Scalding hot tanks

[FM1520]

The shop where I get my LP 95s filled does a great job. They fill fast and hot, hours later sitting in my garage the tanks always cool down to the service pressure or slightly above. For my tanks a hot fill to about 3000 works pretty well. Don't make this harder than it needs to be.

 

[g1138]

.....

 

[Namreg 58]

There is a lot of feelings on both sides of the issue. You put the tank in water to remove heat. Technically you should not have a need to do that. The heat build up is a physical symptom of filling too fast. If you think the out side is hot then you should feel the inside. (If it were possible). .

It is possible by simply dropping a datalogger inside the tank and filling it. Here's a link to 4 pages on this discussion and some actually know what they're talking about.

Topic: cylinder refill pressures (1/4) - Dive-Oz Discussion Forums - www.diveoz.com.au is the biggest and most popular Australian Scuba Diving Resource!.

Speaking from personal experience, when filling two 12 litre tanks off my 6+ cfm portable, I have to put them in water to keep reasonably cool. When I connect four 12 litre tanks I can fill them without a water bath as they only get slightly warm.

If a water bath makes little difference to heat dissipation, why do we bother to wear wetsuits????

Whilst on holidays a few years ago my tanks were filled by a shop that used a 25cfm compressor with only two fill whips and no water bath. The tanks were so hot that I could not touch them and a few months later when the pillar valve o ring blew, I had a fun time removing the VULCANIZED o rings from the groove on both tanks........something to think about.

 

[scubafanatic]

I think the folks that had good luck filling wet were also filling gently (self included) and taken as a whole had good results as long as they handled things to prevent the introduction of water.

A fast fill will be a bad fill any fill short of one taking hours will result in heat and a post fill pressure reduction. Even at 300 PSI / minute you can expect a 200-300 PSI pressure drop. That means having the pressure creep up over 8-10 minutes.

Forgive me if it was mentioned in an interim post but the insulating properties of air are often ignored. Molecules of air enter the tank and get to expand as they enter a lower pressure space. They are doing the happy dance. As the pressure rises they get more and more crowded and like a crowded bar room friction is generated and things get hot. Once this happens you have a body of hot air. Just as we insulate our homes or dry suits with stagnant air the air in the cylinder is not in a big hurry to conduct air to the cylinder wall which can dissipate it. Since we don't have a circulating fan in the cylinder to promote the heat exchange it can take about 4 hours for the whole thing to reach ambient temperature to allow for a meaningful pressure check.

When you consider what is going on in the cylinder you can start to see how limited the effect of a cooling bath is.

Pete

Steel tanks actually heat up fast and cool down fast, so a water bath immersion during the fill process does make a noticeable fast reduction in tank temps and reduce short fills.

 

[BRT]

Steel tanks actually heat up fast and cool down fast, so a water bath immersion during the fill process does make a noticeable fast reduction in tank temps and reduce short fills.

Believe me, aluminum transfers heat a lot faster than steel.

 

[NAM001]

I am not confused. I am not refefrenceing water cooled compressor for removing compressor heat but the after cooler that is a heat exchanger in the fnal presure discharge line it has hp air in and out and a water hose connection in and out to enhance condensation so the condencers will collect more and passs less to the filter stacks. It acts liks a chiller unit for a moisture seperator
although it coes not chill the air. if the water temp is 50-60 degreees fromt he tap then it coools the 150-200 degree air from the final stage to below 100 degrees. Its like a replacement or booster after cooler to the final astage air cooled after cooler. The unit would resenble a flourescent light tube. with hp air entering and leaving n the ends passing through internal tubing. in the side of each end of hte tupe a tap water connectin to provide the cooling water to cool the hp air tube inside.

It is possible by simply dropping a datalogger inside the tank and filling it. Here's a link to 4 pages on this discussion and some actually know what they're talking about.

Topic: cylinder refill pressures (1/4) - Dive-Oz Discussion Forums - [url]www.diveoz.com.au is the biggest and most popular Australian Scuba Diving Resource![/URL].

Speaking from personal experience, when filling two 12 litre tanks off my 6+ cfm portable, I have to put them in water to keep reasonably cool. When I connect four 12 litre tanks I can fill them without a water bath as they only get slightly warm.

If a water bath makes little difference to heat dissipation, why do we bother to wear wetsuits????

Whilst on holidays a few years ago my tanks were filled by a shop that used a 25cfm compressor with only two fill whips and no water bath. The tanks were so hot that I could not touch them and a few months later when the pillar valve o ring blew, I had a fun time removing the VULCANIZED o rings from the groove on both tanks........something to think about.

---------- Post added July 11th, 2014 at 05:56 PM ----------

Namreg. You have a good point about little difference and wet suits.... the differene comes when shops are water bathing them. and doing quick fills, the heat does not even get to the outside fo the tank before the shop calls teh tank full. they hand you a cool tank and then it gets hot onthe outside from the heat transfering from inside to out. Like a wet suit the suit does no good the first minute or so till you warm the water inthe suit. The other big issue with water bath fills is hat the tank is put into the bath and then the whip is put on. Filling air now blows the water into the tank. Your 12 ltr examle is proof that it is a fill rate issue that causes the heat.

I use a 5cu ft compressor and when i dont fill 2-3 tanks at a time I wrap a bath towel around he tank and keep it wet. For those that think it does nothing then no foul. When you fill from a cascade you can contol the fill rate. Not so when using a compressor.

It is possible by simply dropping a datalogger inside the tank and filling it. Here's a link to 4 pages on this discussion and some actually know what they're talking about.

