Possible causes of problem I witnessed

[Rick Inman]

I'm not a RB diver, so my question comes from a "curious but ignorant" perspective.

Yesterday on a charter, a 2 man team of RB divers stayed an additional 30 mins of deco beyond their plan. We were all on the boat looking down at them. When they were on their shallow stop, a crew member dived down and checked on them. They signaled back that they were OK but that one of them needed to complete additional deco.

I never heard what the issue was, but both were OK.

The dive was planned to 200', and that was the bottom, so they couldn't have gone beyond their max depth. They began their deco pretty much with the rest of us (after 20 mins), so I seriously doubt they exceeded their bottom time. In fact, I think their bottom time was cut short. I'm not 100% sure, but I think they were on Megs. They never left the loop.

What could cause the additional obligation? PPo2 setting errors? Some kind of PPO2 error, I would think...

Just wondering...

 

[Hyper-limits]

Set point error is possible, if there were not following tables and using computers it's possible that they did not change the setting in their computers also. At 200' for 20mins they should have been out of the water between minute 50-60, an additional 30 mins is a lot. Too bad you didn't ask why they had to add deco time to their plan.

Cheers

Al

 

[wedivebc]

Set point error is possible, if there were not following tables and using computers it's possible that they did not change the setting in their computers also. At 200' for 20mins they should have been out of the water between minute 50-60, an additional 30 mins is a lot. Too bad you didn't ask why they had to add deco time to their plan.

Cheers

Al

Yeah, run that same profile using 0.7 as the PPO2 and the runtime turns into 103 minutes on v-plannner using +2
An extra 30minutes in Florida is no biggie. How about an extra 30 at Christmas Pt in January?

 

[Hyper-limits]

How about an extra 30 at Christmas Pt in January?

No thank you. I dove Senanus Island last Saturday with Rob and we had a 20 minutes on the line that was long enough.

Al

 

[Dr. Doug Ebersole]

My guess would be a setpoint problem as well. As mentioned above a setpoint of, say, 0.7 versus 1.3 can definitely make for longer deco. A lot of the South Florida CCR divers are active on this board. Hopefully, one of them that was either on the trip or knows them can chime in with the details.

 

[Hyper-limits]

A lot of the South Florida CCR divers are active on this board. Hopefully, one of them that was either on the trip or knows them can chime in with the details.

The 2 RB divers in question could be from around here, Washington State or British Columbia (PNW). Just a guess as Rick is from Spokane Wa. Either way I also like to know what they did wrong or what was wrong with the Rb or the dive plan.

 

[TSandM]

Rick's in Florida right now.

 

[SCUBA_Phil]

Rick,
One other point. On the Meg, you the diver are responsible for performing the set point switchs. Most Meg divers (me included) start at the surface with the system set to 0.7 (can't get above 1.0 at the surface). At the end of the decent (or near the end), the user then selects the new set point (normally 1.2 or 1.3). At the end of the dive (post 20' deco stop), most Meg diver switch the set point controller back to 0.7 What happened here was most likly the diver forgot to perform the switch and did most of the dive at 0.7.

Phil

 

[wedivebc]

Rick,
One other point. On the Meg, you the diver are responsible for performing the set point switchs. Most Meg divers (me included) start at the surface with the system set to 0.7 (can't get above 1.0 at the surface). At the end of the decent (or near the end), the user then selects the new set point (normally 1.2 or 1.3). At the end of the dive (post 20' deco stop), most Meg diver switch the set point controller back to 0.7 What happened here was most likly the diver forgot to perform the switch and did most of the dive at 0.7.

Phil

Likely not a meg since it would be hard to ignore those red flashing lights the WHOLE dive!

 

[Rick Inman]

Rick,
One other point. On the Meg, you the diver are responsible for performing the set point switchs. Most Meg divers (me included) start at the surface with the system set to 0.7 (can't get above 1.0 at the surface). At the end of the decent (or near the end), the user then selects the new set point (normally 1.2 or 1.3). At the end of the dive (post 20' deco stop), most Meg diver switch the set point controller back to 0.7 What happened here was most likly the diver forgot to perform the switch and did most of the dive at 0.7.
Phil

Interesting. Is there a procedure to verify the set point has been correctly set throughout the dive? If the diver realized sometime during the bottom time that the set point was low, might this be a reason to call it early and do the longer deco?