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Inner Triplet Review: Mechanical Design and Analysis Summary

The review on the mechanical design of the inner triplet to ensure no hidden defects and discuss in-situ repair post-design. Includes insights on Q1, Q2, Q3, DFBX, and D1 assemblies. Review involves analyses on forces, welding, and support structures.

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Inner Triplet Review: Mechanical Design and Analysis Summary

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  1. Review of the inner triplet 24-25 April 2007 Summary C. Hauviller

  2. Inner Triplet Review The mandate as stated by Lyn Evans, LHC project leader, is: "A review of the mechanical design of the inner triplet to be sure that there are no further hidden defects. A review of the proposed in-situ repair once the design is complete." Following discussions with US and CERN colleagues, - the mechanical design is interpreted as all engineering related to stresses and displacements and therefore also the alignment - the inner triplet will include all the assembled systems: DFBX, Q1, Q2, Q3 and , when relevant, D1.

  3. LHC low-btriplet – warm assembly

  4. LHC low-b triplet – DFBX

  5. Inner Triplet Review • Review panel: Claude Hauviller/CERN - Chairman Vittorio Parma/CERN – Scientific Secretary Alain Poncet/CERN Jean-Michel Rifflet/ CEA John Herbert Sondericker/BNL

  6. Inner Triplet Review • All presentations are accessible on the CDS at the address http://indico.cern.ch/conferenceDisplay.py?confId=15267 • Treat only the points related to the mechanics. Electrical integrity, magnetic performances,… are not part of the review, neither the organizational issues.

  7. Inner Triplet Review Overview (Ranko Ostojic CERN) Generalities (Jim Kerby FNAL Q1/Q2/Q3 Thermo-Mechanics (Tom Nicol FNAL) DFBX Thermo-Mechanics (Tom Peterson FNAL , Joseph Rasson LBNL D1 Thermo-Mechanics (Erich Willen BNL Integrated systems (Jim Kerby FNAL Activities on the triplets at CERN (Herve Prin CERN) Interconnections including modifications (Cedric Garion CERN) Jacks (Sonia Bartolome Jimenez CERN) Ground (John Osborne CERN) Alignment / Positioning (Dominique Missiaen CERN Fixes (Jim Kerby FNAL

  8. Inner Triplet Review • No guarantee to be full proof. • Complex assemblies • Time too short to be thorough and to swallow all the information • The incident during the pressure test of L5 has generated a lot of work/analysis in the labs

  9. Q1 supports at IP 5L 9

  10. Path of forces Forces originate at the magnet interconnect from bellows spring forces and pressure induced axial forces… …they act on the internal piping and are transmitted to the cold mass through the pipe anchors… …then are transferred to the support structure through the anchor and slide mechanisms… …then to the vacuum vessel through the external support lugs… …and finally to the floor through the external jacks. 10

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

  13. Inner Triplet Review • General • Documentation exists but incomplete • Design standards not uniform • Safety factors • ASME codes for ductile materials typically 3 – 3.5 to ultimate or 1.5 to yield strength (in 1998 Div I was 4 to ultimate) • Welds further derated depending on geometry and inspection • Spider support transverse SF 2 to ultimate • Welding coefficient Z=0.55

  14. Inner Triplet Review • Internal piping and anchoring to cold masses (helium vessels) Unbalanced forces, elbows Extreme cases of loading: • pressure test (traction) • vacuum (compression) Systematic verifications launched (FEM analysis)

  15. 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

  16. Completed cold mass and piping on spider supports 16 27 avril 2007

  17. Q1 pipe support weldment (Q3 similar) 17 27 avril 2007

  18. 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: 41797 psi (288 MPa) Elbow to end dome weld stress: 17383 psi (120 MPa) 18 27 avril 2007

  19. DFBX Piping Layout D1 End Q3 End 19 27 avril 2007

  20. DFBX Summary • Cold shocks, pressure tests and vacuum leak checks were performed at the component level at the manufacturer and CERN • Analysis confirmed that the LHe vessel structure is robust • During the last month the DFBX mechanical structure was reviewed and much of it was analyzed • The analysis confirmed that the bus duct thrust support is marginal • “Weld Clamp” was not welded • Support bracket is too thin 20 27 avril 2007

