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Brazing Components for Refrigeration

Posted by Lucas-Milhaupt Brazing Experts on Sep 24, 2015

Brazing Components for Refrigeration
Today, nosotros address correct brazing alloys as well every bit proper brazing methods for refrigeration components. Our main topics are:

• Alloy selection
• Gas and torch selection
• Brazing method
• Nitrogen purge
• Organisation evacuation and charge

Remember, brazing in the HVAC/R manufacture is much unlike from brazing in the plumbing manufacture. Solder alloy is adequate for plumbing components due to the prevalence of low-pressure h2o or fluid lines. Withal, refrigeration cycles and air conditioning systems are high-pressure, high-temperature systems requiring truthful braze alloys that are stronger than solder alloys.

Alloy Selection
The HVAC/R industry uses these four common base materials:

• Copper
• Brass
• Steel
• Aluminum

From these four base metals, there are 5 different affix alloys:

• Copper-to-copper - This is the most common joint application. The recommended product is Lucas-Milhaupt's Sil-Fos® alloy, containing a chemical composition range of 5-15% silver. With Sil-Fos, you lot do non need paste flux, because Sil-Fos alloys comprise a fluxing amanuensis. Its phosphorus content acts equally a reducing amanuensis to remove the oxides formed during brazing. Copper-to-copper brazing with a Sil-Fos alloy is the just application that does not require a paste flux or using a flux-cored or -coated braze blend.
• Copper-to-brass - Another common HVAC/R application is copper-to-contumely joints. Nosotros recommend Lucas-Milhaupt'south Sil-Fos 15, Silvaloy® 450, or Silvaloy 560 alloy. Unlike copper-to-copper brazing with a Sil-Fos alloy, copper-to-contumely applications practise require the addition of a paste flux or the utilize of a flux-cored or flux-coated brazing rod. Paste flux is required when using solid wire Silvaloy 450 or 560 filler metals.
• Copper-to-steel - The side by side HVAC/R awarding is copper-to-steel joints. We recommend either flux-cored or flux-coated Silvaloy 450 or Silvaloy 560 blend. You can also use solid wire, but you must braze this with a paste flux such as Lucas-Milhaupt Handy® Flux or Ultra Flux®.
• Copper-to-aluminum and aluminum-to-aluminum - In the ac industry, there are ii more mutual joint applications: copper-to-aluminum and aluminum-to-aluminum joints. The alloys we recommend for these joint applications are Handy 1 AL 802 and Handy One AL 822. Handy One AL 822 is recommended for aluminum repair due to its wider melting range.

Some refrigeration joints may require joining stainless steel valves or tubing to other base of operations materials. When brazing any stainless steel components, the use of Silvaloy 505 with Handy Type B-1 flux or Ultra Black Paste Flux is recommended.

Alternative filler metals are available for brazing in this manufacture, Delight contact your Technical Services representative for more data.

Gas and Torch Selection
Subsequently determining which alloy to use for your application, the next step is selecting the correct gas and torch type. At that place are 4 main gasses used in the HVAC/R industry for brazing:

• Propane gas - This gas has a flame temperature of roughly 1800°F (982°C). Use this gas primarily for aluminum-to-aluminum joints and aluminum-to-copper joints, as it has the lowest flame temperature.
• MAP Pro gas - MAP Pro gas is a propylene-propane gas mixture with a flame temperature of roughly 2200°F (1204°C). It can be used for aluminum-to-aluminum joints and aluminum-to-copper joints.
• Air-acetylene - This gas has a flame temperature of around 2700°F (1482°C). This blazon of brazing requires a cylinder of acetylene gas and incorporates atmosphere air to produce the torch flame. Air-acetylene is primarily used for copper-to-copper, copper-to-brass and copper-to-steel joints. It is not recommended for aluminum joints, every bit the flame temperature is significantly college than propane or MAPP gas and can melt the aluminum base metals.
• Oxy-acetylene - This gas has a flame temperature of roughly 4700°F (2593°C). Oxy-acetylene brazing uses a cylinder of acetylene gas and a cylinder of oxygen to create the oxy-acetylene mixture. Yous tin can use information technology for brazing copper-to-copper, copper-to-brass and copper-to-steel joints.

Once you have selected the proper gas, choose the right torch tip before starting to affix. Each torch trunk manufacturer has a listing of recommended torch tips, based on the size of the tubes being brazed. Contact your torch body manufacturer for proper sizes.

Brazing Method
After selecting the right gas and torch blazon, information technology is fourth dimension to braze. Recall these central steps to producing a leak-proof, quality joint:

• Good fit - Make sure the joints fit together well, and the clearance is 0.002-0.005 in. (0.05-0.13 mm).
• Clean metals - Surfaces must be clean and gratis of contaminants. Make clean refrigeration oils and dirt or soot off parts before installing new components or when repairing leaks in installed systems. Besides be sure to properly cut and ream tubes to remove whatever burs.
• Proper flux - Utilize the correct flux for each application of base of operations metals. Flux for this industry comes in three forms: paste, flux cored and flux coated. Use paste flux with whatsoever solid wire Silvaloy production. When brazing with aluminum, you exercise not need additional flux, as the flux is inside the wire of the alloy.
• Fixturing of Parts - Make sure that all tubes seat confronting the bottom of valves and fittings.
• Proper heating - When brazing in HVAC/R, use the correct heating method to course leak-proof joints. When heating the joints, apply compatible heat over both the plumbing fixtures and the tube by constantly moving the torch back and forth over the joint.
• Final cleaning - After brazing with either paste flux or with flux-cored or -coated alloy, the flux residuum must be cleaned off the parts to preclude corrosion. Remove residue using hot water and mechanically cleaning the flux off the joints. Yous do not need to clean flux from flux-cored aluminum products.

Nitrogen Purge
When brazing in HVAC/R, continue the inside of the tube complimentary of oxidation by purging the system with nitrogen. Nitrogen acts every bit a cover gas to prevent surface oxidation inside of the tubes. Note that the industry's move toward polyolester oil (or POE oil), requires purging with nitrogen during brazing. POE oil is very hygroscopic (h2o loving) and reacts with residual moisture in the system if not purged with nitrogen.

Arrangement Evacuation and Charge
In one case brazing is complete, and you have removed flux residue from parts, the adjacent step is checking for leaks in the organization. To ensure that moisture is vacated, the lines must have an evacuation to 500 microns, measured with a micron gauge. If you cannot evacuate the system to 500 microns, this may point a leak. Finally, charge the system with the required refrigerant per customer or manufacture specification.

Conclusion:
In summary, choosing the correct brazing alloy and flux, the correct torch and gas, and and then post-obit the proper brazing methods helps you produce leak-proof, quality HVAC/R joints. Following manufacture-specific practices of purging, then charging the system to the correct pressure, prevents contagion and articulation failure.

This article is Role 2 of a ii-part series on brazing for refrigeration. See Office 1: Brazing for the Refrigeration Cycle for the basic processes within a refrigeration organisation. As an additional resource, our video on Brazing Copper to Copper will walk you through the brazing process. For repairing aluminum joints, please see our video on Aluminum HVAC/R repair.

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Questions nigh brazing? Contact us for farther help. For more than information on HVAC/R brazing, encounter our blogs and website. For detailed questions regarding specific applications, please telephone call Lucas Milhaupt's Technical Department at 800.558.3856.

Topics: HVAC/R, Copper, Steel, Aluminum, Torch

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Source: https://blog.lucasmilhaupt.com/en-us/about/blog/brazing-components-refrigeration

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