1. On the accuracy of port assembly at Wendelstein 7-X
Max-Planck-Institut für Plasmaphysik, EURATOM Association
On the accuracy of port assembly at Wendelstein 7-X
Torsten Bräuer and metrology team
Introduction
Wendelstein 7-X use 254 ports; 2/3 for diagnostic, 1/3 for supply purpose;
Size of ports varies between m in length, m in diameter and mm in wall thickness
Ports bridge the cryo-vacuum and have to be thermal insulated
General assembly tolerance: mm (in global cosy)
Reduced tolerances down to 2 mm in cases of higher accuracy requirements
Position of vacuum vessel openings are taken as they are (after final vessel assembly)
Assembly of ports takes place in 4 steps
Port preparation: length, contour, cabling, sensors ...
Thermal insulation: external company (MAN DT)
Installation of port: adjustment, tack welding
Final welding: controlled by metrology, final checks of weld seam I.
III.
II.
Scan of VV opening
2D contour plot is used to wrap around port and perform port cutting
Final cut of port
Ports and VV of a half module;
outer vessel dismantled; ports are shown with over length
The accuracy of port length and contour is approx. 1 … 1.5 mm
Port assembly in horizontal and vertical direction using a sliding table device; orientation of movement vector is adjusted by sighting method; flange position is adjusted by laser-tracker after dismantling of sliding table
Lateral and axial assembly deviation of port flanges; each point represents one port and its deviation; assembly sequence: module 5, 1, 4, 2; in module 3 no ports assembled up to now; tolerance overstepping are accepted one base of technical arguments.
AEV ports at module separation plan 5/1
Both ports are used for magnetic flux surface measurements
Axis of both ports should be precise in a plan
Modified assembly procedure
Installation and tack welding as usual; usual tolerances
Repeated measurement of actual axis position of both ports
Determination of correction values for welding and control welding process by laser-tracker
Result: axis of both ports are inside a virtual plan within an accuracy of < 1 mm
Accuracy fits with requirements of diagnostic
Metrology support; measurement of port flange using T-probe of laser-tracker (left); measurement of pipe axis (right); laser-tracker looks into port and performs a scan of pipe wall
Conclusion
176 out of 254 ports are assembled at moment
Most ports are inside tolerance without correction measures
Only few ports exceeds tolerances, but actual position is accepted on base of technical arguments
3D metrology turned out to be an important factor to achieve position accuracy
More accurate results than in case of only sighting methods
Controlling of welding process is possible
measurement accuracy of typically 0.3 … 0.6 mm is appropriated to all port adjustment and welding control processes
use of laser-trackers is mainly limited by sighting conditions
Other limitations like air condition, vibrations and bright light sources can be reduced in their influence to an acceptable level
Only a good harmony of adjustment, welding and metrology procedures allows assembly processes with reduced tolerances down to 2 mm
AEK-V2 port in module 2
2 ports of AEK-V2 type, used for NBI heating
Inner cross section should be as large as possible to avoid beam interaction with port wall
Outer surface of port is very closed to surrounding coils
Port is separated in 2 parts
main port body is assembled as usual; pocket is assembled from VV site
Port is scanned before installation and a collision check is performed
Installation of temporary reference point system for permanent micrometer gauges measurements during welding of pocket
Control of main port body welding process by laser-tracker
Result: in critical collision areas the port geometry deviates not more than 2 mm compared to reference
Accuracy requirements on position and contour are achieved
27th SOFT, Liege, 24. –