Whether you are a domestic plumber, an auto engine mechanic or a fitter in a large industrial plant, at some time or another you are going to come across Compression Fittings. Domestic water and HVAC systems require pipework to be placed throughout the building. Automobiles require small bore pipe (often referred to as tubing) to carry fuel from the tank to the engine. Plants like refineries require miles of pipe to carry their fluids throughout the processes.
Pipe Fittings
“Pipe fittings” is an omnibus term applied to components that enable pipes, tubes and even hoses to be joined together in a wide variety of ways. The term can also also cover small pieces of equipment such as the needle valves used to bleed the air out of some domestic pipe systems. Since maintenance often requires sections of a line of pipe to be taken out for repair or similar reasons, it is not usual to weld, braze or otherwise permanently fix pipe connections. For larger pipework, bolted flanges are the most popular joining method but, particularly on smaller sized pipe, a direct, threaded, connection is the norm.
Some pipe fittings are nothing more than a short length of pipe with threads at each end so two lengths of pipe can be screwed into it – this pipe fitting is often called a “union”. For light duties, the male threads of a connection can be wrapped with ptfe tape prior to being screwed together and this will be sufficient to seal off the fluid flowing in the pipe.
Getting A Sealed Pipe Connection
Flanges can be sealed with gaskets but threaded connections can be harder to seal, particularly if the pressure in the pipe is too high for reliance on thread sealants alone. This is the area where Compression Fittings come into their own.
The heart of most Compression Fittings is a metal ferrule (most commonly made from copper or brass). This is a ring that fits over a non-threaded part of the connection. The outer side of the ring has a slope rising from each end to a peak in the center. The outside bevel is designed to interact with the nut as the screwed connection is being tightened. The ferrule will be forced into tighter contact on the inside and deformed on the outside so as to form a metal to metal seal preventing any out flow of fluid from the connection.
This is akin to cold soldering and plumbers prefer them when the install point is in a restricted place making soldering difficult. Compression Fittings are popular amongst plant engineers and motor mechanics because of their easy to assemble highly efficient sealing ability. Should the sealing ferrule become damaged, it can be readily replaced. Any source of general pipe fittings will be certain to have Compression Fittings on their range.