High Pressure Air

Guys,
can anyone tell me how many clubs, Big Gun and/or Fast Gun, are using High pressure air (HPA) at their events instead of CO2? And if being utilized, what safety procedures are being taken? Pros and cons??
thanks,
Steve

 

At the moment, the only club using HPA is a Big Gun club. They have a couple members using it sucessfully in thier ships.

I'm building a Treaty rules ship that will use HPA and hopefully will battle for the first time in mid-August.

In my opinion, HPA should be as successful in model warship combat for all the same reasons HPA is used in Paintball. HPA is not new technology. It has been in the paintball world since 1995. It is safe as long as it is handled with the same caution a person would use with compressed gases like CO2. In fact, there is no documented deaths as a result of HPA use in paintball compared to the 4 documented deaths resulting from CO2 use. That says a lot for the safety of using HPA.

I believe the Big Gun guys are using the metal non-fiber tanks in thier ships. There is a concern that the excessive moisture we subject our air systems to may cause weakening of fiber wrapped HPA tanks. So far, I have found no documented proof of this much less any written rumour of it being a problem.

I am going to use a fiber wrapped tank in my ship and do thorough documented inspections after each day of battling. I also plan on getting the tank hydro tested yearly to make sure there are no unseen problems with the tank. Since hydro testing involves pressurizing the tank in water using water pressure above the tank's rated pressure, I suspect the tank will be fine with moisture.

At the moment, there is no written safety rules in model warship combat for using HPA systems. I heard the big gun guys are crafting a set of rules for HPA. Even so, if a person follows the same safety rules for compressed gas use then there will be no problems.

Probably the biggest HPA con is getting HPA to the lake for refills. My plan is to purchase a scuba tank and a HPA fill station to take to the lake. Hopefully someday, model warship clubs will follow the same path that Paintball did in the mid-1990s and start purchasing HPA compressors to take to the battles.

 

Yes, I am on the development team for the WWCC's HPA rules. So far, asides from the moisture issue, we've only discovered two issues. You know how a lot of people put a few drops of air gun oil in their regulators, then pressurize the system to lube everything and keep it working right? Apparently, a few paintballers got the bright idea to try that with the bottle regulators on their HPA tanks. They put a few drops of oil in their fill port quick-disconnects, then dumped 4,500 PSI into their bottles.

HPA is pressurized air, which contains oxygen... the sudden increase in pressure resulted in a dramatic increase in temperature... and that air gun oil turned out to be highly flammable...

BANG!

the air gun oil ignited, bringing pressure inside the bottle up to probably 10,000 PSI, violently detonating the bottle. The result was not pretty. Fortunately not fatal, or even permanently debilitating, but the person doing the filling was severely burned and injured.

Needless to say, "don't pour oil into your HPA bottle through the fill port" is one of the safety rules we're including.

The other issue is that different HPA bottles are rated for different pressures, and most paintball fields have fill stations for the different pressures. While HPA fill ports are not compatible with CO2, preventing people from putting 3000 PSI in a bottle that can only hold 1.8K, the different ports for HPA are identical. The different pressure fill stations aren't always clearly labeled, either, and there have been a few instances of an HPA bottle getting more than its fair share of air. Fortunately, an aluminum bottle rated for 3000 PSI doesn't explode from 4500 PSI (the burst disk is 5K) but that is a lot of extra stress and wear on the parts. Considering how we're certainly banning carbon fiber bottles, and all aluminum bottles are rated for 3000 PSI, I have recommended that the WWCC's safety rules allow no fill stations greater than 3000 PSI, to avoid issues of overfilling under-rated bottles.

 

A few benefits of HPA:

1) no temperature issues. Since HPA is entirely gas, not a gas in liquid form, there is no chance of freezing regulators or liquified gas getting past the regulator and overpressuring the accumulators. This dramatically increases the safety factor of HPA vs CO2, once it's installed in a ship. HPA is also more resistant to temperature changes affecting your muzzle velocity. This is the single biggest reason for switching over to HPA.

2) price. Filling the club's CO2 tank costs about $20-$25. That's our own tank, that we fill up every battle. On the other hand, I rented a HPA fill station from my local paintball shop for $15. their tank, their fill port, and their air for $15. I've heard that filling up a nice big HPA fill tank costs less than $10.

3) guages. With CO2, you don't have any really accurate way of knowing how much gas you've got left. With HPA, every bottle has a guage on the neck, that accurately tells you how much gas you've got left. So if I look after a battle and see that I've got 2,000 PSI left, I know for certain that I don't need to top off my bottle.

