Visuals on all emptied tanks?

[ScubaScott]

For those in the know, in our country, is it standard practise for a shop to do a viz on any tanks coming in already drained of gas, and looking to be filled?

A bit more info - 2 yr old tanks, all hydro,viz stickers easily read.

SS

[mglasspo]

It's a good idea to have them VIP'ed regardless of how old it is if there is a chance you have gotten water/debris in your tank. I know two of the stores I go to do VIP's on empty tanks. I don't know if you have to tell them it's empty or not, never had an empty tank, but I'm also sure they'll charge you for it.

If they don't do it for you, I would suggest getting it done, regardless.

Mike

[Groundhog246]

I think the short answer is yes.

What's the date on the viz stickers? you mention they're readable, but not the date. A visual inspection is required yearly, so if the tank is two years old with a two year old sticker, you're overdue.
Also, if you reach zero pressure, you risk water or other foreign matter entering the tank and a visual will be required. If you want to lower the pressures for storage (off season) drop em to around 200PSI, but not to 0. If they're at zero because somone shipped em to you, then a visual is definitely indicated.

[Ontario Diver]

If I remember correctly, Transport Canada does not require an internal visual inspection but does require an external inspection prior to any fill.

It is standard practise in the scuba industry to require VIS stickers but I do not think that it is required by law. I DO THINK that it is a VERY VERY GOOD idea tho.

[Bubble Boy]

Ontario Diver once bubbled...
If I remember correctly, Transport Canada does not require an internal visual inspection but does require an external inspection prior to any fill.

It is standard practise in the scuba industry to require VIS stickers but I do not think that it is required by law. I DO THINK that it is a VERY VERY GOOD idea tho.
It is an "industry standard" as they have mentioned above. As Ontario Diver stated TC only requires the vis by law at the time of hydro. Dive shops are looking after your best interests by doing an internal vis on your tank when brought to them empty --ie contaminants could have entered your tank. Obviously if they drain the tank to do a partial pressure fill, this would not apply.

[scubasean]

ScubaScott once bubbled...
For those in the know, in our country, is it standard practise for a shop to do a viz on any tanks coming in already drained of gas, and looking to be filled?

A bit more info - 2 yr old tanks, all hydro,viz stickers easily read.

SS

Yep...I've also been told what others have said...If a tank doesn't have pressure, it may have debris in it...

--Sean

[ERP]

FWIW - I had to drain my tanks recently to ship them, I mentionted it to the local LDS after arriving at the new location. They didn't do a vis on the tanks.

[ScubaScott]

The tanks visuals were done by the same LDS about 1 month ago. What happened was I brought in one tank that had about 100psi and the other completely drained. The shop performed visuals on each tank, and of course charged me for it.

Now - since it is standard practise to check them for debris or moisture, I don't have a problem. I did at the time think the Shop was trying to screw me for some extra $$$$, as I didn't know about this.

Another question - I was under the impression that even 1# of air in a cylinder is enough to keep out moisture and crud - I guess this isn't the case?

Out of air in SSM,

SS

[Doppler]

ScubaScott once bubbled...
The tanks visuals were done by the same LDS about 1 month ago. What happened was I brought in one tank that had about 100psi and the other completely drained. The shop performed visuals on each tank, and of course charged me for it.

Now - since it is standard practise to check them for debris or moisture, I don't have a problem. I did at the time think the Shop was trying to screw me for some extra $$$$, as I didn't know about this.

Another question - I was under the impression that even 1# of air in a cylinder is enough to keep out moisture and crud - I guess this isn't the case?

Out of air in SSM,

SS
<Anne Landers mode on>
Dear Out of Air:

I really think the issue is where were the tanks drained? IF it was done on the surface, then most dive shops will not make a fuss, but if the tank was underwater, well, they view that differently. Of course the worst one is draining a tank underwater and then taking it deeper!

Is you LDS trying to get extra dough, don't know. Ask them to explain their policy so that you fully understand it. Tell them your concerns.

And yes, any pressure above ambient will keep **** out of your tanks. I am not going to talk about changes in atmospheric pressure due to passing fronts and draining a tank in the mountains and bringing it to sea level... but essentially you are correct. However, correct may not be enough to convince a LDS operator.


Doppler

[Groundhog246]

ScubaScott once bubbled...
The tanks visuals were done by the same LDS about 1 month ago. What happened was I brought in one tank that had about 100psi and the other completely drained. The shop performed visuals on each tank, and of course charged me for it.

Now - since it is standard practise to check them for debris or moisture, I don't have a problem. I did at the time think the Shop was trying to screw me for some extra $$$$, as I didn't know about this.

Another question - I was under the impression that even 1# of air in a cylinder is enough to keep out moisture and crud - I guess this isn't the case?

SS

Certainly 100PSI should be enough to keep debris and moisture out, so "gouging" comes to mind. Did they inform you about visuals first, or just ahead and do them. If they just went ahead, especially with 100PSI in the tank, I'd be upset and considering another LDS.

OTOH, why the heck did you have one at 100PSI and one completely drained? In 60 dives, I have only once run a tank under 500PSI when I had a free flow when I took a deep breath on the surface in near freezing temps at the end of a dive. With help from my buddy we got the tank shut off before it went under 300PSI. I always dive rule of thirds. One third out, one third back and one third reserve and usually end a dive with 900 to 1000PSI remaining.

[Butch103]

Groundhog246 once bubbled...


