LET-LOK® type connectors
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.
List of products:

Let-Lok® twin-ferrule fittings for imperial tubes

Let-Lok® twin-ferrule fittings for metric tubes

One-Lok® single-ferrule fittings
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FAQ – Instrumentation fittings
Twin-ferrule fittings are made of AISI 316 steel as standard, but we can also supply fittings made of: brass, Hastelloy C-276, Monel 400, 6Mo steel and Super Duplex on request.
LET-LOK fittings are interchangeable with Swagelok, Parker (A-LOK), DK-LOK, HY-LOK or Superlok products.
Twin-ferrule fittings can be used with pneumatic hoses only if a 760LI reinforcing ferrule is fitted. There is also an option of fittings with PTFE compression ferrules, which can be used as an alternative to standard stainless steel compression ferrules on plastic hoses.