Overfills - Good or Bad? - Scuba Tech Tips: S08E12
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- čas přidán 6. 09. 2024
- A few divers believe overfilling scuba tanks is OK. Alec explains why this practice can be dangerous for the tank, diver and fill operator.
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Absolutely correct on ALL POINTS, Alec! Only 48 years a certified diver starting with the US Navy. Love your current info on the sport.
One of your best tips. I have learned a lot from your tech tips. Keep them coming.
Thanks Aaron.
Alec
As part of a dive club with our own compressor, we usually fill up to around 200 bar (~2900 PSI) then allow the cylinders to cool for 30 mins to an hour before topping up to 230 bar (~3300 PSI). In that time we can then fill others so it works out ok :-)
That's the right way to do it.
Takes time but, you get a good fill, it's safe and your tank lasts longer.
Take care.
Alec
Hi Alec, can you do an episode about trough water communication....!?
Thanks Alec! I found over the years that dive operators have many differing opinions on tank fills. When I’m in cave country 3600 on LP is the norm - outside of Florida operators give me 1000 reasons why they cannot do overfills and that’s fine. If there’s not a danger in the tank exploding and only a reduced life expectancy of the tank - that’s fine by me. My LP 95‘s are over 15 years old and have had very few fills under 3600. The extra 1200 pounds makes a huge difference when your diving thirds So far so good on the Hydro😎
Another great video Alec. I stopped doing business with one of the local LDS stores because they would hot fill the crap out of my tanks. When they handed them back they were so hot they almost burned your hands (nice expensive steel tanks too). Now the place where I go does not mind if I wait and chat with them in the store. i have 2 HP117's (awesome tanks) that I use as my dives are in the 110-130 range and they not only take their time but they also put a fan on the tanks and take pauses as you were showing. I get them back nice and cool and at 3500 PSI. Sure drops 100 PSI or 200 in the water but I am very satisfied and to your point I want those tanks to last for man years to come. Thanks for posting this video.
Great to hear from you again and thanks for your support.
I'd wish you good luck but you don't need it. You're doing things right.
Take care
Alec
I'm excited for the hydrostatic testing video! :D
Working on it.
Just a little practical problem - like finding a facility!
At one time, lots of dive stores had a hydrostatic test station right in the store but that very rare now.
In my area, the GTA (Greater Toronto Area) of about 3 million, we once had 15 dive stores and 5 had a hydro test station. Now there are 10 dive stores and only 1 with a test station.
Don't worry. We'll do it.
Alec
@@AlecPeirceScuba_SeaHunter Awesome! No worries, do take your time!
Jose
I'm fortunate as my dive shop is down the road from my work so I will generally drop it off at lunch and pick it up after work. This does two things. Gives them plenty of time to fill the tank and especially durring the summer gives the tank time to cool to room temp before the fill and keeps the tank from cooking in my car durring the afternoon as well
Purrrfect!!
Alec
hi Alec.I guess the reason most people want a "good fill" is because they do not have good controlled breathing skills? So the air runs out before everyone else's does. That might be a good future topic for the tech tips, how to control your air consumption and still have a great dive. Us guys with more counterbalance (politically correct way of putting it) tend to have bigger lungs so one breath takes in more cf weather we need it or not. Any tricks on slowing down breathing would be appreciated? Thanks Owen M
- Improve your buoyancy control. Once you're not kicking all the time to maintain your position in the water, but can hover in place while not using your hands and fins at all you'll notice you use much less gas.
- Don't overweight yourself. Learn how to perform a weight check so you only bring as little as you need. This means you'll need to put less gas in your BCD and you'll have to work less hard to maneuver. (It's also safer in case your BCD fails).
- Control your breathing. Some people breath full lung volumes like they're on the surface. Instead, find a slow rhythm and give your lungs time to extract oxygen before exhaling.
- Finally, get in shape. Your body will use the oxygen more efficiently.
Hi Ygg42Very good points to try out, with explanations why.thanks Owen M
Sure that one of the properties of aluminum in fatigue is that it does not have in infinite life at any stress level as steel that have an infinite life it the fatigue limit stress is not reached, it is a reason why aluminum is never used in a high cycling application as an engine connecting rod unless the engine is designed for racing where it is often rebuilt and rods replaced ( or a very low value engine as a lawm mower ).
