RFC: PSCR dive plots: Part 2.

[Willem Ferguson]

On 13/03/2018 12:28, Robert Helling wrote:
> On 12. Mar 2018, at 15:58, Willem Ferguson 
> <willemferguson at zoology.up.ac.za 
> <mailto:willemferguson at zoology.up.ac.za>> wrote:
>>
>> b) Adapting the gas partial pressure graphs to reflect what the diver 
>> breathes during bailout. When rendering the dive by creating a 
>> plot_info structure for each sample, the easiest mechanism of 
>> incorporating bailout would be to use the Shearwater approach: have a 
>> byte indicating Loop or Bailout and perform the appropriate 
>> calculation for gas partial pressures. Alternatively, it may be 
>> possible to reference the linked list of existing events, find the 
>> next bailout event and plot the pO2 depending on the type of bailout 
>> event (i.e. Bailout or OC->Loop). But this would incur significantly 
>> more computational overhead since this lookup will be needed for each 
>> plot_info on the dive profile.
>
> how is a bailout different than a gas change event (except semantics 
> of “emergency”). Why don’t you insert a gaschange to OC (i.e. with set 
> point 0)?
>
> Best
> Robert
>
A bailout can be an event where one changes from the loop to open 
circuit, but using the same cylinder.

For instance a CCR diver can use the bailout valve to switch from 
recycling gas to using the same diluent cylinder but using it in an OC way.

For PSCR, a diver can do the last part of the dive using EAN50, but 
recycling the EAN50. However, the last 10-15 m is usually done on OC (no 
emergency implied, just because the pO2 drop across the injector valve 
becomes very large at shallow depths). So, this PSCR diver switched to 
OC without switching cylinders.

So, in the case of rebreathers, bailout does not automatically mean a 
change of gas or cylinders.

Hopes this makes sense?

Kind regards,
willem



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