dfbx thermo-mechanical review joseph rasson, lbl tom peterson, fermilab cern 24 april 2007

DFBX Thermo-Mechanical Review

Joseph Rasson, LBL Tom Peterson, Fermilab

CERN24 April 2007

24 April 2007 DFBX 2

DFBX Presentation Outline

• Introduction• Documentation • Flow schematic• Line pressures• Mechanical Test Protocol• Piping and Interface Layouts• Mechanical Loads• Free body and force diagrams• Peak stresses• Transport• Conclusion• Future Activities


Introduction

• DFBX designed at LBNL and fabricated at Meyer Tool near Chicago Illinois

• Fabrication oversight performed by Fermilab• Present team consists of

– Joseph Rasson (LBL), project manager – Steve Virostek (LBL), engineer – Frederic Gicquel (LBL @ CERN), engineer – Tom Peterson (Fermilab), engineer – Phil Pfund (Fermilab), engineer


DFBX Documentation

• http://www-td.fnal.gov/LHC/Uslhc_accel_docs/Documents.html – Fabrication documentations for DFBX and LQX.

• http://sc-gs.web.cern.ch/sc-gs/gs_ms/TISUS/ – Safety related documentation submitted to CERN.

• http://tomato.fnal.gov/lhcirq/DFBXimages/IndexDFBX.html – Pictures of DFBX during fabrication at the vendor.

• http://www-eng.lbl.gov/~rasson/DFBX%20DWGS_APRIL_07/ – Drawings of the DFBX.

http://www-td.fnal.gov/LHC/Uslhc_accel_docs/Documents.html

http://sc-gs.web.cern.ch/sc-gs/gs_ms/TISUS/

http://tomato.fnal.gov/lhcirq/DFBXimages/IndexDFBX.html

http://www-eng.lbl.gov/~rasson/DFBX%20DWGS_APRIL_07/


Flow schematic

• The inner triplet cryogenic flow schematic was developed in close collaboration between– Rob Van Weelderen (CERN)– Jon Zbasnik (LBL)– Tom Peterson (Fermilab).

• The following are excerpts from the DFBX G/C and DFBX E flow schemes.


Overview of DFBX Flow Schemes

• 8 DFBX’s, 6 different types – QRL on wall side, so left and right at each location

differ in being “left handed” and “right handed”– Points 2 and 8 have the same configuration with cold

D1, so DFBX C is identical to G and DFBX D is identical to H.

– Points 1 and 5 differ from 2 and 8 in having warm D1 and differ from each other in having opposite slopes.


Flow schematic for IP8 left

Following slide shows the DFBXG detail


Helium vessel

DFBX-G lines with 20 bar design (the largest high-pressure lines)


Flow schematic for IP5 left

Following slide shows the DFBXE detail


DFBX-E lines with 20 bar design (the largest high-pressure lines)

Helium vessel


PressuresReference: LHC Project Note 135

Approx. operating pressure (bar absolute)

MAWP (design pressure, surrounded by vacuum) (bar abs)

Test pressure in vacuum (MAWP x 1.25) (bar abs)

Relief valve set pressure (bar abs)

Subatmospheric helium lines (XB, CY1, CY2)

0.016 4.0 5.0 4.0

Lines connecting to the helium vessel and current leads (CC’1, DH)

1.3 3.5 4.4 3.0

Pressurized superfluid lines (LD1, LD2, LD3, MQX1, MQX2, MBX1, MBX2)

1.3 20.0 25.0 20.0

Beam screen tubes (CC’2, CC’3)

3.6 20.0 25.0 20.0

Thermal shield lines (E!, E2, EX)

19 22.0 27.5 22.0

Vacuum vessel 0 1.2 bar abs surrounded by air

1.4 1.05


Mechanical Test Protocol

Tests at the manufacturer (Doc. M989A):• Cold shock all welds at least one cycle• Cold shock chimney bellows 25 cycles• Pressure test all components at set test pressure• Vacuum leak check all components• Final system pressure test and vacuum leak check• Measurements of all critical dimensions

