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
S. WEISZ /TS-IC
1
LHC low-b triplet – warm assembly
27 avril 2007
S. WEISZ /TS-IC
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Completed cold mass and piping
on spider supports
27 avril 2007
S. WEISZ /TS-IC
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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.
S. WEISZ /TS-IC
LHC low-b triplet – DFBX
27 avril 2007
S. WEISZ /TS-IC
5
Q1 supports at IP 5L
27 avril 2007
S. WEISZ /TS-IC
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Cold Mass Support
• A ‘fixed’ and ‘free’ spider support
• Invar rod connecting the two to share
support
S. WEISZ /TS-IC
• 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
S. WEISZ /TS-IC
S. WEISZ /TS-IC
Review of the inner triplet
24-25 April 2007
Summary
C. Hauviller
27 avril 2007
S. WEISZ /TS-IC
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Fix Points
Internal heat
exchanger
D1
LBX
FP Cold MassVacuum Vessel
Q3
DFBX
Fixed Point TripletTunnel Floor
MQXA
Fixed Point
HX-Cold Mass
Q2B
Q2A
MQXB
MQXB
MQXB
Tie Rods Linking
Vacuum Vessels
External heat
exchanger (HX)
Q1
MQXA
Jacks (longitudinal)
38490
27 avril 2007
S. WEISZ /TS-IC
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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
27 avril 2007
S. WEISZ /TS-IC
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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
27 avril 2007
S. WEISZ /TS-IC
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Q1 pipe support weldment (Q3
similar)
14
27 avril 2007
S. WEISZ /TS-IC
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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)
27 avril 2007
S. WEISZ /TS-IC
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DFBX Piping Layout
D1 End
Q3 End
27 avril 2007
C.Hauviller/TS-IC
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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)
Weld
clamp
Allowable stress: 115 MPa (16.7 ksi)
Weld efficiency factor: 0.55
Net allowable stress: 63.3 MPa (9.19 ksi)
Weld stress exceeds allowable
stress dictated by PV code but is
still within material strength limits
27 avril 2007
Thrust
support
C.Hauviller/TS-IC
17
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
S. WEISZ /TS-IC
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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.
S. WEISZ /TS-IC
Repaired spider
27 avril 2007
S. WEISZ /TS-IC
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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
27 avril 2007
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Cartouche / Cartridge
• Affixed at Q1
non-IP end;
Q3 IP end
• Transfer load
at all
temperatures
• Limits
support
deflections
27 avril 2007
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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
27 avril 2007
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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
27 avril 2007
S. WEISZ /TS-IC
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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
27 avril 2007
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Tie rod assembly at warm fit-up
27 avril 2007
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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
WEISZ /TS-IC
C.S. Garion
27
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
S. WEISZ /TS-IC
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External jack stands in warm fitup
27 avril 2007
S. WEISZ /TS-IC
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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
S. WEISZ /TS-IC
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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
27 avril 2007
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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
S. WEISZ /TS-IC
32
Sectors 34 & 45
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Wait for IT to cool-down 45
Nov.
7/29/2017
Dec.
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Option B :
Do not wait IT repairs
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K. Foraz TS-IC-PL
.
S. WEISZ /TS-IC
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Option C:
Do not wait IT repairs for cooldown 45
& minimize QUI interventions
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