C.Hauviller/TS-IC27 avril 2007 1

24-25 April 2007

Summary

C. Hauviller

Review of the inner triplet

C.Hauviller/TS-IC

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.

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LHC low- triplet – warm assembly

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LHC low- triplet – DFBX

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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

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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.

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Inner Triplet ReviewOverview (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

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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

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Q1 supports at IP 5L

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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.

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Fix Points

MQXA MQXB MQXAMQXB

Q3 Q2A Q1

DFBX

Q2B

38490

MQXBLBX

D1

External heat exchanger (HX)

Fixed Point HX-Cold Mass

FP Cold Mass-Vacuum Vessel

Fixed Point Triplet-Tunnel Floor

Tie Rods Linking Vacuum Vessels

Jacks (longitudinal)

Internal heat exchanger

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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

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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 coefficientZ=0.55

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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)

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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

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Completed cold mass and piping on spider supports

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Q1 pipe support weldment (Q3 similar)

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Q1 pipe support weldment proposed modification

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)

Modified pipe anchor stresses

Bracket to cold mass weld stress: 9121 psi (63 MPa)

Elbow to end dome weld stress: 9430 psi (65 MPa)

See Q1 Pipe Anchor Stress Analysis – T. Page, April 19, 2007

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Q3 End

D1 End

DFBX Piping Layout

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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

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Bus Duct Thrust Support Analysis (weld clamp)

Weld Clamp Stress Calculation DetailsMaterial: 304L stainless steelPeak thrust load: 20.1 kN (4510 lb) Weld size: 1.59 mm (1/16”) 2 sides of clampWeld 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: 0.55Net allowable stress: 63.3 MPa (9.19 ksi)

Weld stress exceeds allowable stress dictated by PV code but is still within material strength limits

Thrustsupport

Weldclamp

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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

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Q1/Q2, Q2/Q3 interconnectionsStability issue - Global stability (at the IC scale)

Cold mass and heat exchangerModifications

First global mode: 49.5 bars (Q1/Q2) 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

Stiff restrain on M4 bellows

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Q1/Q2, Q2/Q3 interconnectionsStability issue - Global stability

Pcr ~30bars

Pcr ~60bars

Guiding device to be installed on the end plate

LD

Q1

Aluminium plate

Interconnection support

EE, FF

bellows

bellows

Pcr ~50bars

Thermal shield extremity

Thermal shield: “Soft” boundary conditions

Pcr ~39.5bars

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Inner Triplet Review

Connection of cold masses to vacuum vesselsComposite 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.

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Handling and TransportMean(s) Container Restraints Data Recorder

US to CERN Truck / Boat / (Plane)

Q1/Q3 Fixation on transport Frame inside a metallic container 1 per side

ShockwatchAcceleration Recorders

Q2 Fixation on transport Frame inside a wooden box 1 per side

D1 Fixation on transport Frame inside a metallic container 1 per side

DFBX Fixation on transport Frame inside a wooden box Springs

181 ↔ storage

↔ Smi2Truck

Q1/Q3

 

1 per side

SchocklogsQ2 1 per side

D1 1 per side

DFBX covered truck  

Smi2 ↔ 181 ↔ storage

Truck

Q1/Q3

 

1 per side

SchocklogsQ2 1 per side

D1 1 per side

DFBX covered truck  

Installation Truck

Q1/Q3

 

1 on the non IP side

SchocklogsQ2

1 on the non IP side

D11 on the non IP side

DFBX covered truck  

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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.

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Repaired spider

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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

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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

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Cartouche / Cartridge

• Affixed at Q1 non-IP end; Q3 IP end

• Transfer load at all temperatures

• Limits support deflections

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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

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Q1 Cartridge Modeling

• Cartridge applied to Q1 model including bellows for:– Warm 25 bar

pressure test load– Cold– Cold, 20 bar

quench load

Figure 1. Finite Element Model of Q1 with Cartridge

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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

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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.

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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.

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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

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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

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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

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Tie rod assembly at warm fit-up

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C.Hauviller/TS-ICC. Garion

Q1/Q2, Q2/Q3 interconnectionsVacuum vessel closure

Vacuum longitudinal force:

Max 8000daN

Buckling force (per rod): 5770daN

Buckling force (per rod):1440daN

Is the guide length sufficient to avoid rotation?

Stiff guidance has probably to be implemented

Bellows buckling pressure: 3.7 bars4.8 mm thick

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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

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External jack stands in warm fit-up

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Inner Triplets Supports:fixation to the ground

– Different tunnel ground conditions:

Point 2 (RB24): platform made of concrete blocks and reinforced concrete slabs to continue the tunnel

slope

Point 1: Two holes of ~400mm diameter to fix the supports to the concrete underneath

Point 8 (RB86): reinforced concrete beam

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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

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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

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