Push-together connector handles the pressure
Tom Shelley reports on a device that should save time and cost when assembling hydraulics, especially in marine and offshore applications
A push-fit connector is rated at 20,000 psi (1379 bar) for half-inch (12mm) connections, and 10,000 psi (689 bar) for one-inch (25mm) connections.
It relies on a unique method of deforming a sleeve round the end of the pipe and also the pipe itself in such a way that a portion of it is expanded slightly, firmly locking the arrangement.
The ‘Phastite’ connector from Parker Hannifin Instrumentation Products in Barnstaple is aimed at reducing hydraulic system assembly time, especially in offshore and marine applications.
All that is required is to cut and de-burr the tubes, place them into one of the connector assemblies, attach a special hydraulic tool and apply pressure. If the tool is pressurised from an electric pump, the connection is made in 4.7s, and if the tool is pressurised by a hand pump. It takes about 30s.
The device replaces – and costs about the same as – cone and thread fittings, which take much longer to assemble and can perform badly in applications subject to vibration. Welded connections are cheaper, but cost more to install because of the equipment required. Parker cites figures of $2.09 for installing a Phastite fitting, $42.50 for a cone and thread fitting (including the time required to cone and thread the tube ends) and $76.67 for a welded fitting – more if X-ray or dye penetration non destructive testing is required.
Push-fit hydraulic fittings have been developed before, but none that withstand such a high pressure. Eureka was shown a sample that had not failed until 52,380 psi (3611 bar) whereupon the tube had failed, and not the fitting. Key to its successful development was finite element analysis of the deformation of the sleeve and tube, The device is fully patented.
Parker Instrumentation’s Steve Mullen says: “There has been little significant change in industrial tube fitting design for 50 years. By re-thinking the sealing principle, we have devised a fitting that radically changes the economics of fluid system building.”
The official launch of fittings in sizes from one quarter to half inch is scheduled for this month. The fittings will initially be offered in 316 stainless steel with plans for versions in super duplex stainless steel and nickel alloys. Sizes up to one inch will become available in January 2007.
Applications are seen in high pressure hydraulics, deep water oil and gas drilling, ROVs (Remotely Operated Vehicle) and subsea applications, laboratory testing and high pressure machinery such as water jet cutters.
The range of fittings includes: straight union, union elbow, ‘tee’ and cross fitting shapes in imperial and metric sizes. Several termination connectors provide a link between fixed tubing and elements that need to be disconnected or maintained. The technique is applicable to tubes too thin walled to be coned and threaded, or easily welded. The assembly tool is of a similar size to a soft drinks can and includes a flat working edge that can install tubing in confined spaces such as against a panel.
Parker Hannifin Phastite
* Nominal half inch (12mm) push fit connectors are rated at up to 20,000 psi (1379 bar)
* Nominal one inch (25mm) connectors, to be launched in 2007, are rated at up to 10,000 psi (689 bar)
* Assembly time for tubes with prepared ends is 4.7s with electrical pumping of the hydraulic tool and about 30s for hand pumping
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