Mapp gas works fine on small lines like 3/8 ” and as long as you’re not in a spot where heating for an extended period of time will cause a problem it works O.K. on bigger lines like 5/8″ and 3/4″. When I didn’t have access to an acetylene or oxy/acet torch, I sweated in a lot of condenser units with Mapp gas. I still have extra Mapp gas on hand in case I run out of acetylene or oxygen during a job, especially on a weekend. I wouldn’t try to do an RV with Mapp gas, but you can get away with it for most household tasks.
Is it possible to braze using MAPP gas?
It is determined by the size of the weldment as well as the torch. For little jobs like brazing on a nut or a tab, it should be fine. Some of the newest “turbo” or “swirl” torches are far hotter than older models.
What type of gas is used in the HVAC brazing process?
Today, we’ll talk about the best brazing alloys and procedures for refrigeration components. The following are our key topics:
Keep in mind that brazing in the HVAC/R sector is not the same as brazing in the plumbing industry. Due to the ubiquity of low-pressure water or fluid lines, solder alloy is suitable for plumbing components. Refrigeration cycles and air conditioning systems, on the other hand, are high-pressure, high-temperature systems that require stronger true braze alloys than solder alloys.
- Copper-to-copper is the most prevalent type of connection. The Lucas-Milhaupt Sil-Fos alloy, which has a chemical makeup of 5-15 percent silver, is recommended. Sil-Fos alloys have a fluxing agent, therefore you don’t require paste flux with them. Its phosphorus presence functions as a reducing agent, allowing the oxides generated during brazing to be removed. The sole application that does not require a paste flux or the use of a flux-cored or -coated braze alloy is copper-to-copper brazing with a Sil-Fos alloy.
- Copper-to-brass – Copper-to-brass couplings are another popular HVAC/R use. Lucas-Sil-Fos Milhaupt’s 15, Silvaloy 450, or Silvaloy 560 alloys are recommended. Copper-to-brass brazing, unlike copper-to-copper brazing using a Sil-Fos alloy, requires the use of a paste flux or a flux-cored or flux-coated brazing rod. When utilizing solid wire Silvaloy 450 or 560 filler metals, paste flux is necessary.
- Copper-to-steel conversion – Copper-to-steel couplings are the next HVAC/R application. Silvaloy 450 or Silvaloy 560 alloys, either flux-cored or flux-coated, are recommended. Solid wire can also be used, however it must be brazed with a paste flux like Lucas-Milhaupt Handy Flux or Ultra Flux.
- Aluminum-to-aluminum and copper-to-aluminum – Copper-to-aluminum and aluminum-to-aluminum connections are two additional prevalent joint uses in the air conditioning industry. Handy One AL 802 and Handy One AL 822 are the alloys we propose for these joint applications. Because of its greater melting range, Handy One AL 822 is suitable for aluminum repair.
Stainless steel valves or tubing may need to be joined to different base materials in some refrigeration couplings. Silvaloy 505 with Handy Type B-1 flux or Ultra Black Paste Flux is recommended for brazing any stainless steel components.
The next step is to choose the right gas and torch type for your application after you’ve decided which alloy to employ. In the HVAC/R business, there are four major gases used for brazing:
- Propane gas has a flame temperature of around 1800 degrees Fahrenheit (982 degrees Celsius). Because it has the lowest flame temperature, it’s best for aluminum-to-aluminum and aluminum-to-copper joints.
- MAP Pro gas is a propylene-propane gas mixture with a flame temperature of approximately 2200 degrees Fahrenheit (1204 degrees Celsius). It’s suitable for aluminum-to-aluminum and aluminum-to-copper connections.
- The flame temperature of air-acetylene is roughly 2700F (1482C). This type of brazing necessitates the use of an acetylene gas cylinder with atmospheric air to create the torch flame. Copper-to-copper, copper-to-brass, and copper-to-steel joints are the most common applications for air-acetylene. The flame temperature is substantially higher than propane or MAPP gas, and it can melt the aluminum base metals, so it is not advised for aluminum joints.
- The flame temperature of oxy-acetylene is around 4700F (2593C). To make the oxy-acetylene mixture, a cylinder of acetylene gas and a cylinder of oxygen are combined. Copper-to-copper, copper-to-brass, and copper-to-steel joints can all be brazed using it.
Before you start brazing, make sure you have the right gas and the right torch tip. Based on the size of the tubes to be brazed, each torch body manufacturer gives a list of recommended torch tips. For suitable sizes, contact the manufacturer of your torch body.
It’s time to braze when you’ve chosen the right gas and torch. To make a leak-proof, high-quality joint, keep these things in mind:
- Make sure the joints are well-fitting and that the clearance is 0.002-0.005 in (0.05-0.13 mm).
- Clean metals – Surfaces must be free of impurities and clean. Before installing new components or correcting leaks in existing systems, clean refrigeration oils and dirt or soot from parts. Make sure to cut and ream tubes correctly to eliminate any burs.
