The torch, like all equipment with the use of combustible and comburant gases, are subject to safety regulations (UNI 11627).
In particular, a peculiarity that takes the name of "reverse flow" or commonly called "return of flame" is emphasized.
Why does the "flame return" or "reverse flow" occurs in a torch?
The inverse flow can be verified both within the tubes and the reducers due to a pressure difference between the two gases.
If the oxygen runs out the fuel gas can enter the oxygen tube up to the pressure reducer and the cylinder, obviously if it is not intercepted by the safety valves.
These for legislation must be installed on the handle or at 1.5-2 mt from the same and at the gearbox output (we give more details about it in thisarticle on the expiry of the pipes and equipment)
It will seem trivial but, given the casisitics with which it is proposed, is advised to check first and during the work that oxygen pressure is not less than that of fuel gas.
Reverse flow due to different pressures can occur both in pipes and reducers.
It occurs when:
1. The oxygen cylinder runs out during the use and the oxygen valve on the torch is open, allowing the fuel gas to enter the tube and in the oxygen reducer.
2. Both cylinder valves are closed and with different pressures in the reducers, while the torque valves are closed. If the operator occurs both torch valves to bring out oxygen and fuel gas, the latter would spill before due to lower pressure. Oxygen could therefore flow into the tube and in the reducer for fuel gas.
3. The operator opens both of the torch valves and try to turn on both gases simultaneously. If the oxygen flow is greater than the one that can endure the tip, the system has a reflux and oxygen can flow into the tube and in the reducer for fuel gas.
If the inverse flow flows the mixture of the two gases in the tube and in the reducer for fuel gas, a dangerous explosion can occur if the fuel gas valve on the torch is open and the gases are turned on before the gas mix is completely spilled. With a small tip this can take a few seconds.