Jul 5 2004
Time-consuming cone-and-thread preparation can be a thing of the past for fluid instrumentation users now that Parker Instrumentation has completed its breakthrough family of rapid-assembly 1034bar (15,000PSI) compression tube fittings. With the release of 15 new component shapes, Parker Instrumentation now offers flow arrangements providing an efficient single-piece solution for virtually every common connection requirement.
Using the familiar, industry-standard compression sealing technique - which assembles in seconds by simply tightening a nut - Parker's new MPI fittings save an estimated 20 minutes at least per connection, a time that probably equates to at least 10 Euros of labour cost in Europe. The new fittings are also inherently resistant to vibration, eliminating the additional cost of the vibration gland that is commonly used with cone-and-thread fittings.
For panel builders and OEMs who currently use, say, 1000 higher pressure cone and thread connectors a year, the labour savings alone from switching to MPI equate to around 10,000 Euros - without considering the cost of the special tools required for coning and threading. If these connections were also destined for vibration-prone environments such as drilling platforms and required a vibration gland, the savings total would more than double.
Parker's MPI tube fitting range is available in a range of instrumentation sizes to suit tubing with outside diameters from 1/4 to 3/4inch. The initial complement of common fitting shapes such as straight connections, elbow and tee joints is now extended with a large portfolio of flow arrangements and adapting interfaces.
Among the additions are tube versions in straight or 45 and 90 degree elbow shapes. There are a variety of new adapting options that combine an MPI tube stub end with a connector for existing instrumentation including: NPT pipe threads, flare connections, SAE O-ring connectors and traditional cone-and-thread. There is also a similar collection of straight connector adaptors with the addition of a variant for high-pressure hose connections.
The new fittings may be used on cold-drawn hard (unannealed) 316 stainless steel tubing, or thick-walled (annealed) instrumentation-grade 316 tubing. The fittings also feature nuts coated with molybdenum disulphide, which provides a long-lasting lubricant to help prevent thread galling, and reduces the torque required to create the seal - easing both assembly and the remaking of joints.
Special anti-vibration measures employed in MPI's design automatically provide a high degree of immunity to vibration, and include the action of the ferrules which are spring loaded at assembly - giving additional support for the tube as well as providing a leak tight joint. In contrast, a cone and thread joint necessitates a highly precise mechanical fit in order to create a seal, and it is not uncommon for these joints to work loose - necessitating tightening or even reseating; if such maintenance is required in the field, the associated downtime costs can be excessive. MPI fittings offer the same kind of 'fit and forget' sealing performance as the general-purpose twin-ferrule fittings that are familiar to every plant engineer.
Among the application sectors that can benefit from this innovation are deepwater oil and gas drilling and methanol injection equipment, and industrial laboratories where products are developed and tested under extreme conditions. Instrumentation engineers working in areas such as these can now assemble tubing systems in a small fraction of the time previously required. They also avoid the need for specialised training in installing traditional high-pressure fittings, and the close attention to quality control procedures typically required during assembly.
MPI's ability to operate at much higher pressures comes from a combination of design factors. These include: new geometries for the ferrules which create a dual mechanical hold onto the tubing wall; the application of Parker's exclusive Suparcase hardening treatment to both of these ferrules for enhanced ability to bite into tubing; longer tube supporting areas within the fittings to enhance resistance to vibration and line loads; and the use of 'inverted' threads (swapping the sides on which male and female threads are used). This latter technique allows the pressure-retaining elements of the tube fitting to be made thicker without substantially increasing either the size or weight of the fittings.
Safety assurance was a key goal behind the development of these new higher pressure fittings. As the fittings are based on familiar compression assembly techniques, Parker has designed the component parts in such a way there is no possibility of accidental intermixing with low pressure ferrules for example, or of component interchange with any other fitting. Furthermore, the maximum working pressures of the parts are printed on the bodies of MPI fittings, along with heat code traceability information.
"It can take 30 minutes or more to create the cone and thread required for high pressure fittings", says Steve Mullen, Parker's Product Marketing Manager. "MPI can cut assembly time to seconds, delivering major savings in installation costs, and allowing a common style of tube fittings to be applied plant-wide."
For more information on tubing, click here.