a) (i) Name the two gases most commonly used when gas welding - Leaving Cert Engineering - Question 4 - 2007

One of the flames produced during gas welding is the Neutral Flame. This flame consists of equal amounts of Oxygen and Acetylene, typically appearing as a clear, blue inner cone and a larger outer envelope.

The Neutral Flame is commonly used because it does not alter the chemical properties of the metal being welded. It provides a balanced combustion which is ideal for joining metals.

1. Oxides: When metals are exposed to oxygen during the welding process, oxides may form on their surfaces. These oxides act as a barrier that interferes with the thermal joining process and must be eliminated, usually through fluxes or by ensuring adequate shielding from oxygen.

2. Flashback Arrestor: This device is designed to prevent the reverse flow of gases into the regulator or gas cylinder. It stops any flame from moving back through the hose, thus protecting both the equipment and the operator from potential hazards.

3. Pressure Gauge: A pressure gauge indicates the pressure of gas contained within the welding equipment’s cylinders. It provides essential information to the welder to monitor the gas supply and make adjustments as necessary.

1. Heavy gauge mild steel plate: The suitable method for making a permanent joint is Arc welding. This process uses electrical arcs to generate heat that melts the metals to be joined.

2. Acrylic sheet: The best method to create a permanent joint is through the use of Adhesives specifically formulated for acrylic bonding.

3. Light gauge copper sheet: A suitable method for this material would be Soldering, which involves melting solder to join the pieces together.

1. Never inhale fumes produced by soldering flux. It is essential to work in a well-ventilated area or use a fume extractor to avoid health risks.

2. Always replace a hot soldering iron back into its stand when not in use, to prevent accidental burns or fires.