Portable oxy-acetylene tote outfits? Worth having?

[ultrarunner]

Minor correction to the history of the bottles, mc=motor car, b=bus. A friend of mine quizzed me on that one. He's been welding since the dawn of ages

Here's an excerpt from the car club literature:

According to research, there are two camps for the MC tank size designation.

One group says "Motor Carriage" and the other group says "Motor Cycle." The term "Car" is short from Carriage and was not in the common vernacular till much later... Electric Lamps basically dominated from 1915 on...

The stronger evidence, including antique advertisements and catalogs suggests that MC is "Motor Cycle" because during the brief period between acetylene generators and electrical lighting Prest-O-Lite offered a popular compressed gas conversion kit for Motorcycles

There's even confusion over the "B" size tank. Does "B" stand for "Bus" or is it "Buick?"

Buick was the first to offer Prest-O-Lite lighting on its automobiles over the standard carbide generators of the time.

As a practical matter, MC cylinders are never used on automobiles... only motorcycles.

"B" cylinders are strapped to automobile running board and those designed for this application will have an offset valve instead of being mounted dead center so as to not draw acetone.


As to the usefulness of the MC size here is an example.

On 14 April 1988 USS Samuel B. Roberts (FFG 58) struck a submerged Iranian mine nearly ripping the warship in half. Working feverishly for seven hours, the crew stabilized the ship. To fight massive fires they cut holes in deck above to insert fire fighting nozzles.

Soon after this all Navy Ship's damage control lockers received portable Oxygen/Acetylene MC cutting sets. The sailors in charge of ships DC lockers are HT rating which is USN welder rating.

Note, Acetylene cylinders should never be exposed to atmosphere so standard policy is to return for refill with some pressure remaining.

 

[KML]

Off topic,

"On 14 April 1988 USS Samuel B. Roberts (FFG 58) struck a submerged Iranian mine nearly ripping the warship in half. Working feverishly for seven hours, the crew stabilized the ship. To fight massive fires they cut holes in deck above to insert fire fighting nozzles."

Interesting that you mention the Sammy B. A friend of mine for ~15 years, the man who sits at the desk next to me, was on the Sammy B. when it struck the mine.
When he retired, I replaced him in my current billet (he was hired as a civilian and stayed). His journals were used (in part) to help write the book about striking the mine, "No Higher Honor". He and I will actually be attending a veterans day ceremony at a local school in about 2 hours. Just thought you mentioning this today was an interesting coincidence..

Sorry for the highjack..

 

[deereman75]

I actualy saw one of those victor MC EMERGENCY CUTING OUTFITS. It was at an antique shop. The thing has 2 20cf o2 tanks hooked together, and one mc acct tank. It has the smallest cutting handle I ever saw, and a #1 tip.

 

[ultrarunner]

Off topic,

"On 14 April 1988 USS Samuel B. Roberts (FFG 58) struck a submerged Iranian mine nearly ripping the warship in half. Working feverishly for seven hours, the crew stabilized the ship. To fight massive fires they cut holes in deck above to insert fire fighting nozzles."

Interesting that you mention the Sammy B. A friend of mine for ~15 years, the man who sits at the desk next to me, was on the Sammy B. when it struck the mine.
When he retired, I replaced him in my current billet (he was hired as a civilian and stayed). His journals were used (in part) to help write the book about striking the mine, "No Higher Honor". He and I will actually be attending a veterans day ceremony at a local school in about 2 hours. Just thought you mentioning this today was an interesting coincidence..

Sorry for the highjack..

Being Veterans Day and all I think it should be OK...

Thank you for you and your friends service!

