Failed Regulator or Operator Error ?

[Steve_C]

I would say that half the time I am diving with a new dive partner they check their reg wrong. They take a couple puffs without looking at the SPG. I point out looking at the SPG. Last thing I do before stepping off the boat is take a couple deep breaths and watch the needle even though I had done it again earlier.

Correct way to check should be emphasized more in OW and reinforced later.

 

[boulderjohn]

I would say that half the time I am diving with a new dive partner they check their reg wrong. They take a couple puffs without looking at the SPG. I point out looking at the SPG. Last thing I do before stepping off the boat is take a couple deep breaths and watch the needle even though I had done it again earlier.

Correct way to check should be emphasized more in OW and reinforced later.

I was doing a special instructional session for an experienced couple who were looking to advance their skills through a pool session with an instructor. As we did the pre-dive check, I emphasized that when they checked their air, they should be sure to take several breaths to see if the needle moved, and I explained why. The wife was looking at her gauge intently while she took her breaths, and she asked, "So if the needle does not move, it's OK?" I said it means that the tank is on and more than just cracked open.

We got in the pool and did some basic skills, and she suddenly panicked. When I got to her, she was out of air. When we surfaced, I asked her how much air she had had when she looked at her gauge during the safety check. She said, "The needle was down in the red area, but it wasn't moving."

She was an experienced diver. I think we can never overlook the potential for operator error.

 

[Steve_C]

Wow. Talk about taking a statement literally and focusing on only one aspect. Will keep that story in mind.

 

[John C. Ratliff]

There is one other thing to think about concerning the needle of the SPG, or the digital readout of the computer, and that has to do with the position of the J-valve. If the J-valve is up, in the "On" position, it is possible to get the needle or readout to move with each breath. This is inherent in the J-valve design of at least some J-valves, and can lead to a problem with new divers thinking that this is normal. Us vintage divers understand this, but new divers may not. This is the reason behind recommending in current training that the J-valve remain in the "Down" or "Off" position with modern decompression computers or SPGs.

SeaRat

 

[Akimbo]

It is worth noting that the “watch the needle” trick is not effective on many (probably all) AI computers because they average readings over 1-10 seconds and round to the nearest 10 to 25 PSI. This is a case where analog shines. AI computers are fine for just checking to see if the valve is closed or not.

 

[clownfishsydney]

I have witnessed an spg needle reading low during inhale on a 30m dive.
All pre-dive checks were fine including the cylinder valve open correctly and regs breathing fine.

The dive was aborted early and on further investigation later it was found that the tank valve was faulty in such a way that even when the knob was turned fully open the valve was only slightly open.

just saying .

Yes, I have seen this too. However, on all but one occasions when I have seen it has been operator error.

 

[John C. Ratliff]

I have been in the professional safety field for over 35 years now, and to express a problem in terms of "operator error" or "equipment failure" is bogus. It is not an "either/or" situation, ever. The theory of multiple causation has been around now since the 1970s, but it is hard to get it into the public's head that every accident/incident is a human error, and that is not the question. The questions are the factors (plural) that happened prior to that ultimate error that contributed to the accident/incident.

Here is a model I like to use when I look at incidents and accidents:

*DeJoy, David M., “A comprehensive human factors model of workplace accident causation,” Professional Safety Magazine, Volume 35, Number 5, May 1990, pages 11-16.


John C. Ratliff, CSP, CIH, MSPH
"SeaRat"

 

[Skittl1321]

Are divers still taught the " 1/4 Turn Back " method?

I did OW this year and I was taught to turn 1/4 back. Something about the pressure build up- sounded like an urban legend to me though.

 

[John C. Ratliff]

For the last day or so I've been going through my references, including the U.S. Navy Diving Manual from March 1970, the NOAA Diving Manual from 1975, and my two copies of The New Science of Skin and Scuba Diving, plus several other texts, and I can find no reference to the 1/4 turn back.

However, I always use this practice myself. So I wondered my memory banks, and got out my valves (I have several not on tanks). One is an old USD 3/4 inch valve, that I have partially disassembled in front of me. The stem of this valve, which is what unscrews the seat, has on its top a soft plastic disc that seals the top of the valve. I started diving in 1959, and got certified in 1963 from LA County's instructor, Mr. Roy France. He did teach the 1/4 turn back off full open. And if my memory bank is correct, he had a reason. That soft plastic disc can be scared if the valve is opened "hard." If someone twists that valve open with sufficient force, damage can be done to the top of the valve internally which can lead to a HP leak. Young male types tend to over-do things, and he cautioned to simply open the valve all the way, then back it off 1/4 turn. That way the only pressure on this plastic disc is the air pressure itself and the spring tension from the top of the valve, and not the mechanical advantage that the threads and handle can give against this plastic disc. This technique will lengthen the service life of the valve, because the plastic disc will remain undamaged by the forces of a young (usually guy's) hand on the valve's wheel nut (the thingy you use to open the valve). This plastic disc, on the old USD double-tank valve, is part #26 (U.S. Navy Diving Manual, March 1970). These valves have retained their same basic design since the early days of diving internally. So I think this still applies.

Concerning turning the valve the wrong way, I found on my valves a mixed bag of on-off indicators. Scubapro and Sherwood both had on-off indicated on the valve's wheel. But others, including AMF Voit and USD did not. This is part of what I was showing in the diagram--"Person-Machine Communication" for "Words and Symbols" that can be a factor in an incident/accident. I can go back to what a friend of mine in facility maintenance said. "Lefty-Loosy, Righty-Tighty," said Steve Harris. (Left--counterclockwise; right--clockwise.) I've never forgotten that since he said it.

SeaRat

 

[ArcticDiver]

I would say that half the time I am diving with a new dive partner they check their reg wrong. They take a couple puffs without looking at the SPG. I point out looking at the SPG. Last thing I do before stepping off the boat is take a couple deep breaths and watch the needle even though I had done it again earlier.

Correct way to check should be emphasized more in OW and reinforced later.

Really good idea. More than once boat crew when doing their diver pre-dive check have left the tank valve Off or Partially Open. An antisocial but effective counter to that is to promise amputation if they touch the valve(s).