Header Linkage

Header Linkage
Crossover Piping

Crossover Piping
Single Ball Joint

Single Ball Joint
Dual Ball Joint

Dual Ball Joint
Solar Panel Connections

Hyspan Barco Type N Style II, ASME Class and OW1500 ball joints are commonly used to connect the heat transfer fluid piping of parabolic mirror solar collectors to the main header, and in the crossover piping between adjacent rows of the mirrors. These connections absorb the thermal expansion of the collector tube that extends the length of the mirrors, and allow the mirrors to rotate from the stowed position (facing down) and then rotate to track the sun during operation.

The photograph of the Header Linkage shows the insulated piping with three ball joints located at the end of each mirror. The ball joints rotate as the linkage is actuated when the mirror rotates, and angulate (flex) to absorb the thermal expansion of the collector tube as shown by this video.

The photograph of the Crossover Piping shows the insulated loop connecting two mirrors. In this photograph both mirrors are facing downward. There are two ball joints incorporated into a dual assembly at the center and a single ball joints on each side. Although it is not shown in this photograph the design allows for one mirror to be facing downward with the adjacent mirror focused on the sun.

The ball joints installed in this piping are shown in the adjacent photographs of the single ball joint and the dual ball joint. The center section of the dual assembly is machined from one piece to eliminate welding. The maximum design conditions for the ball joints illustrated were 30 Bar (435 psig) and 393ºC (740ºF) using Dowtherm A®. They rotate 215º and flex +/- 7º.

In order to validate the design, Hyspan performed a life cycle test simulating the 30 year design life of the system. This involved operating a test apparatus for 11,095 cycles (30.3 years). Throughout this test the ball joint remained leak tight and the flex torque and rotational torque remained within specifications. A summary (Summary Test Report, Ball Joint Life Cycle) of the testing is available in the Technical Assistance section.

The Hyspan Barco Ball Joints incorporate design features that are not available in comparable products.
The design includes Inner and Outer Seals which rigidly position the ball, and the outer seal reacts the pressure thrust.
The materials of the seals can be varied to be best suited to the design requirements.
The cavity between the seals is injected with a mixture of graphite flakes and synthetic oil, Grafoil® Flexible Graphite.
Additional graphite packing can be injected through the Injection Ports after the joints are in service without removing the joints. The procedure for injecting packing is described in the Installation and Maintenance Procedures for Type N Style II, ASME Class and OW1500 ball joints.
All Hyspan Barco Ball Joints can be completely disassembled for inspection or maintenance. Sizes through 2" NPS have threaded retainers. The 2-1/2" NPS can be threaded or flanged.
The removable retainers have the added benefit of allowing precision adjustment of the internal resistance (flex torque) of the ball joint.
Nominal Sizes Through 2 Inch (threaded retainer)

Nominal Sizes 2-1/2” and Over (flanged retainer)
Hyspan 2" and 2-1/2" nominal pipe size ball joints designed for solar power plants have been approved for pressure equipment service in accordance with The European Pressure Equipment Directive (PED) 97/23/EC Module A1. In addition these designs conform to the requirements of the ASME Process Piping Code, B31.3, and the Power Piping Code, ASME B31.1

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