Bad SACs?

[Conor]

Hi all

was playing about calculating my SAC using the formula

SAC = [(vol of cylinder(l) x pressure of gas used (BAR))/(pressure at depth (ATM))]/time at depth(mins)

e.g. 40 min dive, average depth 19.2M, 12L cylinder, 160Bar used

(160*12/2.92)/40 = 16.4 lmin-1

I had a look on Google and found this link (http://www.spearfishing.org/bruces_tips/java/sac.html) which claims to be a SAC calculator but brings in your cylinder pressure rating, anyone have any idea why?

BTW what is the usual range for SAC values?

Cheers

Conor

[MATTBIN]

Bsac reckon sac of average diver doing light work = 25l/min
Known sac rates for panicked diver = 100l/min (that's based at surface, so 400l/m at 30mtrs!)

Mine about 23l/min, supposedly I'm a bit heavy on gas, we had a poll on this a while back.

Cyli press - maybe its for 300 bar jobs so as to allow for unequal gas laws etc.

Rgds
Matt

[Colin Marriott]

Eh up conor mate!

I use about 20 - 25l/Min, depending on how deep and dark it is
Up in the Farnes I was doing about 25l/Min on the Somali.

I'm sure some of the girls come out with more gas than they went in with!
( or maybe they've got gills? )

ColinM

[Fiona]

Originally Posted by Colin Marriott

Up in the Farnes I was doing about 25l/Min on the Somali.

ColinM

Eerr, isn't the Somali in about 30 metres, therefore I wouldn't be too worried about 25 litres a min. Unless of course you mean 25 litres per min on the surface and not on the wreck.

[Conor]

Howdo Colin

I think my SAC was about 16.6 on the same dive....assuming I'm calculating it right. You may have used up a bit of extra air getting untangled from the shot .

Fiona, the average depth on the dive was about 19.2, including stops. I'm guessing he means the equivalent surface consumption for the dive, is that what you mean?

Cheers

Conor

[tom]

Originally Posted by FionaB

Eerr, isn't the Somali in about 30 metres, therefore I wouldn't be too worried about 25 litres a min. Unless of course you mean 25 litres per min on the surface and not on the wreck.

Why would you be 'worried' about a surface rate of 25l/min? Yes it's higher than some - you for example are probably a lot lower - but not something to get distressed about.

As Matt said, 25l/min is often quoted as an average figure (though more experienced divers, and lots of women, tend to end up with much lower numbers). I bet there are people out there with higher SACs as well.

My own SAC is normally somewhere in the 20s, probably averaging about 26 at the moment, varying depending on the dive, conditions etc. It's higher than most people's, but so what. I expect it to come down eventually but I'm not losing any sleep over it.

You just need to be aware of your gas requirements and plan your dives / equip yourself accordingly.

[Juz]

My SAC is between 17-20 depending on the dive. Interestingly I find my SAC to be lowest when solo diving.

I consider mine to be high when judged against my peers (divers doing 60m on Tx with one Deco gas).

Juz

[Fiona]

If I remember correctly 25 l/ per min is on the surface so at 20 metres you would be using something like 75 litres per min.

But don't get hung up on air consumption, there has been lots of posts about it. As long as you plan your dive, monitor your air and are back on the boat with some then you have enough. So it really doesn't matter about litres per minute.

[Juz]

Originally Posted by tom

but so what. I expect it to come down eventually but I'm not losing any sleep over it.

You just need to be aware of your gas requirements and plan your dives / equip yourself accordingly.

Well said Tom.

Juz

[Helen F H]

When i dived with Paul at the weekend he was on a 12 and i was on a 10. We both came up with 50 bar left.

I also find that the type of dive affect the air i use - dark, cold and hard work - more, light and easy, less.

Im with Juz with the solo dive thing too.