One of the side effect of the hydrotest ( at 5/3 of the rated pressure ) is to force the micro cracks tips to become blunt so stopping the spreading ( all materials develops micro cracks when summited at high cycling stresses ).
Never heard of the 'micro cracks' before Jacques. I'll have to read up on that.
Thanks.
Alec
That was a very good one Alex!
Thank you Barry. Lots more to share.
There's obviously a risk factor involved with filling a vessel beyond its rated pressure and for the kind of recreational diving that I do, I see no reason to take that risk, however minimal it may be. If I were cave or wreck diving however then I'd likely feel that any risk factor associated with an overfill was vastly outweighed by the safety factor associated with having additional air.
In my view, as a survivor of several stupid things from my youth, nothing outweighs safety for me.
A
@@AlecPeirceScuba_SeaHunter Well, that's why I don't cave or wreck dive. Everything is a matter of how much risk we're willing to take and we wouldn't be diving at all if we were completely risk averse.
Thank you Alec, answers a lot of questions. Would it help to place the tank in a water bath so as to reduce the temperature when filling?
This question has been asked and answered many times Milton.
No - it doesn't help.
Dive stores that still use a cold water bath are simply not aware of the dangers.
There is NO benefit to a water bath.
Take a look back to see if you can find this issue discussed.
Take care.
Alec
@@AlecPeirceScuba_SeaHunter Thanks mate, much appreciated.
We wet bath and slow fill our tanks no issues so far. Great video sir.
Slow fill is great; wet bath not so much.
Alec
@@AlecPeirceScuba_SeaHunter can you please spread some light on why not to wet bath?
When they filled my nitrous bottle for my race car they turned it upside down opened it with the remaining nitrous and it froze the bottle then they filled it frozen all shops done that then we used heat blankets to warm the bottles to get more pressure before a race
@@davidlowery269, it increases the chance that water will get into the valve during the fill whip connection and get pushed into the tank. Splashing from adding/removing a tank from the bath for example could get water on one of the tank valves or fill whips. Otherwise, it's not a problem, but the fill operators do have to be more careful.
You can always fill the tank submerged in cilled water. That will require usually one fill and will be good. We use here fills to 232 bar in cold water. After filling and goind under ice my tank usually is 210 bar wich is perfect. But this procedure happends from time to time when we dive with tight gas planning. And if you have divers arguing on 20 bar.... stop filling their tanks and put them blow wiyh their mouth is that valve until they bring the pressure to the desired value. :)))))
And now in english?
When I dive locally, I fill my own tanks. Have a 35 EAN set up with 3 cascade tanks. I normally fill up to 3000 psi +/- 5% when I get back from a dive with empty tanks. Then top them off before going on the next dive. They are normally about 2700-2800 psi before being topped off. That is the best way, and takes the least amount of time. Unfortunately, that is not possible when traveling.
Love it! Fill your tanks tanks AFTER a dive. Then, if they need topping up, it's quick, easy and safe.
Alec
Dear Alec.. At my dive center we fill our steel tanks with about 30 bar overfill every time. For example an 12 liter 300 bar steel tank we fill to 330 bar, let it cool down and re-fill it if the customer wants to top it up. However we let it cool down first. I did not notice you differed between steel or aluminum tanks, which I would guess makes a huge difference. Aluminum tanks I would suspect stretches more than steel when it gets warm, and it gets warmer faster, am I right? So is steel safer? But it's not only the dive centers here in Norway that does this, all dive clubs do the same thing, overfill by at least 30 bar (before the compressor stops). This will leave us with about 270-290 bar on a 300 bar tank when we suit up to go diving. Not bad at all! I heard steel tanks are pressured tested by manufacturers to at least 600 bar before shipping, not asking you to confirm but I would think a hydro static test or pressure test would go up as much as 450 bar or so.. Anyway, just asking :)
Welllll. You are right that there's a difference between alum & steel. Aluminum should NEVER be overfilled! I'm well aware that it's a common practice to overfill steel tanks. If it is done to ensure a good fill, i.e. to stamped pressure, that's OK. The correct way is to fill to stamped, let cool, top up to stamped, let cool, and repeat this process until tank is at stamped and at room temperature.
Hydro tests go to 5/3 stamped pressure so a 300 BAR tank is tested to 500 BAR. That is done to purposely stretch the steel (or aluminum) walls to see if they can stretch and rebound within limits. You do NOT want to stretch your tank walls every time you fill it, unless you have unlimited funds. And I suggest you stand well away from the fill station!
