1. Status of the low-β triplets
Accident during pressure test on March 27th
Outcome of the review held April 24-25th
Impact on cool-down of Sector 4-5
27 avril 2007 1

2. LHC low-b triplet – warm assembly
27 avril 2007

3. Completed cold mass and piping on spider supports
27 avril 2007 3

4. Q1/Q2, Q2/Q3 interconnections
General view
Heat exchanger line (L)
Cold mass/heat exchanger line (M4)
Pumping line 2 (Xbt)
Instrumentation line (M2) Q3
Thermal shield return line (FF)
Beam line (V) Q2
Main bus bar line (M1)
Beam screen line (K)
4.5 K heat intercept line (C’)
Thermal shield cooling line (EE), filling line (LD) and pumping line (XB) are not visible on this photo.

5. LHC low-b triplet – DFBX
27 avril 2007

6. Q1 supports at IP 5L
27 avril 2007 6

7. Cold Mass Support A ‘fixed’ and ‘free’ spider support
Invar rod connecting the two to share support

8. Tables are the full load cases IF all lines were pressurized to MAWP
27 March test the pumping and shield lines were not pressurized, and failure was at 20 bar
Q1 load 115kN
Q3 load 93kN

10. Review of the inner triplet
24-25 April 2007
Summary
C. Hauviller
27 avril 2007

11. Fix Points D1 Q3 Q2B Q2A Q1 Internal heat exchanger
FP Cold Mass-Vacuum Vessel
Fixed Point HX-Cold Mass
External heat exchanger (HX) D1 Q3
Q2B
Q2A Q1
LBX
DFBX
MQXA
MQXB
MQXB
MQXB
MQXA
Fixed Point Triplet-Tunnel Floor
Tie Rods Linking Vacuum Vessels
Jacks (longitudinal)
38490
27 avril 2007 11

12. Inner Triplet Review Main subjects General
Internal piping and anchoring to cold masses (helium vessels)
Connection of cold masses to vacuum vessels
Forces on vacuum vessels transferred to ground
27 avril 2007

13. Inner Triplet Review
Internal piping and anchoring to cold masses (helium vessels)
Weak points located in the anchoring to cold masses. To be reinforced on Q1, Q3 and DFBX. Can be done in-situ
27 avril 2007

14. Q1 pipe support weldment (Q3 similar)
27 avril 2007 14

15. Q1 pipe support weldment proposed modification
See Q1 Pipe Anchor Stress Analysis – T. Page, April 19, 2007
Modified pipe anchor stresses
Bracket to cold mass weld stress: 9121 psi (63 MPa)
Elbow to end dome weld stress: 9430 psi (65 MPa)
As designed pipe anchor stresses
Bracket to cold mass weld stress: psi (288 MPa)
Elbow to end dome weld stress: psi (120 MPa)
27 avril 2007 15

16. DFBX Piping Layout
D1 End
Q3 End
27 avril 2007 16

17. Bus Duct Thrust Support Analysis
(weld clamp)
Weld Clamp Stress Calculation Details
Material: 304L stainless steel
Peak thrust load: 20.1 kN (4510 lb)
Weld size: 1.59 mm (1/16”) 2 sides of clamp
Weld diameter: 48.3 mm (1.90”)
Shear stress: 61.5 MPa (8.92 ksi)
Equivalent stress: 107 MPa (15.4 ksi)
Allowable stress: 115 MPa (16.7 ksi)
Weld efficiency factor: 0.55
Net allowable stress: 63.3 MPa (9.19 ksi)
Weld
clamp
Weld stress exceeds allowable stress dictated by PV code but is still within material strength limits
Thrust
support
27 avril 2007

18. Connection of cold masses to vacuum vessels
Define the worst case loading of the spider, including tie rods contractions, and pre-stress. Validate by testing that the SF on longitudinal load is at least 4.
Validate the cartridge solution fix:
Complete the thermo-mechanical analysis including a sensitivity analysis on T profiles, in particular including cool-down/warm-up transients, accidental loss of insulation vacuum
Encourages the components and assembly tests proposals, possibly including a LN2 cold test.
Understand the mechanics of the overall support system (component and integrated assembly). Experimental validation recommended.
Check the thermo-mechanical transverse stability/reproducibility of the magnets inside the vessels.
27 avril 2007

19. Meshing of the supports was refined to include three elements through the half-inch thickness of the G11.
The G11 was treated as orthotropic; in the plane of the support (the xy plane in the analysis) bending is resisted primarily by the tension or compression of the relatively stiff glass fibers; the Young's modulus is dominated by the glass, and was set to 3e6 psi in both the x and y directions. For the z-direction (through the thickness), loads are perpendicular to the glass fibers, and the stiffness is influenced more strongly by the epoxy matrix; a reduced modulus of 1e6 psi was used for this direction. Note that while this is technically "orthotropic", it really assumes isotropy in the xy plane.

