Oxygen-acetylene torch: A checklist to choose the right one
Oxygen-acetylene torch: A checklist to choose the right one
An oxygen acetylene torch is used to cut and weld steel and metals.The main advantage of using a welding torch over other tools is portability. It operates using oxygen and acetylene gas as fuel at high temperatures with the maximumbeing 6000 degree Fahrenheit.
The main components of the welding unit are the two source cylinders – one for oxygen and one for acetylene gas, two regulators and two rubber hoses – one attached to each cylinder, and a torch itself. The torch comprises of connection to the two hoses and two control valves – one each for flow of oxygen and acetylene, the torch handle where the welder can hold, two gas tubes on the other end that runs through the handle from the hoses, a mixer chamber where oxygen and acetylene are mixed, and a welding tip attached to the end of the torch through which the mixture feeds the flame.
There is another crucial component, the check valves, fitted between the regulator and hoses to prevent the feedback of oxygen and gas mixture into the hose that could cause backfiring.
In general, welding torches are rated according to the thickness of sheet to be welded. The torch that operates on sheets of thickness up to 2mm is considered light duty and that on sheets up to 25 mm thickness is regarded heavy duty. Each torch can be fitted with varying size tips or nozzles that are selected according to thickness of the workpiece.
Below is a checklist that can be used tochoose the torch appropriate for your needs:
The welding component uses two cylinders – one for compressed oxygen and one for acetylene, a combustible gas. The maximum pressure limit of the oxygen cylinder is 300 psi and that of acetylene cylinder is 15 psi. It is very important to distinguish between the two gases and use them at the right pressure to avoid any explosions.
To ensure safety, the cylinders are color-coded, with oxygen cylinder in green and the acetylene cylinder in red in the US. It is important to make sure that the cylinders are not leaky. They must always be held in upright position and the cylinder valves must be closed when not in use.
One regulator is used for each cylinder. These regulators are basically adjustable valves whose function is to lower the pressure from cylinders and maintain the required working pressure for the torcheven when the cylinder pressure dropsduring the job.
Regulators have screws or knobs that are used to adjust the flow of gas into the torch. They also consist of two separate gauges: a high pressure gauge that displays the pressure in the gas cylinder and a low pressure gauge that shows the working pressure that is fed to the torch. It is highly important to note and adjust the set pressure for each gas.The pressure of the mixture used to generate flame is usually 2 psi.Oxygen to acetylene ratio in the mixture can be varied to generate a neutral, oxidizing or a reducing flame. Welding is usually done using 1:1 ratio of oxygen and acetylene, thus generating a neutral flame.
The regulator attached to the oxygen cylinder must have a rating of at least 300 psi, the pressure in oxygen cylinder. Conventionally, the acetylene cylinder and regulator have left hand threading, and the oxygen regulator and cylinder have right hand threading.
There are two types of regulators – single stage and two stage. Two stage regulators are strong and sturdy, and are used for heavy-duty purposes. Compared to single stage, the two-stage have longer life and require less maintenance. They are better at maintaining constant pressure than the single-stage units.
Selecting the right size tips or nozzles
The welding tip is attached to the end of the torch. The mixture of oxygen and acetylene serve as feed to the flame through the tip. Tips come in a variety of shapes and sizes in order to suit various jobs.The manufacturers identify the tips with a number that signifies the size of the hole. The bigger the number, the higher the diameter and the thickness of the material that can be welded. It is very essential to usethe appropriate size tip to achieve maximum speed and performance, and lower the gas consumption. If the tip is too big, the efficiency and speed of the torch is reduced. If the tip is too small, it results in increased gas consumption.
In addition, the size of the tip determines the size of the flame, which can be adjusted accordingly using the regulator and valves. Thus, it is very important to first select the tip according to your needs, and then adjust the regulator.
In general, welding tips have one hole and cutting tips have a center hole surrounded by many smaller holes on the circumference. Oxygen is fed from center hole and the preheat flame is fed from the surrounding holes for cutting.
The two regulators are usually connected to the torchwith a double line rubber hose. They are color coded with a green oxygen line and red acetylene line in the US to enable safe operating pressure of gases. Hoses are identified with the following specifications: Light, standard or heavy duty hoses, I.D – inner diametersize in inches, and a set maximum working pressure of 200 psi. Hoses are manufactured in four different sizes (I.D inches) and different grades of hoses are used for Acetylene. They are marked Grades R & RM for acetylene only. The fittings on the hoses are clearly marked as to right and left handed threads.
Oxyacetylene torches are used for a variety of applications. They need to be carried around either within a job site or from one site to the other itself. Given its utility, it is very essential for oxy-acetylene torches to be lightweight and easy to operate. The durability and flexibility of the hoses are important factors that make the torch portable. The hoses must be long enough to reach the nook and corner of the work area. They must be flexible enough to be twisted and turned around corners, yet robust enough to withstand cracks and kinks.