FPT hydraulic equipment for the construction of the ELT – The Extremely Large Telescope

The World’s Biggest Eye on the Sky
elt cerro


FPT hydraulic equipment





Extremely large telescopes are considered worldwide to be one of the highest priorities in ground-based astronomy. They will lead to a greater advancement of astrophysical knowledge, allow a deeper exploration of our Universe, and give sharper views of cosmic objects than ever before. Since 2005 ESO has been working with its community and industry to develop an extremely large optical/infrared telescope. ESO’s Extremely Large Telescope, or ELT for short, is a revolutionary ground-based telescope that will have a 39-metres main mirror and will be the largest visible and infrared light telescope in the world: the world’s biggest eye on the sky.

An extraordinary telescope calls for an exceptional site. Great care was therefore taken to ensure that the home of the ELT was the best possible. This required a high, dry site — perfect for observations.
On 26 April 2010, the ESO Council selected Cerro Armazones as the site for the planned 40-metre-class ELT. Cerro Armazones is a mountain at an altitude of about 3046 metres in the central part of Chile’s Atacama Desert.

With a mirror 39 metres in diameter, the ELT will gather 100 000 000 times more light than the human eye.

Extremely Large Telescope (ELT)

Main mirror diameter
39 metres

Light collecting area
978 square metres

Number of main mirror segments

Alignment precision of the different segments that make up the main mirror
Tens of nanometres (10000 thinner than a human hair) across its entire 39-metre diameter

Find out more about the ELT here

FPT hydraulic equipment for the construction of the ELT

FPT Fluid Power Technology has been involved on the ELT project for the design and manufacturing of the hydraulic bolt tensioners, HPU hydraulic power units and related hydraulic system used to tension the anchor bars of the carpentry modules. The full project is carried on with Cimolai, construction company, one of the main contractors for the building of the world’s largest telescope in the Chilean desert, project owner the European Southern Observatory (ESO).

In details FPT has designed dedicated custom-made hydraulic bolt tensioners to tension WR36 Dywidag bars and M27x3 threaded studs. The need was to tension the anchor bars, align the supports of the azimuth truck of the telescope and making them integral with the reinforced concrete foundations. Thanks to the FPT hydraulic bolt tensioners has been possible to achieve the pre-established preload forces.

Furthermore, the main carpentry modules that compose the bearing ring of the azimuth truck have been made integral with each other thanks to the tensioning of Macalloy bars size 75 and ensuring the tightening of the joints. The small encumbrances available, the horizontal axis arrangement of the bars and the high preload force demand have led FPT to design and develop a special two-stage and spring return hydraulic bolt tensioner to facilitate operations and to be able to fulfil to this delicate job. Part of the scope of the supply is also bolt tensioners M42, high pressure HPU hydraulic power units, with a maximum working pressure of 1500 bar, with remote control easy to be used even at in Cerro Armazones, at an altitude of about 3046 metres in the central part of Chile’s Atacama Desert.