Using an Oxy Acetylene Cutting Torch: Setting Up, Lighting, Using, Shut Off

Does the thought of using an oxy acetylene cutting torch intimidate you? We feel you. After all, dealing with two tanks that are at risk of catching fire as you work sounds risky. You would rather have all your body parts firmly attached as you work, right?

Don’t let this safety risk stop you from using a cutting torch; the worst-case scenario you are thinking of doesn’t really happen that often. If you have the right settings for the entire system, you can safely use an oxy acetylene torch for all your projects.

But, it doesn’t stop there. You also need to properly set it up before you start using one, the same way you’d need to set up an engine driven welder the right way.

Not only that, you must light the torch and shut it off correctly. Yes, there are proper ways to do all that.

Don’t worry because we will show you that all these are not as hard as you think.

How Does a Cutting Torch Work?

Before you set up your cutting torch, you must first understand how it works so that you can handle it properly. Not only that, this will allow you to get a cut of good quality, which is only possible if done correctly. For more serious cutting jobs, we do recommend the use of a plasma cutter, though.

An oxy acetylene cutting torch allows oxygen to mix with acetylene to combust and produce a flame that has a temperature exceeding 3000 C. This kind of flame is the only one hot enough to cut through mild steel, specifically any kind of steel that only has a maximum of 0.3% carbon.

Steel has an ignition temperature, ranging from 700 to 900 ℃, which is enough to remove components that protect it against oxygen while keeping it in solid form. The cutting torch pre-heats steel for it to reach that temperature; a cherry red color on the steel will be the sign that it has been adequately preheated.

When oxygen from the cutting torch reaches the unprotected steel, an exothermic reaction occurs that causes it to form oxidized liquid steel or slag. Because steel has a higher melting point, this slag that formed can easily be blown away by oxygen. This then reveals the solid steel that has not been oxidized.

The exothermic reaction that occurs is continuous as long as the cutting torch is lit up and the flame hits the steel. This constant reaction prevents a crust from forming on the steel, which immediately occurs if the protection against oxygen is still present on the steel. Because there is no crust that forms, the oxygen from the cutting torch can now penetrate the exposed solid steel and cut through it.

Due to the acetylene present, the flame produced by the cutting torch is the highest among all oxyfuel cutting processes. This means you can make cuts much faster and of better quality than the other methods.

How Do You Set Up an Oxy Acetylene Cutting Torch?

Large cylinder tanks. Hoses. Regulators. Valves. Torch. With all these components, setting up an oxy acetylene torch can be an overwhelming experience. While we admit that setting it up is not a straightforward affair, it is still doable even by beginners.

Setting up such a system is pretty standard, but you must first check for any unique instructions the manufacturer of your cutting torch may have. The manufacturer’s instructions will always take precedence over the following standard instructions:

  1. Secure the oxygen and acetylene tanks to a sturdy post, wall, or the like in an upright position. It would be better to use cylinder carts if available since they will do a better job of keeping them in place.
  2. Check and remove any protective coverings placed on the tanks. But if no covers were used, clean the tanks first to remove any debris or dust that settled, especially in the valves. When cleaning the valves, stand away from the opening and quickly turn it on and off. This short burst is enough to blow off the dust present.
  3. Ensure that the regulators to be connected to the valves of the tanks have matching threads. If not, connect the regulator to an adaptor first, then connect the other end of the adaptor to the valve. Screw them in place by hand first, then finish tightening the connection using a wrench that has a fixed opening.
  4. Identify which hoses are used for oxygen and acetylene respectively; the hose for acetylene is typically red and green is for oxygen. Attach the right hoses to the regulators of the right tanks without contaminating it with any kind of lubricant.
  5. Once the hoses are firmly in place, connect the other ends of the hoses to the handle of your torch.
  6. Connect your cutting torch to its handle and tighten the nut by hand. Ensure that the valves on both the torch and the handle are closed.

After setting up, you still need to do some checks before attempting to light your cutting torch. Make sure that the regulators are facing away from you when you do the following:

  1. Open the valves of both tanks, but do it slowly and only one at a time.
  2. Adjust the screws of the regulators so that the gauge will reflect a psi between 40 to 60 for the oxygen tank and 10 psi for the acetylene tank.
  3. Slightly open the valves for both oxygen and acetylene on the cutting torch, but make sure that the valve for acetylene is not open by more than 1/8 of a turn or exceeding 45 degrees.
  4. Do a leak test on all the connected parts using a solution specifically for leak testing or a paste made using dissolved Ivory soap. Use it to coat the valves, hoses, and regulators and watch out for any bubbles that form after a few minutes. If present, it means a leak is present and you need to adjust or tighten the connections.
  5. Repeat the leak test until no bubbles appear.

After successfully doing a leak test, you can now light up your oxy acetylene cutting torch following the instructions of the manufacturer.

