to light or not to light

[chromalloymachi112]

Is there any danger igniting acetylene in preheat mode on metco 6c with flows at air 12 oxy 37 and acy 55? Engineer swears that this is the correct method but wont these flows cause backfires and flamebacks? I am pretty sure that its supposed to be in idle. On one ocassion the flame arrestors were triggered and the whole guntip siphon plug orings melted and disintegrated. How dangerous is it for an operator to utilize igniting the gun on full flows?

[Stephen Booth]

According to the Manual on the 6P (is that the same as the 6C) the trigger has 3 positions:

3. Running position to open fuel gas and oxygen
2. Lighting position has reduced gas flow for an easier ignition of the fuel gas and oxygen mixture
1. Closed position to close fuel gas and oxygen

4.3.3 Lighting
For proper lighting, the nozzle and siphon plug jets must be clean and
undamaged.
1. Make sure the oxygen and fuel gas pressures are set to the values
shown in the Spraying Tables.
2. Make sure the nitrogen carrier gas is flowing.
3. Open the gas valve until you feel it click into the lighting position
(about half way to full open).
4. Spark the lighter in front of the nozzle to ignite the gases.
5. Open the gas valve all the way.
After lighting, adjust the needle valves on the Type 3GF Gas Flowme-
ter until the flow readings correspond to the values in the Spray Table.

[chromalloymachi112]

According to the Manual on the 6P (is that the same as the 6C) the trigger has 3 positions:

3. Running position to open fuel gas and oxygen
2. Lighting position has reduced gas flow for an easier ignition of the fuel gas and oxygen mixture
1. Closed position to close fuel gas and oxygen

4.3.3 Lighting
For proper lighting, the nozzle and siphon plug jets must be clean and
undamaged.
1. Make sure the oxygen and fuel gas pressures are set to the values
shown in the Spraying Tables.
2. Make sure the nitrogen carrier gas is flowing.
3. Open the gas valve until you feel it click into the lighting position
(about half way to full open).
4. Spark the lighter in front of the nozzle to ignite the gases.
5. Open the gas valve all the way.
After lighting, adjust the needle valves on the Type 3GF Gas Flowme-
ter until the flow readings correspond to the values in the Spray Table.

thank you!