Vacuum leak checks and measurement of critical dimensions were repeated at CERN after shipping:

See Doc LHC-DFBX-001-10-00


Q3 End

D1 End

DFBX Piping Layout


DFBX – Q3 Interface


Mechanical Loads

• Mechanical loads on the DFBX are Generated from:– Thermal contraction of spool pieces and magnets– Thrust load from bellows (positive and vacuum

pressures)– Internal pressure (positive and vacuum pressures)– Gravitational loads (weight)


Forces from Thermal Contractions

• Dominated by contraction of magnet ends away from DFBX – Q3 lines pull back 16.3 mm – D1 lines pull back ~20mm D1 fixed support at Center

• Internal DFBX components: Max thermal contractions is ~ 6 mm

• Design Approach:Neutralize mechanical forces generated from thermal contraction with the use of flex hoses


Design Approach for Thermal Contraction

Flex hoses to take up thermal contraction

and pipe misalignment

Pipes are installed such as flex hoses are preflexed half way when warm.

Flexhose moves +/- thermal contraction length

Welded ring to carry weight of pipe on G10 Spider Assy


Large diameter flex hose: 50.8 mm Dia

Welded ring to carry weight of pipe on G10 Spider Assy


Gravitational Loads

• Weight of most spool pieces is supported on G10 spiders in jumpers

• Spiders also provide mean to keep the pipes aligned during and after interconnection

• Weight of LHe vessel and bus ducts is transferred to vacuum vessel via 4- 19 mm invar rods (to be discussed later)


Double spiders in jumpers carry the weights of small pipesand guide/align pipes

6.4 mm mm thick G10 split Pipes

12.7 mm thick G10 plates


22.2 mm thick G10 plate

12.7 mm thick G10 plates

Non Load Bearing G10 Support SpidersD1 End

Bus duct SS support clampsand split rings

Beam pipeCenter support

Attached toLHe vessel

Q3 End


Thrust Loads in DFBX

• Limited to components with bellows at the ends for ease of interconnect and to allow for thermal contraction:

• XB: Q3-DFBX pumping line• MQX1: Q3-DFBX bus duct• MBX1: D1-DFBX bus duct• LD cross-over line inside the box whenever we

have cold D1 (4 boxes)


DFBX Thrust Loads

Si UnitsEnglish Units

LineD mean

(in)

Pres Design (bar)

F (lb)

XB 4.45 4 902

MQX1 4.45 20 4510

MBX1 3.16 20 2274

LD 2.54 20 1469

LineD mean (mm)

PreDesign(bar)

F (N)

XB 113.0 4 4012

MQX1 113.0 20 20062

MBX1 80.4 20 10116

LD 64.5 20 6536


Q3-XB Thrust: 4 KN

D1 20 mm Thermal contraction

XB Line with Flow Separator

Flex hose for thermal contraction

Flex hose for alignment


3 Gravity Vertical Supports

2 Thrust Supportsto vacuum vessel

XB Supports


XB without Flow Separator

2 Horizontal Thrust Supports

One gravitational support


Q3: 20 KN

LD: 6.5 KN

D1: 10.1 KN

Bus Duct Assembly: Thrust Load

Thrust Support Brackets


LHe Vessel Support


End view showing helium vessel axial supports and beam tube support


LHe Vessel Bottom Support to Vacuum Plate


DFBX-E 17 Feb 05


Free Body Diagrams

• General diagrams showing approximate magnitude of force

• More detailed analysis will be presented at the component level


635 mm (25.0 in)

767 mm (30.2 in)

16.7 kN (3750 lbf) x 2 (rods in tension)

Forces on DFBX-E due to pressure of 3.5 bar in the helium vessel plus gravity 66.8 kN (15000 lbf)



20.0 kN (4500 lbf)

10.0 kN (2250 lbf) x 2

635 mm (25.0 in)

767 mm (30.2 in)


3.0 kN (680 lbf) x 2 (rods in compression)