Many stores will overfill well beyond stamped to save time. In some cases to give the diver extra air. This practice will stop the first time a safety disc blows. It's NOT a fun experience. Legit stores, meaning stores that are concerned about their customers safety and their continued business will not exceed stamped.
The litigious North American society has at least one thing in its favor - unsafe practices are less common. No dive store owner, charged with negligent manslaughter, wants to stand in front of a judge and try to explain why he filled a tank beyond its stamped pressure.
Take care down there.
Alec
@@AlecPeirceScuba_SeaHunter Thanks Alec for the elaborated answer.. FYI I finally got my DM, swimming and all ;)
Hi Alec thanks for another great video hear in the UK at my local dive club we work in bar as you will know and are standard is 232 bar we fill to about 270-280 and nobody has ever had an issue but will take it in to consideration in the future. Could you do a video on your thoughts on rebreathers vs sidemount. Thanks Adam
Rebreathers is a wholly different animal. Usual comparison would be between twinset and sidemount.
@@ChaosTheory666 thanks for your reply I understand the differences just looking for opinions for where to move into the world of technical diving excluding twin sets thanks Adam
I have a new faber steel 100 cubic foot rated for 3500 psi i have it slow filled to its max of 3500 all the time and even though they slow fillmit over eight hours when i get home its at 3300 psi
In any filling there is heat created that takes time to cool down. This is what you see even with a slow (20-30minutes), fill time.
A
You mentioned in another video that the tanks shouldn’t be filled while in a bath. Why? I’ve seen it quite a few times, especially when visiting North America, Thailand etc
what is harder on a HP steel tank - a fast fill to 3500psi (dive boats I get on seem to fill a tank in ~5min I would say given they have 24+ to fill with 4 wips, but tend to max at 3500 especially with Nitrox membrane - jut got back from wkd trip - they get HOT) OR a store filling them to 10% more but over a longer 15-20min period (they don't get nearly as hot, but cool to 3500) ?
What is considered a fast fill vs normal safe one ?
Would be great to create a computerized fill whip valve that would remove user's interaction other than tank PSI -- it would measure pressure in and out and adjust the opening valve accordingly to have a 30min fill or some fill rate....
Hey Mr. Peirce I've heard some time ago about some fill stations usually in other countries filling tanks with "bad air." Causing some diver injuries. How can you be sure when traveling that the air in your rented tanks is good quality? Thanks again for the great info and videos. Safe diving!
Most dive facilities now are modern enough to have air tests and most should have that test posted. Check for it and check the date. It should be no more than 6 months old, preferably 3 months.
If you are diving in a very remote location where there is no such test data available, the best way to check if the air is good is the "AP Air Test" (that's the Alec Peirce Air Test).
It's simple:
1. buy 6 beers and a couple of bags of chips.
2. get down to the dive shop really early, like, opening time.
3. sit on the beach, the boardwalk or the sea wall in front of the dive store and watch the divers coming in for air.
4. stay close to the store until later in the afternoon, about 4 o'clock should do it.
5. if the same divers come back for refills, the air is AP OK!!
It worked for me.
Good luck.
Alec
😆😆😆😆
Yeah I've seen 350 bars go down to 270 bar at room temperature.
Hi Alec! I think you just solved a lingering question for me that I hope you can confirm. I mostly dive in Monterey Bay with steel HP80s. At the surface before getting in the water my gauge normally reads around 3500, sometimes 3600, but when I get down to the bottom my new air integrated CPU normally reads about 3300 to 3200 PSI. At first I thought my CPU is just conservative but my SPG reads the same. The I wondered how in the hell I was sucking down 300 PSI between filling my BcD and the 3 minutes it takes to descent 20ft, but I guess part of it is the temperature decreasing in the tank during the surface swim due to the ideal gas Law. Is this correct?
No question about it Laura.
Commonly called Charle's Law but more correctly called Gay-Lussac's Law, the pressure of a gas in a fixed volume container (a scuba tank) is directly proportional to the temperature.
Now, disregarding a dozen technical aspects (absolute temperature among them), this means that if you have 3000 psi in your tank at room temperature (71 degrees) and you take that tank into water that is near freezing (35 degrees) the pressure will drop significantly. Not by 1/2 as 'directly proportional would indicate since we are not using the absolute scale, but a lot!
