acetylene vs propane

[e-RICHIE]

I've been <cut>

Just a reminder atmo -
http://www.velocipedesalon.com/forum...rum-36866.html

[ThomD]

Thanks for the reminder. I guess it is the not full name thing? I fully support the terms of use. I'm a read only guy by choice, I just forgot. I should have contacted Doug on Bikeforums about the rosebud head. I would be obliged if you would pull my post(s).

Is Turpentine someone's full name, that's up there with Moonunit.

[turpentine]

can't edit it in I hadn't posted here in like... a year +?
put it in my sig.

[boyracer]

PSA:

There is an invacare oxygen concentrator at Rytel International in Cincinnati for $99. It looks like it works.
I got mine for $85 just by calling and being nice. If you call they will probably cut you a deal. Shipping is just market.
(513) 561-1200
seems pretty cheap compared to going rate on craigslist etc and they seemed to not have any problem with shipping them since they are a big company with a big warehouse.
They also said they could get more if people wanted them.

I might have to investigate getting one of you fine gentlemen to send me an O2 concentrator.... cheapest one in Australia i can find ,even secondhand is ~ 1000!
Even after purchasing a transformer to run 110/240 volt I would still be better off.

[turpentine]

what's the shipping cost like for a 40# rectangle?

[Doug Fattic]

I might have to investigate getting one of you fine gentlemen to send me an O2 concentrator.... cheapest one in Australia i can find ,even secondhand is ~ 1000! Even after purchasing a transformer to run 110/240 volt I would still be better off.

I called M&M Medical repair in Beaverdale, PA where I bought my refurbished oxygen concentrator and asked them about international shipping. They said the problem was that customs in other countries were restrictive. For example getting them in Canada was very difficult. They didn’t know about Australia. You might find out if there are oxygen concentrator customs regulations for your country before you consider having one shipped over. The medical industry in Australia may purposely keep import restrictions high to preserve their profit margins.

Their price is currently $300 for a 5 liter per minute model of your choice. That comes with a 3 year warranty. The 10 lpm units ran $500 with a 1 year warranty. The weight of these units can vary a lot from 36 to 56 pounds. I got the impression from Bill at M&M that the heavier units were more durable and lasted longer. The lighter ones had a marketing edge for the elderly but came back for repair more frequently. The heaviest one was the Invacare Platinum model.

Doug Fattic
Niles, Michigan

[boyracer]

Thanks Doug for the information. I will ask some medicos i know over here as well.
I thought as much about customs, etc. I would be most likely to try get one in Utah after speedweek, or have it sent there...

[Mark Kelly]

If the invoice value is under $AUD1000 (including shipping) it will pay no Tarriff or GST.

If over $AUD1000 you will have to pay a Customs processing fee and GST on the "deemed value" which is usually set at some percentage above the invoice value (Customs assumes you paid less than the amount it's worth in Oz, otherwise you wouldn't import it). From 1 Jan 2015 all US originating goods come in Tarriff Free unless specifically excluded in schedule 5A (which it isn't, only things like tobacco and alcohol are still included).

BTW if it uses an SMPS (which it almost certainly does) you possibly won't need a transformer, most are universal 90 - 260V input these days.

The reason these things are so cheap in the US is that the US health insurance system distorts the market, inflating the value of new medical goods and destroying the value of these same goods second hand. It is to the insurers' benefit to make everything so expensive that you have to carry insurance so they do things like insisting that only brand new certified units be used.

[Astrapower]

I've just got together my oxy propane rig here in the UK and thought I would share my experience so far.

My rig comprises 20L oxygen and 19Kg Propane bottles with single stage regulators. I use a Harris 19-6 torch with a No.3 LW Nozzle (countersunk with a 4mm drill bit). Im running the oxygen at 2bar and the propane a 1bar.

I have only used this system for a couple of days now and prior to this I have only brazed with acetylene (over a year ago). I haven't brazed since. I don't have any issues with keeping the flame attached and seems to work fine with a No.3 nozzle.

The following pictures are of my first attempts. I have been only practising on 18swg box section steel with Cycle Design LFB flux.