- Use the appropriate flux for each application of base metals. Flux is available in three forms for this industry: paste, flux cored, and flux coated. Use paste flux with any Silvaloy solid wire product. You don’t need any additional flux when brazing with aluminum because the flux is already present in the wire.
- Fixturing Parts – Check that all tubes are seated against the bottoms of valves and fittings.
- Proper heating – To make leak-proof joints while brazing in HVAC/R, employ the proper heating procedure. When heating the joints, move the torch back and forth over the junction to impart homogeneous heat to both the fitting and the tube.
- To prevent corrosion, the flux residue must be wiped off the pieces after brazing with paste flux or flux-cored or -coated alloy. Remove the residue by rinsing the joints with hot water and physically scrubbing the flux away. Flux-cored aluminum goods do not need to be cleaned.
Purge the system with nitrogen before brazing in HVAC/R to maintain the inside of the tube free of oxidation. Nitrogen functions as a cover gas inside the tubes, preventing surface oxidation. It’s worth noting that the industry’s shift to polyolester oil (or POE oil) necessitates nitrogen purging during brazing. If not purged with nitrogen, POE oil is particularly hygroscopic (loves water) and reacts with remaining moisture in the system.
Following the completion of brazing and the removal of flux residue from parts, the next step is to inspect the system for leaks. The lines must be able to evacuate moisture to a depth of 500 microns, as determined by a micron gauge. If you can’t get the system down to 500 microns, you might have a leak. Finally, according to the customer’s or industry’s specifications, charge the system with the needed refrigerant.
To summarize, using the suitable brazing alloy and flux, as well as the proper torch and gas, and then following the proper brazing processes, you may create leak-proof, high-quality HVAC/R joints. Contamination and joint failure are avoided by following industry-specific techniques of purging and then charging the system to the proper pressure.
This is the second part of a two-part series on refrigeration brazing. The main procedures within a refrigeration system are covered in Part 1: Brazing for the Refrigeration Cycle. Our video on Brazing Copper to Copper is an excellent resource that will lead you through the brazing procedure. Please view our video on Aluminum HVAC/R Repair for more information on repairing aluminum joints.
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Is it possible to braze using MAPP gas and oxygen?
Also, compared to a smaller, hotter flame, it produces more copper-oxide corrosion. As a result, Mapp gas-air brazing of heat-pump reversing valves, filter-driers, and compressors is not recommended.
Is it possible to braze with a Bernzomatic torch?
Use the appropriate brazing rod material for the metal you’re working with. The brazing rod should be melted by the heat of the metals being connected, rather than by coming into direct contact with the torch flame. Make use of a torch with a high-intensity flame.
What sort of brazing torch is used?
The fuel gas (acetylene, propane, or natural gas) can be burned with air, compressed air, or oxygen, depending on the temperature required for your assembly. Torches with several points or flames can be employed by shifting the flame constantly to diffuse the heat uniformly throughout the assembly and avoid localized overheating, which can damage the joint’s strength. Depending on the assembly that needs to be welded, these are the various equipment procedures.
- You’ll want to utilize torches with the lowest heat and flame temperature for brazing small components and thin sections. The air-natural gas and air-acetylene torches are employed for these applications.
- Oxygen with natural gas, or other gases such as propane or butane, produce good results in many brazing applications. Although these provide a greater flame temperature, for best results, brazing should be done with a slightly decreased or neutral flame.
- Because it operates at a lower temperature, the oxyhydrogen torch should be used to braze aluminum and nonferrous alloys (metals that do not contain significant amounts of iron).
- Flux-covered or cored filler metal rods are required for torch heating to fill in joints of your assembly. The moderate flame temperature of natural gas is ideal for this approach because it decreases the risk of scorching the joint and metal filler. Only copper-phosphorus fillers, which are employed in brazing in the absence of flux, are self-fluxing. Fluxes, on the other hand, are required for all other filler metals. As the joint is prepared for brazing, the filler metal can be preplaced or face-fed into the joint. Remember that torch brazing procedures for oxyfuel gas welding differ from those for oxyfuel gas welding.
- Without automation, manual torch brazing is a basic method. This method is generally used for assemblies with sections that are not all the same size. Only the braze joint is visible, because it is the only part of the body that receives direct heat. The torch in question features a single tip, which is commonly used to control single or multiple flames. If you need to make a large number of assemblies, a mechanical option can be set up to move the assembly components, the torches, or both during the brazing process.
Is it possible to braze copper with a propane torch?
Most metals can be brazed together using a propane torch. Propane torches are frequently accessible at local hardware stores, plumbing supply stores, and metalsmith and jewelry supply stores.
Can MAPP gas be used to braze copper pipe?
We utilize MAPP gas with a shield, which works well up to 7/8 copper tube only, and the braze joint must be kept away from any huge bulk of metal because heat can be pulled away almost as quickly as it is applied.