Topic: cylinder refill pressures (1/4) - Dive-Oz Discussion Forums - [url]www.diveoz.com.au is the biggest and most popular Australian Scuba Diving Resource![/URL].

Speaking from personal experience, when filling two 12 litre tanks off my 6+ cfm portable, I have to put them in water to keep reasonably cool. When I connect four 12 litre tanks I can fill them without a water bath as they only get slightly warm.

If a water bath makes little difference to heat dissipation, why do we bother to wear wetsuits????

Whilst on holidays a few years ago my tanks were filled by a shop that used a 25cfm compressor with only two fill whips and no water bath. The tanks were so hot that I could not touch them and a few months later when the pillar valve o ring blew, I had a fun time removing the VULCANIZED o rings from the groove on both tanks........something to think about.

 

[spectrum]

Speaking from personal experience, when filling two 12 litre tanks off my 6+ cfm portable, I have to put them in water to keep reasonably cool. When I connect four 12 litre tanks I can fill them without a water bath as they only get slightly warm.

You have the added disadvantage of filling with hot gas. Some of the best insta-fills we ever got were on a fall morning. The gear was in a the van for cool night that approached freezing. When we got to the dive shop the banks were full and had cooled overnight and she filled at a reasonable rate.

If a water bath makes little difference to heat dissipation, why do we bother to wear wetsuits????

The water bath does a dandy job of cooling the cylinder. Unfortunately the issue with regards to a good fill is the self insulating ball of air within, most of which is oblivious to the aquatic shenanigans happening outside. Ironically an accurate understanding of what makes a wetsuit work demonstrates the folly of water baths.

 

[Namreg 58]

You have the added disadvantage of filling with hot gas.

On the contrary, my 4 stage portable is a bundle of all finned intercoolers and the air entering the coalescer between third and fourth stage (also carries the bulk of the condensate) and the final coalescer after the fourth stage are at ambient temperature. The final coalescer has a very faint mist on blow down and the filter tower is also near ambient..........it's when the compressed gas hits the tanks, things start to get warm.

I'm more inclined to think the reason for shops not using a water bath is to minimise the potential for back injuries through lifting tanks in and out of the water plus the mess it makes when an o ring blows whilst filling in water.:nuke:

Even on my K14 Verticus the plumbing to the 4 bank cascade is cool but the cylinders gradually warm up as they get filled.

With respect to water in the tanks, we are aware that when we dive from a boat and change tanks at the surface interval, the used tanks stand in racks with the valves exposed to any water that may splash on them whilst the boat is heading to the next dive location or to the boat ramp. For this very reason it is good practise to ALWAYS evacuate the tank valve and fill whip before connecting them for a fill.

 

[Basking Ridge Diver]

http://www.cochranescuba.com/forms/Case for Dry Filling Scuba Tanks.pdf
Interesting article on wet or dry.

It was always my understand although not explicit in this article that the water bath was a safety factor. If the tank blew you as the operator were safer to have it in a water bath than on an open floor. Like a hand grenade the shrapnel would be less likely to kill you. Interesting that no one has brought that up - when I fill my tanks they are in a blast casing in the filling station - for my protection not for cylinders or any other reason. But dry and slowly filled - I dont need to stress out my own tanks - for my benefit I don't want to replace them if I keep hot filling. I don't have a problem overfilling but always slowly...

 

[NAM001]

I think you have the right approach to it.

It surprixed me to find out that AL tanks were tempered at such a low temperature <200F. Steel is in the neighborhood of 400F. It stands to reason that fast fills really push the limits on AL tanks.
There has always been so much discussion on wet vs dry filling. It seems reasonable that fast fills, AL tanks, low ttempering proceses is a formula for desaster. No if but when. I dive steel!!!

I just breezed through the article and it is biased to the point of supporting only fill to the stamped pressure. A tank filled to 3000# (AL80) that is at 40 degrees F is over filled. It is also overfilled at 2950. The working presure is rated at a reference temperature and at sealevel. They some how left that out... The pressure is a psi corrected for temperature. Its funny how they quote thte regs when temps exceed 3000 but ignore it when the tank temp is well below the reference 60 or 70 degree F. Their only solution to make a one rule fits all is to say fill slowly.

Think for a moment ... what if one presented an argument that the tank be cooled in a bath to 70F , removed and then filled dry. The answer would be water in the tank. This argument makes as much sence as dont get your dive computer wet. I have seen many fills done like this. Tank is given to shop after sitting out side and it is well over 100 F. They fast fill to 2950 in a minute and give you your tank back. Why 2950??? cant exceed 3000.. you get in the water and you spg says 2300. You check it with other gages and they range from 2300 to 2350. You talk to the shop because thier gages are off. They say theydoesnt matter, they cant fill beyond 3000 gage psi. The shop has no intrest to get a properly reading gage cause it is making money by giving short fills. I guess its all in the presentation. So the hot fill kicked the inside temps up to say 180f thats 110 above 70 times 5 and thats 550 psi there is the 2450 corrected for temperature. Of course they recommend for your safety that you come back for a refill at 1000 psi.

http://www.cochranescuba.com/forms/Case for Dry Filling Scuba Tanks.pdf
Interesting article on wet or dry.

It was always my understand although not explicit in this article that the water bath was a safety factor. If the tank blew you as the operator were safer to have it in a water bath than on an open floor. Like a hand grenade the shrapnel would be less likely to kill you. Interesting that no one has brought that up - when I fill my tanks they are in a blast casing in the filling station - for my protection not for cylinders or any other reason. But dry and slowly filled - I dont need to stress out my own tanks - for my benefit I don't want to replace them if I keep hot filling. I don't have a problem overfilling but always slowly...