didn't realize yoke O-rings were such an issue. This changes my mind on my valve choice. 

Appreciate reviewing this topic.

Steve

On Thu, Feb 20, 2020 at 2:23 PM T Novak via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Just a case in point about DIN versus yoke, during the Flathead Lake expedition we blew two yoke O-rings on the Gama scuba tanks. It goes without saying that spare O-rings are a necessary inventory item to have on hand during sub ops.

Tim

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org <mailto:personal_submersibles-bounces at psubs.org> ] On Behalf Of Cliff Redus via Personal_Submersibles
Sent: Thursday, February 20, 2020 10:25 AM
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> >
Subject: Re: [PSUBS-MAILIST] Scuba Tank Purchase Questions

Mine are aluminum for primary and I have a composite tank internal as a backup HP source.

With a name like yours, you could not find a better boat name.

Cliff 

Sent from my iPhone

On Feb 20, 2020, at 10:57 AM, Steve McQueen via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Cliff, thanks. Good to hear about actual field issues. I will reconsider my thoughts a.ccordingly.  I have completed my contribution for Pisces VI and have refocused on finishing my project. Having your own compressor is a nice advantage. Are your MBT HP tanks aluminum or steel?

 My K-250 is named "The Great Escape" (get it?).

Steve

On Thu, Feb 20, 2020 at 11:36 AM Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote:

Steve, if it were me, I would go with DIN fitting on scuba tanks.  About 2 years after I built my boat I had an O-ring blow while I was on the boat ramp ready to launch. If this would have happened during a dive, I would not have been unable to blow my MBTs by myself.  I would have had to have divers to manually inflate my MBT with open vent ports.  My experience is that most scuba shops can fill scuba tanks with DIN connections.  After the incident, I switched my MBT HP air supply to DIN values and have never had any trouble since then.  Also, last year I purchased a portable scuba compressor that came with an adapter to let you fill Yoke or DIN valves.  Also this compressor is capable of filling a steel HP tank if I want to.  To me, the real benefit of steel tanks with DIN connections is the ability to fill to a higher pressure.  If you don't need the higher pressure, then aluminum are lower cost.

We are all looking forward to your sea trials for your lime green K250.  I love the paint job on your boat.  Has she got a name yet?  I am surprised you have had any time to work on your boat with the PLC work you been doing for Scott on his Pieces 6.

Looking forward to catching up with you this year at one of the psub events.

Best

On Thursday, February 20, 2020, 09:54:59 AM CST, Steve McQueen via Personal_Submersibles <personal_submersibles at psubs.org <mailto:personal_submersibles at psubs.org> > wrote: 

All, getting ready to buy 2 scuba tanks for my K250. Just wanted to see if anyone had an opinion of my thoughts?

1) Choosing steel vs. aluminum (prefer its weight/buoyancy characteristics)

2) While I was wanting as much air volume as possible I decided against a HP version as I have heard most places won't (can't?) fill to that capacity anyway

3) Deciding on standard pressure steel 80s with K-valve (yoke fitting)

I've been watching for a while (including Black Friday) but it seems there isn't much mark up and these tanks don't appear to go on sale.

Thanks,

Steve

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