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Plastic Propane Injection System...Safe?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Plastic Propane Injection System...Safe?

Unread postAuthor: revans » Tue Feb 19, 2008 1:17 am

Would it be possible to make a propane injection system out of plastic bsp fittings such as those here:
http://www.hoseshop.co.nz/products.php?loc=hs&sid=6
(Scroll down to Plastic BSP Fittings)
Is it fine to use propane from your regular Bernzomatic bottle with these sort of fittings or do I have to go the full haul with brass etc?

Also, it possible to rig a system just by having one fitting threaded into the chamber with a hose running straight to the propane tank and just the one regular torch valve to control the flow? Say open it for 5 seconds then close it? Or do you need multipe valves to keep it safe?
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Unread postAuthor: Pete Zaria » Tue Feb 19, 2008 1:22 am

If you'd search around, this has been asked a few times before.


Yes, it can be done. Everything needs to be rated to at least 150psi to be safe, and higher is better.

One problem is that liquid propane straight out of the bottle is quite cold (well, I should say that, as it evaporates it has a surprising cooling effect) which can make the plastic pipe brittle.
Using a regulator immediately after the tank solves this problem. A "ghetto-rig" is to simply put a loop or two of hose after the propane tank to allow any potential liquid propane to evaporate into gas before it comes into contact with the plastic pipe.

Yes, you can rig up a system where you open up a valve and "count" to meter out your propane, but it will be very inefficient.
The reason we use propane meters is because it measures out a perfect mixture (around 4% propane to 96% air) for combustion. You can't get anywhere near a perfect mix by counting "one Mississippi two Mississippi" etc...

Read up on propane meters; there's an article in the Wiki and several in the How-To section.

Search around next time, please :)

Peace,
Pete Zaria.
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 1:28 am

You're not a Kiwi are you? I noticed the .co.nz website.
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Unread postAuthor: revans » Tue Feb 19, 2008 1:47 am

Yeh I am, from auckland
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 1:50 am

Same here.

Nice find with the site, hadn't seen it before.
Though you can't order online which is a bummer.

Where do you get your stuff from? Made any cannons?
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Unread postAuthor: revans » Tue Feb 19, 2008 1:51 am

Sorry about that Pete, just wanted to know if that particular pipe would be alright.

You can order online just get a quote or email them and you can sort it out via email. You can pay via bank transfer and they'll ship it out. That's what I plan on doing.
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 1:58 am

By the way if you go to a Plumbing Merchant such as LG Carder, threaded metal pipe is actually cheaper.

It cost me $7 for a 150mm long 32mm threaded galvanised barrel nipple, so it must only be a few dollars for a 15mm or 20mm one.

That and PVC fittings cost the same as brass in those sizes.

Edit:

I merged your posts, please read <A HREF="http://www.spudfiles.com/forums/viewtopic,p,136508.html#136508">The Posting Etiquette</a>.

I'd still prefer if they show their prices online, do you know how expensive they are compared to other places?
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Unread postAuthor: revans » Tue Feb 19, 2008 2:22 am

I got a quote from them and the plastic fittings I asked about above were about $2-3 each, their polyprop camlocks were $10-20 and 50mm ball valve was $30. I don't know how good this is but, it's cheaper than other online places I've seen. Do you have any good online stores you use for ordering?
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 2:27 am

Hmm I might get a quote from them for some stuff.

Not really, there is one site very similar to this, except they have a nice range in pressure rated PVC products up to 50mm. You order through email as well.
http://www.pacgro.co.nz/product_catalog.asp?g=1#sg165
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Unread postAuthor: revans » Tue Feb 19, 2008 2:38 am

While we're on the topic on buying stuff,:
Do you know you can find suitable regulators and pressure gauges for propane meters?
And also propane bottles, I haven't been able to find any like people use in the US. Thanks
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 2:45 am

I use these:
http://www.trademe.co.nz/Building-renov ... 488175.htm

Budget but they work, just don't tighten the fitting too much otherwise you'll snap of the male thread, like I did once.

Yeah they sell them at Mitre10, propane bottles are about $20-$25, MAPP bottles are about $30-$35 and the propane bottle with torch adapter about $30-$35.

MAPP is better for performance but is more expensive.

You're supposed to unscrew the torch adapter and use the fitting for your propane meter, but just recently i've found out the threads aren't 1/8" or 1/4", they're in between. And no one sells any fittings for them. So I can't connect my propane bottle to the meter.

So i'm not sure what you can do as they're the only fittings you can use with those blue propane bottles as they require a pin type fitting to let the gas out.
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Unread postAuthor: revans » Tue Feb 19, 2008 2:57 am

Thanks for the regulator, it's cheap and looks decent too.

You could get one of the propane bottles that come with a torch head and attach a hose to the torch nozzle and run that to a hose tail which connects to your meter. (Could you?)
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 3:02 am

Yeah you could, just fasten it with hose clamps and you'll be fine.

Have you built any cannons?

If you plan on building a pneumatic but don't want to folk out $50 for a sprinkler valve, I use <A HREF="http://www.trademe.co.nz/Home-living/Outdoor-garden-conservatory/Garden-gear/Watering/auction-141659208.htm">These</a> valves, only $35, 25mm, rated to 145psi and very easy to mod.
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Unread postAuthor: revans » Tue Feb 19, 2008 3:08 am

Thanks, but I'm not quite into pneumatics yet. I've built a basic combustion with a peizo, fan and silencer and I'm know working on an advanced combustion. I guess a pneumatic will be next up when my wallet has recovered. A pneumatic would probably be good around Auckland I guess (quieter) with the laws regarding spudguns.

Also, how have you gone about connecting the regulator gauge to your propane meter near the tank, or does it not matter where it is along the meter.
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Unread postAuthor: MrCrowley » Tue Feb 19, 2008 3:15 am

Wait until you build a piston valve or burst disk pneumatic, unbeliveably loud at even low pressures.

Once you go pneumatic, you don't go back.

I started out with a basic combustion too, then went pneumatic, think i've got about 5 or 6 pneumatics, working on two more, also have a hybrid in the making and possibly an advanced combustion.
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