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Guest Message by DevFuse

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How to use a cutting torch

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9 replies to this topic

#1 idosubaru


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Posted 03 May 2011 - 09:57 PM

Picked up a cutting torch set up - Oxy-propane. Guy said it worked fine and the propane tank was full, I had the oxygen tank filled.

With the propane flowing out of the torch tip, it only lights for a second and then goes out? Keep it pointed at another flame and it stays lit just fine. Seems like the tip is probably clogged?

I'm not confident on how the controls work:

How do i know if this torch/set up has a flashback arrestor?

Each tank has a valve obviously - open/close.

Then it appears the regulators have a dial/valve of some sort - what do I do with those?

The torch has a dial for each gas line and then one other dial - what is that dial for and how do I set it?

What's the typical Oxy-gas start up method - open gas, light it, then dial in the Oxy?

Edited by grossgary, 03 May 2011 - 10:06 PM.

#2 MilesFox


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Posted 03 May 2011 - 11:14 PM

You need to set the pressures with the regulator for the different gases. Oxygen is typically about 30-35. dont get too rich beyond 35 with the oxy.

I am not sure what the propane would be for welding. In welding class 10 years ago we had acetylene, and the pressure was 15 psi, and any more, it could self combust at higher pressures. I would assume propane to be 30 psi if i remember right from working at u-haul filling propane. Try to look that up to be sure.

On the torch, you want to turn on the propane first, the red hose, and set a good foot long flame. then dial in the oxygen so the flame has blue spikes about 1/4 in long out of the holes on the tip. The lever on the bottom is to inject a plast of oxy to blow out your puddle of melted metal.

if you are cutting, you want to warm up a white hot spot first, and then blow it out and move at a rate you can melt it.

in heating to cherry red or hotter, dial the oxygen lower and dont use the blow lever

It has been millions of years since i used one, but this is what i remember.

#3 idosubaru


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Posted 04 May 2011 - 06:52 AM

thanks miles, i'll check those pressures.

a little reading suggests i probably need to clean the tip. haven't figured out what to clean it with yet.

#4 davebugs


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Posted 04 May 2011 - 07:23 AM

They make tip cleaners.

ANy welding supply or my local auto parts place has them.

Also I have a document or link here Skip gave me years ago I'll look for. I hadn't run torches since the late 70's and needed a "refresher".

#5 MilesFox


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Posted 04 May 2011 - 07:25 AM

Oh yeah, one more theing, For safety, stand behind or off to the side of the regulator in case the knob blows out, this is safety practice fro pressure tanks. and be sure tho cap the valves when not in use(on the tanks)

There is a procedure for open ing and closing the valves, so the pressure doesnt shock the system. I dont remember what order that is, but its another safety tactic.

#6 Scott in Bellingham

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Posted 04 May 2011 - 07:55 AM

you want to neutralize the flame, im sure theres good details on the web



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Posted 17 June 2011 - 06:06 PM

Just to add to this old thread
LPG is really only good for cutting as it does not get hot enough for a good welding flame...
the torch has handle should have 2 valves one for O2 and one for Fuel( LPG in this case) then their will be a connection for either Cutting or welding tip,the cutting tip will have another adjustable valve and a cutting lever...
there will also be 2 regulators one on the Oxy cylinder and one on the fuel cylinder,these will have either one or two guages on them,if 2 guages then one is cylinder pressure,and the other is delivery pressure which is adjustable,I am not sure on the fuel adjustment for LPG as I have always used Acteylene,the O2 pressure will vary as to fuel,tip size,and whether you are welding or cutting :)( typically a higher pressure when cutting )...
The torch handle valves are used differently depending on if you are cutting or welding, both are used for the fuel/oxy mix when welding,only the fuel is used for adjusment when cutting and the O2 should be fully open then back 1/4 turn,the oxy adjusment for flame while cutting is adjusted via the valve on the cutting head...
adjusment of the flame is a science/dark art :) best bet would be to watch some one or maybe see if there is any Youtube videos :)
with cleaning the tips,get tip cleaners and use the appropriate cleaner for the size of the hole, the cutting tips will have a larger centre hole surrounded by smaller holes,the smaller holes are the ones for the flame the larger centre is for the blast of oxygen..

#8 General chaos

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Posted 18 June 2011 - 12:48 AM

in my personal opinion. propane is too slow to heat the metal to even use as a cutting torch. i dont like using it.

#9 3eyedwagon


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Posted 18 June 2011 - 01:35 AM

Wow, this thread is scary. You need to find some authoritative information before you start screwing around with this stuff. This isn't the kind of thing you should just mess with until you get it right.

Some of the startup procedures listed were right, but, propane is a different animal than acetylene. You need to find a chart that will guide you to correct pressures depending on the tip size you are using. For what most people are doing you will need to run about 5psig of Propane, and 25/30psig of Oxygen. YOU DO NOT NEED TO RUN 15+psig. That is terrible advice. Most people will never encounter material thick enough to need 15psig of propane/acetylene pressure. To those that don't know what you're talking about, PLEASE AVOID GIVING TERRIBLE AND DANGEROUS ADVICE. Over 15psig can blow a regulator, and result in a not so fun fire.

Here is a good tip chart, and pressure chart PER WHAT MATERIAL THICKNESS YOU WILL BE CUTTING. That will get you started getting dialed in.

Cutting with propane can be a little more tricky than with acetylene, but, far from difficult. Most large scrapping sites use strictly propane for cost, and they are often cutting incredibly thick material. They utilize torches that mix the gasses a bit better, but, it's not anything that anyone couldn't do. We used natural gas torch setups for extremely accurate cutting of 1"+ thick WABO test fixtures. It worked extremely well. In most cases preheating only takes moments longer. If you know how to set up the equipment...:rolleyes:

#10 WoodsWagon


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Posted 23 June 2011 - 10:07 PM

Propane is used in scrap yards all over because it's cheaper than acetylene. There's also an acetylene shortage and rationing right now because one of the two suppliers plant's blew up in the midwest.

Now, like miles said, NEVER GO ABOVE 15psi with acetylene on the regulator. It can self ignite and blow up in the hose. Also, never drop or bang an acetylene tank, it can start a reaction inside the tank that causes it to explode hours later. Store acetylene tanks upright, and if they've been on their side for transport, store them upright for a few hours before using them. It's not liquid in the tank, it's gas dissolved in a substrate, so there's handling precautions.

Now oxygen, never get any grease or oil in the hoses or on the couplers. It can self ignite and blow up in the hose.

Open the fuel bottle valve only 1/2 a turn so it's easy to shut back off in an emergency.

Store the torch with both tank valves off and the lines and regulators de-pressurised. Shut the tank valves off, then open the torch valves until the pressure gauges drop to zero. Close the torch valves.

3 knobs on the torch, 2 are oxy controls, one is fuel. Close all 3 valves to start with. Open the main oxy valve by the fuel valve a turn or so. Open the fuel valve 1/4 turn and light it. Adjust it so you have the longest flame, but still attached to the tip. Then use the oxy valve 1/2 way up the torch to adjust the flame to be neat blue cones. Heat the surface until it's glowing and wet looking, then pull the handle to blast oxy into it. The steel actually burns, it's accelerated rusting in fact. Keep the torch pointed at a 45 degree angle in the direction your cutting and take it slow. If you loose the burning section, go back to heating it and pull the handle again.

With acetylene, I usually run 10psi and 25psi on the oxy when cutting. When using a welding tip, the acetylene psi I adjust to match the number of the tip. Not precise, but it works. Adjust the regulators with the torch flowing gas.

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