Forces on DFBX-E due to M1 line pressure of 20 bar plus gravity (no helium vessel pressure)

4.4 kN (1000 lbf)


20.0 kN (4500 lbf)

10.0 kN (2250 lbf) x 2

635 mm (25.0 in)

767 mm (30.2 in)


66.8 kN (15000 lbf) (Combined pressure and gravity)

Forces on DFBX-E due to 20 bar M1 line pressure plus 3.5 bar in the helium vessel



Forces on DFBX-C due to 20 bar M1 line pressure

plus 3.5 bar in the helium vessel

20.0 kN (4500 lbf)

5.0 kN (1110 lbf) x 2

635 mm (25.0 in)

767 mm (30.2 in)



10.1 kN ( 2280 lbf)

82.3 kN (18500 lbf) (Combined pressure and gravity)


635 mm (25.0 in)

767 mm (30.2 in)

Forces on DFBX-C due to 3.5 bar in the helium vessel 82.3 kN (18500 lbf)



DFBX Detailed Analysis

•Analysis assumptions and methodology

•He vessel supports - stress analysis

•Upper, vertical support rods and attachments•Lower, axial supports and attachments•He vessel cover plate weld – stress analysis

•Bus duct & thrust support – stress analysis

•XB line – load and stress analysis

•Vacuum Vessel Bumpers

Analysis Assumptions and Methodology

•Analyses assume worst case operating loads•3.5 bar absolute in helium vessel•20.1 kN (4510 lb) bus duct thrust load (20 bar)

•XB line thrust•4.0 kN (902 lb) thrust load (4 bar)•Possible added load from D1 line

•All components are assessed based on the material and weld allowable limits set forth by the ASME Pressure Vessel Code•Code limits are for guidance and not a hard requirement

Helium Vessel Support Loads

•Reaction loads are based on the results of the helium vessel FEA model runs

•A portion of the bus duct thrust load is reacted at the stack bellows due to their high lateral stiffness

•Vertical strut loads are affected by the moment from bus duct thrust load

•The worst case vertical support rod and axial support loads are used for all analyses•Peak axial support load: 8.7 kN (1962 lb)•Peak strut tensile load (Q3 side): 15.9 kN (3570 lb)•Peak strut tensile load (D1 side): 19.6 kN (4414 lb)•Peak strut compressive load: 3.03 kN (682 lb)

Pressure Vessel Code Stress Limits

•Material stress allowable limits from code•SS 304L: 115 MPa (16.7 ksi) tensile stress•SS 18-8: 130 MPa (18.8 ksi) tensile stress•Invar: 276 MPa (40 ksi) yield stress (not from code)

•PV code limits have built-in safety factors•S.F. ~2 on yield and >4 on ultimate stress

•For welds, efficiency factors are applied based on guidelines in PV code

•Tensile and shear stresses are combined using von Mises formulation

Lower He Vessel Axial Load Blocks (weld)

Calculation Details

Material: 304L stainless steel

Net axial load: 8.7 kN (1962 lb)

Weld size: 9.65 mm (0.38”)

Moment arm: 36 mm (1.4”)

Weld A: 1560 mm2 (2.42 in2)

Weld I: 4.40x105 mm4 (1.06 in4)

Tensile stress: 13.4 MPa (1.95 ksi)

Shear stress: 5.6 MPa (0.81 ksi)

Equivalent stress: 16.6 MPa (2.40 ksi)

Allowable stress: 115 MPa (16.7 ksi)

Weld efficiency factor: 0.55

Net allowable stress: 63.3 MPa (9.19 ksi)

Weld

Lower He Vessel Axial Load Blocks (mat’l)

Calculation Details




Block A: 2903 mm2 (4.50 in2)

Block I: 3.51x105 mm4 (0.84 in4)





Lower He Vessel Invar Rods and Nuts

Rod Calculation Details

Material: Invar ½” all thread


Rod stress area: 91.5 mm2 (0.142 in2)


Yield stress: 276 MPa (40 ksi)

