Tri-Clamp fittings, originally trademarked by Alfa Laval as "Tri-Clover" fittings over 50 years ago .
They are used in processes in the dairy, food processing, bio-pharm and cosmetics industries where even tiny crevasses, such as pipe threads for example present too much of a contamination risk.
Tri-Clamp connections consist of a clamp, 2 ferrules or fittings and a gasket to maintain a tight and hygienic seal as picture below.
Tri-Clamp Size is determined by the outside diameter of the pipe, NOT the outside diameter of the ferrule.
The ferrule ( the end piece that makes half of the connection to another TC fitting) is about 1/2” larger than the items tube size.
In other words, a 1.5” TC fitting will have a ferrule whose outside diameter is about 2”. Confusion arises with 1” TC fittings because they use the same ferrule as 1.5” TC fittings.
The same applies for 1/2'' and 3/5'' Tri-Clamp fittings and valves.
Pictured is a 1'' L14AM7 long ferrule with a 1-1/2'' long ferrule.
Please see the sizing chart below