IMG_2255.jpgIMG_2262.jpgIMG_2263.jpg

From what I'm noticing my heat control needs to improve, a lot! The filler rod either melt too quickly or becomes solid. I also find it hard to see the puddle as the flux flames when the torch gets closer.

Any tip are welcome.

Frank

[austinws]

Hi there everyone. This is my first post but as has been said many times before, having this forum as a resource is invaluable, so thank you to everyone who contributes. I'm just staring down the framebuilding path and have 1 frame under my belt using oxy-acetylene. Where I live I cannot store or use an oxy-acetylene setup on my residential property and with a new baby, affording a shop of my own along with the insurance for such a space seems a little out of reach considering I'm at the beginning of the framebuilding timeline. I do however have access to a community welding center which supplies oxy-acetylene rigs, gas, workspace, and various other equipment for a very reasonable monthly rate. Being that it is a community space, however, it's far from ideal for the majority of the framebuilding process as a lot of the non-welding equipment has seen a lot of use. My question is this: What, if any, issues might I encounter if I were to set up an oxy-propane system at home within my cities guidelines with which I could tack the frame, then transport that tacked frame to my welding center to braze with oxy-acetylene. My initial thinking is that this would afford me the benefit of using my own tooling for alignment, mitering, etc. and also have access to the benefits of oxy-acetylene. Am I missing something? I live only blocks from this center and it would be far cheaper than my own space, especially considering I've got a lot of leaning yet to do before (or if ever) I get to the point of marketing myself. Again, thank you to all, and I apologize if this question has already been addressed and I missed it.

Austin Holiday

[Doug Fattic]

Austin, there are 2 possible authorities that might have power over the use of propane at your home. The 1st is city codes and 2nd – if you are renting – does the rental agreement prevent the use of a propane BBQ grill. It is probable that both will allow the use of a propane tank at home because grilling is a popular American past time. You can avoid the problems of a pressurized oxygen tank (which can be a big red flag to authorities) by using an oxygen concentrator.

By the way there is very little difference between brazing with propane or acetylene for an experienced builder. I can switch between the two (I have both in my shop) without any effort at all. They each have their characteristics but for most purposes, one is not better than the other just slightly different. What I’m saying is that if you can spot braze your frame at home there is no reason you can’t braze it there too unless of course your cast iron alignment table is at the community welding center.

Doug Fattic
Niles, Michigan

[waterlaz]

I use propane and I've made a recess in my acetylene tip about twice the diameter of the tip. I had to flatten the drill bit to do so, but it was worth it. The flame is much more stable now and I think it is also narrower.

[William Chitham]

Any tips on getting consistent propane pressure? I have burned about 9kg of propane and 20L of oxygen in the year since I bought my first kit and I'm pretty happy with the set up but for one thing, inconsistant propane pressure. When I was shopping for equipment a lot of suppliers said there was no need for gauges on the propane regulator but on the advice here I persisted and ended up with a single stage reg with output pressure gauge. However, I always find the pressure dropping off as I'm working and often have to adjust the reg, always at the most inconvenient moment of course. My impression is that the supply pressure drops as the tank cools down and it probably levels out after a while but I rarely have the torch lit for more than 10-15 mins so I'm always having to fiddle with it. Would a two stage reg help?
Thanks,
William Chitham.

[Will Neide]

Any tips on getting consistent propane pressure? I have burned about 9kg of propane and 20L of oxygen in the year since I bought my first kit and I'm pretty happy with the set up but for one thing, inconsistant propane pressure. When I was shopping for equipment a lot of suppliers said there was no need for gauges on the propane regulator but on the advice here I persisted and ended up with a single stage reg with output pressure gauge. However, I always find the pressure dropping off as I'm working and often have to adjust the reg, always at the most inconvenient moment of course. My impression is that the supply pressure drops as the tank cools down and it probably levels out after a while but I rarely have the torch lit for more than 10-15 mins so I'm always having to fiddle with it. Would a two stage reg help?
Thanks,
William Chitham.

I use a Harris Propane specific regulator and it's been great.

Harris Model 25GX Single Stage Propane Regulator CGA 51P 25GX-5-51P

[bambuko]

If it is any consolation William, you are not alone...
I use Wescol (propane specific) single stage regulator (link) and have exactly the same problem.
It usually doesn't take very long (once you re-adjust the regulator) for things to settle down.
Two stage regulator wouldn't make much difference.

