Stronger support avoids high pressure tube joint leaks

Problem: The traditional way of making high pressure connections is to use a fitting that requires coning and threading the end of the tube. This can take 30 minutes or more to make, according to Graham Johnson, Business Development Manager of Parker Hannifin's Instrumentation Products Division. Traditional types of instrumentation compression fittings are not suitable for these high pressures. Solution: Parker Hannifin has come up with a compression fitting suitable for high pressures. Designated MPI it is now being offered in half inch pipe sizes. The MPI design, made of 316 stainless steel, only requires that the tube ends be cut off without burrs. They are held by a novel compression fitting with two ferrules, both of which 'bite' into the tubing when the nut is done up to push them into the tapered inside of the fitting. The ferrules are driven in by the outermost end of the nut, which has a male thread, in contrast to traditional two ferrule compression fittings where the ferrules are held against the inside of the body, which has a female thread. The new arrangement increases support on the front ferrules, because of the availability of the full diameter of the fitting which, is an inverted design and therefore does not have to machined down to create an external thread. It also gives a much longer tube support zone inside the nut, which is molybdenum disulphide coated. Applications: New half inch sizes are suitable for high tensile, duplex and super duplex tubing often favoured for running down high pressure deepwater wells. The new option is in addition to existing choices of 1/4, 3/8 and 9/16 inches. The fittings are available in a variety of shapes and flow arrangements including straight connections, elbow and tee joints, bulkhead unions, reducers and adapting interfaces. TS Parker Hannifin