High-pressure tube fittings

Parker Instrumentation is announcing a radical new design of tube fitting that can deliver substantial cost savings to builders of industrial equipment involving fluids.

Assembled by means of a simple push-fit operation, the new fittings provide permanent connections for fluid systems operating at up to 1379 bar (20,000 psi).

For permanent connections, and these elevated pressures, system builders would typically use either welded or 'cone and thread' style fittings, which are time-consuming and expensive to install.

Compared with these types of fitting, Parker Instrumentation estimates that its new Phastite fittings could reduce installation costs by 90 per cent or more.

There has been little significant change in industrial tube fitting design for 50 years notes Parker Instrumentation's Steve Mullen. By starting with a blank sheetand re-thinking the sealing principlewe have devised a fitting that radically changes the economics of fluid system building - providing the prospect of major cost savings for millions of industrial companies worldwide."

Phastite employs a compression assembly principle using a novel form of toothed profile that makes the seal. The fittings are supplied as one-piece componentswith no loose parts to be mislaid or incorrectly assembled. To make a jointall that is required is to insert the tubeand then push the collar along the fitting body until it reaches a dead stop. This operation is performed by a simple handheld hydraulic tool and takes a few seconds. The tool requires no skill to useand assures users of right-first-time connections. A flat side on the tool ensures that joints can be made even in confined spaces.

This assembly approach contrasts with the requirement to perform a 360-degree weld around the circumference of a tubean operation requiring skillconsumablesexpensive equipmentand up to 10 minutes of time. Likewisethe coning and threading of a tube end to prepare it for use in a screw-together fitting requires skilland time - in this case up to 30 minutes or more. For many applicationsthe quality of the weld is also tested by means of dye penetrationor X-ray inspectionadding further significant costs - and time delays - to the installation process.

Inside the Phastite fittings there is an innovative sealing systembased on a collar that slides along an angled body and compresses a number of circular profiles into the tubing. At the end of the short travel there is a vertical face (end stop) that provides confirmation of correct assembly.

Phastite is much faster to assemble than welded or cone-and-thread fittingsand the process is also deskilledthereby removing a major element of industrial system building cost. The very high degree of control over make-up that the tooling automatically imposes also ensures right-first-time assembly. This is not the case with welded or cone-and-thread fittingswhere many users expect that there will a certain degree of rework. When used to replace a welded fittingthe Phastite fitting also eliminates any need for a 'hot work permit'which is another major expense faced by many organisationsespecially where repairs are called for.

The 1379 bar (20000 psi) pressure rating of the Phastite fittings opens up an extremely large market potential. Welded and cone-and-thread fittings are used in industrial applications where there are pressures above those that can be handled by ferrule types - which is typically above 413 bar (6000 psi). Applications include high-pressure hydraulicsdeepwater oil and gas drillingROVs and subsea equipmentlaboratory testingand high-pressure machinery such as waterjet cutters. Welded fittings are additionally used in lower pressure applications if there is a need for the 'peace of mind' that comes from a permanent connectionor where a leak could have serious consequences. Examples include subsea applicationsaerospaceboat building and military equipmentand plants that are remote or unmannedor have safety implications such as nuclear materials. Phastite fittings are highly tamper-resistantwhich has implications for both plant integrity and safety.

Another benefit of the Phastite fittings is that they are said to be more resistant to vibration and flexing than welded or cone-and-thread fittings. In tests performed by Parker Instrumentationcone-and-thread fittings suffered from fatigue failures after around 750000 cycleswhereas the Phastite fittings showed no sign of fatigue after 20million cycles. Furthermorecone-and-thread fittings can work loose in some circumstanceswhich means that regular retightening of the connections is required. Not only is this costlybut there is a risk that a fitting may be missedleading to a leak.

The Phastite range currently includes straight unionunion elbow'tee' and union cross fitting shapes in imperial and metric sizes from 6 to 12 mm or 1/4 to 1/2 inch. There is also a range of termination connectors that provide a link between the equipment's fixedpermanent tubingand any element that needs to be disconnected or maintained. These termination connectors are locked to a dead stop using a spanner.

Parker Instrumentation has developed a dedicated hydraulic tool for assembling Phastite fittings that is similar in size to a soft drink can. The small pump that drives the tool is available in a shoulder-carried versionproviding great flexibility of movement for operators. The cost of the tool is equivalent or less than the equipment required for weldingor coning and threading.

Phastite fittings and tools are available for order from October 2006.

For more informationvisit www.parker.com/ipd