MAINTENANCE ISSUES ON THE ANU 14UD ACCELERATOR TANK OPENINGS #117 through #122. Alistair Muirhead. ATF rd May 2014

Transcription

1 MAINTENANCE ISSUES ON THE ANU 14UD ACCELERATOR TANK OPENINGS #117 through #122 Alistair Muirhead ATF rd May 2014

2 2 The 14UD Van De-Graff accelerator National Electrostatics Corporation 15MV terminal potential 3 Charging chains ~25 m height x 6m dia vessel Tandem, electron stripping at mid length using carbon foils or gas

3 Systems within the 14UD Shaft drive motor Shaft driven alternator, powering terminal systems (obscured) Terminal Gas stripper Carbon stripper Charging chain x 3 Chain x 3, drive motors Shaft drive motor Shaft driven alternator, powering terminal systems (obscured) 3

4 4 Some simpler issues easy fixes Snail trails on perspex drive shafts Broken chain 65k hours TO Tube resistor failure TO Charging system failures TO 121

5 5 Chain charging system failures Spark damaged Standoffs Leaking HV co-ax supply) HV feedthrough - Silicon grease to eliminate air spaces, raise permittivity. Experiment not a success

6 6 More significant issues 2-years saga: introducing SF6 to gas stripper Motivation for introduction was from positive ANSTO experience fixing gas stripper leak Ceramic insulators- column and tube vital statistics in-situ diagnostics of ceramic and resistors service platform upgrade investing in stock of posts and tubes: $$$

7 14UD Gas Stripper 7

8 8 Post Opening Performance Dates TO# Faulty components Leak fixed by Leak is back at GS pressure with tank pressure, PSIA turbos off, mtorr 5Jul-24 Aug A Added SF6 gas 22 Aug B O2, SF6 bottles, solenoid valve to O2 bottle 25Oct-23Nov Feb-1Mar Jul-19Jul Jan-26Feb Mar-5Mar Mar-12Mar Crucial observations Solenoid valve replaced with Tube, back to single gas Four 4BK swagelock valves Tightened gasket initially rose to in two sudden jumps in Nov Going OK. (U13 sparking/ Leaking tube ceramic) 121 4BK valves (screwed assembly) Replaced with welded 4BK Valves, bake out traps 122A GS turbo O-ring suspected No fix, GS valve closed to separate it in 2 parts for test, gas up and check @80 PSI 43 Raised to >1000 because of no pumping 122B Swagelock elbow Tightening of nut on elbow

9 9 Crucial observations Post Opening Performance Dates TO# Faulty components Leak fixed by Leak is back at GS pressure with tank pressure, PSIA turbos off, mtorr 5Jul-24 Aug A Added SF6 S gas 22 Aug B O2, SF6 bottles, solenoid valve to O2 bottle 25Oct-23Nov Feb-1Mar Jul-19Jul Jan-26Feb Mar-5Mar Mar-12Mar Solenoid valve replaced with Tube, back to single gas Four 4BK swagelock valves Tightened gasket initially rose to in two sudden jumps in Nov Going OK. (U13 sparking/ Leaking tube ceramic) 121 4BK valves (screwed assembly) Replaced with welded 4BK Valves, bake out traps 122A GS turbo O-ring suspected No fix, GS valve closed to separate it in 2 parts for test, gas up and check @80 PSI 43 Raised to >1000 because of no pumping 122B Swagelock elbow Tightening of nut on elbow

10 10 Crucial observations Post Opening Performance Dates TO# Faulty components Leak fixed by Leak is back at GS pressure with tank pressure, PSIA turbos off, mtorr 5Jul-24 Aug A Added SF6 S gas 22 Aug B O2, SF6 bottles, solenoid valve to O2 bottle 25Oct-23Nov Feb-1Mar Jul-19Jul Jan-26Feb Mar-5Mar Mar-12Mar Solenoid valve replaced with Tube, back to single gas Four 4BK swagelock valves Tightened gasket initially rose to in two sudden jumps in Nov Going OK. (U13 sparking/ Leaking tube ceramic) 121 4BK valves (screwed assembly) Replaced with welded 4BK Valves, bake out traps 122A GS turbo O-ring suspected No fix, GS valve closed to separate it in 2 parts for test, gas up and check @80 PSI 43 Raised to >1000 because of no pumping 122B Swagelock elbow Tightening of nut on elbow Comprehensive bake-out of turbo backing traps, outside and in-situ.

11 Crucial observations Bagged Swagelok elbow fitting. 11

12 12 Current status of GS Adequate performance for all applications in spite of remaining minor leaks Prepare to upgrade with VCR fittings and welded pipework AMS reported operational experience with SF 6 contaminated O 2 gas: with Cl beam the optimum for pure O 2 was 20 mtorr; for contaminated O 2 it was 10 mtorr

13 13 Ceramic insulators and their condition Ceramic health of 14UD vital statistics in-situ diagnostics of ceramic and resistors variable speed drive for platform- causing damage? investing in stock of posts and tubes: $$$

14 14 14UD electrical structure 74 tube resistors R S =22.2 GW across 37 ceramic gaps per unit x 28 units 36 post resistors R S =35.4 GW and 72 ceramic gaps in posts per unit x 28 units

15 Post reconditioning Old post 1970 s and spark-damaged endcap De-greasing Abrasive blasting Aluminium shim Fitting stainless steel endcaps Machining posts to length Tolerance ± inch Clamping end Ti electrodes to new endcaps

16 Refurbishment and replacement 14UD posts TO#112 November 2009 Protrusion of Al foil from manufacturing Propagates breakdown. 2 nd generation posts installed in 80 th April 2011 Eight posts have been ordered from NEC as EIF upgrade RECEIVED and ALL INSTALLED

17 Faulty posts removed during TO#121 and #122 Five posts removed during TO#121 Two posts removed during TO#122 Replaced with least worst spares

18 Faulty posts: Collection is Growing Stocktake, 2014 Jan- Two NEC post assemblies received May- Four NEC post bondments ordered ONLY four used posts suitable for re-furbishing STATUS: work in progress

19 Post-mortem every thing old is new again Quotes from Post-mortem An autopsy of NEC column posts, 1985 Weisser/Brinkely others. - dangerous and expensive - old age at 15, we are now 40 plus - sparking, post end flanges, cleanliness - less sources of dust now - excessive SF 6 pressure, 110psia

20 20 Repairs during TO#120: 5 faulty tubes Repairs up & down shorted gap shorted gap (also open circuit resistor) shorted gap shorted gap replaced post (crack in insulator) replaced open circuit post resistor shorted gap repaired electrode

21 Standard entry and exit 30 kv test crack/current leakage thing is probably not new, just that we ve been a lot more careful in our tests. Our range of acceptance, has narrowed a great deal. - Peter Linardakis

22 22 Conclusion Faulty posts and tubes or the discovery of them, is growing due to (a) age and (b) diagnostics The electrical industry standard of life span of HV ceramic is <30 years Review historic conclusions!!! Column deflection can be significant Improve the service platform drive - fine control. Review the technique of mounting Al casting covers less push/shove on column

23 23 14UD team John Bockwinkel Alan Cooper Gareth Crook Caleb Gudu Allan Harding Justin Heighway Peter Linardakis Nikolia Lobanov Lorenso Lariosa Thomas Tunningley