Compression fitting

Compression fittings are used extensively in hydraulic, gas, and water systems to enable the connection of tubing to threaded components like valves and tools.

[1] Compression fittings are suited to a variety of applications, such as plumbing systems in confined spaces where copper pipe would be difficult to solder without creating a fire hazard, and extensively in hydraulic industrial applications.

When the nut is tightened, the ferrule is compressed between the nut and the receiving fitting; causing both ends of barrel shaped copper olives to be clamped around the pipe when the middle of the ferrule bows away from the pipe, in the case of hydraulic style ferrules they currently have one end which is larger with a 45 degree chamfer which tapers away (from installation contact with the nut) and the small end generally has two internal biting edges, for applications demanding much higher pressure, that penetrate the outside diameter of the tube, the fittings must be tightened to guidelines as per DIN2353 as not to exceed the elastic limit of the steel ferrules, The result is that the ferrule seals the space between the pipe, nut, and receiving fitting, thereby forming a tight joint.

However, a small amount of plumber's grease or light oil applied to the threads will provide lubrication to help ensure a smooth, consistent tightening of the compression nut.

It is critical to avoid over-tightening the nut or else the integrity of the compression fitting will be compromised by the excessive force.

The integrity of the compression fitting is determined by the ferrule, which is easily prone to damage.

Compression fittings are popular because they do not require soldering, so they are comparatively quick and easy to use.

Compression fittings are especially useful in installations that may require occasional disassembly or partial removal for maintenance etc., since these connections can be broken and remade without affecting the integrity of the joint.

A soldered joint is highly tolerant of flexing and bending (such as when pipes knock or shake from sudden pressure changes e.g. caused by water hammer).