Arkansas HVACR NewsMagazine May 2022

HVACR NewsMagazine May 2022

Tech News

a proper striker when lighting your torch; cigarette lighters, matches, and butane grill lighters are potentially more dangerous.

Flame type and appearance

You should have a neutral or slightly carburizing flame. That means that the oxygen and acetylene content should be pretty balanced. A neutral flame will have a white cone in the middle of the blue flame, and there may be a VERY SLIGHT cyan secondary feather. A carburizing flame has a large cyan secondary feather around the white cone.

Before we flow nitrogen, we will first want to purge the lines to chase everything out of them. You can use a flow regulator to purge the lines, usually at a rate of 20-100 standard cubic feet per hour (SCFH). Flowing requires us to move a lot less nitrogen, as your typical flow rate will be 2- 5 SCFH or just a whisper of nitrogen. Although brazing rods and fluxes are critical, the success of a braze job depends on how well we heat the base metal. If we don’t heat the base metal properly, we may fail to draw the alloy into the joint and create a proper seal. To heat the base metal properly, we need to make sure our torch rigs, flames, and brazing practices are sufficient. First of all, we have to pay attention to our torch rigs. Many of us will be using an oxyacetylene torch (though some people may use air-acetylene). In the case of the oxyacetylene torch, you must have just the right mix of oxygen and acetylene, typically five and five or ten and ten. In many cases, you can light the acetylene first and then bring on the oxygen after you have a flame. Only use Proper torch use Preparing the torch rig

In any case, you will want to avoid an oxidizing flame, which has a very short white cone in the center and no secondary feather. These flames are oxygen-heavy, meaning that they could react with the copper and cause a black scale to form. That black scale is called cupric oxide, which can lead to restrictions if it’s inside the copper. You can help prevent the buildup of cupric oxide by flowing nitrogen while brazing.

Heating the joint properly