I am puzzled BTW by two gauges on Harris regulator?
AFAIK bottle pressure will remain the same regardless of the quantity of propane remaining in the bottle, so what is the purpose of 400psi gauge?

[Mark Kelly]

Two stage regulator wouldn't make much difference.

I am puzzled BTW by two gauges on Harris regulator?
AFAIK bottle pressure will remain the same regardless of the quantity of propane remaining in the bottle, so what is the purpose of 400psi gauge?

No, the OP had it right:

I always find the pressure dropping off as I'm working and often have to adjust the reg, always at the most inconvenient moment of course. My impression is that the supply pressure drops as the tank cools down and it probably levels out after a while

The tank pressure is the equilibrium vapour pressure of the liquid propane. Since the liquid refrigerates as it releases gas (due to enthalpy of vapourisation*) its temperature, and therefore the equilibrium vapour pressure, goes down as gas is withdrawn. At a constant flow rate and constant ambient temperature it will eventually stabilise.

* the gas has higher kinetic energy than the liquid and this energy has to come from somewhere, in this case it is the liquid, which cools as energy is withdrawn. This is called the enthalpy of vapourisation.

A better way of thinking about this is to use statistical thermodynamics: only the most energetic molecules are able to escape the liquid into the gas phase. Losing the most energetic molecules lowers the average energy of the remaining molecules. Lower average energy = lower temperature.

[William Chitham]

So it looks as if my regulator (same unit, same supplier as yours Chris) is unable to cope with the falling supply pressure as the propane cools. I have to say I'm not surprised it struggles considering that it has an output range of 0 - 100psi odd so I'm barely cracking it open to get the 2 - 5 psi I need. Most devices work better when you crank them up a bit I guess, especially if they are not of the best quality. That Harris reg may be a higher quality unit, whether or not the second gauge is redundent, if I can find a version with UK fittings I might be tempted.
Thanks for the replies,
William.

[Doug Fattic]

My 2 stage fuel regulator gives me rock solid flame control. It never wavers after I set it the first time. Actually it is an acetylene regulator that I had reconditioned to work with propane. So its pressure range only goes up to 15 psi. Having said that the new propane regulator that I got for use in Ukraine that doesn't have any pressure gauges seldom needs a flame adjustment either. It has only a modest sized diaphragm and is priced low to sell in a country with a terrible economy. However the tank we use there is about twice the size of an American BBQ tank so that might have an impact.

I'm one that finds any flame adjustment after starting to be a real nuisance. Whatever I have to pay to have really good brazing equipment is worth it to me. Of course I also have frame building class students that already find it hard enough to learn how to braze so I can't add to their learning difficulties.

[William Chitham]

My 2 stage fuel regulator gives me rock solid flame control. It never wavers after I set it the first time. Actually it is an acetylene regulator that I had reconditioned to work with propane. So its pressure range only goes up to 15 psi.

All makes sense, as I understand it the advantage of a 2 stage regulator is that it copes better with a fluctuating input pressure. This business of range seems crucial to me, most sytems don't work well at the very limits of their operating range, especially simple/cheap, ones. I notice that the Harris reg recommended by Will Neide is available in various ranges including 0-15 psi. I've emailed Harris to ask if they can supply to the UK with UK fittings but yet to hear from them; I've been looking for adaptors without luck so far. Maybe an adapted acetylene reg is a possibility, I'll see if I can find anyone over hwere who could do it, does it involve new parts (different diaphragm to resist corrosive effect of propane?) or is it just calibration?
William.

[Will Neide]

I think it would be worth it to buy a "turn key" regulator instead of trying to convert one. I honestly don't know what makes one propane specific, BUT I have had no issues with this regulator on my propane tank. My previous regulator, don't recall brand or style, would fluctuate like crazy and drive me nuts. Bad diaphragm? The Harris regulator is solid and steady. You can definitely watch tank pressures change depending on large fluctuations in room temp (day to day changes), but the outlet pressure and flame remain constant regardless of tank pressure. I suppose the tank pressure gauge is unnecessary, but it's "nice to have."