Question Enriched air analyzer needed?

[bradlw]

Maybe the newer analyzers are more standardized and things are better...but back when I was actively diving I was always 'troubled' by the lack of standardization and consistency in the analyzers and testing methods. I realized that mostly though that was just caught up in the analysis paralysis of my 'engineering' brain. For this reason I would love to have my own analyzer...at least in theory....but I never did.
When I went through my technical diving and blending training I was taught to be very methodical about the way the analyzer is used. My instructor's analyzer was calibrated based on 1atm, static flow rate.... and if you cracked the valve open and let the gas flow across the sensor at higher velocity it would read higher because of the increased partial pressure. Some shops tried to hit a certainly standard flow rate with their analyzers usually with no great way to measure that rate.... Not many shops I ran across had analyzers set up to actually measure 1atm static flow....and rarely would I be familiar with the particular specs and operation of their particular brand/model of analyzer so I'd juts have to take them at their word.....

 

[tursiops]

Maybe the newer analyzers are more standardized and things are better...but back when I was actively diving I was always 'troubled' by the lack of standardization and consistency in the analyzers and testing methods. I realized that mostly though that was just caught up in the analysis paralysis of my 'engineering' brain. For this reason I would love to have my own analyzer...at least in theory....but I never did.
When I went through my technical diving and blending training I was taught to be very methodical about the way the analyzer is used. My instructor's analyzer was calibrated based on 1atm, static flow rate.... and if you cracked the valve open and let the gas flow across the sensor at higher velocity it would read higher because of the increased partial pressure. Some shops tried to hit a certainly standard flow rate with their analyzers usually with no great way to measure that rate.... Not many shops I ran across had analyzers set up to actually measure 1atm static flow....and rarely would I be familiar with the particular specs and operation of their particular brand/model of analyzer so I'd juts have to take them at their word.....

There are a lot of things that can screw up an analysis....but the underlying issue is how close do you need to be? Within a percent is fine for the OP; exactly the flow rate and exactly the humidity and temperature are for precision work, which is not needed at the OP's level.

 

[Tracy]

Maybe the newer analyzers are more standardized and things are better...but back when I was actively diving I was always 'troubled' by the lack of standardization and consistency in the analyzers and testing methods. I realized that mostly though that was just caught up in the analysis paralysis of my 'engineering' brain. For this reason I would love to have my own analyzer...at least in theory....but I never did.
When I went through my technical diving and blending training I was taught to be very methodical about the way the analyzer is used. My instructor's analyzer was calibrated based on 1atm, static flow rate.... and if you cracked the valve open and let the gas flow across the sensor at higher velocity it would read higher because of the increased partial pressure. Some shops tried to hit a certainly standard flow rate with their analyzers usually with no great way to measure that rate.... Not many shops I ran across had analyzers set up to actually measure 1atm static flow....and rarely would I be familiar with the particular specs and operation of their particular brand/model of analyzer so I'd juts have to take them at their word.....

There is an old saying, it goes "Measure with a ruler, mark with a chalk, cut with an axe."
Basically, the calibration needs to be good enough for the application. In recreational nitrox, if your analyzer varies plus or minus a percent, that is good enough. You shouldn't be doing any diving close enough to a line that a analyzed 32% tank that is actually 35 will be your end.

 

[boriss]

OP, you've received good advice, but one thing that wasn't discussed is to ensure you know how your tanks are filled. If you're always diving the same banked nitrox this information isn't as important, however, many times you get a top-up (of a potentially different mix) or they'll partial blend a mix for you, etc. It's important to let the gasses mix. I've had mixed results testing partially blended tanks upon picking them up. If I know they were blended, I'll shake them around, roll them, etc.

I'm sure someone can explain how all that works, but wanted to just give you a heads up. You don't want to just get a reading from the last gas that was filled.

 

[broncobowsher]

The Nitrox class I had states that you must verify yourself what gas is in the tanks and mark it yourself. The shop has a log book for every Nitrox fill of your reading and you sign off on it.

 

[rhwestfall]

big nitrox wrap stickers on them because one shop requires that

The only tank I stickered was because it is black..... thankfully shops here aren't that silly.

In SB fashion of derailing, do they remove the stickers to do a VIP?

 

[gmerick]

I have taken my own analyzer on every dive trip. It is in a sealed pelican 1050 case and has it's own pocket in my regulator bag.

When I signed up for the local Nitrox class, I bought my own analyzer the same evening. I showed up for the class with it. What good is "verifying" a tank with the same analyzer the shop uses? I've also been to three dive resorts and a liveaboard where they fill Nitrox from their bank, sometimes days prior. All of them did their analysis at the bank, not at my tank. While not that often, I have had differences between my analyzer and the operator stated content. Once it was because my O2 sensor had given up the ghost, and I got a good reading after switching to my spare. The other times, the operator re-checked what was coming out the fill whip, and discovered the actual content was off by 2% or more. Once the fill whip was dispensing EAN40 instead of the stated 30%. As the dive was planned for less than 80 feet, the whole group re-analyzed tanks, and decided to go ahead with the dive, respecting the planned depth. The operator apparently had a long night ahead getting a 6 tank bank rebalanced at the intended 30%.

 

[NothingClever]

Owning your own analyzer is cheap insurance for a safe dive.

Similar to another poster here, mine is stored in a padded case and stays in my boat crate.

 

[Marie13]

The only tank I stickered was because it is black..... thankfully shops here aren't that silly.

In SB fashion of derailing, do they remove the stickers to do a VIP?

Every other year.

 

[tursiops]

Every other year.

You mean they only remove the stickers every other VIP, or you only get a VIP every other year?