Basics of Oxyacetylene Torch – Safety & Security Tips

Oxyacetylene TorchAs the word says it is torch consisting of gases like acetylene and oxygen which burns together to give flame of high temperature of 3000°C that helps to cut metals or join them through process called welding. The temperature heats the metal such that it melts and when allowed to cool gets joined. This is the only gas mixture that can cut steel.

The oxyacetylene equipment is steel cylinders that are portably consisting of oxygen and acetylene gases that are stored under pressure. The cylinders have regulators that are fitted with flexible hoses leading to the blowpipe. There is a safety device fitted between the hoses and regulators. This safety device helps in preventing flames from reaching cylinders. Moreover, there are certain features that are universally followed like a combination of oxygen versus acetylene to get high temperatures.

Basics:

The ratio combination of oxygen versus acetylene is the main criterion for getting to a high temperature. There are 3 settings namely neutral, oxidizing, and carburizing. Most of the welding process involves neutral settings which is a combination of oxygen and acetylene in equal quantities. The flame is obtained by adjusting the oxygen flame and the carburizing flame is achieved by enhancing the acetylene flow.

There are various settings to be achieved based on the metal thickness to be cut or welded. If its single hole welding, the setting of the fuel-gas regulator to single-digit indicates that both fuel pressure and oxygen pressure are each set at that specific Psi.

Below is table giving basic insights

Tip sizeMetal sizePressure (Oxygen-acetylene)
(inches)AcetyleneOxygen
0001/83 – 520 – 25
00¼3 – 520 – 25
03/83 – 525 -35
01/23 – 530 – 35
1¾3 – 530 – 35
213 – 635 – 40
324 – 840 – 45

Settings

  • Acetylene regulator should not be introduced above 15psi
  • Acetylene Cylinder valves should be open not more than 1.5 turns.

Oxyacetylene torch temperature

As there is combination of oxygen and acetylene gases, the flame reaches a very high temperature of 3480°C. The reaction between acetylene and oxygen is exothermic reaction and acetylene being highly reactive results in formation of carbon dioxide and water.

Oxyacetylene torch safety

The two main aspects related to oxyacetylene torches are safety procedures and safety equipment. The rays and sparks from torches can lead to loss of sight, inhalation of fume causing lung damage, accidents causing burns, or fires.

Watch Video: Oxyacetylene torch safety by Welder Expert

Safety equipment

*Safety wear like gloves, apron, boots, goggles, face shield and safety shoes

*Separate cylinders for oxygen and acetylene with tip united

Oxygen cylinders are usually green colored and are stored at a pressure of 2200 psi. When handling an oxygen cylinder, care must be taken such that there is no grease or oil to prevent catching fire due to the presence of oxygen that can catch fire easily.

Acetylene cylinders are stored at 250psi and should not be introduced above 15psi

*Proper regulators to adjust the outlet pressure

*Proper check valves to prevent reverse gas flow and can be placed between gas hose and torch

*Flashback arrestors installed to prevent fire to flow back to the cylinder as it shuts off the gas supply.

Safe Operation

  • The cylinders must be placed apart and securely fastened to wall or post using chains.
  • The cylinders must be used in vertical position.
  • The outlet must be cleaned off dust or dirt accumulation.
  • Connect the cylinders to regulators using proper wrench
  • Check for flow of gas slowly
  • Acetylene valves must not be opened more than 1 and half turns.
  • Keep all the tools in reach so that adjustment can be done easily
  • Hoses connected to cylinders must be checked for cracks and replaced
  • Oxygen hose are green and acetylene are red which must never be exchanged
  • Don’t use lubricants for connecting the gas supply to torch
  • Make sure for adaptors for 2 oxygen connections -one for preheat and other for cutting jet
  • Thoroughly check for connections before operating
  • Tighten the hoses and check for leaks
  • Make sure of the fuel supply requirement for heating tip so as to maintain gas supply
  • Do not withdraw acetylene beyond 30 cubic feet per hour
  • In case of backfire, the tip needs to be shut down
  • To prevent backfires, reverse flow it is required to check vales and flash back arrestors
  • The flow capacity of the check valve and flash back arrestors need to be checked

Oxyacetylene torch tips

Tips of oxyacetylene torches produce positive pressure (around 1 psi) wherein there is equal pressure of acetylene and oxygen. These copper alloy tips are single holed which is attached to torch handle and is connected to mixture wherein fuel and oxygen are mixed before passing through welding tip and is burned. The design is based on the characteristic of the flame of fuel gas used. It usually comes in a single and two-piece style.

The one-piece tips are made from a copper alloy so as to withstand the heat of the cutting process and is used with acetylene. To produce exact holes the copper alloy is machined, drilled, and swaged over wires. There are tips that are made with four, six preheat holes and eight preheat holes so as to allow light, medium, and heavy preheats. There are specific tips to gouge out welds, or cutting sheet metal. There special one-piece tips made of methylacetylene propadiene and propylene.

The one-piece tips that have oxygen bores come in two configurations namely straight bore and divergent bore. The straight bore handles the pressure of 40-60psi for hand cutting while divergent bore handles the pressure of 70-100psi and gives a tapered outlet for machine cutting.

The two-piece tip has outer shell and splined insert which does not require numerous preheat holes. The various combinations of configurations allow different fuel gases to burn efficiently.