 

[lostcause]

i've got one of the portable setups like you see in the big box stores, and also in the welding gas stores. mine has been around since the 80's and it originally had the 20cf oxygen tank, but instead of acetylene it used disposable mapp cylinders. over the years the hoses became brittle, and the tiny proprietary torch body and regulator developed leaks, so i purchased an mc acetylene tank and a fairly compact set of oxy/acetylene torches and hoses. that setup has been working for me for the last 15 or so years just fine.

a few years ago i got a contract for large bottles, and that's what i primarily use - mainly because you don't run out very often, and it's way cheaper per cubic foot used when filling large tanks. i admit i had not heard of the 1/7 volume per hour rule, and i've used mine for 100% cutting or heating on 1/4" average steel, but often up to 1/2". i haven't blown up yet, which is good, but i'll try to monitor the next full tank and see how much i use at a time and figure out how fast i use it.

as i said i rarely use them because i have the larger bottles in the shop, but having a 40lb one hand carry torch is sometimes worth its weight in gold. i would never try to use it for day to day or even hobby level fabrication (though i really used to).

bottle contracts are getting more and more expensive around here, so what i'm planning on doing when my contracts expire next year is to turn the large bottles in and buy a plasma cutter for the stuff i do within reach of the plug. i'll have the portables to fall back on for the cases where i have to heat something or cut something in the field.

one last thing:
me and the safety police on here don't see eye to eye, and for that matter we shouldn't even be put in the same room. that aside, i won't dispute about the consumption rate issue, though i think everyone has the right to decide whether they can adjust the cutting flame to a level where they don't over use it. those small tanks will certainly work fine for cutting steel - don't let anyone tell you they are for sheet metal. they are certainly not for constant production use, but they are perfect for intermittent use. as far as transportation, check the laws yourself, because i don't know. what i can tell you is that the 20cf oxygen and 10cf (mc) acetylene tanks do not have threaded collars so they cannot have covers on them. i'm guessing that those sizes fall under the llimits that some bean counters decided was acceptable to transport without a top. if not, all your disposable propane cylinders might as well have them too.

 

[dstig1]

OK, now im way confused. Ive cut LOTs of steel and brackets, rebar over the tears with my little setup. I use a rosebud tip also for over 10 years without any issues.

except for length the bottles will last, whats the big issue??

A look at the Wikipedia entry for Acetylene should explain it, but I'll take an unofficial whack at it here.

Basically, Acetylene is highly unstable. It cannot exist as a normal gas you think of. You will note that most industrial gasses are pressurized to very high pressures >2000psi, but acetylene cylinders come with serious warnings not to exceed 15 psi. That is because if you have Acetylene gas at or above 15 psi, it can auto-ignite and go BOOM. Dats bad. Well a cylinder at 15 psi is all but useless as it holds nothing for gas quantity in a reasonable size.

But Acetylene has a characteristic that it is very soluble and much more stable in solution in Acetone. This is how Acetylene cylinders are designed. They are a matrix of a foam-like material and then filled with acetone. Then they pump Acetylene into it at a rate that it will dissolve into the acetone. That way they can pack a useful amount of acetylene into a cylinder without it going BOOM.

The problem is a thermodynamic one. As you depressurize the cylinder (liberating and withdrawing acetylene from the solution), you run into a thermodynamic limit where if you withdraw any more, the system cannot equilibrate fast enough and so it actually starts to suck the liquid acetone into the regulator and hoses. This will screw them up big time and can cause the unfriendly BOOM we previously discussed. Thus there is a maximum withdrawal rate that is set at 1/7 of the volume of the tank. You pull it out at a rate higher than that per hour, and you will suck liquid acetone and probably BOOM or at least screw up your reg and hoses.

But people have done higher rates and survived, right? I'm sure. Like anything in engineering you add a safety factor to ensure if anything unexpected happens the user should still be safe. For very short times, I suspect even very high withdrawal rate will not suck acetone, but understanding the issue, I would not push it unless it was an emergency. Frankly I haven't gone deep into the science to know what the limit truly is, so I trust and abide by the guidelines. Plus it will all depend on temp - at 100F you can surely pull a higher rate than at -10F.

So the questions come down to things like "Do you feel lucky punk" (please don't) or this is a life and death issue and I need to cut this beam off Uncle Joe to free him from the earthquake collapse. The reasons are sound, so avoid overdrawing acetylene cylinders at all cost, IMHO. Get a bigger set or manifold a few smaller one together to get the rate down.

