What to do in case of back fire/ flash back in gas welding?


Are you associated with gas welding? Flash back/ back fire is a great hazard in welding. How to deal in emergency situation of back fire? This article provides comprehensive coverage on the subject. Read the article and get prepared to deal the emergency situation.

Introduction

The gas welding process has many hazards. Back fire/ flash back is one of the hazard associated with gas welding. Let us understand back fire. Back fire is an incident when the welding flame disappear suddenly with violent or hissing sound. Flame enters into the nozzle or torch and continue burning. Acetylene (C2H2) gas start burning across the hose and travel towards C2H2 cylinder. This incident is called back fire/ flash back.

Gas welding

Gas welding is a process of joining the similar metals with the application of heat and filling materials. Base metal is brought to melting point and the filler material is added to make the joint.

Gas welding plant

Gas welding plant has the following items/components and accessories.
  1. Oxygen cylinder
  2. Acetylene cylinder
  3. Regulators
  4. Hoses
  5. Nozzle/ cutozen
  6. Goggles
  7. Gloves


Gas welding plant

Hazards in gas welding

There are the following welding hazards in gas welding:
  1. Ultra violet and infrared rays radiation
  2. Skin burn
  3. Flash back or Back fire


Flash back or Back fire

Let me define the flash back or back fire first. Back fire is an incident when the welding flame disappear suddenly with violent or hissing sound. Flame enters into the nozzle or torch and continue burning. Acetylene (C2H2) gas start burning across the hose and travel towards acetylene (C2H2) cylinder. This incident is called back fire or flash back. If the fire reaches to acetylene cylinder, the cylinder can brust like bomb and can damage a lot.

Causes of Flash back /Back fire


Below are the of Flash back /Back fire:
  1. Low cylinder pressure
  2. Over heating of welding nozzle
  3. Inexperienced operator
  4. Blocking of nozzle
  5. Touching of nozzle with job


How to prevent back fire or flash back ?

Below are the steps to deal with the emergency situation in case of back fire:
  1. Change the cylinders if the pressure is low
  2. Place a non return valve (NRV) between Acetylene cylinder and welding/ cutting nozzle
  3. Calibrate the regulators once in a year
  4. hoses condition should be fine and should be free from cuts and Greece
  5. Nozzle/ cutozen should not be block, clean it if blocked
  6. Cool down the nozzle from time to time
  7. Keep a bucket of water for cooling the nozzle


What to do in case of back fire/ flsh back. ?

Below are the steps to deal with the emergency situation:
  1. open oxygen valve little more
  2. Close the acetylene cylinder with the help of regulator
  3. If is OK, reignite the flame
  4. If smoke is coming from the hoses cut/ remove the hoses from cylinders
  5. Take the acetylene (c2h2) cylinder out in open space
  6. Dip the cylinder into fire pond for cooling
  7. If no fire pond call fire brigade to cool down the cylinder with the help of water jet


Conclusion

Flash back or Back fire is very dangerous and may leads to heavy damage and destruction. So it is the duty of the operator and supervisor to acquaint themselves with gas welding hazards before taking up any such job. All the precautions should be observed to avoid such incident. Still it happens deal the situation as described in the article. Mock drills can be conducted to teach and trained the workers. Take care and be safe. Wish you all the best.


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