Metal Seal Connectors – A better alternative to tapered threads February 21, 2018 Machined faces were added to tapered pipe threads in an effort to address some of the shortcomings of pipe threads. A deep 30 degrees chamfer was added to the face of thread to form a seat. This is a modification that is only really seen in hydraulic products due to the high pressures involved. While a tapered pipe thread is still used, the thread no longer provides the sealing function. The thread now only provides the holding function, which is a fundamental change in its use. The machined face provides the following benefits: Easier orientation Better sealing No need for sealant The 30 degree machined face was first developed for the British pipe thread, BSP. That way the advantages of the sealing on the machine seat are available in the America thread also. Metal Seal Pipe Thread Types British Pipe Threads: British Standard Pipe Taper (BSPT) British Standard Pipe Parallel (BSPP) American Pipe Threads: National Pipe Taper (NPT) Advantages of Metal Seal Pipe Threads These connectors have a greatly reduced leakage when compared with simple pipe threads. Disadvantages of Metal Seal Pipe Threads However they still have underlying problems: They still cannot accept hydraulic hose unless the tube is welded or soldered to it The machine face cannot be used in port applications This led to the development of the JIC coupling and later RYCO’s market leading JSEAL™. JIC Metal Seal Connectors During the 1930’s in America, there was a group formed to assess the “proliferation” of threads in the many different industrial fields. There were threads of mechanical engineering, railways, automotive, plumbing, electrical, aerospace, hydraulics and more. This group was formed into a committee and laters a council called The Joint Industries Council. This council’s charter was the evaluate the many threads that were available with a view to creating industry conventions and standards. For the hydraulic industry, their suggestions was to adopt a machined face coupling that could accept both mating threads and tube. This became known as the JIC solution, or simply JIC. Note: The letters JIC should be spelled out, and not pronounced “Jick”. Advantages of JIC Connectors The JIC has all the advantages that a machined face coupling provides: Easier orientation Better sealing No need for sealant Plus, it can also accept tube. JIC has a 37 degree sealing face and a UNIFIED thread form (an American standard). It is still the most commonly used hydraulic connector. Disadvantages of JIC Connectors However, for all of its advantages, the JIC connector still has some problems. The JIC sealing face is very exposed. The sealing face is susceptible to damage It is a metal to metal seal, so it will leak or loosen with vibration The tube joint relies on a high quality flare The Evolution of Metal Seal Connectors As hydraulic system pressure climbed, machined faced were added to threads to control leaks and improve usability. But as pressures continued to climb, and leak free systems became desirable, it became clear that these coupling types still had leakage issues and problems with vibration. Common Machined Face Coupling Forms The most common types of machine face couplings are: British Standard Pipe Taper (BSPT) – when machined with face British Standard Pipe Parallel (BSPP) – when machined with face National Pipe Taper (NPT) – when machined with face NPSM JIC SAE (Automotive threads) Metric (DKL, DKS, DKM) Want More Information? For an overview of the different hydraulic connector types, check out our introduction to hydraulic connectors. You can also learn more about tapered pipe threads and soft seal connectors. Make sure you select the right hydraulic hose for your next project. Download our 15 Keys To Selecting The Right Hose guide today.