HTH
Dave

 

[IslandTractor]

As a member of the so called "safety police" in this thread I have to respond to the experienced users who ignore or are completely ignorant of the safety concerns.

I don't think it is such a big deal to use the portatorch setups for working on more than the sheet metal they were designed for. Obviously you can cut a railroad tie if necessary without self immolation. However it is a problem if people using these things aren't even aware of the risk and how to avoid it. Responsible use of any tool requires an understanding of how it works and how things might go wrong. The industry obviously hasn't done a very good job in educating casual users about the safe use of acetylene. Most acetylene accidents occur with industrial users not homeowners or farmers but it doesn't hurt to raise awareness. The potential impact on others is another reason to raise awareness. If you are a jerk and misuse a chainsaw it is typically just your own limb or life at risk. An acetylene accidental explosion can obviously affect other lives so a higher standard for safety awareness and compliance is reasonable IMO.

Again, we all stretch safety rules so using a portatorch for something it was not designed to do is no biggie in and of itself. Being ignorant of safety issues might well be due to lack of formal training. However, it isn't so cool to just poo poo safety concerns especially on a forum where people come for advice in lieu of formal training. You may well drive your car for fifty years without using seatbelts and then die peacefully in your bed but that is hardly a justification for telling others to ignore seatbelt use.

 

[lostcause]

i'm not trying to start a war here, but there have been some posts in this thread that have said or implied that these are for light gauge material only, and that they are being misused if you use them on thicker material. i'd contest that is only an opinion, based on the manufacturer's specs. this is the victor page for one of theirs, and it states 1/2" cutting capacity with the included equipment.

http://www.thermadyne.com/victor/products/detailProduct.html?prodID=0384-0936

i'm not disputing the issue of emptying the tank too fast on thicker material, but like every other dangerous tool, you need to understand how to operate them safely. i'm just not a fan of misinformation for the sake of safety. tell the facts and educate of the dangers.

 

[ultrarunner]

I was going to post this the other day...

http://www.thermadyne.com/IM_Uploads/Literature/lit_356_106_65-2007.pdf

There is an asterisk on the small set about "Sufficient Acetylene and Oxygen Supplies"

 

[IslandTractor]

I was going to post this the other day...

http://www.thermadyne.com/IM_Uploads/Literature/lit_356_106_65-2007.pdf

There is an asterisk on the small set about "Sufficient Acetylene and Oxygen Supplies"

Exactly. The fine print. What these companies are doing with these torch sets is misleading. The torch itself is perfectly capable of cutting 1/2 steel safely. Just hook it up to a 80cuft acetylene tank and similar sized oxygen tank. Same with welding. The torch kit is your basic medium/light duty torch. Of course it can weld 1/4 inch steel. So long as you run a #2 or #3 welding tip which requires about 7cuft flow from a 10cuft tank.

I called Lincoln tech support to discuss this issue. They were very clear that their torch guidance on cubic feet per hour of acetylene consumption precluded using the mini tanks for all but light duty sheet metal welding. Cutting was likewise limited. Brazing and soldering would be fine even with the mini tanks.

With the AWS and other safety boards recommending a max of 1/7 and more recently 1/10 consumption/hr rate of acetylene consumption as function of tank size it is just not possible to meet those recommendations with those 10cuft acetylene tanks. Look at the owners manual for the torch itself and see what the gas consumption per hour figures are with different tips. Obviously lots of people either ignore these recommendations or more likely are just flat out ignorant of the safety issue and use them to do more than AWS considers safe.

Call up Lincoln and ask to speak with tech support and see what they tell you. They made very clear to me that while the torch was fine (again read the fine print), the 10cuft acetylene bottle was not appropriate for many of the advertised capacities. If you doubters don't believe Lincoln, call your local welding supply company or post a question on Welding Web or one of the other welding forums and see what oxyfuel pros say.