Assume load is shared equally on both sides of 2-sided rodNut Calculation Details

Material: 18-8 stainless steel


Nut shear stress area: 211 mm2 (0.33 in2)

(based on load carried by 3 threads)



Both rods and nuts can carry the full load at one end of the rod if machining and assembly tolerances lead to unequal loading

Lower He Vessel Axial Stanchions

Calculation Details




Area: 1976 mm2 (3.06 in2)

Mom. area I: 3.25x105 mm4 (0.78 in4)

Bending stress: 28.4 MPa (4.12 ksi)

Shear stress: 2.2 MPa (320 psi)



One stanchion can carry the full load if machining and assembly tolerances lead to unequal loading

Peak Stress

Lower He Vessel Axial Stanchion Bolts

Bolt Stress Calculation Details


Bolt size: M16-1

Assume tensile and shear carried by 1 bolt

Axial force due to moment: 4.7 kN (1065 lb)

Stress area: 175 mm2 (0.27 in2)





Thread Engagement Details

Bolt length: 45 mm

Stanchion thickness: 25.4 mm

G-10 shim thickness: 3.3 mm

Washer thickness: 3.0 mm

Net thread engagement: 13.3 mm

No. engaged threads: 13

Minimum threads required: 3 to 5

One bolt in one stanchion can carry the full load if machining and assembly tolerances lead to unequal loading

Lower He Vessel Axial Stanchion Friction

Calculation Details


Bolt size: M16-1

Stress area: 175 mm2 (0.27 in2)


Bolt load: 24.1 kN (5420 lb) @ 50% yield

Force per stanchion: 48.2 kN (10.8 k-lb)

Coefficient of friction: 0.4 (G-10/SS)

Static friction force: 19.3 kN (4336 lb)

Axial stanchion force: 4.4 kN (981 lb)

•Friction force is sufficient to prevent slipping, even if the full force on one side acts on a single stanchion

•If slipping occurs due to low bolt torque, motion is limited to 0.75 mm radial clearance on bolt holes

•Stanchions, bolts and rods can handle full force on one side

He Vessel Clevises for Vertical Struts (weld)

Calculation Details


Maximum strut load: 19.6 kN (4414 lb)

Weld size: 12.7 mm (0.50”)

Moment arm: 59 mm (2.31”) (longer clevis)

Weld A: 1866 mm2 (2.89 in2)

Weld I: 10.4x105 mm4 (2.50 in4)







Weld

He Vessel Clevises for Vertical Struts (mat’l)

Analysis Parameters




Shear Pullout Calculation Details

Shear pullout area: 317 mm2 (0.49 in2)

(load spread over 4 areas at each clevis)



Clevis Bending Stress Calculation

Moment arm: 24 mm (0.94”) (at base of rod end cut-out)

Area: 1288 mm2 (2.00 in2)

Mom area I: 1.76x105 mm4 (0.43 in4)



Equivalent stress: 80.6 MPa (11.7 ksi) (load shared over 2 clevis sides)

Clevis Pin Calculation Details

Pin diameter: 19.1 mm (0.75 in)

Pin area: 285 mm2 (0.442 in2)



He Vessel Vertical Support Struts

TensionIn Strut

Strut Body Stress Calculation Details

Material: Invar

End thread size: ¾”-16 UNF

Peak axial force: 26.7 kN (6005 lb)

Thread stress area: 241 mm2 (0.373 in2)



Strut Buckling Analysis

Material: Invar

Modulus: 141 GPa (20.5 Mpsi)

Rod diameter: 19.1 mm (0.75”)

Mom. area I: 0.647x105 mm4 (0.016 in4)

Rod length: 760 mm (29.1”) (pinned ends)

Peak compressive force: 3.03 kN (682 lb)

Critical load: 15.6 kN (3513 lb)

Strut Rod Ends

Rod end: Aurora ¾” S-12

Peak load: 19.6 kN (4414 lb)

Allowable load: 32.7 kN (7364 lb)

He Vessel Top Plate Support (horiz wall weld)