Alec
@@AlecPeirceScuba_SeaHunter the gay lussac law is the expression of the pressure in relation of the temperature if you use the rankin scale ( deg F +460 ) or kelvin (deg C + 273 )
so if you have a tank with 1000 PSI at 100 deg F ( 560 deg R ), to reach 2000 PSI, you should heat the tank at 1120 deg R ( 660 deg F )
the coincidence between the rankin and the kelvin scale is 0 deg R or 0 deg K also called the absolute zero where the molecular activity is nil, the supraconductivity of the materials is in this temperature range.
Hey Alec !
Great video again ! Just wondering, are those rent tanks are always in good condition and always get proper filled or there are some risks to it ?
Thank you :)
all depends on how the shop fills them... likely same way you bring yours. Just observe. If you buy their and only fill there and they fail hydro then at least you might have a case.
As Alain says it always comes down to the shop and how they conduct business.
Rental tanks should be inspected even more often that an owners tank. It's very difficult to know how that tank was treated while out for a weekend of diving.
Was it emptied at some point? Did it get good air? Was it dropped? etc.
All rentals should have a visual no more than 6 months old.
A good shop will show you their rental tank inspection sheet that shows when each tank was last checked.
It's not easy but just watch the shop. If it's professionally run, the tanks are probably OK.
If it's a dump with sloppy employees and junk all over, move on.
Take care.
Alec
Doing a "hot fill" to a pressure above the tank's rating is not necessarily an overfill. Tanks are rated to be filled to not merely their marked pressure, but rather their marked pressure when the gas inside is stabilized at a temperature of 70 degrees F. (in the USA).
Obviously, tanks can vary in temperature, with their pressure changing as a result. If a tank rated at 3000 psi is filled to that pressure with the temperature of its contents stabilized at 70 F, and it is then placed under the equatorial sun for a couple of hours, its pressure will rise above 3000 psi. Does it suddenly become illegally filled? What would the difference be between that hot tank and one given a "hot fill" to say 3500 psi that contains 3000 psi after it cools to 70 F.?
'Illegally filled' really means filled beyond it's specified rating.
And that applies only to the filling process.
So, you're quite right in that a tank can be filled beyond its stamped pressure if the temperature is higher than 70 degrees.
We'll assume the fill operator knows how to convert the pressure to 70 degrees. At 70, it should be at stamped pressure.
Therefore, if a properly filled tank sits in the sun and the pressure increases, it is not illegally filled, nor even unsafe.
One beef from my dive store owner background is divers who love a tank that shows more than proper tank pressure right after a fill but complain when it's less after they jump in the water.
Not only unfair but it illustrates their ignorance of basic scuba physics.
Take care.
Alec
A local shop near me fills them the minute you walk in and def overfills. They say "Hey, it's fine!". Maybe they want your tank to wear out so they can sell you a new one in a few years. Not good
I doubt that. They probably are just too lazy to do a good job. But, of course, they want to give you a good fill so you don't complain.
Lazy + wants good fill = overfill.
Find a new LDS.
Alec
that's my shop too... pain to find and drive to another shop, but I recalled they had one of their HP steel tank fail first hydro which made me wonder about the testing facility (which I called before I sent mine which was the same Worthinton) but now makes me wonder...
So a fast fill up is maybe okay to test your gear, if you may bought a regular, you would love to test before you buy, but if you prefer to dive as safe as possible, if you want to keep the pressure as high as possible, you may wait 90 or 100 minutes.
If I understand correctly, you said, if you fill it slower and if you give them more time, the drop is much more less when you went diving.
But I wonder what do you think would be the best time to wait?
I just guess after a while it doesn't make any difference any more or does it still makes a different?
I just wonder what would be the best speed to fill the tank to keep it as long as possible near 3000 psi?
How long should I wait to get the most less loss, when I feel a tank.
As far as I understand then shorter than faster, then higher the dropon the real psi in my tank, correct?
Fast filling a tank is bad for the tank over time as it degrades its elasticity. Some dive shops fast fill to get customers out who are waiting. There is no agreed upon speed or wait time for filling. Tanks heat when filled so a fast fill up to say 3,000 psi after an hour would cool to say 2,850 psi range. Slow filling: say 40-45 minutes vs 10 minutes, would heat slower with less cooling drop. Dive stores generally fill to 3,100 to 3,200 psi to allow cooling to around 3,000. Smart stores use a pressure checker to verify tank pressure after filling and again after cooling before handing over to the owner.
