shoebox compressor question

[Geoff]

I did not see this, so wanted to clarify ...  the graph below shows an X next to some tank sizes.  does the X mean the compressor will NOT fill a tank of that size ?

do you all fill an 88cf tank to 4500 psi ?    do you do it in stages over a couple days ?

I just don't understand what the X means as usually that means NO when one puts it in a graph.

thank you

[grobe1458]

the gun and scuba max limit is 3000 psi so the 4500 are not applicable so x's are there.

[Motorhead]

Yup ... X = Does not apply

[Geoff]

Yup ... X = Does not apply

so it will not fill an 88cf tank to 4500 psi ?  just trying to clarify to I understand before I bought one.  thanks

[dv8eod]

It will fill tanks that are rated for 4500psi, the chart is listing items mostly rated at 3000psi. When you look at the Freedom 8 in the chart it shows the top off times for 3000-4500.

[Motorhead]

Yup ... X = Does not apply

so it will not fill an 88cf tank to 4500 psi ?  just trying to clarify to I understand before I bought one.  thanks

Good point in the question you ask

YES it will fill a 88 to 4.5k ...

If said 88 was down to @ 3K and your filling was only to top off the upper 2.5k getting at 4.5k the run time on compressor would be much less.

Also a sales tool being the 88 is a VERY LARGE tank the higher capacity SB unit certainly would be the better choice filling it.
So ya have to read between the lines and use some common sense here ....

Personally have a 1st gen chain drive SB and run the snot out of it ... my cylinder rebuild intervals are frequent because of my per-say "Over use" of its practical capacity.


As to filling a 3k tank off a 4.5k compressor
The MAX has NO WAY to shut itself off at 3K and would nun until 4.5 k OVERFILLING said lower capacity tank. DANGER DANGER !

The Freedom 8 compressor uses an adjustable shut off able to be set to either 3K or 4.5k shut off pressure.

[rsterne]

There isn't an 88 CF SCBA tank in that chart, guys!.... The X is in the row for the 80 CF SCUBA tank, which is rated at 3000 psi, in the column for 0-4500 psi fills.... How much clearer does it need to be, you can't fill that tank to 4500 psi.... For the fill time for an 88 CF SCBA tank to 4500 psi, simply double the number for the 44CF SCBA tank....

I have an 88CF tank, and the initial fill took 24 hours.... I lube my ShoeBox every 3 hours, and I now have over 450 hours on it with 4 partial rebuilds.... I have replaced the high pressure cylinder O-rings and check valve O-ring 4 times and the low pressure cylinder O-rings and check valve O-ring once (after 285 hours)....

Bob

[William]

The X means you either do not fill it to that pressure or it isn't a feasible fill rating.

You can fill any tank you want as long as you DO NOT exceed the pressure limit of the tanks specifications.

The diagram just gives you an idea of how long it will take to fill from the listed pressure already in the tank, whether it be from 0-3000 or 0-4500 or 3000 to 4500 and of course it depends on the size as well.

One confusing point is the "Paintball 68 CI tank" where it has an X in the column under 0-3000 PSI, but, it has a time factor for filling it from 0-4500 PSI. The X is in the 0-3000 column because it is generally not filled to just 3000 PSI and the time for it under the 0-4500 fill should give you an idea of how long it would actually take if you chose to fill it to just 3000 PSI. Like I mentioned above you can fill it to what you want, as long as you do not exceed the limitations of the tanks recommended max pressure.

Anyway on to more and exciting things... lets all go out and shoot some lead! Its a nice day for it just about everywhere!

William

[Geoff]

thank you all for the clarification.  I just wanted to be certain before I bought one (not that I am planning to do it soon was researching options)

I appreciate your answers .  Thank you

[Humdinger]

That chart isn't the easiest thing to interpret, and leaving out fill times for 88cf tanks at 4500 psi is omitting the most common fill up using Shoeboxes.  However, you can use the data in the chart to calculate the fill time for your 88cf tank.  An 88cf tank has 550 cubic inches capacity.  A Freedom 8 fills each cubic inch to 4500 psi in 1.5 minutes.  So 550 inches x 1.5 minutes is 825 minutes divided by 60 is 13.75 hours using a Freedom 8, according to the chart.  Hope this helps. 

Bear in mind that this is only a one time fill.  From that point on, you could top off your tank from 3000 psi to 4500 psi 1/3 of that time.  Also, as long as you do your lube stops, the Shoebox can run as long as you care to run it.  It doesn't overheat, it just requires lubrication of the piston rods.

[Gatorproof]

Point of interest as I understand it.

Not really realative to Shoebox. When your dive tanks are sent out for "stamping" or recertification,  there are stressed well beyond 3000psi.
I can't remember, but I think the tanks are filled 1.5 times their stated limit. So an aluminum tank rated for 3000psi is filled to say 4500psi.
A steel tank has a slightly higher rating of normal use like say 3400psi.

This does not mean your should over fill your tanks. They are placed in a special pool and filled to 1.5x under special watch. So you certainly don't want to set one on your shop bench and  test it to 4500psi every time you fill.

The tanks are designed to allow to a 5% over fill. (I believe, it has been 20 years since I got my P.A.D.A. dive certifications,  and I only had 3 levels).
I think that the ambient temperature is involved in there somewhere.

So "Can you fill an Aluminum tank to 4,500psi? Probably,  SHOULD YOU, ☆☆☆☆OF COURSE NOT★★★

Be Well,
Gator