OTOH, why the heck did you have one at 100PSI and one completely drained? In 60 dives, I have only once run a tank under 500PSI when I had a free flow when I took a deep breath on the surface in near freezing temps at the end of a dive. With help from my buddy we got the tank shut off before it went under 300PSI. I always dive rule of thirds. One third out, one third back and one third reserve and usually end a dive with 900 to 1000PSI remaining.

...........It took me 100 dives to drain a tank. In error of course. And I drained it at surface essentiallly.

Long story, and I bailed for my own safety............

[seahunter]

It is and has been a scuba industry standard to require a visual of any empty tank before filling.
How rigorously this standard is enforced is unknown. I suspect many newer dive store owners don't even know about it.

At my LDS (insert chuckle here!) we have posted on a large sign the regulations we follow re air fills. Such items as no overfills, required hydros and visuals, etc are spelled out.
Our posted policy is that "No tank with less than 50psi will be filled without having a visual exam."

Now for the practical details. It's very hard to measure 50psi or even 100psi. Many gauges simply don't measure accurately below 500psi. We use the simple process of opening the tank valve. If a good blast of air comes out, it's OK. If no air or a very meager amount comes from the valve, it's judged as less than 50psi and requires a visual.
I don't need the $10 or $15 so badly that we would make up visuals. I will not irritate a diver/customer for any amount given a choice. It's a safety issue. The diver can either wait for and pay for the visual or take it elsewhere. At least he knows that we are concerned about his tank and his and our safety. If he wants to take it somewhere else where he can get a fill without the required visual, he will have to live with the knowledge that the other store doesn't care.

As I wrote this reply I realized there is an issue that has not been discussed and maybe not even recognized by those of you who like to sniff out potential problems. Do you realize that there is no training required nor even available for dive store owners?
Many of these 'industry standards' developed over several years and are well-known to the established owners but, someone who has just started a new store does not have that knowledge and there's no place to find it.
Where does it say that a dive store operator should NOT fill an empty tank?
Dive store owners do not necessarily have PSI Training, air station maintenance training, scuba equipment repair training, professional instructor training or any other scuba related training or experience necessary to operate a scuba facility safely!!

How about another related and equally emotionally charged issue? At our LDS, we do not put tanks to be filled in a water bath unless requested. Water baths, while common, are an anachronism. They never were of any benefit and even less so today. Current research based on modern physics and metallurgy demonstrate this fact to be true. I warrant however, that many divers would be upset if told their precious tanks was not going to put in water when being filled.

[DA Aquamaster]

A water bath does allow a faster fill as long as the water is colder than the tank as it dissapates the heat faster. This is also bigger issue I think with steel tanks as aluminum sheds heat very quickly wet or dry. Of course if you let the tank cool to room temp and then top it off you can achieve the same thing and ensure a good fill.

The biggest danger of a water bath is that any water that gets in the valve or in the fill whip can and will be blown into the tank. Sloppy filling with a water bath is in my opinion and experience the leading cause of water getting into tanks.

If your tank is anywhere near the water bath with the fill whip unattached, the tank valve needs to be opened briefly to blow any water out of the valve. If the tank/valve has been in any kind of water in the recent past, this should be done anyway to ensure any left over or stray water that may be in the valve is blown out. It's a good idea for you to do this when you bring your tank in for a fill as the under paid summer help at the LDS may not.

[ScubaScott]

Groundhog246 once bubbled...


OTOH, why the heck did you have one at 100PSI and one completely drained?

I live on the water of big, beautiful Superior. However, it stays about 5-10' deep for almost a km, until you reach the shipping channel. I was on holidays last week, and with the beautiful weather, I went in a played, along with my dog.

The drained tank was after 1hr, I starting purging my reg while my dog is swimming on surface, catching him and freaking him out with all the bubbles. The 100 psi tank was just exploring and practicing drills for upcoming DIRF in the same location.

Before anybody gets out of hand on the dangers of diving solo and draining tanks, remember I could stand up and be out of the water.


Thanks for the input guys

SS

[Doppler]

seahunter once bubbled...


SNIPPED

At our LDS, we do not put tanks to be filled in a water bath unless requested. Water baths, while common, are an anachronism. They never were of any benefit and even less so today. Current research based on modern physics and metallurgy demonstrate this fact to be true. I warrant however, that many divers would be upset if told their precious tanks was not going to put in water when being filled.

I agree. Fact is, I usually insist that my tanks are not filled while in water. The filling procedures used in conjunction with cold water baths are

1/ functionally useless -- there is no practically significant effect on the internal temperature (i.e. the gas) unless the tanks sit for longer in the bath than is customary... and frankly a slow fill goes most of the way to acheiving the same results

2/ is potentially harmful to the tanks and manifold... water can very easily be introduced into the system. Uninformed LDS staff pick up tanks incorrectly while putting in or taking out tanks.

3/ encouranges fast fills. Uninformed LDS staff believe that the cold water bath fixes all ills and is a licence to crank gas at full bore... this increases gas temperture... see reason 1.

All that said, there is a store in North Florida that features a refrigerated water bath. The tanks are connected to the whips and then put into the bath and a very slow fill commences. Quite the sight to see your pressure gauge rise when you jump in to start your dive!

