Instrumentation connectors double ferrule – general information
Precision pipe fittings with two compression ferrules were invented around 1945. They are designed for leak-free operation in extreme conditions: high pressure, vacuum, vibration and high temperatures. Two conical ferrules are pressed against the conical seat in the fitting body with a nut, gripping the tube at the same time. The cone of the back ferrule slides under the front ferrule, lifting it and pressing against the conical seat inside the fitting body. The tube gets slightly deformed from the compression load of the ferrules. This is a precise mechanism that holds the tube firmly in the fitting, ensuring perfect leak tightness at high pressure and vacuum, with no unnecessary stress in the joint. It is all-metal, so the maximum working temperature can be as high as 650ºC.
With all these features and benefits, the twin-ferrule fittings can be used in process engineering and instrumentation systems in the chemical, petrochemical and pharmaceutical industry, power plants, nuclear plants and other sectors where high performance is critical. Today, they are manufactured by many companies according to the same industry standard. However, their quality (leak tightness, durability, reliability, corrosion resistance etc.) depends on the precision and countless technology details and for seemingly same elements from different manufacturers is basically different.