4) no need to bleed off gas to cool. HPA doesn't care how warm or cool the bottle is when you fill it. With CO2, you need to bleed off a certain amount in order to cool down the bottle so you can get a good fill. HPA doesn't waste any gas like that.

5) ballast. I've done side-by-side comparisons of a 20-oz CO2 bottle and a 48 cu HPA bottle. Their *filled* weight is very similar, and they seem to provide the same number of shots, but the 48 cu of HPA weighs significantly less than 20 oz of CO2. So when you empty both bottles, the HPA will have less effect on your ship's ballast than the CO2 will. Not sure why, but my own tests have suggested this.

6) environmental stuff. CO2 is bad for the ozone, while HPA isn't. I know our hobby represents an infinitissimal percent of worldwide carbon emissions, but I keep hearing rumors about CO2 being banned from paintball and others. If our supply of CO2 suddenly dries up, I'd like to have some easy-to-implement alternative ready to go.

A few downsides:

1) small selection of bottle sizes. paintball HPA bottles are available in 13ci Al, 48ci Al, and larger. The 48ci Al bottle is equal to a 20oz CO2, and the 13ci Al bottle is between a 4oz and a 7oz. no 9oz, 12oz, 14oz, or 16oz. Apparently SCUBA "pony" bottles and "spare air" bottles can fill in these sizes, but they are much more expensive.

2) um... running out of ideas here...

 

You pretty much got all of it.

I still do not understand the ban on fiber wrapped bottles. Is it because of max pressure ratings?

 

Presently HPA is not authorized in Treaty. We'd have to get a rule in R&D to allow it.

 

Actually, the way Treaty rules are written right now, HPA is not prohibited. Only ozone depleting propellants. Treaty rules do have a section on CO2 safety which would apply to an HPA system.

Still, I'll pose the question to the Treaty email list for interpretations and/or solutions.

 

I dont get how a HPA tank would have moisture issues. even when not in a boat, it would have to deal with moisture in condensation and rapid air release due to the high densifty diffrences inside and outside the tank. its like an air compressor, let out all the air and you get alot of water too. or a spray can. sometimes condensation forms on them after use as they rapidly cool. Im not sure but just saying.

 

You're correct. My mistake!

 

HPA is probably going to replace CO2 the way CO2 replaced freon propellant.

 

Stephen of Strike Models is the guy who warned us about the moisture issue. I don't recall the full details, but it was something about continued, long-term exposure to moisture, that causes it to lose strength. A quick dip for a hydro test wouldn't do it, and neither would the first few times you sink. But year after year of getting wet from water sloshing around in the hull might trigger it. You'll have to ask him for further details.

There is a 13ci HPA bottle, that is somewhere between a 4oz and 7oz CO2. I see them in my local paintball store, and they're pretty small, but apparently they're not very common. I've also seen a number of compact "pony" SCUBA tanks and "spare air" bottles.

 

CO2 is bad for the ozone? How is that?

CFC's were suspected/argued to be bad for the Ozone layer, but that was junk science (they are heavier than air, for one thing - the chorine that gets that high is primarily from volcanos).

CO2 is a natural gas that is required for life on earth (no CO2, no plants). In fact, Japanese researchers discovered decades ago that CO2 levels on earth were more than 200 times current levels (for long enough that specific species of algea had evolved to thrive under those conditions).
And, before you go all "greenhouse gass" on this, remember, the biggest greenhouse gas is water vapor. Ozone may also be a greenhouse gas, apparently.

Cheers,

 

Oh Please, let’s not get into a discussion on environmental groups.

Stating that CO2 is a gas that needs to be reduced to protect the environment makes about as much sense as having screen doors on submarines

For those of you who are of voting age, Please register and Vote this and every election. It is VERY Important! Your vote can make a difference!
Being an Election Judge for a number of years (Since 1997), I could not help but notice that only about 50% of the registered voters show up to vote at each election!

The reason I bring this up is because I believe that if everyone had voted in past elections, we would not be seeing legislation for regulating CO2.

OK, I will get off of my soapbox now. And back to our regular scheduled discussion.

Back in my Air Force days, we would use HPA a lot. I recall seeing a trap on the compressor for the removal of water vapor from the air being compressed. (Water has a nasty habit of freezing at altitude!) In our case, I can see where removing all water vapor would be a help to prevent rust from building up inside of the bottle. I have seen where rust has caused a landing gear strut to fail. (Thank goodness that no one was injured on the landing!) So my point is, that the bottles should be drained, and the inside inspected on a regular basis.

