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Good and safe work practices are important before doing any type of welding. Always check for hazards in the workplace such as oily rags or flammable or combustible material near welding sparks. Ensure your workplace is clean, well lit, well ventilated and with appropriate fire fighting equipment close at hand. Don’t perform any part of this setting up procedure near a source of ignition or while smoking!
Before starting, inspect all equipment for damage and ensure no oil or other contamination is present on fittings, hoses and blowpipe. Pay particular attention to all connections.
When using gas products always read the labels and safety data sheets before use. Ensure both cylinders are restrained securely.
Ensure that the regulators are in good condition and safe to use.
In Australia the pressure adjusting knob of regulators are colour coded to assist with fitting them to the correct gas cylinder: Black — Oxygen, Red — Acetylene, Orange — LPG.
Fit the correct BOC flashback arrestor to both regulators — blue for oxygen and red for acetylene.
For side entry cylinders always make sure that the acetylene regulator outlet connector faces away from the oxygen cylinder.
Attach the regulators to their respective cylinders and tighten sufficiently to prevent leaks.
Attach the hoses to their corresponding regulator end flashback arrestors — blue for oxygen red for acetylene. Open the cylinder valves slowly.
Slightly screw in the adjusting knobs of both regulators to clear regulators and hoses of any dirt and dust. Back off adjusting knobs and close cylinder valves. Do not stand in front of or behind the regulator when opening the cylinder.
Attach the other ends of the hose to the correct oxygen (RH thread) and acetylene (LH thread) on the welding blowpipe.
It’s important to attach flashback arrestors to both ends — regulator end and torch end as described in the Code of Practice for Welding Processes and AS4839.
Attach the other ends of the hose to the correct oxygen and acetylene flashback arrestor on the welding blowpipe.
For brazing, select the correct welding tip for the job and screw into mixer. Unscrew the sleeve on the mixer to rotate the welding tip to the required position, retighten sleeve.
For this demonstration we are brazing a 25mm diameter copper pipe and using Prosilver 15 filler material.
The most common type of joint used for brazing is the lap joint or the sleeve joint in the case of tubular components.
For a good, strong lap joint it’s important to consider the joint gap and the degree of overlap. The general rule for tubular joints is that the overlap should be one pipe diameter for sizes up to 25mm diameter tube.
When heating a joint for brazing it is essential that it is slowly and evenly heated to the brazing temperature. The type and size of the flame will depend on the parent material and the mass of the components.
Once the area is hot enough use the pipe expander to widen the pipe. This will create a sleeve for the copper tube to fit into.
Apply slow, even heat to the joint ready for brazing. As a temperature guide, either the colour of the metals or the condition of the flux may be used eg the flux on a joint that has reached the correct temperature for brazing should be clear, fluid and flow over the joint area like water.
When the brazing temperature is reached the filler metal is applied by touching the joint gap with the rod and applying some indirect or splash heat from the torch to the parent material. The molten filler metal will follow the heat from the flame as it is directed along the joint. The brazing alloy should be applied according to its flow characteristics; an alloy with free-flowing characteristics such as ProSilver 56T should be touched at one point on the joint, from where it will flow into and around the joint by capillary action.
A less-free flowing alloy, such as ProSilver 39T, should be applied along or around the entire joint, building up a fillet of alloy. If phosphorus bearing filler rods are used, such as ProSilver 5, the colour of the metal should be a dull cherry red before the rod is applied to the joint gap.
Once brazing has been completed the heating should be discontinued, as excess heating may cause metallurgical problems with the parent materials and porosity in the filler materials.
When the alloy has solidified, the joint can be quenched in water to help remove flux residues. Quenching should only be carried out when it will not damage the properties of the parent metals, or cause cracking because of stresses caused by the thermal shock.
Working with gas is as easy as BOC. Check us out instore or online at www.boc.com.au
Post time: Jun-13-2017