  21. 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

  22. 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 • Too low safety factor for the global stability of the piping. Recommended to add extra supports. Note that the H pieces have been modified to increase stability of the cold mass lines and reliability of the heat exchanger inner copper tube.Can be done in or near the interconnections

  23. Q1/Q2, Q2/Q3 interconnections Stability issue - Global stability (at the IC scale) Cold mass and heat exchanger Modifications First global mode: 49.5 bars (Q1/Q2) Stiff restrain on M4 bellows • 1 mode suppressed • First mode with limited displacement • Critical pressure of ~49.5 bars for Q1/Q2 and ~49 bars for Q2/Q3 (rescaling) • Assembly of H pieces done by welded sleeves  minimum of shear pres-stress in the bellows

  24. Q1/Q2, Q2/Q3 interconnections Stability issue - Global stability LD bellows Interconnection support Aluminium plate Pcr ~30bars Guiding device to be installed on the end plate Pcr ~60bars Q1 EE, FF bellows Thermal shield: “Soft” boundary conditions Thermal shield extremity Pcr ~39.5bars Pcr ~50bars

  25. Inner Triplet Review Connection of cold masses to vacuum vessels Composite parts inside the magnets. Bars in the DFBX. Integrity of all the composite parts not guaranteed. Movements not properly controlled during transports. No specific action proposed. Limit the load where possible.

  26. Handling and Transport

  27. Inner Triplet Review Connection of cold masses to vacuum vessels • Inside the DFBX, eliminate LHe vessel vertical rods linkage dependence on friction generated by bolt tightness. Check load case when rods are in compression • Safety factor to ultimate too low for composite parts in Q1/Q2/Q3. Repaired part not acceptable. To be replaced.

  28. Repaired spider

  29. Inner Triplet Review Connection of cold masses to vacuum vessels • Inside the DFBX, eliminate LHe vessel vertical rods linkage dependence on friction generated by bolt tightness. Check load case when rods are in compression • Safety factor to ultimate too low for composite parts in Q1/Q2/Q3. Repaired part not acceptable. To be replaced. • Fixes in Q1 and Q3 to be finalized and qualified: cartouche proposal. Unload the spiders from longitudinal loads

  30. 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 30

  31. Cartouche / Cartridge • Affixed at Q1 non-IP end; Q3 IP end • Transfer load at all temperatures • Limits support deflections 31

  32. 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 32

  33. Figure 1. Finite Element Model of Q1 with Cartridge Q1 Cartridge Modeling • Cartridge applied to Q1 model including bellows for: • Warm 25 bar pressure test load • Cold • Cold, 20 bar quench load 33

  34. 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 34

  35. Spider and tie bar assembly • 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.

  36. 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.

  37. 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

  38. Load Transfer • Alignment Requirements for the LHC Low-Beta Triplets (LHC-G-ES-0016, 2002). Main points concerning supports: • CERN supplies jacks, cups and other equipment for installation to the tunnel floor. • Lateral load specified as 1 ton • No reference to vacuum load (assumed taken up by the tie-rods). • Decision to use PMPS jacks for the inner triplets (2004?) • Jacks designed to take loads up to 8 tons • Specification for the motorization of the PMPS jacks (IT3200, 2004) • Lateral load specified as 1.3 tons • Anchor specification (date?) • Lateral load specified as 5 tons • All cases referred to assumed vacuum loading 38

  39. 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

  40. Tie rod assembly at warm fit-up 40 27 avril 2007

  41. 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

  42. 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

  43. External jack stands in warm fit-up

  44. 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

  45. Inner Triplet Review. • 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 (use the overall FEM model prepared by FNAL) • Take into account the transverse adjustment requirements for alignment

  46. Inner Triplet reviewMain 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 46 27 avril 2007

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