Thanks

[pufferfish]

PSI Filling Cylinders in Water- Time to Review (http://www.psicylinders.com/library/wetfills.htm)

The Case for Dry Filling (http://www.naui.org/pdffiles/tankfill.pdf)

So why do I see so many shops still doing wet fills? How about a new law against that! :D

[Doppler]

pufferfish once bubbled...
PSI Filling Cylinders in Water- Time to Review (http://www.psicylinders.com/library/wetfills.htm)

The Case for Dry Filling (http://www.naui.org/pdffiles/tankfill.pdf)

So why do I see so many shops still doing wet fills? How about a new law against that! :D


OH NO!!! THE TANK POLICE!!!


Tanks for the links Puffer... good info and confirming that "gut feeling."

More smog today, eh?

See yer

[pufferfish]

The only Scubaboarders in Ontario who don't have to be concerned about smog (SO2, NO2, ozone, and fine particulates) in their tank fills are Cat and Scubascott in Thunder Bay and the Sault. The rest of us are coughing and wheezing down here in southern Ontario.

Ontario Air Quality (http://www.airqualityontario.com/reports/summary.cfm)

Mississauga, Windsor, and Sarnia get particularly bad with respect to SO2, particulates, and NO2. These contaminants are poorly removed by the activated charcoal in the compressor filtration system and end up in the fill. Hyperbaric ozone is not an issue as it is removed very efficiently by the charcoal but on surface it may worsen things like asthma.

The way around this is to move to Thunder Bay or only use the compressor at night when the temperatures, humidity, and smog levels are lower.

There are some out their in the know who think some of these contaminants particularly hyperbaric SO2, NO2, and fine particles may affect the respiratory and cardiovascular system adversely particularly the unfit diver over the age of 45 or those with pre-existing heart disease. Pulmonary edema of diving comes to mind. I suspect for the healthly young twenty year old diver hyperbaric smog would be reasonably tolerated, but if this could be avoided like second hand smoke all the better.

Once again suggest to your LDS not to fill during during smog advisories if possible or to wait until after midnight (check air quality web site) and use the compressor when the air quality moves into the 'moderate' or better quality zone.

A message from your local smog inspector:D

[seahunter]

Puffer and I on the same page! Who'da thunk?!

Read the PSI link that puff has supplied dopp and you'll see that the refridgerated fill is even less desireable than the water bath. Mind you this is from a safety point of view. I'm sure that divers are flocking to that Florida shop under the impression that they are getting a 'better' fill.
I've never been quite sure what is meant by a 'better' fill. Most divers assume that's a fill to or above the stamped pressure. If the pressure in your tank is above 3000psi even after you get into the water in Toby in May, is that a good fill?

Should I offer "Free, Refridgerated Fills"? I'll need to increase my personal and staff life insurance first. It is after all, invariably scuba store staff, not divers, that suffer in a tank accident.

The suggested proper rate for filling is 300 - 600psi per minute. At that rate the tank will remain as close to room temperature as is practical. That is the rate we try to stick to at S2K but many divers are simply impatient and won't wait the required 10 minutes. Putting the tank in water does NOT help!

Our posted sign also clearly states that there will be a loss in pressure. Some divers complain about that but it's really dumb. The same divers usually bring in their tanks with between 900 and 1500 psi to be filled. What's the problem with a loss of 2-300 psi? Of course they also complain about the high cost of our free fills (kidding!!).
Filling your tanks properly is safer for you and for me. It's better for your tank too. Bottom line it's the way it's supposed to be done!! Save your criticism.
Besides, I don't give free fills so you can whistle in and out without a second glance at the neat, new stuff in the store - think about it.

[divebuddydale]

S.H.

I understand totally the "free fills" aspect of your shop. It is pure unadultrated MARKETING. I think it is a good method to get divers to visit your store. (although I never have visited because I am not close enough).

Now about the Loss of pressure, why do some tanks lose pressure (is it because of the ambient air Temperature?) My tank is on 3000 PSI, and was the day I got it filled and still is now..

Just curious.

Dale

[wetman]

I think hes referring to the pressure thats lost just after a fill in the time the tank cools down.

But speaking from a purely consumer point of view - all these regulations asside, I'd go to the place where i get the "best" fills. And in a consumer sense - that is the place where my tank comes out with the most air just before i hit the water. I'm not talking aluminum here, only steel. However, I'd bet theres even a bit of play in the aluminum world because having gone to cozumel, every al tank we got was filled to 3200 +- a bit. Given the years of history of overfilling on steel tanks, there has to be some safety margin if for no other reason than companies like PSI must know this is going on.

My bet is all their warning against it is them covering their collective asses. Anywhere we've gone in the states has pretty much asked us what we wanted tanks filled to. I've heard people say its only a few hundred psi - well, true, but that few hundred psi could translate in to many minutes more of a perfectly enjoyable dive. I'll take every second i can get down there.

So, basically, if i have to choose between two tive shops for fills, all else being equal, i'd go to the shop that gives me a longer dive. Its just that easy. And i'd imagine, shops have that mind set to contend with when they're doing this stuff so it must play into their descisions regarding such things.

steve

[DA Aquamaster]

At the risk of really starting an argument, the concept of a service pressure is based on the air being at room temp.

Even at 300-600 psi/min a tank will heat a little and when it cools you will have maybe 2800 psi rather than 3000psi. Now if you intentionally overfill it by about 200 psi, you will be at your 3000 psi service pressure rather than at 2800 psi after it cools it room temp. This isn't a problem and it is preferable to the pretty standard 2800 psi fill.

The only other option is to fill to 3000 psi and let the tank cool completely then top off the remianing 200 or psi you need to fill the tank.

