Observation

Candidates had no difficulty responding correctly to these questions. The required responses are given below.
                                    (a)        Differences between gas and arc welding     

• In gas welding, gas is used while in arc welding, electricity is used to generate heat.
• In gas welding, filler rod is used while in arc welding, electrode is used as filler material.
• In arc welding, higher temperature is obtained than in gas welding.
• In arc welding, stronger joints are achieved than in gas welding.
• In arc welding, heat affected zone is limited than in gas welding.
• Electric shock is possible in arc welding but not possible in gas welding.
• The risk of explosion is higher in gas welding than in arc welding.

• Arc welding equipment

• Electrode holder
• AC or DC machine
• Welding cable
• Welding shield
• Earth clamp
• Welding return cable
• Chipping hammer                  

                                    (c)        Safety precautions in gas welding

• Test for gas leakage with soapy water only.
• Do not transfer gas from one cylinder to another.
• Do not use compressed oxygen for ventilation.
• Do not drop cylinder from a height.
• Do not leave lighted torch unattended to.
• Wear safety goggles while welding.  
• Cylinders must not be used for transportation in form of rollers.
• Cylinders must be used in a well-ventilated area
• Do not allow cylinders to have contact with grease or oil
• Do not allow hot sparks or metal to have contact with hoses or connections
• Acetylene cylinders must be kept upright always.
• Always close cylinder valves after welding