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Using Flare Fittings

It is more common to join refrigeration pipework by Brazing and Soldering for todays technicians however flare fittings are still a reliable way of joining copper piping. It is especially useful when working in areas where open flames are not allowed.

Flare fittings have special names depending on their application.  For this reason it is a good idea to get to know each name of the flare type and its size, this will avoid confusion when on the job.

The fittings are divided into two main groups which are grouped into male and female. 

The type of fitting which has visible threads on the outside is known as a male fitting. 

The opposite is a female fitting which has threads on the inside.

Each fitting has its own particular name such as a flare nut, half union, tee, elbow etc.

Below are some of them.

Flares come in five main sizes which are 3/16", 1/4", 3/8", 1/2", 5/8" of an inch.

Flaring Copper Tube

Flaring is a a mechanical way of joining pipework.  Before beginning any flaring activity all tubes have to be clean, squared of and still round at the end.  This can be achieved by using correct pipe cutting tools which are designed to do just this. 

Once a clean cut has been made its next necessary to place the correct size flare nut over the pipe. This is not needed for a while so it's best to move the nut away from the end so you can now use the flaring block
The flaring block is a two-piece tool that reshapes the end of the copper tubing, "flaring" it to fit into the flare fitting.

Choose the hole in the flaring block that matches the outside diameter of the tubing. Clamp the tool onto the tubing. Align the compression cone on the tubing's end, and tighten the screw. As you turn the handle, the cone flares the tubing's end. Inspect your work carefully after removing the tubing from the block. If the end has split, cut off the flared portion and repeat the process.  It is essentail to take a really good close examination of your work to ensure a clean fitting

Flare/nut union

Seat the flare union against one of the flared ends of the tubing, slide the nut down, and hand-tighten. Do the same on the other side. You should note have to use a wrench in the early stages and the fitting should be easy to hand tighten if done properly. No pipe joint compound is necessary.  Its now time to tighten the joint by placing one wrench on the union and one on a nut.

Don't over-tighten a flared joint. Once snug, give it a half turn on each nut and that should be a gas tight join.