I use steel tanks exclusively and do fill with a water bath with proper precautions. I get good fills without having to let them sit forever which is an issue when filling maybe a dozen tanks at the end of the weekend. Outlawing a water bath would be another great example of the government protecting us from the unthinking types who sadly enough just find something else to screw up anyway.

[pufferfish]

Seahunter once commented:

"G&S is a fine store and has great air. They are our recommended shop in Tobermory. We take over 500 divers to Tobermory each summer and we use the services of G&S."


Yes they and the other shop have 'great' air as they both use Maxxam Analytics to check it,.....are we still on the same page? :mean:

Since you must be doing at least a thousand or so tank fills up in Toby, what do you say about your tanks being wet filled? I imagine that when the owner is doing it (I saw him filling tanks three weekends ago) one need not worry too much about water getting blown into a tank. However last summer it was the pubertal help filling my tank I was concerned with regarding water.

Maybe you can have a word with the powers that be up there and suggest they not wet fill as per modern science suggests.
Cooling tanks (http://www.gswatersports.com/fill.html)

[seahunter]

It'll be as hard to get dive stores to stop using water baths as it is to get divers to stop spitting in their masks!

Toby is a good place to start though. They will often fill 4 or more tanks at once in the same bath and do this all day long. By late afternoon the 'cool' water bath is about 90 degrees. As well, they generally completely submerge the tanks in the bath which greatly increases the likihood of a problem. It ought not be a problem once they are educated since they already do a relatively slow fill. They fill from the compressor rather than from a cascade. Filling from a cascade is much faster (instant!) while filling from a compressor, especially multiple tanks, is filling at the right speed for the best fill anyway.
The air in Toby is fine but that's NOT because they get it tested at Maxdollar. I know you're being facitious because you can't possibly think the air test center affects the air quality!

Please read the links that puff provided BEFORE you comment on this thread. The info you want is in there.

By law I can fill a tank to it's stamped pressure only. If filled properly, you get a full tank. If a dive store owner is prepared to break that law (assuming he evens knows about it!), what other laws do you suppose he would break to make money??

[pufferfish]

seahunter once bubbled...
Toby is a good place to start though. They will often fill 4 or more tanks at once in the same bath and do this all day long. By late afternoon the 'cool' water bath is about 90 degrees. As well, they generally completely submerge the tanks in the bath which greatly increases the likihood of a problem. It ought not be a problem once they are educated since they already do a relatively slow fill.

Let's be a little more accurate here SH with our facts. Your "they" is one shop in Toby who does wet fills. The other shop across the street does dry fills. There is a choice here and like Doppler said he does not let anyone wet fill his tanks especially when that fill station help listens to Avril Levigne and The Back Street Boys. We all know the recent research on teen brains which basically says they should have a sign on their forehead which says, "under construction."

You state "they" completely submerge the tanks which increases the likelihood of a problem and yet you get over a thousand fills a year there. Why don't you use your commercial clout to request they switch their practice backed up by the science of course? If they won't consider it there is always a dry alternative across the street.

[mglasspo]

I'm going to weigh in on a couple of issues here. I'll start off with fills :)

I consider a "good fill" to be when I leave the store, it is filled to the service pressure. When I connect my SPG, at surface, it should read between 2900PSI-3200PSI (accounting for temperature of the tank -- it has just been pulled out of my car)

I have only once been unsatisfied with a fill, and I think it was just due to a mistake when filling, I once got a tank at 2600psi.

As for running out of air, I've had it happen twice, unfortunately, and it's not due to me trying to stretch my bottom times, it was due to equipment failure, more specifically, my SPG started to stick, so I ran out in about 15ft of water during my safety stop. We had a look at the SPG after the dive, thought we'd fixed the problem, had 2 uneventful dives, and then the guage stuck again. So that led to a replacement (temporary) of my SPG, followed by some shopping around and purchase of my air integrated dive computer. Of course, both my problems were handled properly as I like to keep company with attentive buddies.

Mike

[seahunter]

To get a fill to 3000 psi at room temperature (70 degrees (20 for you kids)), you need to take at least 30 minutes for a fill at the dive store. Even then the pressure will still drop a bit. When you arrive at the dive site where you normally put on your regulator and SPG, the air temperature is certain to be less so the tank pressure will definately be less than 3000 and likely closer to 2500.

Let's discuss this fact and the problem for the store owner in that divers assume they're being ripped off if they don't get a 3000 psi fill when in fact, that's impossible to do if you follow the proper fill procedures - definately impossible given that most divers won't wait around for 30 minutes.

I'll start with a few suggestions of my own:

1. Educate yourself - read the links that puff has provided on this post.
2. Buy your own compressor and then overfill your own tanks.
3. Bring (or buy) a magazine to read while you're waiting for your fill at the dive store. We provide a lounge with cold drink and snack machines for that very purpose.
4. Get real - why is 200 or so PSI so important when you never use all the air anyway. An informal survey this past week showed 10% of all tanks coming in for fills at at over 1000psi, 80% at 800 to 1000 psi, 5% between 200 and 800 and 5% requiring visuals because they were under that.
5. Check your safe diving rules - you should have 1000 (1/3) of a tank remaining after every dive.
6. Buy more tanks. This is not unrealistic nor self-serving. I make about $15 ($15 not 15%) on a tank and nothing on air fills so I don't really care about making a sale. I do care about keeping you happy!
7. Give me a break - gasoline is .08 cents per millilitre (cc). That's barely enough to start a fire much less your car. Gasoline is sold by volume and is much more greatly affected by temperature changes than is air.