 

Not sure how much of an issue rust is going to be, since the HPA bottles I've seen (asides from the carbon fiber ones) are aluminum. Last I checked, aluminum doesn't rust.

We have, however, discovered one further issue with HPA. It isn't allowed by NAMBA. We're working to correct that now, of course, but until the issue is resolved, using HPA in any ship will void your insurance coverage. Not sure about MWC's insurance, but it's best to check before you use HPA.

 

Kotori-

I hope you don't mind but I will be reposting this to the Treaty list as we use NAMBA and I don't think everyone is a member of this site. I'd hate for the word to not get out.

 

I'm a member of WWCC (Big Gun club, of which Katori is also a member ), working on assignment from the club president, directly with NAMBA on this issue. I have done extensive research into this subject, in preparation for a report I need to present tomorrow night to the club leadership.
Under current NAMBA RC warship combat safety rules, there is no provision for the use of HPA. HPA (which includes pure Nitrogen, as well) is not mentioned at all. Only CO2 is covered in the rules, and while it's possible that NAMBA insurance would pay an HPA-related claim, the fact that it is not specifically covered under the current safety rules makes the issue in doubt.
We have drafted and submitted language which would add HVA and Nitrogen to the rules, and we are waiting for NAMBA approval before allowing HVA to be used in WWCC events. This is on the advice of NAMBA HQ. We're hoping on a resolution within the next week or so, but no prediction yet.
My recommendation to all is to stop using HVA in RC warship combat until HVA is officially approved by NAMBA, i.e., added to the NAMBA safety rules for combat.
As for composite-wrapped aluminum tanks currently rated at 4500 PSI: There is no available data that would lead to a definitive conclusion that they are any more or less safe for use in RC warship combat than plain aluminum or steel bottles. It's true that composite-wrapped (generally resin-infused fiberglass or carbon fiber cloth) bottles have a 15 year lifespan, compared to the theoretical unlimited lifespan of a standard aluminum bottle, but that is because it is the integrity of the composite wrapping that enables an aluminum bottle, normally rated to a maximum of 3000 PSI, to be rated at 4500 PSI.
Keep in mind that these composite-wrapped bottles are designed to be lightweight and worn on the human body, usually under harsh conditions (firefighting, emergency rescue, paintball, etc.) where they are subjected to impacts against trees, debris, tossed into piles in trucks or concrete floors in firehouses, etc. Under those conditions, it's no wonder that their maximum lifespan has been set at 15 years. How does use in RC warship combat compare to that sort of abuse? We have no data, and we won't, until HPA use becomes widespread in our hobby/sport.
All of that said, that's actually an argument for not using composite-wrapped bottles in our ships, until actual concrete test results in our environment, and under our conditions, is available. I'm saying this because I personally feel uncomfortable with the idea of being in proximity to a model ship with a 4500 PSI pressure vessel installed in it, under fire by other model ships, with no established safety data or track record. But that's just me.

Rob Wood
Western Warship Combat Club

 

Although I agree with the NAMBA side of things when it come to insurance, I do disagree about signaling out fiber wrapped tanks. Though there has been limited testing of all-metal HPA tanks in ships, there has not been extensive testing that would point out they are any safer (or less safe) than fiber wrapped tanks. It doesn't matter if a fiber wrapped tank can hold 4500 psi vs an all-metal 3000 psi tank ... they both can to do enough damage to seriously hurt someone. The 1500 psi difference isn't going to matter.

With that said, if there is concern about using 4500 psi in a ship instead of 3000 psi, then perhaps a temporary max fill limit should be used until more data is available to alleviate safety concerns.

 

The main issue isn't that 3000 PSI is safer than 4500 PSI, but rather with the fact that it is only the integrity of the composite wrap that allows them to be DOT-approved for the higher pressure. Many of the composite-wrapped tanks on the market actually have thinner aluminum walls at their core - made up for by the strength of the composite wrap. Because these composite-wrapped SCBA tanks are expected to take a lot of abuse in the field (i.e., firefigting and rescue work in harsh and extreme conditions where the composite wrap is expected to become compromised), DOT regulations limit their lifespans to 15 years. Standard aluminum tanks and bottles (3000 PSI rating) have unlimited lifespans (assuming they pass hydrotesting, that is).

Rob