Can someone tell me what the preferred and proven safe method for shutting off an oxyacetylene torch?
I have been taught to turn off the acetylene torchvalve first and then turn off the oxygen torch valve.
But, some manufactures explain it just the opposite.
By aevald 
Date 12-21-2008 08:21
Edited 12-21-2008 08:23
Hello deburr, there are a number of lines of logic and reasoning for using both of the methods that you have heard of or been told. Many like to turn the fuel gas off first, as it is believed that there is less sooting of the internals of the torch assembly as the oxygen will clear the fuel gas residue when it is done that way.
Personally, I prefer to turn the oxygen off first because if there is any issue with the fuel gas shut-off valve it will show-up when you try to turn the fuel gas off last. If it is leaking, a small flame will continue to burn and will give you a heads-up on this condition. Although it is likely that you could also smell a leak, if you were in a rush to go to lunch or something it is possible that you might just shut off the torch, set it down, and leave without shutting down the tanks and by doing so run the risk of pooling fuel gas that could cause an explosion. By knowing that the valve was leaking a bit, you would either have it repaired or at least shut off the tanks and only have them on long enough to accomplish your cutting or welding task and then have it properly repaired at a later time. That's my $.02 and certainly subject to change when a better explanation comes along. Best regards, Allan
I thing the logic behind shutting the O2 off first is related to stopping any burning. Without O2 nothing can burn back inside the torch body.
I have always used the 02 1st method. Have you found any mfgs that suggest the other way ? I had always thought that when being told to turn the acet off 1st that it was based on a "wives tale" that was being passed around. It would be interesting to know what the different mfg have to say. Maybe its one of those things that can be done either way, but I don't find any evidence supporting that but my library is limited.
"Victor", the torch people have the procedure listed in their booklet about torches.
I will bring mine home and post it here, word for word.
I would like to think they have developed the procedure based on facts, not hearsay or wivestales.
Griff
Turning on the Cylinders
1. Be certain that the tension on the regulator adjusting screws has been released. Stand so
that the cylinder valve is between you and the regulator.
WARNING
Never stand, nor have anyone stand in front or behind a regulator when opening the
cylinder valve. Always stand so that the cylinder is between you and the regulator (see
Figure 10, page 29).
2. Slowly and carefully open the oxygen cylinder valve until the maximum pressure registers
on the high pressure gauge. Now, open the oxygen cylinder valve completely to seal the
valve packing.
3. Slowly open the fuel gas cylinder valve in the same manner.
CAUTION
Open the acetylene cylinder valve approximately ¾ of a turn and no more
Upon Completion of all Cutting Operations
Shut off the 1. oxygen preheat valve. Then, close the torch fuel valve. Be careful not to shut
off the fuel valve first, this may create a "pop" type sound. When the "pop" happens it
throws carbon soot back into the torch and may in time partially clog gas passages and the
flashback arrestors.
2. Close both cylinder control valves on the gas source supply.
3. Open the oxygen valve and depress the cutting oxygen lever. Release the pressure from the
system and then close the oxygen preheat and the torch handle oxygen control valve.
4. Turn the adjusting screw on the oxygen regulator counterclockwise to release all spring
pressure.
5. Open the torch fuel control valve and release the pressure from the system. Close the fuel
valve.
6. Turn the adjusting screw on the fuel gas regulator counterclockwise to release all spring
pressure.
7. Check the inlet gauges after a few minutes to ensure the cylinder valves are turned off
completely and no pressure remains in the system.
8. Remove slag left on the cut edge with a chipping hammer or brush. Never remove slag from
the cut edge with the torch head or cutting tip.
All of that is from Victor.
HTH
Griff
Hey Guys, Thanks for the input. I was flipping back through my Modern Welding Textbook (Goodheart -Wilcox Company) and it says just the opposite. This is the textbook that my students use in their high school welding course. This is what is written in the book. "To shut down the oxyacetylene outfit:
1. Close the acetylene hand valve on the torch, then the oxygen valve. This extinguishes the flame and eliminates the soot.
2. Tightly close the cylinder valves
3. Open the hand valves on the torch, bleed lines, close hand valves on torch, turn regulator adjusting screws all the way out".
The confusion started with me when I bought a new set of Smith torches and read what I thought was different than the text book. Again, I want to look at this from a safety standpoint with the amount of students that come and go each year.
The "only" safe way.. Is to obey manufacturers instructions.
Victor teaches... Light fuel gas, add 02..... Shut down by turning off 02 and then fuel gas... If you have a Victor torch this is how you should do it... Trust them.
If Smith says differently... They are not wrong... They are different... With a Smith torch... Obey Smith directions.
Far more important that the lighting/extinguishing sequence... Is the importence of selecting the proper size tip for the cut being performed in order to avoid starvation of the tip, which is the cause of most Oxy-Fuel troubles.
I agree with Lawrence. Do what the manufacturer says.
Personally, I'd do what victor says, when shutting gas off first you are creating an explosion in the mixing chamber. torch gets hot. your torch should never get hot to touch or you don't have the flame set right. (the tip may get warm when close to plate) but you should be able to hold the tip when the flame is burning in the air. I have seen a torch that was blown apart in the mixing area due to an explosion. gas and oxygen are an explosive mix, and compression can cause it to explode. that is the reason behind turning your gauges to zero before opening the bottles.
I just seen a regulator that had the back blown out because the oxy. ran completely out and the acet. with more pressure pushed into the oxygen hose and into the regulator that was wide open.(from emptying the oxy and turning gauge up to get every last drop), when the 1200Lbs opened up, it compressed so fast into the gauge, and what happens when you compress? it gets hot. so it became a grenade.
If you take a 1/4" steel tube, about a foot long, hook it straight to the brass fitting that attaches your gauge to the bottle, and put a match in the end, cap it and open the oxygen, the compression will light the match. it will get hot enough to light a match on the outside of it also. I wouldn't recommend trying this at home. but don't take lightly the safety warnings about cylinder and torch safety!
