Barbanotti, S. Buhr, C. Hintz, H. Jensch, K. Lilje, L. Maschmann, W. Pierini, P. Wagner, A. JACoW Geneva, Switzerland 978-3-95450-178-6 10.18429/JACoW-SRF2015-TUPB108 English 883-887 TUPB108 linac cryomodule vacuum cryogenics operation Contribution to a conference proceedings 2015 2015-12 http://dx.doi.org/10.18429/JACoW-SRF2015-TUPB108 http://srf2015.vrws.de/papers/tupb108.pdf The European X-ray Free Electron Laser (EU-XFEL) cold linac consists of 100 assembled cryomodules, 6 feed-/end-boxes and 6 string connection boxes fixed to the ceiling of the accelerator tunnel; the injector consists of a radio frequency gun, one 1.3 GHz and one 3.9 GHz cryomodule, one feed- and one end-cap lying on ground supports. The components are connected together in the tunnel, after cold testing, transport, final positioning and alignment. The cold linac is a pressure equipment and is therefore subjected to the requirements of the Pressure Equipment Directive (PED). This paper describes the welding and subsequent non-destructive testing of the cryo-pipes (with a deeper look at the technical solutions adopted to satisfy the PED requirements), the assembly of the beam line absorbers and the final steps before closing the connection with a DN1000 bellows. A special paragraph will be dedicated to the connection of the injector components, where the lack of space makes this installation a particularly challenging task.