HVAC/R Tubing Flared Connections

flared connections

The most common connection used in connecting tubing to fittings is the flare connection. Flared connections are accomplished with a set of tools and lubricants, if needed. This type of connection is a compression fitting process usually done with soft steel, copper or aluminum. Flared connections are classified as a cold forging process.

The flare connection is a leak proof process that uses a flare nut to connect the flare of the tubing to the inside flare of the fitting. It is pressure resistant and last a long time. Flared connections are used when the application and situation do not allow the use of a flame or soldering techniques. National Model Codes allow flare fittings and local codes should be consulted.

Flared Connection Tools

The primary tool for this action is one that contains a dye that holds the tube while a mandrel is forced into the end of the tube to make the flare. A mandrel can be either a round ended object against which material can be shaped or a part of a tool such as a chuck that grips materials.

The following steps outline the process of creating single thickness flared connections.

  • Prepare the end of the tubing by ensuring the cut is straight and square with the tubing. Remove any burrs by using a reamer and ensure no filings fall into the tubing.
  • Use a file to smooth over the end cut. If any reaming is necessary after the filing, do that.
  • Put the flare nut on the tubing. Face the open end of the flare nut towards the open end of the tubing. Insert the tool into the flaring tool allowing for enough tubing to actually create the flare opening. Tighten the clamp.
  • Place a drop of refrigerant oil on the flaring tool spinner. The action required to create the flare is one that requires the technician to tighten the spinner ½ turn and then loosen it ¼ turn. That action is repeated until the flare is created.

NOTE: Don’t overtighten the flare nut when you attach it to the flare. Do not overtighten the tool you are using to do the flaring process. Take good care not to over-tighten and cause cracking or changes in the structure of the tubing.

The goal of the flaring process is to create a surface in the end of the tubing that exactly matches the preformed flare inside the flare nut. You want a smooth, round flare of sufficient size and length to completely match the inside surface of the flare nut.

Type L copper tubing may be flared according to many plumbing codes in cities and municipalities across the nation. The National Fuel Gas Code allows for flared connections of copper tubing with LP, natural gas, and propane.

Flared connections are both a science and an art. Give equal importance to both.