Hope this gives you all the answers.
A.
Every dive shop in Florida overfills if you don't get on them to not do it. -.-
I have to bring a transfer rig to make them fill all three of my tanks at the same time so they don't fill one of them too fast.
With three tanks in battery they fill it closer to the time it is supposed to, no more than 300psi per minuet.
Some dive shops encourage overfills... Which makes me upset as I can't leave and expect my tanks to be filled properly and not overfilled fast.
What should I do?
First, realize the reason for the overfilling - dive shops get lots of complaints about tanks not being filled but few about overfills. So they overfill to avoid complaints. It's simply not fair. A proper fill to 3000 say, at the store at room temperature takes time not to mention expense. The diver jumps into the water and the gauge shows 2700! He thinks he got ripped off and complains. Other divers hear him and soon the store has a bad rap that's not true.
If you care about safety and about the life of your tank, tell the staff when you go in that you want a slow fill to 3000 psi. At the end of the fill, you should not be able to feel warmth from the tank at 3000. Tell them that you know the pressure will drop a bit in the ocean but that's OK.
The silly part is that the same divers who complain about losing 200-300 psi usually come up with 500 to 1000 psi still in the tank! Sorry if I spell it out - those divers are just dumb! And unfair.
Take care.
Alec
@@AlecPeirceScuba_SeaHunter
I do tell them to fill the tanks slowly, the tanks are always hot enough at the end of the fill (If they only fill one at a time) to need almost 2 hours to cool off to room temperature. Thus why I bring a transfer setup and make them fill 3 tanks at the same time, then they only take about an hour to cool of to room temperature.
I also have to tell them to never exceed the 3000PSI limit even if I am short air, just to prevent over fills if I can not be there to observe them.
I'm leaning towards getting high pressure steel 3440psi tanks and only having them filled to 3000psi to offset this crap.
What if you filled a tank that was partially submerged in water? We did that in the military.
If you mean filled up in a water bath, it would make no difference unless the tank was down 2 to 3 atmospheres. You did crazy things in the military.
I don't let anyone overfill my aluminum cylinders. My low pressure steel tanks are filled to 3600 psi. They are slow filled I usually pick them up the next day. The same tanks are filled in Europe to 4000 psi every day. Is it against the law yes, but it's done that way all the time.
Steel tank overfills are not good but it is done.
Never overfill an aluminum tank! You are quite right.
Alec
Hey not related to this video but on your vintage scuba you had a underwater speaking device called the sea voice. Any similar products around now that are like that without using a microphone?
Nope. There have been a dozen similar devices over the years but none really worked well.
And the many electronic U/W communications systems that came and went weren't much better.
There are a couple of modern systems that do work OK but it's hardly like talking on your cell phone and very expensive.
For the rest of my life anyway, it seems it will continue to be the silent world.
Ok by me.
Alec
@@AlecPeirceScuba_SeaHunter yeah the serenity is a good you'd lose that bonus. Was just wondering for something I could tuck in my bc in case its needed. Found a modern one called the toucan very funny looking thing probably going to skip on it ha.
@@TheMoldydog A blank dive slate and appropriate pencil is what you are looking for.
Question: Would it be safe to fill the tanks in water? That is, attach the HP whip, set the tank in a tub of water and then begin filling. I'm thinking that the water would act like a heat sink to keep the tank cool as the air pressure climbs and you could get a more accurate 3000psi fill in less time. I don't know what that would do to the tank though, if anything. :S
Nevermind, found your answer to this below! Thanks!
You may get condense and as a result rust in your tank. Just wait 15 min and top the tanks off.
@@carlokop556 Thanks! Yeah, I did some reading on the subject... Turns out it's not the smartest way to do things! Ha!
I have my own 5 CFM compressor I fill 4 tanks at a time , there lp's & i have it set to shut off at 2700. I always end up with around 2600 or just a little above. I refuse to let my tanks get filled at the quarry they fill so fast its not good i have seen a lp108 filled to 3500 in 30 seconds. They dont care, some one asked them do slow down the fill and the tank was disconected and they were told to take it and go somewhere else if they did not like it.
You're right! Don't be discouraged by lazy, uninformed people.
If ever the saying "Slow and easy wins the race" applied to something, it is to the filling of scuba tanks!!!
