Standard and Procedures

[maxITA]

I'm new of this fantatic and very interesting ScubaBoard.
I have a question.
When we teach for example trimix normoxic course we planning this dive :

D = 60mt T = 20'
Botton Ppo2 : 1.4
Deco Ppo2 : 1.6
TMX 20/30
Ean 36 and Ean 80
38m 1' TMX20/30
27m 1' Ean36
18m 1' Ean36
15m 1' Ean36
12m 1' Ean36
9m 4' Ean 80
6m 3' Ean 80
4.5m 18' Ean 80
Total Time = 58'

Other my customers and divers
planning Ppo2 bottom : 1.2 o 1.3
Deco Ean50 and O2.
Athor planning deco with some Helium, I'have already read the last message about Helium or Nitrogen DECO, but I don't very sure about Helium deco.

I have check on Proplanner or GAP but
is very minimum the difference from
Ean50/O2 and Ean36/Ean80, but
the CNS is much low with 36 and 80.

I'have heard about RGBM, but I don't know because is very new alghoritm.
With ZHL alghoritm, we and IANTD have make a lot of dive without any problem.

There is any one that could write the
standard on deco planning for alls
tha technical diver agencies ?

TDI
ANDI
GUE
NAUI TEC
Other ??

Thanks a lot !

Max

 

[padiscubapro]

ANDI doesn't use standardized mixes per se. The ANDI philosophy is the diver choose what nartoci potential they are willing to accept - usually with a max of 4.0 ATA PN2, the calculate the mix from there.. ANDI's max bottom PO2 exposure is 1.45 and a Deco exposure of 1.6. In general most instructors will plan a 60m, dive with a single deco gas of 50%. ANDI advocates the use of 50% as a standard deco mix. On longer profile Oxygen will be introduced after the 50%, but on most trainng dives it is unnecessary.

Usually when oxygen is intoduced in most dives its added for additional margin, not to reduce decompression time.. ANDI teaches if you need the gas for decompression you must carry it with you at all times (unless situations force a single enrty/exit like a cave). Dives are planned with 50% for the deco, so the oxygen is staged at the proper ascent point. Carrying oxygen is useless since it can only be used at very shallow depths. If all goes well, and you get to your staged point, you can switch to oxygen and still run your 50% table decrease your tissue loading but are still running the same profile (if you don;t no harm since you planned on a 50% deco). There are dives that require oxygen for optimal deco, and in that case it would be carried.


Keep it simple if a second decmpression gas is not needed don't use it.. Its another point for diver error.

ANDI allows the use of any decompression software, its not tied into one specific application.. I personally use VPM and RGBM profiles in my classes others the good old buhlman..

WHen using a buhlman alg its best to get off He fairly early unless there is a great change in helium concentrations then an intermediate mix should be considered.. If using bubble models the switch can be done much later.

For many ANDI classes your 60M dives are a bit short.. Technically we could reach standards doing 4-6 dives with 60 minute durations, but most instructors strive for Trimix dive durations for a minimum of 90 minutes per dive.
ANDI has an intermediate trimix program (its not in the normal student progression - but merely for locations that cant reach depth requirements for full trimix certifications). We normally run technical (max 50m - 30 minutes deco)- ext range (max 50m - unlimited deco), then full trimix (100m in training, no depth limit for cert)

This is an abreviated outlook, Hope this helps a bit..

Personal note:
For a 60m dive I generally do bt of 30-35 minutes using straight buhlman this is around 90 minutes total run time, if I use GF its about 120 minutes, using VPM-b its also around 90 minute run times..

With CCR trimix students I usually do BT of 60 minutes or so for a 60m-65m dive.

 

[flw]

padiscubapro once bubbled...

This is an abreviated outlook, Hope this helps a bit..

Personal note:
For a 60m dive I generally do bt of 30-35 minutes using straight buhlman this is around 90 minutes total run time, if I use GF its about 120 minutes, using VPM-b its also around 90 minute run times..

With CCR trimix students I usually do BT of 60 minutes or so for a 60m-65m dive.

I think that may be an 'area' thing - or a 'site' thing - around here it's rare for anyone to do more than 90-100 minutes in water because beyond that cold becomes the issue, also at 60 deg N and the junction of the Atlantic and N Sea our weather patterns are very unstable, we've nearly come unstuck more than once when it's deteriorated quicker/earlier than expected.

rgds
F

 

[padiscubapro]

Thats still longer than the <60 minutes, that MaxIta posed..
90-100 minute durations for a trimix class are definately acceptable.. I think 60 minutes is on the low side(but I can reach standards using 60 min minimum rt).. Thats more inline with beginning technical divers.. Conditions have to come into account, but we are basically saying upon certification you don't have a depth restriction.. If I never had students do longer dives would I be doing my job?? Even a 100m dive for 10 minutes will easily exceed a 60 minute runtime.. (the graduation dive I try and do with CCR trimix students (depends on experience) if in warm water is 90m-100m for 20-30 minutes). I wouldn't do this in cold water since the decos are longer than I would want as mandatory in these conditions with students.

I don't believe in bounce dives, there should be useful bottom time.

Water temp does come into play.. Many times of the year your (especially south western UK) water temps are higher than mine..

Typical bottom temps are around 4.4C (40f), late summer the surface MAY reach 22C (72), the last deco stops near the end of the summer are usually around 15c (60f)..

Off ny waters my dive time is usually limited to about 1.5 to 2 hours although I have done longer..

Our patterns are very changeable also but we don't do drift decos like you guys.. we always tie (re:chain) securely into the site.. Sometimes we get abused on the shallow stops but you get used to it.

our recommended dives are 60m 20' runtime 78'(planned using 50% only, oxygen reduces deco by 12mins (but can be used for a safety margin), 60m-25 rt 98', 80m-15 rt 102', graduation dive planned by student.

 

[flw]

Fair enough - I'm actually about 1000miles from SW UK, and I believe the water is nice and toasty there - I hail from the Shetland Isles, about half way between N Scotland and Norway, so although our water is warmer than you'd expect for latitude, it tends to vary between about 3-4 deg in Feb/Mar up to high of 11 deg at the end of summer, because it's oceanic there's not much difference between the bottom and the surface -although one day I got 12 deg this year - unfortunately the very best vis is mid winter inbetween gales, but the lack of daylight can be a bit of a hitch.
We almost always do drifting deco, which is is warmer than 'anchored' and easier, but there are very few 'reefs' worth diving deep on, more wrecks

 

[IndigoBlue]

flw once bubbled...



I think that may be an 'area' thing - or a 'site' thing - around here it's rare for anyone to do more than 90-100 minutes in water because beyond that cold becomes the issue...
rgds
F

My friends quiver when I propose anything longer than 45 mins to 1 hour in-water. They always say, "Wait until we go to Mexico where the water is warmer !"