The best preheats are propylene and MAPP as it utilizes fine rectangular spines. The V-shaped splines are more efficient and are used in large tips while small tips have small splines.

FAQ’s

  1. What metals can be welded with oxyacetylene?

For a good weld, the carbon content of steel must not be changed and there must not be any change to the properties of base metal. Besides, as steel show affinity towards the components of air, when steel melts it combines with carbon, oxygen, and nitrogen in the air forming a molten oxide and nitrate compound. This compound lowers the strength of steel.

Hence, low carbon steel, low alloy steel, cast steel, and wrought iron are easily welded. These ferrous materials are gas welded mostly.

  1. Can aluminium be welded with oxyacetylene?

Yes, oxyacetylene torches are mostly used for welding aluminum. Here, the hydrogen burns with oxygen using the tips used with acetylene but the temperature is not high. Also, the sizes of the tips are large. The aluminum sheets fall in the range of 0.8mm to 25.4 mm. But heavy material is not has welded as there is a large amount of heat emitted making it difficult to apply sufficient heat with a torch.  Moreover, the heat input for this process is not concentrated which can cause distortion if care is not taken.

  1. What are the two major uses of oxyacetylene equipment?

The oxyacetylene equipment is used for welding purpose in metal fabrication. It uses a torch that is supplied with oxygen and acetylene gas mixtures to heat the metal parts that are to be welded and sometimes filler rods are used to add material to the weld. It does not require electric power and can be used in any environment. The equipment is used to harden flame and temper workpieces of varying sizes especially for cutting and welding of metals. There are other operations like brazing and soldering.

The main uses are cutting metals sheets to smaller portions such that it can be used for other purposes. Welding is a process wherein two metal pieces can be joined together through the process of melting the joints.

  1. Can you solder with oxyacetylene?

No, the process of soldering with oxyacetylene is difficult. The reason being that in soldering alloys the melt is all below 427°C but while using oxyacetylene flame the flame might be so hot wherein the overheating of metal cannot be avoided.

  1. Is oxyacetylene welding still used?

In recent years, there is a decrease in the use of oxyacetylene in industrial applications but as far as shops or fieldwork, these torches come into play. It can be extensively seen in repair shops, automotive repair shops, fabrication, and plumbing applications. It finds a place in artisan welding as well. The purpose of cutting metal sheets of joining stele pipes are done by oxyacetylene welding.

  1. Can you braze with just acetylene?

Yes, brazing can be done with just acetylene as braze welding require to smore heat than brazing for which acetylene gas is commonly used. Here there is no use of capillary action.

The process of brazing involves the drawing of filler metal into the joint through capillary action instead of depositing of the joint like fusion welding. This process is involved in the fabrication and installation of copper tube piping systems which use the oxyacetylene torch.

  1. Is acetylene bad to breathe?

Yes, inhalation in large amounts can cause severe lung damages. Inhalation of acetylene causes dizziness, headache, fatigue, vomiting, nausea, tachycardia. If a person is exposed in large amounts, it can cause loss of consciousness and also death.

  1. Can you smell acetylene?

Yes, it has an unpleasant garlic-like odor as it contains traces of phosphine that causes unpleasant garlic-like odor. It is a colorless gas and has marked odor due to the presence of impurities.

  1. Why is acetylene dangerous?

Yes, acetylene when decomposes breaks down to carbon and hydrogen with the release of heat that can cause it to ignite even in absence of air or oxygen. The flashback or exposure to intense heat can trigger this decomposition. Direct impingement of flames on the cylinder can cause it to decompose and cause to explode. Hence, all cylinders are provided with honeycomb material called monolithic mass. There is acetone also inside absorbed by honeycomb structures that dissolves the acetylene holding it and making it stable.

  1. Can acetylene tanks explode?

No, there are various safety means to input into tanks or else there are chances for exploding in the absence of those factors. There is a porous honeycomb structure that has acetone and the acetylene dissolves in the acetone. This honeycomb structure absorbs acetone containing acetylene and keeping them in a stable condition. This honeycomb structure is distributed throughout the cylinder preventing the presence of large voids which reduces the chances of decomposition.

  1. Why is my acetylene torch popping?

The popping of torch is due to leaking or loose fittings. The sound of pop is due to gas igniting. There are certain factors when torch pops;

  • Due to backfiring: The flame enters the nozzle with a loud popping sound and the flame does not go entirely. As the flame is not traveling too far back in line, it will display this sound. This may be not a big issue related to safety.
  • Sustained backfires due to presence of flame inside the torch for too long
  • Flashback: There is not going inside the torch and gas is running back the line and supply line. This can be disastrous and to avoid this installing flashback arrestor would help.
  • Backflow: Here the high-pressure oxygen is pushing back the low-pressure acetylene and mixing in the hose which can be avoided using arrestors.
  • Nozzle is dirty: It happens when dirt blocks the tip of nozzle that restricts flow of oxygen and acetylene
  • Setting of flow: If the flow setting are improper, there is chances of pop sound.
  1. What is the hottest torch?

The hottest torch is oxyacetylene torch from which the flame can go up to a temperature of 3480°C if the oxygen and acetylene are in pure form. It is useful to cut steel. The other torches like propane and butane give a temperature of 1995 °C while propane-butane torches go up to 1225°C.