L-bracket Weld Calculation Details



Weld size: 6.35 mm (0.25”)

Block depth: 64 mm (2.5”)

Block width: 38 mm (1.5”)

Moment arm: 19.1 mm (0.75”)

Weld A: 912 mm2 (1.41 in2)

Weld I: 5.36x105 mm4 (1.29 in4)







Vessel Top Plate Support (horiz wall bracket)

Added Clevis Weld Calculation DetailsMaterial: 304L stainless steelMaximum strut load: 19.6 kN (4414 lb) Weld size: 6.35 mm (0.25”)Weld length: 38 mm (1.5”)# of welds per support: 4Weld area: 684 mm2 (1.06 in2) totalShear stress: 28.7 MPa (4.16 ksi)Equivalent stress: 49.7 MPa (7.21 ksi)

Allowable stress: 115 MPa (16.7 ksi)Weld efficiency factor: 0.55Net allowable stress: 63.3 MPa (9.19 ksi)

Addedclevis

WeldsBolt

Clevis Shear Pullout Calculation DetailsShear pullout area: 242 mm2 (0.375 in2)Shear stress: 27.6 MPa (4.00 ksi) (load spread over 4 areas at each clevis)

Equivalent stress: 35.1MPa (5.10 ksi)

He Vessel Top Plate Support (vertical wall)

Boss Weld Stress Calculation DetailsMaterial: 304L stainless steelMaximum strut load: 15.9 kN (3570 lb) Weld size: 12.7 mm (0.50”)Moment arm: 64 mm (2.50”) w/adapterWeld A: 1328 mm2 (2.06 in2)Weld I: 3.81x105 mm4 (0.916 in4)Tensile stress: 50.4 MPa (7.31 ksi)Shear stress: 12.0 MPa (1.73 ksi)Equivalent stress: 54.5 MPa (7.90 ksi)


Clevis Shear PulloutSame shear area as horizontal wall support with a lower load

Helium Vessel Cover Plate Weld Analysis

• Vessel cover plate is welded to frame using a single, continuous external fillet weld

• Allows for cover removal by grinding if access is needed

• This weld type is an exception to ASME pressure vessel code

• A 2D finite element model predicts the actual weld stresses to allow exception to code

• Allowable stress is exceeded only in very small zone at the root of the weld (root stress < yield stress)

Vessel frame

Cover

Weld


Bus Duct Thrust Support

Weld Clamp

Thrust Support Plate Welded to LHe Vessel

Thrust Load


Bus duct thrust support

“Weld Clamp”

Support Bracket

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)


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

Thrustsupport

Weldclamp

Bus Duct Thrust Support (thrust plate weld)

Thrust Plate Weld Stress CalculationMaterial: 304L stainless steelPeak thrust load: 20.1 kN (4510 lb) Weld size: 6.35 mm (1/4”)Weld area: 940 mm2 (1.46 in2)Weld mom. Area I: 1.61x105 mm4 (0.388 in4)Equivalent stress: 106 MPa (15.4 ksi)


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

Thrustplate

Q3 Side - Bus Duct Thrust Support (thrust plate bending)

Plate stress exceeds material strength limits – thrust support plate needs reinforcement

Thrustplate

Thrust Plate Bending Stress Calculation


Peak axial load: 20.1 kN (4510 lb)

Plate thickness: 12.7 mm (0.5”)


Area: 1787 mm2 (2.77 in2)

Mom area I: 2.40x104 mm4 (0.058 in4)

Bending stress: 304 MPa (44.0 ksi)


Equivalent stress: 304 MPa (44.1 ksi)

Allowable stress: 115 MPa (16.7 ksi) Weld Clamp Ear Stress Results

Equivalent stress: 127 MPa (18.4 ksi)*

Thrust Plate Ear Stress Results

Equivalent stress: 146 MPa (21.2 ksi)*

* Both exceed PV code but are < yield

Ears

Bus Duct Thrust Support (D1 side)

Thrustplate

Thrust Plate Bending Stress Calculation





Area: 1787 mm2 (2.77 in2)

