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oxy vs air & oxy regulator

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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oxy vs air & oxy regulator

Unread postAuthor: Moonbogg » Tue Jun 02, 2009 5:43 pm

I will be using oxygen to increase power rather than using compressed air. Is the power the same between the two assuming of course the correct amount of oxygen is used to equal the same you'd get from compressed air? I wasn't sure if it would be faster burning or more powerful due to the greater purity of the oxygen.
I don't want to spend a million dollars on an oxygen regulator. Whats so special about them anyway? Can a regular air regulator be used for oxygen just like many people use them for propane and mapp? I read somewhere that the grease or seals can catch fire or something like that.
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Unread postAuthor: jimmy101 » Tue Jun 02, 2009 6:18 pm

To a first approximation they are the same (pure oxy versus higher pressure of air to get the same oxy concentration).

To a second approximation, the pure oxy will be better since there isn't all that nitrogen hanging about sucking up heat. The heat capacity of most gasses, along with their density, means it doesn't usually take much heat to raise their temperature but it still takes some.

As to regulators, yes oxygen regulators are special. (1) They aren't lubed with oil since oxy at high pressure + oil is a combustable, if not explosive, mix. (2) They typically have special threads so that it is impossible to put an oxy regulator on anything but an oxygen tank or attach a non-oxy regulator to an oxy tank. You can go ghetto and get the adaptors to make it work but is isn't a good idea. It is certainly against OSHA reg's to do it. (OSHA can at times be a bit anal but when it comes to compressed gases, oxy in particular. But you are talking about a substantial explosive device if you do somehting wrong. "Substantial" as in you house is gone and if they are lucky they might find small bits of your body. :shock: )

So, go with a real oxy reg. If you want to save some money then buy a cheap oxy-acetylene tourch setup. That give you what you need, and a torch to boot.
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Unread postAuthor: Moonbogg » Tue Jun 02, 2009 6:35 pm

jimmy101 wrote:If you want to save some money then buy a cheap oxy-acetylene tourch setup. That give you what you need, and a torch to boot.
:idea:


Thanks for the reply. I have seen those torch kits and they say that the mapp gas has a regulator while the oxy only has a flow control valve, otherwise it would be great. Either way i'll make sure to use a proper regulator. Thanks.
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Unread postAuthor: rp181 » Tue Jun 02, 2009 6:58 pm

oxygen regulator's are also stainless steel, so it does not oxidize.
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Unread postAuthor: dewey-1 » Tue Jun 02, 2009 7:20 pm

Moonbogg; Are you looking for something like this?

http://www.harborfreight.com/cpi/ctaf/d ... zmap=94846

You could try this and if doesn't function as planned, you won't be wasting as much money as high quality regulator. (read pricey brand name)

Then again it may last for the life of the spudgun.
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Unread postAuthor: jimmy101 » Tue Jun 02, 2009 8:33 pm

Moonbogg wrote:Thanks for the reply. I have seen those torch kits and they say that the mapp gas has a regulator while the oxy only has a flow control valve, otherwise it would be great. Either way i'll make sure to use a proper regulator. Thanks.

The ones I'm thinking of have real reg's for both the fuel and oxy.
Home depot has one for about $170, model KH656

Harbor Freight's has one for $120, part 98958
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These are both oxy-acetylene rigs. The oxy regulator is the green one. If you've got the $$$ ...
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Unread postAuthor: Technician1002 » Tue Jun 02, 2009 8:56 pm

rp181 wrote:oxygen regulator's are also stainless steel, so it does not oxidize.


Not always. Mine is brass. In another post with a photo of a kit, the OX reg in the kit is brass.
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Unread postAuthor: rp181 » Tue Jun 02, 2009 10:32 pm

I stand corrected, thanks.
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High pressure Oxygen DANGER

Unread postAuthor: Technician1002 » Wed Jun 03, 2009 6:21 pm

Moonbogg, A couple very important points in regards to using pure Oxygen.

1, It supports combustion and may lower the ignition temperature. It increases the rate of combustion to the point many flammable materials become explosive.

2, Friction from leaks may cause auto ignition.

An oxygen regulator used for any other gas should NEVER be used with oxygen again. Oils, or other contaminates may cause an explosion when the high pressure is applied.

Attached is a Youtube video of a Oxygen cylinder repair gone bad. The dialog in the video missed some important points. It mentions some melted parts inside the cylinder and thread ares. It failed to mention it was melted because of combustion. The attempt to remove the vale caused ignition of the sealant either from friction, or as the seal cracked, compression caused auto ignition.

When a cylinder is filled slowly the heat if compression is kept low. Moving the valve raised the temperature of a flake above ignition point (much lower in high pressure oxygen) or escaping oxygen caused autoignition in the threads. The resulting fire inside the tank caused the tank to burst.

