Beginner needs help with OA

[STCL01]

Hello, I've been lurking around for a while. I just picked up a used Harris torch and set of bottles to go with my Hobart 140. Nothing big, but just to use to make a few odds and ends and fix things around the place when I break them. It's been a long time since I used a torch, and that was where I worked years ago. The guys that really did the work on the floor made most of the adjustments and helped me. I need to know what I'm doing. Does anyone have any tips on getting the torch adjusted for cutting, and what's the 1/7 rule that I have seen mentioned in some of the threads? Thanks for the help.

[hankj]

Welcome aboard.

The 1/7 rule is simple: Don't try to draw more than 1/7 of the gas volume from your acetylene tank per hour. If you have small 40CF tank, that means you can't run any tips that need more than 5 SCFH. Divide the cubic volume of your tank by 7; that's how many cubic feet per hour you can draw safely for long periods.

You can exceed that draw for short periods. I've done it often with a #4 Victor cutting tip using my small (40CF) rig.

As for pressures, Google a tip chart. There are plenty of them on the internet. Use the settings as ball park numbers and tune for your particular rig.

Generally, acetylene cutting pressures for any manufacturer's tips between sizes 000 and 1 run from 3 - 5 PSIG, with O² pressures running from 20 - 35 PSIG.

Hank

[TexHand]

There was quite a discussion on the 1/7 rule a month or so ago - search and ye shall find - there was a lot of useful info in there.

Also I would recommend going to the Harris website and d/l the manual for your torch. That will tell you what you need to know to get started. Lighting procedures, flame adjustment, shutting down procedures, etc.

[villemur]

Also, if you want an in-depth guide to O/A, check out the ESAB O/A handbook at: http://www.esabna.com/EUWeb/OXY_handbook/589oxy1_1.htm. It's also available in hardcopy, and I highly recommend it.

[STCL01]

thank you for all the advice. I'll get it down eventually.

[weldgault]

Hello, I've been lurking around for a while. I just picked up a used Harris torch and set of bottles to go with my Hobart 140. Nothing big, but just to use to make a few odds and ends and fix things around the place when I break them. It's been a long time since I used a torch, and that was where I worked years ago. The guys that really did the work on the floor made most of the adjustments and helped me. I need to know what I'm doing. Does anyone have any tips on getting the torch adjusted for cutting, and what's the 1/7 rule that I have seen mentioned in some of the threads? Thanks for the help.



Acetylene - As requested

--------------------------------------------------------------------------------

Acetylene is filled into a cylinder that is filled with a very porus material and filled with Acetone, which absorbs 25 times its volume , with acetylene, which is formed by adding water to calcium carbide and pumped into the cylinder very slowly. Acetylene = 14.7 cuft per Lb. The weight of the cylinder, with acetone added is stamped into the cylinder as TW 125#(example), then filled to 250# at 68 Degrees F. After filling, the cylinder is weighed again (150#) 25 lbs. of gas = 367.5 cuft., which is stamped on the outside of the cylinder or a tag with the amount of gas inside the cylinder is attached. You as the customer, not knowing this will except a large cylinder at a given amount (400 cuft). The LWS will be shocked if you ask them to weigh the cylinder and charge you for exactly what is in the cylinder. I hope this will answer some of the questions ask in other threads. Remember that 15#'s is the max. psi, which should be withdrawn from the cylinder and the 1/7 rule applies. Example: 400 cuft = 57 cuft that can be removed from the cylinder, without the gas becoming unstable and a #15 MFA heating head requires a min. of 90 cfh to operate correctly, so 1 large acetylene is not enough to run that rosebud, manifold 2 together, otherwise live with the backfire from not having enough volume of gas supplying the tip. More information, upon request. John Gault