Take care.
Alec
@@AlecPeirceScuba_SeaHunter have or can u do a video on how to tumble a tank properly and I have seen people use a whip on a drill to clean up tanks mark
Tumbling tanks used to be standard procedure but is seldom done anymore. Aluminum tranks should NOT be tumbled and there are better ways to clean a steel tank. Tumbling is not a bad procedure and could still be used in some cases most commonly when restoring an older steel tank (pre-1980's)to service.
Basically, it involves no more than rolling a tank over and over with a mixture of carbide grit in SLIGHTLY soapy water. It can easiest be done with a tank roller but I have done it on a bench or floor. Just takes time.
The carbide whip is better for aluminum tanks as it doesn't remove much material. Generally, aluminum tanks have only a thin surface coating that needs cleaning so the whip work swell.
Alec
Where the hell is a 5 to $10 air refill cause my area is like 10 to 25 and I'm still OK with those prices
All depends on where you are and what a LDS charges. Some offer bulk filling rates that bring the price way down. Keep searching as its still much cheaper than setting up your own filling station.
@@AlecPeirceScuba_SeaHunter yeah understand
Where the crimey are you bud? Even in California a fill is 6 dollars. Renting a tank is only 12.
3,700 psi burst disc on a 3,000 psi tank? That is awfully low, typically the burst disc is 5/3 service pressure which is 5,000 psi on a typical aluminum 80, though it isn't unusual to see 5,250 psi burst discs (since burst discs are rated +/- 10% and it is easier to stock one set for 3,500 and 3,000psi tanks).
Quite correct Peg Leg. It's my age showing.
Having been trained on and dived with the good old steel 72 cubic foot tank for many, many years, my mind often uses that as a quick reference. The burst disc pressure for that tank was 3700psi. They typically used the old 3-piece safety and the copper disc that was inserted as one of the three pieces was clearly stamped 3700. That has stuck in my mind since then.
Currently, PRDs (Pressure Relief Discs) are almost invariably the newer 1-piece assembly and they are rated by the tank service (stamped) pressure. A 3000 psi service pressure tank, your typical aluminum 80, uses a PRD with a release pressure of 5000 psi. However, finding that information is not as easy since the proper PRD is marked as 3000, the service pressure, not release pressure.
Similarly, LP steel tanks rated at 2400 psi use a disc with a release pressure of 4000 psi and HP steel tanks of 3442 stamped pressure use a safety with a release pressure of 5250 psi.
It's common to use the 5/3 formula that applies mainly to hydrostatic test pressure measurement rather than burst discs and that works reasonably well. The correct formula is actually 1.67 times the service pressure which yields a pressure of 5010. One must beware of aftermarket burst discs that I have seen offering a disc with a release pressure of 5250 for a 3000 psi tank. At a cost generally less than $10, it seems unwise to buy aftermarket rather than from a manufacturer through your LDS.
Also be aware that the release pressure is highly variable as you have hinted. While the manufacturer specifies a possible 10% + or - variance, it can be much higher or lower depending on temperature. Tests have shown that a temperature variation from the manufacturer's specifications (usually room temperature) can result in a burst disc variation as much as 20%!
Also, the age of the disc, meaning the number of fills the disc has experienced, can affect its release pressure. Each fill loads the disc and releases it and that action has shown to be instrumental in premature failure of the disc. Again, at such a low cost, concerned divers (and dive store service personnel) should be in the habit of changing that disc at least at every 5 years hydro test date.
Having experienced several burst disc failures over the years, all on the surface, I can tell you that it is an exciting scenario!!
An underwater failure, while less likely, would also tend to raise your heart rate!
I did see your comment about dive stores stocking one set of 3500 psi burst discs for all their tanks and can only think that the dive store in question is more concerned about convenience and profit than safety. The cost of these items is very slight and not worth the possibility of compromising anyone's safety. Generally, it is the dive store staff who suffer.
Thanks for your excellent comments and correction to my information.
Alec
The heck was that Kevin?
Shhh!
When you see Kevin you'll know. You won't have to ask!!!
Alec
Certificate of completion to Martyna Pietkiewicz - Poland is a great country !
We had several tanks come in to our local store for their 5 year hydrostatic tests. They were "fast filled" by a competitor. All of those tanks failed Hydrostatic testing. These tanks looked like new! Beautiful 5 year old tanks had to be thrown away. Don't do it....... These were quality
steel tanks.