The point is that I'm open to suggestions but save your criticisms. The scar tissue from puff, GTA, divebuddy, dopp and hundreds more before you has rendered me pretty much immune to crying.

[pufferfish]

seahunter once bubbled...
7. Give me a break - gasoline is .08 cents per millilitre (cc). That's barely enough to start a fire much less your car. Gasoline is sold by volume and is much more greatly affected by temperature changes than is air.

The point is that I'm open to suggestions but save your criticisms. The scar tissue from puff, GTA, divebuddy, dopp and hundreds more before you has rendered me pretty much immune to crying.

Seahunter and we figured you were down for the count after a whole week away from the board :D

Now about that claim above re gasoline being more affected by temperature than air. I make no claims to any expertise in physics (I will leave that to Doppler) but my gut feeling said I had better check that SH fact about gas vs. air expansion with temperature.

From my Schaum's outline I think this applies to the question.

Change in volume is proportional to the original volume, the change in temperature, and the volume coefficient of thermal expansion.

The coefficient for gasoline is 950 x 10 (-6)/ degree C
The coefficient for air is 3400 x 10 (-6)/ degree C

Doesn't this mean that air is far more affected by temperature changes than gasoline?

Doppler can you set the record straight here.
Is SH on the mats again,...one, two,.......:D

[cat]

T'ain't physics, it's physical chemistry, so I'l take this one on...

In a nutshell: pV=nRT (Ideal Gas Law)
Hold n (the moles of gas in the tank), and V (the volume of the tank) constant. R is the gas constant.

That means p/T (store) = p/T (in the water) where T is measured on the absolute scale (Kelvin = degrees C + 273). You can measure p for this exercise in psi, bar, atm, KPa, whatever floats your boat (just don't tell my old chem instructors that I'm mixing SI and imperial units).

Assume the tank is at equilibrium in the dive store on a hot, 35C (308 K) southern Ontario summer day. It's filled to 3000 psi. Jumping into 10C (283 K) water at Toby would do this:
3000 psi/308K = ? psi/283K

Now there's only 2756 psi in the tank.

Jumping into Lake Superior's 4C water with the same tank gives me only 2707 psi - but that's about as extreme as the difference gets.
(I like tanks that are dry filled in nice cool rooms and topped up after equilibrating for a while :D - so long as they don't get too hot in my trunk enroute - stretched tanks.. eeew)

Volume changes for liquids (expansion and contraction with temperature) are, as pufferfish stated, much lower. Hardly worth pouncing on seahunter over that, though - you two were playing *so* nicely together only a short while ago, too. You'd think you were siblings, the way you fight :rolleyes:

(Not sure why I have to get back with 1000 psi - rock bottom for a good chunk of my present diving is less than that and I use some of that allowance on the way up)

PS: no smog but we do have a pulp mill. The prevailing wind is *usually* the other way but when it isn't... yuck! So far I've had no Bowater-flavoured tank fills...

[Doppler]

pufferfish once bubbled...


Seahunter and we figured you were down for the count after a whole week away from the board :D

Now about that claim above re gasoline being more affected by temperature than air. I make no claims to any expertise in physics (I will leave that to Doppler) but my gut feeling said I had better check that SH fact about gas vs. air expansion with temperature.

From my Schaum's outline I think this applies to the question.

Change in volume is proportional to the original volume, the change in temperature, and the volume coefficient of thermal expansion.

The coefficient for gasoline is 950 x 10 (-6)/ degree C
The coefficient for air is 3400 x 10 (-6)/ degree C

Doesn't this mean that air is far more affected by temperature changes than gasoline?

Doppler can you set the record straight here.
Is SH on the mats again,...one, two,.......:D

I cannot find a reference for the Volumetric Coefficients of Gasoline and of Air... puffer, you really have a Schaum's close at hand!? That's a brilliant series! And you are a strange man! I like that. :D

ANYHOW... we'll take puffer's numbers as given... now remember folks, we consider thermal expansion in three discrete forms... Linear, Area and Volume. We are talking volume here I guess since both liquids and gases take nicely to the shape of the container that holds them and therefore tend to exist -- in both a mathematical sense and in the real world in multidemensional states usually -- and somewhat erroneously -- termed : three dimensional.

So volume... well, the math is pretty simple, but let's make it even more simple... and let's not consider the expansion and contraction of the vessel holding our gas and ... gas.

Ten to the minus 6 is present in both expressions... so let's lose it. We are left with 950 and 3400 and the statement that this has something to do with temperature... and the temperature is also present with both expressions, so let's lose it too.

OK. So now we have a coefficient... something that effects something else. And one is 950 and the other is 3400. Expressed as a ratio this is about 1:3.5 and a bit. Which basically means that for a given quantity of stuff and a given rise in temperature, gasoline will NOT expand as much as air. Or conversely, one could state that similar changes in temperature have a greater effect on Air than on Gasoline.

Thermal coefficient is an expression of several forces acting on a substance from within the substance... but in the final analysis, SH is out!

Doppler

And yes... this is the borderline stuff... gas laws are chemistry and all that stuff takes place on the outside of the "atom" while the forces hold everthing together are at work deeper int he "atom" and fall into the nice neat and exciting world of physics... real science
TEHEHEHEHEHEHE

[cat]

Biology, explained well enough, is chemistry.
Chemistry, explained well enough, is physics.
Physics, explained well enough, is mathematics.