How to Light a Cutting Torch

Because of the gases involved, lighting up a cutting torch is done differently. Unlike other torches, a cutting torch will not produce a flame with just a push of the button.

Most cutting torches are lit up using this method:

  1. Slightly open the valve for acetylene on the cutting torch. Make sure that it does not exceed a half-turn.
  2. Use a flint striker or spark lighter to ignite the acetylene gas flowing out of the torch’s nozzle. Soot or black smoke may come out once it is lit up, which is considered normal. You can wait it out or adjust the acetylene valve to make the smoke disappear.
  3. Once the smoke is gone, slowly open the oxygen valve of the torch to remove all the yellow spots of the flame and adjust to get a neutral flame needed for cutting. This neutral flame consists of a small, white, cone-shaped tip near the nozzle and a bigger blue core.

You should only use a flint striker to light a cutting torch because using smaller lighting devices, such as a match or lighter, are too small and will put you at risk of burning your hands as you light up the cutting torch. Also, you must make sure that the tip of your cutting torch is facing away from you, other people, and any flammable objects.

But if your cutting torch has its own ignition device, skip the above steps and follow the instructions given.

How to Shut Down an Oxy Acetylene Cutting Torch

Because there is also no knob or button present on the torch to stop the flame, you must manually shut down your oxy acetylene cutting torch by cutting off the gas being supplied. If you are not yet aware, there is a seemingly never-ending debate about which gas supply to switch off first – oxygen followed by acetylene or acetylene then oxygen.

While both methods are considered correct, manufacturers generally advocate shutting off the oxygen valve first before acetylene. This method allows the acetylene still flowing to blow off the soot that settles in the crevices of your torch; any soot present can affect the seal of the gas valves and cause a leak.

Not only that, but this order also allows you to conduct a leak test before cutting off the gas supply. Once you cut off the oxygen supply then acetylene, the presence of a small flame despite no gas flowing to the torch will indicate a leak. Early leak detection helps prevent an explosion.

Another advantage of cutting off the oxygen supply first is that mini flashbacks are less likely to occur. Despite most cutting torches having protective features against it, flashbacks can still happen. Mini flashbacks occur in the form of a loud pop or bang. While generally considered harmless, mini flashbacks can still cause accidents.

If you are done with your work and need to return your equipment to its storage, you must follow the following steps:

  1. Cut off the oxygen and acetylene gas supplies by switching off the valves at their respective tanks.
  2. Purge the gas that remains in both hoses or gas lines by reopening the oxygen valve on the torch so that the remaining gas in the hose will flow out. Close the oxygen valve once no more gas is flowing out.
  3. Repeat the purging with the acetylene gas line. Make sure to purge both hoses separately.
  4. Once you finish purging, disconnect all components and store them properly.

When storing the oxygen and acetylene tanks, make sure to keep it in a dry and airy location far away from any flammable objects. Always keep them in a vertical position.

Can You Cut Cast Iron With a Cutting Torch?

Have you ever attempted to cut cast iron using an ordinary blowtorch? If so, you may have realized that it is a futile effort. But if you are using a cutting torch to do so, the result will be different.

Because an oxy-acetylene torch has the highest flame temperature present, it can easily cut through even steel that is at least 200 mm thick. But when it comes to cutting cast iron, it is also possible but it will not give you a clean cut and is a bit harder to do.

Preheating the cast iron is crucial to cut through it, and this is done by setting the cutting torch so that it produces a carburizing flame, instead of a neutral flame, and with the highest possible temperature. This type of flame offers better preheating to the cast iron and also stops oxides from rapidly forming. Preheating should be done from the top all the way to the bottom and with more acetylene so that the heat will deeply penetrate the cast iron.

Once it is sufficiently preheated, make small semicircles around the preheated line to melt the iron. Finally, use the oxygen jet to blow off the molten iron and cut through it. You may need to use flux to help you make the cut.

Because of the complicated process, using an oxy acetylene cutting torch to cut through cast iron is not often used. In fact, there are other methods specially developed for this purpose.

Can I Weld With a Cutting Torch?

Are you wondering if you need to buy separate welding equipment if you already have a cutting torch and need to do some welding? If so, we have good news – you can also use your oxy acetylene cutting torch for your welding needs. In fact, this process is known as oxy acetylene welding.

Basically, the metals are placed side by side, with a small gap present between them, and are melted together by the oxy-acetylene flame. When they cool down, the melted sections are already bonded to form a weld seam. Oxy acetylene welding can be used if quickly joining metals together is your only concern because the weld seam formed is not as neat as the ones created by other welding methods.

A neutral flame is also used for welding using a cutting torch, but you need to move your torch in a circular manner so that the metals will melt and pool towards the small gap present between them. While the weld seam formed using this method is strong enough, you can also add filler material using a rod to increase its strength.

An oxy acetylene cutting torch, contrary to its name, is not only used for cutting. You can also use it in different ways, making it such a versatile tool that you must have in your workshop.

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