Whether you believe in overfills or not, aluminum tanks should never be overfilled. Even in cave country, where they wouldn't think twice about filling a steel tank to almost 4,000psi, aluminum tanks are filled to 3,000 psi just like everywhere else.
You have a point Peg.
Aluminum is much more susceptible to problems related to overfilling. It's the nature of the metal.
Steel is more resilient, but it too must be treated with care.
Take care guys.
Alec
$5 - $10 bucks.............yeah right.
It can be with pre-paid packages or promo's.
A
We call it a cave fill. Not suitable for recreational use.
Thanks Chris.
I hope you don't take offense when I say that an overfill is not suitable for any diver, common practice among tech and cave divers notwithstanding.
It has nothing to do with your training, your experience or your dive profile.
It is simply hard on the tank, and risky too.
As a trained cave diver you know how to reduce all the inherent risks to a minimum to ensure as save a dive as possible.
Then your LDS overfills your tank!
Take care.
Alec
@@AlecPeirceScuba_SeaHunter I completely concur Alec! I appreciate your reply here as it's wise! I'm certain others were thinking what I wrote. Now it's settled...Need more volume, bring another tank.
@@AlecPeirceScuba_SeaHunter Risk is a ever-present variable in diving. I fully agree with never overfilling an aluminium tank. They are not meant for it. Overfilling a steel tank? Well, my particular steels are rated for 200,000 hydro tests. I find it hard to worry about overfilling that remains under the hydro test pressure. I would be lucky to approach that many dives in 40 lifetimes. The legal issue remains, but tanks are designed to take what they are designed to take. I have read many more facts and experiences that say modern lp steels can be safely overfilled than I have heard they can't.
Ask the manufacturer what they think.
I gotta' believe the people who make them know best.
I just read a post on another site from a guy, a cave diver he claims, who is another of those factual people you refer to.
He obviously believes that overfilling is OK and he even includes detailed instructions, with pictures, on how to plug the safety with a screw and solder so the safety won't blow out when you overfill.
Not my buddy I can assure you!!
Alec
Load of old bollocks. Anywhere you can go cave diving generally have Ice baths and fill 232 bar tanks to 250-260 on the regular. Tanks are designed to be filled waaay higher than their rating...
I didn't tell you to not do it Ryan.
I DID tell you reasons to not do it.
Your choice.
Filling a 232 BAR to 260, particularly in an ice bath, is a recipe for disaster.
By manufacturers specifications and by testing institutions standards, the stamped pressure, AT ROOM TEMPERATURE, is the safe maximum pressure.
If a cave diver safety line is rated at 1000 lbs breaking strength, would you use it to carry 999 lbs?
It has always struck me as odd that cave divers who claim to be more safety conscious than other divers, routinely break the rules established by the experts who don't have an agenda.
Best of luck.
Alec
@@AlecPeirceScuba_SeaHunter Why do we continue to get blokes that think they can work outside the working pressures? I am at a loss?
@@AlecPeirceScuba_SeaHunter, as a cave diving instructor let me add some insight. First, I have never seen an "ice bath" used at any cave diving fill station so not sure what the OP is talking about there, but we absolutely do overfill certain types of tanks. Fairly modern steel tanks only and often to ~3800 PSI. It's not that we don't recognize that there are risks involved in overfilling the tanks. It's that we have to weigh those risks against the risks inherent in cave diving. SCUBA tank failures from "cave filling" steel scuba tanks are almost nonexistent (I don't know of any off hand). Running out of gas due to an emergency/problem while cave diving is a real concern and one that has killed people I knew personally. So one risk is mostly theoretical and the other risk is quite real.
Given those two opposing choices, we err on the side of caution. I know it doesn't seem that way to those that don't cave dive, but the statistics back that up.
While less important, there is also an issue of logistics. Because of the risks involved in diving overhead environments, we have to be very conservative with our gas supply. We only breath 1/3 (at most) of our air before turning the dive and exiting. We can only bring so many tanks on a dive before the equipment becomes unmanageable. Overfilling the tanks makes it feasible to reach parts of the cave that would not be possible otherwise. Often we are thousands of linear feet from the surface. This really is related to the first point though. Which is to say, we need all the gas we can get since we can't just head to the surface when we get to ~800 PSI or encounter a problem.