Warning, the video is graphic. The failure resulted in a fatality.
[youtube] http://www.youtube.com/watch?v=9lw_fhNAIQc[/youtube]

Oil in threads or in a regulator will cause the same diesel ignition when the tank valve is opened.

On the low pressure side, it was mentioned that the lack of nitrogen doesn't remove heat from the combustion. This is true and can cause some very high combustion temperatures. In addition, with more oxygen, more fuel can be added to the same space.. Air is about 80% nitrogen. Oxygen can support 5 times the amount of fuel in the mix. On just a oxygen mix, it is like having a 5X hybrid as 5 times the oxygen and fuel are in the same space... But, without the Nitrogen the heat and rate of combustion is greatly accelerated.

Please don't use pure oxygen. It may even be against the Forum Rules.
Explosive device: Any device that has the capability to release large amounts of stored energy rapidly.
Many oxygen/fuel mixes are in this category.
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Unread postAuthor: rp181 » Wed Jun 03, 2009 7:46 pm

Wow....

moon,
If you insist on using a oxygen cylinder, check with a hospital. They have regulator's built in, the pressure is selectable from .1psi to 25psi, Im pretty sure its a E cylinder in most hospitals. Tank pressure is around 2.5kpsi.
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Unread postAuthor: Technician1002 » Wed Jun 03, 2009 7:51 pm

rp181 wrote:Wow....

moon,
If you insist on using a oxygen cylinder, check with a hospital.


I was thinking more along the lines of getting to know the staff well when I read that.. :D He may be spending time there..

Welding gas is much lower cost. Breathing grade oxygen is more expensive than industrial gas. Hit a welding supply.
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Unread postAuthor: rp181 » Wed Jun 03, 2009 8:39 pm

I meant ask them if they have any to spare =)
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Unread postAuthor: Moonbogg » Wed Jun 03, 2009 10:59 pm

I picked up my golf ball barrel insert and a bigass bottle of MAPP tonight. I was about to grab a torch kit and try the oxy/mapp setup, but didn't want to waste money on a setup that isn't ideal. None of those torch kits that sell for $50.00 have real regulators as far as I can see. It is just flow control.

@dewey-1: thanks for the link. I didn't know they came that cheap. I am looking for something smaller and indistinguishable from the corresponding mapp regulator that will be installed beside it. I will be testing the setup with my existing Venom cannon and will install it in a new design I am working on.

Technician, thanks for the heads up on the unexpected power and heat increases. I suspected it wouldn't be the same as a regular hybrid mix and until I come to fully understand exactly how the pure oxy will alter combustion, I won't attempt it. I like my eyebrows where they are :lol: I now see that anything that can possibly burn thats anywhere in the high pressure oxy line could burn so fast it would basically explode. In the back of my mind I was still sort of thinking (oh its no big deal, the line is narrow and a little flame flickering in there won't do anything) kind of like how we all use propane and feel its safe. Anyways, I am going camping starting tomorrow night and will attempt to go super with the golf balls (using my bike pump) and will sort out the oxy/mapp setup soon enough.

This is what I have in mind. They are the same looking for both oxy and mapp/propane. It would make a very clean oxy/mapp setup. I just have to make sure to get the fully adjustable ones as many of these friggin mini's come "preset". I assume that means output pressure is fixed and only allows flow control.
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Re: High pressure Oxygen DANGER

Unread postAuthor: Biopyro » Thu Jun 04, 2009 5:57 am

Technician1002 wrote:Please don't use pure oxygen. It may even be against the Forum Rules.
Explosive device: Any device that has the capability to release large amounts of stored energy rapidly.
Many oxygen/fuel mixes are in this category.

Every cannon on this site has the "capability to release large amounts of stored energy rapidly"! That rule needs rewording a little. As for the inbuilt oxidisers rule, that is usually interpreted as gaseous oxidisers (N2O etc) are allowed.
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Unread postAuthor: inonickname » Thu Jun 04, 2009 6:28 am

Depends on your definition of large amounts of stored energy rapidly. Spudguns have nothing on TATP, ANNM, TNT.. whatever explosive. Even a good flash will make a spudgun seem weak.. A good magnalium-Ti flash is actually very scary..

Better get off that topic though.

Gaseous oxidizers are fine. Liquid, bit of a grey area but the general consensus is no. Solid definitely no. DO NOT use liquid oxidizers, you WILL kill yourself.

Oxygen is harsh, you should clean your gun up (EVERYTHING) before use. Remove any oil, grease deposits, try to limit oxidizable materials (except for the fuel ofc), clean it all up with mineral or something. Make sure you get everything.

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Take care, don't push your luck.
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