Posted on A5OG by Evil Minion

HPA FAQ

Quote:
Originally Posted by Psycho Acumen
Compressed Air FAQ

Preface:
The amount of questions that people have on this topic is nowhere near that to the amount of information available on this topic. Since this is the Newbie Forum, I have created a short type-up that goes over the generally asked questions concerning compressed air/nitro tanks. I tried to be as informative as I could, while still keeping it simple at the same time. For further explanation with what I am saying, as well as other resources “on the nation” about this topic, refer to the following links directly below.

* PBNation Air Systems Forum
* Three or five year hydro?
* Tank Regulator recharge rates
* Differences between Comp Air, N2, and CO2
* How many shots will I get?

* This is a retype of a previous Compressed Air FAQ I had done under a different screenname. The information is the same, but explanations will be different for the most part to clear up any past confusions.

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Terminology:
I am going to start with the basics; the terminology used for the air tank. There are several different terms used, but the most accurate (as well as politically correct) term to use nowadays is “compressed air.” Some of the other jargon you may have heard would be: nitrogen, nitro, and HPA. “Nitro” is quite simply short for “nitrogen,” which makes up around 78% of the air we breath. Although nitrogen is the main element found in compressed air, it is incorrect to call compressed air tanks “nitrogen tanks” nowadays. HPA is short for “High Pressure Air.” That is another valid name to call compressed air because the air is under high pressures. I am using the term “nowadays” because tanks did in fact used to be filled with compressed air when they first came out for use in paintball. No matter the terminology used, the tanks can be filled with either compressed air or nitrogen, but the vast majority of fields nowadays fill the tanks with compressed air and not nitrogen. The terminology may not be the same, but the tanks are the same.

Tank size/pressure:
The next thing I am going to cover is the numbers on the tanks. Such as the 68/4500 or 88/3000 along with all the others. The first number (In this case, the 68 or 88) refers to the tank's physical size. The measurement they use is in Cubic Inch (CI), which states the volume of air it can hold. The 68/4500 has 68ci of space inside and an 88/3000 has 88ci of space inside. The second, larger number refers to the pressure the tank can hold in terms of Pounds per Square Inch (PSI). The 68/4500 can hold 4,500psi of air pressure per each cubic inch. The 88/3000 can hold 3,000psi of air pressure per each cubic inch. I will get into the correlation between these two sets of numbers very shortly.

Cubic Inches:
The size, in cubic inches, of the tank has a roll in the amount of shots you get [Refer to the "How Many Shots Will I get?" link]. The smaller the tank, the less shots you get. The larger the tank, the more shots you get. However, players do not choose their tanks based on the amount of shots they can get out of it; they base what tank they should get by how comfortable the tank is to hold. Younger players tend to stick towards the 45ci and 48ci whereas the matured, as well as older adults, generally stick to 68ci or 88ci tank range. However, you should not get a tank just because of what I said. You should go down to your local field, with your marker, and talk to the sales person and explain that you are looking to purchase your first tank. Tell them that you would like to screw the different sized tanks onto your marker to get an idea of how they feel so you can make a good decision. After you get the feel for the tanks, go home and decide which tank size you felt was the most comfortable for you.

Pressure:
The amount of pressure your tank can store has a roll in the number of shots you will get as well [Refer to the "How Many SHots Will I get?" link]. The pressure rating is expressed in pounds per square inch. Tanks come in three different pressure ratings: 3,000psi, 4,500psi, and 5,000psi. The pressure your tank is able to hold does not affect the physical size of the tank. The only way to get more air into a fixed volume is by “stuffing” it into the tank, which is the case in the pressure ratings. There are factors that play into the pressure your tank can be filled to, but that is further on in the reading.

Materials:
As I promised earlier, I am going to explain the difference in material that tanks come in. They come in either Steel or Fiber wrapped. Steel tanks are generally cheaper because of the technology they use is simple, it is a steel canister with a regulator on it. Steel tanks are heavier than Fiber wrapped as though. When it comes down to the pressure a steel tank can hold, they are limited to 3,000psi. Fiber wrapped tanks are more expensive because there is more technology involved in making them. The entire tank itself is not all Fiber wrapped, the fiber is glued to an metal canister that is normally made of aluminum. These tanks can hold 3,000psi, 4,500psi and 5,000psi. Steel tanks are also generally going to be your smalled sized tanks such as 45ci and 48ci. Sometimes people are confused with this section on what material can handle what, so let me break it down once more.

