OSTC 2 : BO gas requirement

OSTC's running hwOS sport or tech
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stryke
Posts: 9
Joined: Friday 7. July 2017, 19:10

OSTC 2 : BO gas requirement

Post by stryke »

Hi,

It is a pity that the calculation of the bailout gas requirement stops as soon as the depth with a theoretical PpO2 of 1.6b. Could it be possible that the calculation takes into account the depth of change indicated in the setting?

Some photos to understand. Dive with Rebreather and BailOut Nx40%
- Up to 30M with Nx40, the calculation is done normally
- At 31M the calculation stops. Sorry the time to take the photo there were a few additional bars, but no change after between 32 and 48 minutes.
- Back at 30M the calculation starts again ...
Attachments
Simu.jpg
Ralph
Posts: 662
Joined: Saturday 24. June 2017, 11:31

Re: OSTC 2 : BO gas requirement

Post by Ralph »

Hi,

thanks for your contribution! This is the response from the one who implemented this part of the firmware. At the heart of the BO gas calculation is the same routine that does the OC gas calculation. It scans all activated gases to find the best suited gas for the current depth (and repetitively along the calculated ascent), that also fulfills the ppO2 limits. In case no gas is found that has a change (better to say MOD) depth than the current depth and that is within the set ppO2 limits, it can't start its calculation run. As in OC you are typically not diving outside your gases MOD, it will always find a gas to start the ascent calculation with. This is different in CC, as the gas in the loop is different from the carried diluent and BO gases and you can bring down the ppO2 in the loop to levels lower than your dil gas will yield at the current depth. But this should be considered dangerous, as for example you are then cut off from a dil flush possibility (the OSTC will show the "no B/O" attention in this case, alerting you that you are to deep for a bailout). So the above mentioned situation should also not occur in CC diving, at least if your dil doubles up as a BO gas. Anyhow, the tech firmware now has the "high ppO2 option" compiled in, allowing you to set the ppO2 Max Deco to up to 2.0 bar, and thus allowing you and the OSTC calculations to switch into a gas whose ppO2 would be too high as of accepted standards, in situations that are meant to be "in transit", i.e. while in an ascent. So the solution to your situation should be to increase the ppO2 allowance if i havn't overlooked other aspects in your case.

best regards,
Ralph
stryke
Posts: 9
Joined: Friday 7. July 2017, 19:10

Re: OSTC 2 : BO gas requirement

Post by stryke »

Thanks for your interest Ralph,

2 questions:
- Which firmware version allows the use "high ppO2 option" ?
- Where is the parameter in the menus ?
Ralph
Posts: 662
Joined: Saturday 24. June 2017, 11:31

Re: OSTC 2 : BO gas requirement

Post by Ralph »

Hi,

the extended ppO2 range is in the HWOS tech firmware, it does not need to be enabled, it's just that the max limits have been raised.
To set the ppO2 limits, goto: main menu -> Dive/Deco Setup -> ppO2 Setup. The max work & max deco will allow setting of up to 2.0 bar - pls. know what you are doing when setting values > 1.4 / 1.6 bar!

BR
Ralph
stryke
Posts: 9
Joined: Friday 7. July 2017, 19:10

Re: OSTC 2 : BO gas requirement

Post by stryke »

Hi Ralph,

I modified PpO2 max and restarted a simulation (B/O=Nx40%, depth=40m, PpO2 max=2). At the beginning everything goes well but the calculation stops after a few minutes as soon as the alarm "B/O Gas" is displayed

And I don't understand why this alarm is displayed ...
Ralph
Posts: 662
Joined: Saturday 24. June 2017, 11:31

Re: OSTC 2 : BO gas requirement

Post by Ralph »

Hi,

the B/O calculation is not done when the -B/O gas- alarm is shown, as in this case the OSTC can't find any breathable OC gas to switch to.
To have a gas to switch to, the gas needs to fulfill all of the following requirements:

- its change depth needs to be >= current depth,
- its ppO2 at current depth needs to match the ppO2 min and ppO2 max setting,
- the gas needs to be availabe (enabled) and not set to lost.

As all of these requirements seem to be met in your case, are you sure you set the correct ppO2 max to 2.0 bar? There are two ppO2 max, one for work and one for deco. You need the ppO2 max work here being set high enough to allow the OSTC to pick the Nx40.

BR
Ralph
Last edited by Ralph on Sunday 5. December 2021, 23:17, edited 1 time in total.
stryke
Posts: 9
Joined: Friday 7. July 2017, 19:10

Re: OSTC 2 : BO gas requirement

Post by stryke »

Hi,

OK, I forgot to change the PpO2 max deco. Now the calculation is ok

Thanks a lot
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