... and no-one seems to be able to explain mathematics well enough :D

[Doppler]

cat once bubbled...
Biology, explained well enough, is chemistry.
Chemistry, explained well enough, is physics.
Physics, explained well enough, is mathematics.

... and no-one seems to be able to explain mathematics well enough :D

Run away with me Cat.... :wacko:

[pufferfish]

Thanks professor Cat and Doppler for your chemisty and physics classes there. It is nice to have some experts around for us jack of all trades, master of none types.

Now Cat you have a serious problem if you are doing fills downwind of that Bowater plant. They are number two in the country for air pollution releases and you might have a serious problem taking some of those nasties to depth. Hydrogen sulphide is the one that gives that sweet smell right? I guess that is the one time the PADI tank taste and smell test might actually work!

Have you been up to the Rossport Inn yet for dinner? Awesome food and real nice atmosphere as the Inn was built in the late 1800's. Down a little further the Kinniwabi Pines restaurant in Wawa is real nice too. And if you want to try your hand at kayaking the Pukaskwa coast I'd highly recommend David Wells op in Wawa, Naturally Superior Adventures. Stunning scenery there.


Ok back to the tank fill pressure thread.

[cat]

The list of chemicals that can be scented on the air around many pulp mills (Cornwall's is really horrible, IMO) is long and varied and includes things like mercaptans. Definitely puts me off eating on the rare days that wind blows in the wrong direction. H2S, the stench (I wouldn't call it a sweet smell, pufferfish) of which I commonly associate with black anoxic mud and Alberta gas wells, oxidizes fairly readily to sulfur oxides (which still stink). Fortunately, the days where the wind blows from the mill to the town are very infrequent. Haven't had a stinky tank yet, nor heard of one. Suspect I won't - the guys who fill tanks and change the filters at Wally's (including Wally and his son) breathe more of it than I ever do - enlightenened self-interest is a good thing.

I have not had time to do much non-diving related travelling - it's busy season for us aquatics types (thought I counted as a JOAT too :rolleyes: ) Still managing to take in a decent dose of stunning scenery - there's rather a lot of it up here, so it's unavoidable.

Doppler: What? And leave all this stunning scenery? :D

[Doppler]

cat once bubbled...
SNIPPED


Doppler: What? And leave all this stunning scenery? :D

Scenery... you can't see it for all those Rocks and Trees. (Heard the Rocks and Trees song, at Mariposa this last weekend. Do you know that one??)

Rossport is the launching point for our Gunilda dives and the Rossport Inn has quite the rep. with our crew! Strange and eccentric owner!

Tank fills!!! Puffer, what would you suggest one does for a portable compressor? Any suggestions regarding filter set up or ways to manage the risk of contamination while on Expedition... to places like Rossport where there is no "local" air station.

[ScubaScott]

...... wow. I'm confused......

SS

[Doppler]

I must say that as much fun as we get poking holes in each other's posts... Scar Tissue, really!!! SeaHunter is correct on several scores when it comes to the "Short Fill" issue.... First of all, it's not a big deal. A couple of hundred psi or a few BAR shouldn't make much of a difference to your dive plan. Secondly, there's not much that one can do to change it... "Yer cannea defy the laws o' physics, Captain!"

Of course, the CGA regs do allow for a percentage overfill to compensate for temperature / pressure drop, but even so, you gotta be more flexible in your expectations for a fill guys.

Now if it were liquid air the thermal effects would be less... HAHAHAHA

Doppler

[Bubble Boy]

seahunter once bubbled...

By law I can fill a tank to it's stamped pressure only. If filled properly, you get a full tank. If a dive store owner is prepared to break that law (assuming he evens knows about it!), what other laws do you suppose he would break to make money??
The main thing to do is follow the manufactures specifications and fill at a rate not exceeding 300-600 psi/min. CSA B-340 clearly states that the service pressure shall not be exceeded when the container temperature is 15 degrees C and 125% service pressure when the container is 55 degrees C.

I must agree with you SeaHunter that 200 psi should not make a difference to some one that plans their dive and dives their plan.

[pufferfish]

Doppler once bubbled...
I must say that as much fun as we get poking holes in each other's posts... Scar Tissue, really!!! SeaHunter is correct on several scores when it comes to the "Short Fill" issue.... First of all, it's not a big deal. A couple of hundred psi or a few BAR shouldn't make much of a difference to your dive plan. Secondly, there's not much that one can do to change it... "Yer cannea defy the laws o' physics, Jim!"

Of course, the CGA regs do allow for a percentage overfill to compensate for temperature / pressure drop, but even so, you gotta be more flexible in your expectations for a fill guys.

Now if it were liquid air the thermal effects would be less... HAHAHAHA
Doppler

I would have to agree with you Doppler that Seahunter was bang on with respect to his commentary on tank fills. Had he just left off that point #7 it would have not set off my fact or fiction radar,..ha,ha. Now Cat if Seahunter fills a tank at 20 C and takes the appropriate time say of ten minutes to do a dry fill and fill to 3000 psi, what would the pressure drop be after letting the tank cool back to 20 C. And after a fill done in five minutes? Probably no less than 2800 psi right? Now I get it free fills, free coffee, and a forced ten minute respite in the shop to look at stuff I need. Very smart indeed :D

So Dopp have you dove the Gunilda? Wow 240 feet in the mother of all fresh water lakes no less. You are right about the owner of the Rossport Inn who I believe is an ex USAF pilot. He has all kinds of stories to keep guests entertained. I can't remember how he met his wife but that was a neat story too. I do recall when one goes to register at the desk there is a large newspaper article on the wall to the left about the Gunilda and a diver death on it. I guess this is just to warn divers before they take the plunge on her.

