Starting an Oxyacetylene Torch

Both starting and stopping an oxyacetylene torch is a procedure which requires care, attention to detail, and a correct sequence of actions to be carried out successfully and safely. Not all welders agree on the proper sequence in which certain of these actions should be performed, however, so there is some latitude for personal experimentation and opinion. Indeed, in the case of bleeding gases out of the hoses at the end of an oxyacetylene session, there is fundamental disagreement among welders on whether this should be done at all.

The first step in starting the flame of your oxyacetylene torch is to pressurize the welding torch and the hoses leading to it. Even here, however, there is disagreement on which gas should be used to pressurize the system first, with some advocating that oxygen should be opened first, and others favoring acetylene. In order for pressurization to occur, the valves on the torch itself must be closed firmly so that the gas will not simply escape when you open the regulators.

In the first method, the fuel gas (usually acetylene) regulator is opened ¾ of a turn. All methods recommend opening the acetylene regulator only ¾ turn because in this position, because less pressure is needed from this tank and also so that it can be shut off quickly if a fire should ever start. You should then open the fuel gas valve on the welding torch and set the regulator screw to the torch tip’s working pressure. Closing the torch’s fuel gas valve, you then open the oxygen regulator fully, and set the pressure regulating screw on the torch to the appropriate PSI for the torch tip. You then close the torch’s oxygen valve as well, and the torch is ready to use.

In the second method -- which is a much more direct, and perhaps casual, technique of preparing your oxyacetylene torch for use – the oxygen regulator is fully opened first. Note that the oxygen valve is always opened completely – it should either be fully open or fully closed, never partially open, as this is an invitation to leaks that could cause an oxygen-enriched, fire-prone environment in your work area. The acetylene regulator is then opened the typical ¾ turn. This is all there is to the second method – the torch is considered to be ready for striking.

Striking the torch is the process of lighting the flame, and here, at least, there is agreement on all welders on the correct procedure to follow. A purpose-made spark striker should be used to light the torch flame – trying to use a match, another welding torch, or a piece of hot metal to light the gases is an invitation to disaster.
Open the acetylene valve on the torch body and immediately use the spark striker to light the flame. This will initially be crimson, and if it is elongated, adjust the acetylene flow down until it is only a short blaze close to the torch tip. While sparking, the striker should be beside the tip and at right angles, rather than straight-on to the end. Once the red acetylene flame is present, open the oxygen valve, and feather it until the flame is blue-white and “neutral,” around 6,000˚ Fahrenheit.