Course 12: Welding and Brazing February 10th and 12th, 2015 1 Objectives 1. Describe and demonstrate the safe process of brazing copper tubing. 2. Describe and demonstrate the use of the PPE, tools, and materials needed to braze copper tubing. 3. Describe and demonstrate the preparaon required. 4. Describe and demonstrate the brazing process. 5. Describe and demonstrate the process of brazing copper tubing to dissimilar metals. 2 Brazing Applications • Low-pressure steam lines • Refrigerant lines • Medical gas lines • Compressed air lines • Vacuum lines • Fuel lines • Other chemical lines that need extra corrosion resistance in the piping joints 3 Brazing Safety • Wear clothing made of non-flammable fabric • Wear a long-sleeved shirt and pants with no cuffs • Wear flame-resistant gloves and high-top work boots • Turn off the gas cylinder securely when not in use • Keep a fire exEnguisher handy • Always solder in a well-venElated area • Wear respiratory equipment in areas with poor venElaon 4 Fuel Gas Safety • Store acetylene cylinders in upright posion. • Secure cylinders to a cart or structure. • Safety caps must be installed on boZles when not in use. It is illegal in some states to transport a cylinder with a regulator aached. 5 Fuel Gas Safety (cont.) • Oxygen and fuel gas cylinders must be stored at least 20' (6.096m) apart or separated by a wall at least 5' high with a 30-minute minimum fire rang. • Never handle oxygen cylinders with oily hands or gloves. Keep grease away from the cylinders and do not use oil or grease on cylinder aachments or valves. • Acetylene becomes unstable and volale above 15 psig. An acetylene cylinder that has been laid down should be placed in the upright posiEon for at least 20 minutes before using. • Do not allow anyone to stand in front of the oxygen cylinder valve when opening. • Acetylene cylinder valves should only be opened ½ to 1 turn, and the wrench should never be removed from the valve during use. 6 Oxyacetylene Brazing Setup ACETYLENE OXYGEN REGULATOR CYLINDER VALVE CONNECTION OXYGEN CYLINDER ACETYLENE VALVE REGULATOR CONNECTION OXYGEN REGULATOR ACETYLENE HOSE CONNECTIONS REGULATOR AT TORCH TORCH OXYGEN AND ACETYLENE VALVES TIP FLASHBACK ARRESTERS FLASHBACK RED HOSE ARRESTERS GREEN HOSE 03104-13_F15.EPS 7 Gas Regulators Oxygen hoses have a right-handed thread, while fuel gas hoses use a lee-handed thread. The female fings with lee-handed threads have a groove cut into the nut for further visual idenEficaon. 8 Brazing Torch Handles Medium- and light-duty handles are generally preferred by HVAC technicians due to their compact size and ease of handling. Note the difference in where the control valves are, in relaon to the hand. 9 Brazing Tips Brazing Eps must be selected to fit the handle in use! Only proper torch Ep cleaners and files should be used to clean brazing Eps. 10 Tip Sizes for Common Tubing Larger numbers indicate larger openings. Tips are available in other sizes, both smaller and larger, but they are rarely used in HVAC/R work. 11 Brazing Filler Metals WARNING! BAg-1 and BAg-2 contain cadmium. Heang when brazing can produce highly toxic fumes. Use adequate venElaon and avoid breathing the fumes. 12 Brazing Flux Brazing flux is more corrosive than soldering flux. For this and other reasons, the two should never be mixed. 13 Brazing Prep BEFORE the Torch Comes Out… • Measure • Calculate final length • Cut the tubing to length • Ream • Clean • Apply flux • Assemble • Wipe off excess flux • Check alignment 14 Brazing Equipment Prep WARNING! • Do not handle acetylene and oxygen cylinders with oily hands or gloves. • Keep grease away from the cylinders and do not use oil or grease on cylinder aachments or valves. The mixture of oil and oxygen could cause an explosion. • Make sure that the protecEve caps are in place on the cylinders before transporEng or storing the cylinders. 15 Brazing Tip Operational Data Operaonal data for a series of Eps from one manufacturer. Always ensure that the proper informaon for the Ep(s) in use is consulted. 16 The Oxyacetylene Flame 17 Lighting the Torch Step 1 Set up the torch. Step 2 Adjust the torch oxygen flow. NOTE: Always fine-tune the pressure seng with the torch valve open. When it is closed, the pressure may register slightly higher. Regulators are incapable of making pressure adjustments without flow. Step 3 Adjust the torch acetylene flow. CAUTION: Be sure to leave the valve wrench on the acetylene cylinder valve while the cylinder is in use so that the valve can be closed quickly in case of an emergency. 18 Lighting the Torch (cont.) Step 4 Light the torch WARNING: When lighEng the torch, be sure to wear flame-resistant gloves and goggles; use an appropriate device, such as a cup-type striker, to light the torch; and point the torch away from you. Always light the fuel gas first, and then open the oxygen valve on the torch handle. NOTE: It is not unusual for visible soot to form in strings and float away from the acetylene-only flame. However, they can fall on an otherwise clean surface and be somewhat messy. Take the surroundings into account as you light the torch and be aware that soot is likely to form from the iniEal flame. 19 Lighting the Torch (cont.) Step 5 Shut off the torch when finished brazing. Step 6 Properly stow the hoses while any final preparaons to braze are made. 20 Air/Acetylene Tips Remember that a larger Ep does not increase the flame temperature, only the volume of heat being applied. 21 Nitrogen Purging Setup WARNING! Never use oxygen to purge tubing. An explosion could result when oil and oxygen are mixed. 22 Brazing Procedures Step 1 Prepare the work area and place a fire exEnguisher within easy reach. Step 2 Set up the nitrogen gas to purge the tubing. Step 3 Put on welding goggles. Step 4 Set up and light the oxyacetylene brazing equipment as described previously. Step 5 Apply the heat to the tubing first, in the area adjacent to the fing. Watch the flux (if used). 23 Brazing Procedures (cont.) Step 6 ConEnue to move the heat back and forth over the tubing and the 1 fing. For 1 ⁄4" and larger tubing, a small rosebud may be more producEve. Step 7 Touch the filler metal rod to the joint. Step 8 Hold the filler metal rod to the joint, and allow the filler metal to enter into the joint while holding the torch slightly ahead of the filler metal and direcEng most of the heat to the shoulder of the fing. 24 Brazing Procedures (cont.) Step 9 For larger joints, small secEons of the joint can be heated and brazed. Step 10 Aeer the filler metal has hardened and while it is sEll hot, wash the joint with a wet rag. Step 11 Allow the joints to finish cooling naturally. Maintain the nitrogen flow. 25 Silver Brazing Allow A BAg-5 filler metal such as this is a beZer choice for dissimilar metals. 26 Wrap Up Prepare for welding and brazing lab next week. 27 Questions 28 .