Heating torches for 'MC' cylinders - acetylene withdraw rates

I was browsing a Victor catalog for information on their turbo-torches and noticed that their smallest tip sizes seem to demand no less than 2 CFH of acetylene - even the kits sold for use with 10 CF 'MC' cylinders. Some of them to up to 8.3 CFH with CGA-200 connections. They even sell a 7 CFH torch tip in a kit with an 'MC' cylinder tote.

Is there more to acetylene withdraw rates than the general 1/7 rule? How is it that these torches operate safely? Are they designed to burn acetylene and acetone together?

These are UL-listed products, mind you.

http://www.rsdtotalcontrol.com/assets/prod/756.pdf

Pages 10-13.

It looks like the Lincoln Port-A-Torch kit comes with a #3 welding tip, good for 5-11 CFH acetylene.

How is it that a 10 CF cylinder can run a 5-11 CFH tip without issues in spite of everyone constantly going on about the 1:7/1:10 rule?

Something doesn't add up here. Either the withdraw rate rule is wrong or the manufacturers are wrong. I've used these Port-A-Torch kits before without issues. They wouldn't sell the things if they didn't work.

What gives?

The MC tank is too small. They are lying.

By a factor of 7... and yet they still work without widespread complaints?

If everyone who bought one of those kits took it out of the box, put it together, lit it up and immediately had it spit acetone because it's drawing 3.5 times more CFH at minimum heat than the holy 1:7 ratio dictates then I don't think they would still be selling.

If that were the case then 'MC' cylinders wouldn't even exist. The only thing in the world that draws such a tiny CFH that I can think of are jeweler's torches - and for that application portability isn't required so it would be far more economical to go with a 'B' cylinder instead. Much of the cost of recharging acetylene cylinders is the labor involved as I understand it. They have to be emptied, weighed for acetone content and then refilled over a sufficiently long time for the acetylene to dissolve. That means there is a relatively constant overhead per cylinder regardless of it's size. It wouldn't make sense for jewelers to want MC tanks.

Rooftop HVAC repairmen with their 3-7 CFH turbo torches and anyone with the odd remote cutting job on the other hand...


We're missing a vital piece of information here and I don't know what it is.