ZHL-16 Calculations

[dmainou]

Hi,

After reading Mark Powell's Deco for divers, I have been attempting to perform some calculations on how the ZHL-16 model works. (i.e. to see at work the concepts around the book). However, it seems that I left high school too many years ago as I'm really struggling to put the formulas together with the right data.

I have been looking, for days, for a website where all parts are put together to calculate a decompression plan.

Do you know any website that contains such information or could you share a paper that puts everything together on a step by step basis?

I know that there is plenty of software that does the calculations accurately within seconds but I really want to take a sneak peak under the hood to feel more comfortable with what's happening.

Alternatively, would you please be so kind to describe a worked example for one tissue? (maybe in excel)

Thank you very much,

D

 

[gcbryan]

Read this article :http://njscuba.net/gear/trng_10_deco.html

I wrote a spreadsheet based on this.

 

[dmainou]

Hi,

Thanks for that.

I did come across that site. However, nothing happens when you "Click image to download spreadsheet."

Could I get a copy of your Xls? (definitely not for commercial use and not for diving just to see the principles at work)

much appreciated.

D

 

[gcbryan]

That link didn't work for me either. I just had to use the example for one tissue and figure out how to adjust that for 16.

I'll send the spreadsheet by PM if attachments are allowed (haven't checked yet). It's in a Works spreadsheet format. I don't know if it will work for you but I'll send it.

 

[Mr Carcharodon]

The material linked from the New Jersey site is very nice. But they left out Schreiner's equation that deals with gas loading during ascents/decents. That might be important depending on the dive profile.

Two others to look at:

Stuart Morrison's "DIY Decompression" DIY DECOMPRESSION

and Erik Baker's paper: "Some Introductory "Lessons" About Dissolved Gas Decompression Modeling" www.oceanwreckdivers.com/.../some_i...bout_dissolved_gas_decompression_modeling.pdf

 

[dmainou]

Have those two as well.

One of most useful have been workman's original Navy paper. It defines every part of every formula on a repetitive basis very illustrative.

Thank you very much.

D

 

[Dr Deco]

Hi Folks.

I am pleased that some folks have responded. I am very busy and things are not working for me, time wise.

 

[lamont]

The material linked from the New Jersey site is very nice. But they left out Schreiner's equation that deals with gas loading during ascents/decents. That might be important depending on the dive profile.

you can always approximate this with a series of extremely short stops to approximate a constant ascent rate. not very computationally efficient, but a modern processor is going to get really bored anyway...

 

[scubajim 1]

thanks for the paper it make for and interesting read

 

[tlj3071]

I have always wondered why Haldane, Buehlman, et al all used half-life as the basis for on- and off-gassing formulae rather than other statistical models (e.g. time-constants). In the long haul (> 9 or 10 periods) there is little difference, but in the short-haul there is. Comparing half-life to TC, for the 1st 6 time periods:
HL: 50.0%, 75.00%, 87.50%, 93.75%, 96.88%, 98.44%
TC: 63.2%, 86.46%, 95.02%, 98.17%, 99.33%, 99.75%

Are there any studies/documents that detail why the half-life model was chosen?

Tom