Remembering I am not an expert on compressors but do consider myself quite well informed now (in a large part thanks to SH and self-interest) I would say your concern about air quality using a portable compressor (?gas) would be the number one risk management issue on such an expedition. The reason I say this is I assume divers heading down on the Gunilda are the cream of the crop and therefore have the best equipment and many years of deep mixed gas experience before attempting such a dive. Please don't tell me that deep diving has or is becoming like climbing Mt. Everest where anyone with the desire and $$ can be guided down to the Gunilda.

Again as I had mentioned to you before it always amazed me that tech divers obsess about this configuration, that training agency, and that hose length but not a peep about their air quality. In the US one hears a lot more about oxygen compatible air (OCA) and debates about not only the amount of particulates or hydrocarbons in the air but the size of those particulates. Here in Ontario we debate (we being recreational divers mainly) whether using the OUC unaccredited lab once or twice a year is a prudent way to manage contaminant risk. And the worst offenders of all for either denial, arrogance, or ignorance seem to be the tech shops in Kingston, Mallorytown, and St. Catharines. These tech guys (on the bleeding edge of dive info) who really should be up to speed on the reasons why OCA air is important at depth (effective concentration of contaminants at 7 atm) continue to mix uncertified OUC air to a 1985 standard with your 'medical' grade helium and oxygen. Sounds to me like the, "I'll have a diet coke with the big mac and fries syndrome"! That OUC air is what you got to worry about and using medical grade He won't mitigate the risk of OUC air at 7 atm.

Ok I will get back to your question but that topic hit a raw nerve with me,.. mixed gas stations using OUC air,...kind of like when you mention Maxxam to Seahunter where unpredicatable things get said :D

Assuming I was going to dive the Gunilda (only in my dreams) I would think of all the risks I might encounter and can control. Pretty much everything like equipment, training, pre dive sleep, diet, psychological prep is all in my control. If I screw up here I am the one that will become a statistic. Now the one huge risk I cannot control and might not know much about is my air source. Someone else likely supplies a portable compressor which I have no idea about the quality, when the last filter and oil changes were done, etc. If you search under 'compressors' on this site as I did and read some of the threads from experts on portable compressor and filtration the number of issues to consider with regard to air quality is huge. Types of filters, intake placement issues, filter order issues (guys putting the dessicant after the charcoal), back valve issues, oil issues, the list is huge. If you don't own the compressor and maintain it I would hazard to guess the portable compressor is your greatest concern re risk management.

So what to do? I would simply tell the guy setting up the compressor to get up there a few days before and set up. I would then arrive at least a day before ideally more (to let the HPA axis settle after the long drive) and have a sample bottle from either Seatech or (shhh) Maxxam on hand. Run the compressor at least a half hour and then fill the bottle over twenty minutes. Call Purolator to the Rossport Inn to pick up the bottle and have them rush the sample to Halifax or Toronto. The lab will do a sample on 6, 24, or 48 hr notice for a fee (see www.seatech.ns.ca). Don't worry about the $$ as this is the one risk factor worth spending the money on to reduce the contaminant risk to its lowest level when at 8 atm. The next day you get the result back on the compressor setup exactly where you intend to use it. That way if there is some strange gas drifting in from Bowater at Thunder Bay you might know about it. Also you don't have to worry about all those issues you can't possibly check like oils, filters, backvalves, etc. You will have a air cert done one day before you dive that reflects that compressor setup one day before you dive. That way you don't have to worry about the typical yada yada, "oh yah I changed those filters last week or I dove the air last week and it was fine, trust me."

On the day of the dive I would inspect the wind direction and where my exhaust and intake are. Forest fires which are very common up that way with smoke in the air would be an absolute contraindication to a deep dive. Likely lots of CO2 and CO if there is smoke in the air.

As a final check on my tanks to be used on the day of the dive I would use my portable CO monitor and assess the dewpoint as well. For that type of dive (deep and cold) I would accept a CO level of zero and the dew point should be very low (<-60F). If either of those start to creep up during the expedition I would be suspect of a filter problem. One can use serial CO and dewpoint levels over days, weeks, or months to detect possible early filter degradation by moisture. A CO level that goes from zero to five ppm or a dewpoint that rises quickly assuming no new intake sources or CO or humidity might be your 'smoking gun' to look a little closer at that compressor and how it is being operated. Remember in the six months between air certs as is required by the Ministry of Labour a lot can happen to a compressor especially when it is working overtime during the hot busy summer months. The serial CO/dewpoint technique may allow the diver an interim assessment of fill station quality.

The last issue you will see in some of the compressor posts is one of particulate matter quantity and size in the fill. I would only accept an oil and particulate level of <.1 mg/m3 for a deep dive. As far as particulate size this is open to debate although there is a lot of recent medical research on particulate matter (PM) less than 2.5 microns causing cardiorespiratory problems in susceptible people. Theories include cytokine production, changes in blood clotting componenents, or direct cardiac toxic effects. Personally I think this is where the answer to pulmonary edema of diving might lie or the 'sensitivity' to it in some individuals. If you are getting your air locally in Rossport PM concentrations are not an issue although I would check the MOE air quality index for Tbay as it has had some higher levels when wind conditions are right from the States. As for filters I would insist on some sort of hyperfilter at least down to the US Navy standard of 5 microns (the smaller the particles less than 10 microns the deeper they penetrate the respiratory tree). ANDI 1994 specifies < 2 microns which is even better but adds additional cost to the fills. Lawrence Factor (www.lawrence-factor.com) I think sells a portable hyperfilter you can attach to the fill whip. In anycase for those deep dives with higher effective concentrations I would go for a minimum of 5 micron in the fill.

