Working Copper tubing, bending, flaring, expanding etc. can be difficult if the copper is hard and brittle. It can lead to fracturing of the copper. By annealing the copper you can soften it to make it more workable and easier to bend. The process involves heating the copper to change its structure and allowing it to cool quickly.
- Set up your oxyacetylene and Nitrogen . Although you are annealing the copper, not brazing, there will still be oxidization formed on the copper which can be stripped by the system refrigerant and deposited in the system. By purging with Nitrogen during the heating process you can stop the formation of carbon inside the copper
- Set up the nitrogen and start purging the copper pipe before applying any heat. Light the oxyacetylene and apply the flame to the area you wish to anneal. Move the flame over the whole are and avoid leaving it in one place which may lead to melting the copper. Continue until the whole area starts to become cherry red.
- Turn off the oxyacetylene but leave the nitrogen running until the copper has cooled down. As you are working with a refrigeration system do not be tempted to quench the copper with water.
- Once cool the copper can now be worked as the copper will be softer, this process can be repeated if it becomes hard again after working.
A good resource can be found on the Institute of Refrigeration UK at www.ior.org.uk