land tank (compressed air)

[sam_14]

Okay so since I have learned from Reading on here that a normal air compressor isnt advisable for paintball (dirty air, seen pictures of when they go bang) I will be needing to go to a diving shop to fill up for use on private land (practice amd get used to marker) clearly not going to pop down for my marker bottle so would he looking at getting a land tank. What size is advisable for a half days training with 7 - 10 people or is that simply soo much to ask from one tank? I also understand that you need a specialised rug to fill the marker bottles. any advise would be welcome and please correct me if I've made a mistake.

 

[Tom]

With 7+ people it's going to drop fast

To maximise the number of fills you would want more than one scuba cylinder
Top up the paintball cylinders as often as possible, use one scuba cylinder as the master to fill as much as it will go then finish the topup from the 2nd scuba cylinder

The larger the physical capacity of scuba cylinder the better, but you then get to the practicality of transporting it to be filled and out to the field
Also a higher pressure one at 300bar/4500psi gives you more air, but then you still ideally want to put less into the paintball cylinders such as 2500psi per time so you're not draining the scuba so far

http://www.scubatoys.com/paintball/scubafills2.asp

You would need a fill rig with the correct diving fitting for the scuba cylinder, and to a paintball female fill fitting

Not essential but ideally a regulated fill rig will let you limit the pressure it will feed to your paintball cylinders, either to fill 3000psi max from a 4500psi scuba, or to limit down to maximise number of fills eg 2500psi
You can fill a 3000psi paintball cylinder from an unregulated 4500psi scuba but need to do so cautiously to not overfill and blow burst disks
Another benefit of a regulated fill station is it limits the speed of fill and the heat generated. Otherwise you need to fill in a disciplined manner to keep it slow

 

[Tom]

Familiarize with this
http://www.oaklandsfestival.host56.com/web_documents/air information.pdf

 

[Tom]

And watch this as an example, noting that it's American orientated, and running an unregulated 3000psi scuba to a 4500psi fibre (obviously only to 3000psi) and he notes that it gets warm

 

[sam_14]

well that's one he'll of an answer! So I should be looking for two cylinders one for taking the bottles from empty to nearly full (2500 - 3000?) Then use the other one to top up after each 'round' making sure to fill slowly and pause the fill if the tank starts to feel warm? What size would I be looking for 12L X 2? What are the main risks or common mistakes people make? I've dealt with flammable gasses before and understand the dangers of ignorance! Thank you for the in depth reply by the way!

 

[Tom]

I can't really comment on how many fills for a number of people, I've only realy ever used scubas as mobile fill stations on site to stay out for longer in a remote part of the field

For the number of people you've mentioned the practcality would need a minimum of 2 scuba cylinders

Ideally you never want to start from a realy low paintball cylinder, so the preference would be to start on a paintball site and leave with a full 3000psi fill. So you're then starting your practice day with full cylinders

You may not know a good fill level until you have an idea of the efficiency of everyone's guns
Let's guess that 2500psi will do you for a full level and that in s round you wont drop below 2000psi

So for the first round or two don't top up at all as you had 3000psi

At the third round or so it's dropped below 2500psi, say 2000 to 2200 so go to scuba 1 and fill to 2400
Scuba 1 will take quite a hit and its pressure will begin to go fast

Move over to scuba 2 and top up from 2400 to 2500
Most of the hard work has been done by scuba 1 so scuba 2 wont drop so quickly

Play another round and then go back to scuba 1. Get up to 2400
Move to scuba 2 for 2500

Keep going and you will see scuba 2 lasting much better than scuba 1



At the end of the day go back to the dive shop etc for a new fill
Its up to you if you get one or both filled. You will pay a fixed fee per fill so in theory halve your refill costs if you only fill the lowest (scuba 1)

If you've only filled scuba 1 then make that the top up bottle
Start filling with scuba 2 and top up with scuba 1
If you fill both at the scuba shop then it does not matter which order you use them
But always first fill from the lowest and top up from the highest

The problem with multiple scuba cylinders is you need multiple fill rigs, and the expense of multiple retests

 

[Tom]

The main risk would be lack of respect for high pressure air

The bad news situation would be over filling or fast flash filling. That was the cause of most cylinder explosions you will see in photos, a combination of oil contamination and hot fast fills

Be careful and fast fills / heat won't be a real issues
Normally on site with access to a compressor I would say to slow fill, pause, slow fill. And possibly return a few minutes later allowing the air to cool and top up

Your cylinder will drop in pressure as it cools so you want to top up
But off site and relying on scuba only, do it as slow as possible to minimize heat but don't grab a final top up as it cools. You want the scuba to maintain pressure for longer, so accept the small drop

 

[sam_14]

Thank you for all your help dude! Turns out a friend has a diving tank from when his dad used to fill his markers. So will pick that up and test it if needed. hope fully will be in good shape. Will ask the guys at the dive shop to have a look over it if it's not needing a test for a few years.