So there you have it. I am not a deep diver but have been to 20,000 ft above sea level and experienced mild AMS. Did the climb without much knowledge of AMS and after reading about the physiology behind this a few years later I realized lots of dumb things were done on my part. You know the saying of bold vs. old! Would do things very differently now. As you know 'knowledge comes from books, but wisdom come from life' but sometimes wisdom does come from doing dumb things and then realizing in hindsight boy I am lucky to be talking about this.

Hope this long post (as bad as SH I know) helps or at least gives you some things to think about to help reduce that large blind spot in risk that really does exist for tech divers called air contamination. As I said I am no expert but these would be issues to consider and an approach to the problem. Looking forward to hearing some ideas too from JimmyB :mean:

[Jimmy B]

I still think the best approach would be to lobby the OUC to move to your perferred testing station. Then everyone would be in the loop and OUC would again start to grow some teeth. Instead of reinventing the wheel why don't we re-engineer what we have.

JB

Just because Puffer asked.

[pufferfish]

Jimmy B once bubbled...
I still think the best approach would be to lobby the OUC to move to your perferred testing station. Then everyone would be in the loop and OUC would again start to grow some teeth. Instead of reinventing the wheel why don't we re-engineer what we have.

JB
Just because Puffer asked.

JimmyB I have no preferences of testing stations in Canada as long as they are accredited by the Standard Council of Canada. You choose from Seatech, Cantest, or Maxxam based on price, location,friendliness, and ability to answer your technical questions.

The problem is the OUC does not choose an air test lab but claims to be a reliable test lab. They own the equipment and do their own testing. A large portion of their budget I imagine comes from offering this shoddy testing. The only way for the OUC to reinvent itself is to get out of air testing all together and leave that for the professionals. Think about it. Why is the OUC testing diver air in Ontario? There is a conflict of interest here where you join their club and they are testing your air. It would be like PADI running their own air test facility. Air testing should only be done by independent, accredited outside labs who have no financial incentive to not tell the air station they failed the test.

The best way to 'lobby' the OUC to close their lab is for you to stop using them. The more shops that do this, the sooner the OUC can get back to its raison d'etre of promoting the interests of Ontario divers. Surely offering substandard air station testing is not in your best interest. How about arranging for that shop you keep mentioning to start making some phone calls to either Seatech or Maxxam and bring the boys in Kingston into the 21st century :)

[seahunter]

I can hardly type for the tears in my eyes! You guys make me feel so good! Almost like I'm one of the .. the .. guys!!

Anyway I do appreciate any respect I get on this board. BTW how are we coming with getting other store owners to share their ideas in public or am I the only patsy?

Coupla' things:

Please shorten your posts puffer. After a while I thought I was reading my own reply but couldn't remember having written the words. I had to go all the way back to the top to recall whose post it was.

Thanks for the recognition of my ability to sell scuba. Free Air Fills was only initiated to get divers talking about and visiting S2K. It worked! It's over! See http://www.scuba2000.com/new.htm for the latest newsletter which appears every Wednesday afternoon.
Not only have I ended the Free Air policy therein but I've educated the divers about dry fills too. Not to blow my own horn (toot, toot!), this is at least the 3rd example in recent memory where I have used information and ideas gleaned from these discusssions to improve S2K service and/or to educate the thousands of divers who read our newletter.

Trace Analytics is a major accredited air test lab and provides all the test analysis for those seeking Z-180 rating.

Having used portable compressors many times, I can only say to use your common sense and uncommon good knowledge as demonstrated on this board to protect yourself from both environmental problems and self-inflicted problems of intake vs exhaust placement, compressor maintenance and air purification.
Do that and they are fine. Don't and they will kill you!

[pufferfish]

Seahunter I just about spilled my coffee this morning on the keyboard when I read your post. Did I read that correctly about 'no more free air' or was I hallucinating? I thought I was reading one of my posts and had to scroll back to the top to check who the author was :D

You're right about the post length though, but hey expeditions are exciting!

Doppler I see oxycheq has a nice new CO monitor available but a little steep in price. So far mine for $99 from www.aeromedix.com is working great with using the bag technique. I will be doing serial CO measurements on several compressors over the summer to see what changes one can expect with heavy hot summer use.

Oxycheq (http://www.oxycheq.com/Oxygen_Analyzer_Main_Page.html)

[pufferfish]

Just a post script here on the Toby situation. Both shops Diver's Den and GS Watersports are doing dry fills. The water baths although present in both shops are dry as a bone.

So divers in Toby get dry fills and accredited air from both shops. That is how it should be at all fill stations across the province in the 21st century.

[johnny]

Dear Scott,

I found an email sent from you sent mentioning Smugglers Cove, south of Kenora. If you are from the island of Smugglers Cove Lakeof the Woods, Ontario; I am thrilled to find you.

I spent my summers at Smuggler's Cove when I was a boy. Those were the finest days of my childhood, Scubacott!

My aunt and uncle owned the island. They sold it about fifteen years ago.

Please write to tell me whether or not are a link to the Smuggler's Cove of my childhood. Your reply is of great interest to me.

Thank you for your kindness.

Johnny