Steel Tank Pressure:

* 3,000psi

Fiber Wrapped Tank Pressures:

* 3,000psi
* 4,500psi
* 5,000psi


Output Pressures:

* High Pressure Preset:
Depending on the brand, they can have an output pressure of between 800psi and 850psi.
* Low Pressure Preset:
Depending on the brand, they can have an Output pressure of between 400psi and 450psi.
* Adjustable:
Depending on the brand, they can have an output pressure of anywhere from 0psi to over 1,200psi.


Filling Sources:

* Bulk Tank:
Bulk tanks are very common place at fields that don't see a very high volume of traffic. Bulk tanks are portible and get the job done to fill tanks to 3,000psi.
* Booster:
Boosters work along side bulk tanks. Bulk tanks store air at 3,000psi so in order to fill tanks to 4,500psi or even 5,000psi, fill stations use boosters that take the 3,000psi from the bulk tank and compresses the air even further to get higher pressures.
* Air Compressor:
Air Compressors are specially designed compressors for paintball that compresses the air that surrounds us to the extremely high pressures that we fill our tanks. They are an alternative to bulk tanks and bulk tanks with boosters. Note: Your garage compressor or gas station tire pumps will not prove anywhere near as much pressure as paintball specific compressors can.


Hydro Testing:
Hydro testing is required by law every three to five years [Refer to the "Three or five year hydro?“ link] to ensure they are safe. Only the tanks are tested during these tests, the regulators are removed and set aside. Tanks are required to pass two types of inspections: Visual, and integrity. The visual inspection consists of the removal of the regulator and making sure the tank is in good condition with no dents or layers of fiber unpeeling (on fiber wrapped tanks). If the tank passes the visual inspection, it then moves on to the integrity test. The tanks are placed into large containers filled with water and then the tanks are filled to a certain pressure above what they are normally rated at using water, not air. The tanks are going to expand during the test and will displace water. On the side of this large container are gauges that measure the amount of water displaced by the tank. The tank can only displace (expand) so much before it is deemed unsafe. If the tank passes the visual and integrity inspections, the testing facility applies a new stamp that verifies when it passed inspection and returns the tank to you. If a tank fails testing (rarely does a tank fail), the testing facility is required by law to drill out the bottom of the tank so it can never be used again.

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Okay so I'll be the 1 to break the ice, I live at 5600 feet in elevation, my paintball store will only fill my 4500 psi tank to 4000 psi because they say if I go up and play in the mountains that the tank pressure will rise and I will run the risk of my burst disk rupturing. I thought hpa is not affected by elevation or temperature that much? Am I wrong or are they wrong? Any thoughts on this? I feel like I'm being jipped every time I have my tank filled ($4.50)!

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Fully upgraded Project Salvo, back up guns are Nelspot 007 and Splatmaster in original condition bought in 1984.
new to the collection:
2012 Invert Mini olive/black,Tippmann A-5,Tippmann 98c

There is some truth to what they say, Daltons law and Henry's law are pretty much what you are dealing with... I will see if I can find an article on it for you...

i believe it has to do with the difference in atmospheric pressure as you climb in altitude. at higher altitudes the air pressure decreases, which means less exterior pressure on the tank which conversely allows for the air inside to expand as it tries to equalize pressures. if i am right, then it would seem that their logic is sound. if i am not, then we need an engineer to chime in here...

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Actually it's Boyles law, which is part of the combined gas law : Combined gas law - Wikipedia, the free encyclopedia

ok sorry i must be a little slow today, if i read Boyles law right then there should be no change?

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Fully upgraded Project Salvo, back up guns are Nelspot 007 and Splatmaster in original condition bought in 1984.
new to the collection:
2012 Invert Mini olive/black,Tippmann A-5,Tippmann 98c

(I AM NOT AN EXPERT) I believe when they hydro test these tanks, they pump them up with 7500psi, the tank expands, and then they empty the tank. They then look for cracks to see if the walls are still structurally sound.

Also, I thought the burst disks were there if the internal pressure exceeded 4500 psi. I didn't think the altitude would affect the internal pressure of the tank. It definately affects the external pressure pressing in on the outside walls of the tank.

Let me see what I can find from an authoritative source.

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if you take a tank to a higher elevation it may increase the pressure but not very much.

also heat will drop the fill pressure down from 4500 untill it cools.

i say you do the experiment and take the 4000 psi fill tank to the higher elevation and find out.

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Ninja paintball
PROUDLY MADE IN THE USA!!!!

DOT RIN G777

You can't get more authoritative than that^^^

Thanks Ninja!

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And there you have it!