Filling Tanks - How Hot is Too Hot?

[Scuba Duck]

I just read danobee's post. Here is something that might interest you. This gentleman has developed a 6 cylinder engine. Its essentially a 4 stroke engine that adds a steam cycle at the end. Captures the heat in the cylinder, turns the water into steam, and adds an additional power stroke. Get 40% more useful energy from regular old gasoline.

I'm interested to see if it makes it into full scale production someday considering the price of gas.

Damn Interesting » The Six-Stroke Engine

 

[Hoosier]

Another change I made was to add double accumulator filter towers from Jim at Shelden Sporting Goods, Inc., which was an extremely good choice for extra filtration. I don't know if that had anything to do with having cooler tanks downstream, but I must be doing something right by making at least the first two changes.

Thanks!

More filtration is definitely helpful to cool down air temperature, but it is depending on your filtration size. In my case, after adding two more 32" chambers, I can say that the air temp. is lower than before.

 

[pescador775]

Update on hot tanks.......I shortened my fresh air intake hose by about 6 feet and started pumping air from inside of my garage, which is cooler than the outside air. Since I'm starting the process with cooler air, the air going into my tanks is now warm like it should be instead of hot. My guess is that I was working the compressor too hard by having an air intake hose that was way too long, and this may have been a contributing factor to my problems. (clipped)Thanks

Any extra work is done by the motor, not the compressor. There is a guy on decostop quoting some professor who says that if the intake air is at reduced pressure as it enters the first stage, that the pressure ratio (intake to final) is increased and thus increases head temperatures due to the act of raising lower first stage intake pressures. However, this overlooks the physics of compressing lower masses of air which are the real source of heat. Less air mass, less heat. Also, it appears that compressors operated at altitude show no such effect; at least, I can't find any. So why the reports of compressors overheating when the intake is restricted? If this is so, I submit that the reason that compressors overheat if starved of air is due to friction. Compressors are 90% efficient. Ten percent of work is lost as friction/heat. If the air intake is stopped or restricted there is little or no flow to carry away heat from the cylinder bore.

Another interesting comment on decostop concerns oil consumption. Apparently, relative vacuums in the compressor cylinders cause more carryover of oil (oil consumption). This finding was the outcome of some testing conducted at a university. I cannot confirm or deny but it seems reasonable.

 

[coldsmoke]

Glad to see this thread. I was actually going to pose the same question.

I am a new compressor owner. I have a mako repacked bauer capitano 5cfm. I am waiting on new oil and filter media so it's not running yet, but I was a a new dive shop the other day and was wondering about the heat issue. They filled my hp 100 dubs directly off the compressor. They have a bauer 7cfm compressor. (not sure the model) My tanks got hot. I could touch them and could even hold my hand there but it wasn't comfortable and it's much hotter than any "quick" fill I have ever gotten off my lds's cascade.

I started to get concerned since I have always thought that you didn't want your tanks to get hot during filling. After seeing how hot they got from filling directly off the compressor I thought that I might need to add a cascade before using my compressor. That would suck since I have already broken the bank with scuba stuff this year. I just don't have the $$ for cascade bottles and all the other stuff that goes along with them.

Hunter

 

[Isaac-1]

If you really are concerned about too much heat while filling from your 5 cfm compressor, the cheapest solution is to add a second fill whip for about $150 and always fill two tanks at a time.


Ike

 

[pescador775]

I have a Capitano and feel that heat build up is a minor issue. If the concern is pressure drop, allow the tanks to cool and top off. Alternately, adjust the final relief to a slightly higher pressure. Or, one can use the Captain's setup of water cooling.

 

[coldsmoke]

I'm not concerned about the heat as long as it won't damage the tanks.

 

[rjack321]

Yes and no; Luxfer recommend against "hot fills" which translates to jamming an aluminum cylinder in less than five minutes. Typically, this is done in a bath. The negative water bath sentiment came about when some dive shop owners felt that water baths were too much trouble including housekeeping, etc. An association of dive stores, and I forget which one, asked a guy to provide cover by putting together a "white paper" in which every spurious reason that could be imagined were incorporated into this anti-bath opinion and later published on the net. One could probably still locate it. The one defensible argument that I could isolate from the paper is the same as mentioned previously, that a careless operator could blow droplets into the Scuba tank. The rest was bull, aimed at gullible readers who lacked understanding of physics.

Bill High of PSI note is one detractor on water baths.
Wet Fills

Locally, I find shops using water baths often give wet fills. Sloppy handling or poor filter care I don't know which. I fill at home and have no space nor need for a water bath.

 

[Hoosier]

I don't get the point for the water bath for the personal fill station.

Why do you care?

If a tank is hot, stop to fill and top it off later. Otherwise, find other solutions, such as multiple tank filling, cascade, more filtration, etc.....

Just my 2 bar...