Mom area I: 2.40x104 mm4 (0.058 in4)





Material stress exceeds allowable stress dictated by PV code but is well within material strength limits

Short, doublePlate design

XB Line/Surge Tank Load Analysis

4.0 kN

4.0 kN.44 kN

3.4 kN

.80 kN3.4 kN

.65 kN1.0 kN

.65 kN1.0 kN• XB pipe and surge tank uses 3

vertical and 2 horizontal stainless rods to resist thrust loading

• A simple FEA model using beam elements was used to determine the support reaction forces

• Loads: XB bellows thrust (4.0 kN), D1 line force (0.44 kN), gravity and thermal contraction

• Assume that rods do not support large moments due to pivoting at ends and localized yielding (i.e. forces in rods are essentially axial)

XB Line/Surge Tank Stress Analysis

3.4 kN (worst caseaxial rod load)

1.0 kN

1.0 kN

Worst case verticaltab weld load

.80 kNHorizontal supp’tweld load

Axial Support Rods





Surge tank brackets


Weld size: 2.8 mm (0.11”)

Peak vertical load: 1.0 kN (233 lb)


Peak horizontal load: 0.80 kN (179 lb)





XB Line/Surge Tank Stress Analysis

3.4 kN

3.4 kN (worst caseaxial rod load)

Bending stress onforked bracket

Forked Bracket Bending Stress Calculation





Area: 403 mm2 (0.625 in2)

Mom area I: 5.42x103 mm4 (0.013 in4)





Material stress exceeds allowable stress dictated by PV code but is well within material strength limits

XB Line (w/o surge tank) Load Analysis

4.0 kN

2.0 kN

2.0 kN0.2 kN

• XB pipe (w/o tank) uses 1 vertical and 2 horizontal rods to resist thrust loading

• Load centered on the 2 horizontal supp’ts• Rod loading less than case with surge tank

Circular Plate Bending Stress Calculation


Support load: 2.2 kN (501 lb)



Area: 1089 mm2 (1.69 in2)

Mom area I: 8.23x103 mm4 (0.020 in4)





Circularthrustplate

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


Bumpers

Hilti anchors HSL M24/60Allowable working load in Tension 9860lb (43.8kN)Allowable working load in shear 17950lb (79.8kN)

Stand offs rated at 20000lb each

9770lb(43.5kN)

Worst case scenario: -Warm D1 -jacks on IT fully react load-jacks on DFBX do not react load

=> full vacuum load 19540lb (87kN) on 2 bumpers

Prying force (spread on 2 anchors):F=13/10*9770=12701lb (56.5kN)

=> 6350lb per anchor

Shear force (spread on 4 anchors):F=9770lb (43.5kN)

=> 2442.5lb per anchor

Prying force

Pivot point

13”

10”


Bumper FEA model

Local Max stresses at 136 MPaYield at 190Mpa


DFBX Shipping

Boxes C & G at CERN.One of two shock recorder mounted on frame is shown in insert. Another is mounted on the other side and two are mounted on the top plate of each DFBX.

Boxes C being placed in base of shipping frame. Shock recorders have been mounted on each side of frame (one visible on this side). Two more are mounted on the top plate of DFBX.

The DFBX were shipped in pairs, each in its own three-piece shipping frame


DFBX Summary• Detailed analyses were performed during design phase

based CERN requirements• Continued oversight during the fabrication phase to insure

that specifications were met• 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– FNAL organized two peer reviews


DFBX Conclusion• The analysis confirmed that the bus duct thrust

support is marginal– “Weld Clamp” was not welded– Support bracket is too thin

• Review and analysis of other components of the box revealed additional that should be upgraded– Eliminate LHe vessel vertical rods linkage dependence

on friction generated by bolt tightness


Future Activities• Continue reviewing and analyzing key aspect of

DFBX as built• Design and implement improved bust duct

support• Perform simulated thrust load tests• Review of all cooldown and warmup conditions to

look for potential interferences