20. Repaired spider
27 avril 2007

21. Requirements for a Fix In Situ
Does not move fix point of the assemblies
React loads with sufficient stiffness to limit deflection – 150kN design load (slide 4)
Acts at any temperature 300K to 2K
Focus on implementation in Q1—Q3 solution tuned for length will then accommodate
27 avril 2007 21

22. Cartouche / Cartridge Affixed at Q1 non-IP end; Q3 IP end
Transfer load at all temperatures
Limits support deflections
27 avril 2007 22

23. Pieces….
Cold Mass Bracket, mechanically and thermally attaches AL cylinder to cold mass volume
Vacuum vessel bracket, transfers Invar load to Vacuum Vessel
Cartridge, Invar rod centered in Al tube
27 avril 2007 23

24. Cartridge Initial Analysis
Cartridge looks very promising, and is the proposed solution
Worst case Q1 spider support longitudinal deflection < 2mm limit
Worst case Q1 spider load < ¼ load that caused failure during recent pressure test
Does not move magnet fix point
In fact fixes Q1 / Q3 better than currently
Magnetic effect negligible
Design is ongoing to look at:
Length; diameter of rod (not 10% effect in various models)
Steady state thermalization BC’s
Thermal performance under upset / transient conditions
Attachment details to cold mass (corrector containment volume shell)
Attachment details to vacuum vessel, including effect on O ring groove due to
Cartridge bracket / tie rod ear deflections
Cooling of the Vacuum Vessel due to additional heat leak
Q3 attachment
Consolidation of design variants and anlayses
27 avril 2007 24

25. Inner Triplet Review Forces on vacuum vessels transferred to ground
Overall approach unclear.
Not clearly specified/ understood.
Two extreme cases:
Case 1: - loads transmitted to the DFBX and then to ground through the tie bars (initial specification)
Case 2: -loads transmitted to the ground through the jacks
27 avril 2007

26. Tie rod assembly at warm fit-up
27 avril 2007 26

27. Q1/Q2, Q2/Q3 interconnections
Vacuum vessel closure
4.8 mm thick
Bellows buckling pressure: 3.7 bars
Vacuum longitudinal force:
Max 8000daN
Buckling force (per rod): 5770daN
Is the guide length sufficient to avoid rotation?
Buckling force (per rod):1440daN
Stiff guidance has probably to be implemented
27 avril 2007
C. Garion

28. Inner Triplet Review Forces on vacuum vessels transferred to ground
Case 1: - loads transmitted to the DFBX and then to ground through the tie bars
Resistance of tie bars and tie bars supports not adequate. Can be modified in-situ.
Free the jacks
Global (in)stability to be assessed
27 avril 2007

29. External jack stands in warm fit-up
27 avril 2007

30. Inner Triplets Supports: fixation to the ground
Different tunnel ground conditions:
Point 1: Two holes of ~400mm diameter to fix the supports to the concrete underneath
Point 2 (RB24): platform made of concrete blocks and reinforced concrete slabs to continue the tunnel slope
Point 8 (RB86): reinforced concrete beam
27 avril 2007

31. Inner Triplet Review Forces on vacuum vessels transferred to ground
Case 2: -loads transmitted to the ground through the jacks
Longitudinal forces on jacks limited to 4 tons due to anchoring and local floor conditions
27 avril 2007

32. Inner Triplet review Main Recommendations
Internal piping and anchoring to cold masses (helium vessels)
Weak points located in the anchoring to cold masses. To be reinforced on Q1, Q3 and DFBX. Can be done in-situ
Too low safety factor for the global stability of the piping. Recommended to add extra supports. Can be done in or near the interconnections
Connection of cold masses to vacuum vessels
Safety factor to ultimate too low for composite parts in Q1/Q2/Q3 (spiders).
Integrity of these parts not guaranteed. Limit the load where possible.
Repaired part not acceptable. To be replaced.
Fixes in Q1 and Q3 to be finalized and qualified (including transients, accidental loss of insulation vacuum, a LN2 cold test): cartouche proposal. Unload the spiders from longitudinal loads.
Forces on vacuum vessels transferred to ground
Clarify the situation and decide on the option.
Reinforce tie bars and tie bars supports. Can be modified in-situ.
Study carefully the load sharing
Take into account the transverse adjustment requirements for alignment
27 avril 2007 32

33. Sectors 34 & 45 Option A : Wait for IT to cool-down 45 Option B :
Mar.
Apr.
May
Jun.
Jul.
Aug.
Oct.
Sep.
Nov.
Dec.
Jan.
Feb. 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 . 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09 10 11 12 13 14 15 16 17 19 18 20 21 22 23 24 25 26 27 29 28 30 31 32 33 34 35 36 37 39 38 40 41 42 43 44 45 46 47 49 48 50 51 52 01 02 03 04 05 07 06 08 09
Option A :
Wait for IT to cool-down 45
Option B :
Do not wait IT repairs for cool-down 45
Option C:
Do not wait IT repairs for cool-down 45
& minimize QUI interventions
4/24/2018
K. Foraz TS-IC-PL