SCH Controls Readiness Review – Cold Mass Iain Dixon November 4, 2015.

SCH Controls Readiness Review – Cold Mass

Iain DixonNovember 4, 2015

2

Overview

• Cold mass design description• Structural design criteria,

metallic components– Stress summary– CICC quality controls

• Structural design criteria, insulation components– Major electrical quality control

measurements• Manufacturing procedures• Risk assessment & CreADo

3

Cold Mass Design

• Cold Mass: Winding pack and components associated with the coil at 4 K• Major components

– CICC Coil– Insulation – Magnet frame – Lead anchor and splice ties– Lead supports– Terminal and splice joints– Plumbing circuit– Voltage isolators

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Structural Design Criteria, Metallic Components

• The structural design criteria is adopted from the Fusion Ignition Research Experiment (FIRE)• Static

– The design limits are a function of the material’s yield or ultimate strength, Sm

• Sm = the lesser of 2/3 sy or (1/3 su, welded, 1/2 su, non-welded)

– Usage factor • For normal conditions (full field, power supply trips), k = 1.0• For anticipated conditions (quench), k = 1.1• For unlikely conditions (insert shorts), k = 1.2• For extremely unlikely conditions, k = 1.35

• Fatigue– The stress condition is compared to SN curves

• A safety factor of 2 on stress and 20 on lifetime is applied– FCGR is used to determine the minimum detectable flaw size

Stress CategoryStress Intensity

Limits

General primary membrane k Sm

Local primary membrane 1.5 k Sm

Primary Membrane (general or local) plus bending 1.5 k Sm

Primary plus secondary 3 Sm

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Static Stress Summary

• Ratio of Maximum Stress to Design Stress Intensity for Metallic Components

Operating Condition MembraneMembrane +

BendingPrimary + Secondary

Normal, Static 0.96 0.64 0.35

Quench 0.95 0.74 0.41

Fault 0.83 0.87 0.54

Loss of Vacuum 0.87 0.58 0.32

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Fatigue Stress Summary

Fatigue Test Results at 4.2 K of Welds in Comparison to Base and 45 T Hybrid 316LN (mod.)

0

200

400

600

800

1000

1200

1400

1600

1000 10000 100000 1000000Cycles to Failure

Cy

clic

Str

es

s, M

Pa

Ref 316LN BaseRef 316LN Butt WeldSCH HF Base SCH Weld 12SCH Weld 13SCH Weld 5

2 x Operating Stress= 736 MPa

20 x Service Life= 400,000 cycles

Service Life = 20000 cyclesOperating Stress = 368 MPa

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Fatigue Stress Summary

• Using Linear Elastic Fracture Mechanics an allowable flaw size is set based on the lifetime of the component

• From the Paris Law, a majority of the crack propagation behaves in a linear manner on a log-log plot and can be described as

da/dn = CKm

• With an initial flaw size of a, it will take n cycles to propagate a crack through the conduit wall

• An important requirement dictated by the FIRE Code is that one must detect a flaw size half of the initial (or allowable) flaw size. This detectable flaw size is the minimum requirement for the x-ray inspection that will be performed.

• For the SCH the allowable flaw size is a = 0.206 mm. This results in a minimum detectable flaw size of 0.10 mm.

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CICC Quality Controls - Conduit

• Fabricated by Salzgitter-Mannesmann Stainless Tubes (SMST)• Quality Control Parameters

– Tube Length– Dimensions– Chemistry– Mechanical Properties– Porosity and Inclusions– Grain Size– Precipitate Carbides– Surface Finish

• The vendor and NHMFL conducted the quality control measurements

• NHMFL contracted out three independent companies for verification measurements of the chemistry

MF Conduit at SMST During QC Checks

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CICC Quality Controls - Jacketing

• Jacketing performed at Criotec Impianti, Italy• For each tube size, an optimal weld schedule was developed with the objective of

high ductility and fatigue strength at low temperature and after aging in a similar style as the superconductor heat treatment.

• Weld qualification tests consisted of physical property measurements at 4.2 K of aged samples measuring ultimate and yield strengths, fatigue life

• Three inspections were performed after welding of each conduit1. A plug with a diameter 0.2 mm less than the average tube inner diameter was

passed across the weld region to check for potential obstructions with the cable during insertion.

2. A visual inspection outside and inside using a high resolution borescope were made.

3. Digital x-ray images were taken for detection of small internal and surface flaws (0.08 mm resolution).

• All welding/inspection was monitored by FSU or HZB personnel • A weld rejection level of 14% was obtained• A helium leak check on the fabricated CICC was performed on each piece-length

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CICC Quality Controls & Inspection

Borescope Images of Welds with Full and Lack of Penetration

Weld and x-ray stations (above) and example image (below)

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Structural Design Criteria, Insulating Components• Compressive stress < 2/3 ultimate strength at temperature• At the interface of the conduit and insulation

– no primary tensile strain is allowed– secondary strain < 1/5 of the ultimate tensile strain

• In-plane tensile strain < ±0.5%• The shear / compressive stress at the interface between the conduit and insulation

< 2/3 of the shear/compression limit curve• Evaluation is performed on the insulation for each conductor turn

Shear/Compression Properties of Flexibilized DGEBA and S-2 Glass

0

50

100

150

200

250

300

0 200 400 600 800 1000 1200 1400

Compressive Stress (MPa)

Sh

ea

r S

tre

ss (

MP

a)

2/3 Stress Limits

Stress Limits

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Structural Design Criteria, Insulating Components

Location of Maximum Integrated nLocation of

Maximum Peak n

Operating Condition

Compressive Stress

Compressive/Shear Stress

Primary Tensile Strain

Secondary Tensile Strain

In-plane Strain

Normal, Static 0.14 0.48 None None 0.37

Quench 0.13 0.49 None None 0.36

Fault 0.37 0.60 None 0.01

Ratio of Maximum Stress or Strain to Design Limit for Insulating Components

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Major Electrical QC Measurements

• Impedance Spectrum– Performed after winding each layer– After heat treatment– After VPI– After surge test

• Paschen Test– Tests the ground plane insulation– Coil with voltage isolators attached, 4.0 kV– Fully assembled coil in cryostat, 3.5 kV

• Surge Test– Checks for internal shorts/weak insulation– Performed after VPI– 3 kV pulse across leads

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Major Electrical QC Measurements

• Impedance Spectrum– Performed after winding each layer– After heat treatment– After VPI– After surge test

• Paschen Test– Tests the ground plane insulation– Coil with voltage isolators attached, 4.0 kV– Fully assembled coil in cryostat, 3.5 kV

• Surge Test– Checks for internal shorts/weak insulation– Performed after VPI– 3 kV pulse across leads

Final resistances of 0.8 G at 2.5 kV and 0.5 G at 4 kV were achieved

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Major Electrical QC Measurements

• Impedance Spectrum– Performed after winding each layer– After heat treatment– After VPI– After surge test

• Paschen Test– Tests the ground plane insulation– Coil with voltage isolators attached, 4.0 kV– Fully assembled coil in cryostat, 3.5 kV

• Surge Test– Checks for internal shorts/weak insulation– Performed after VPI– 3 kV pulse across leads

Voltage Isolator Requirements, QC’s

• Requirements– Voltage: 3 kV– Pressure:

• 15 bar (room temperature)• 18 bar (4 K)

• QC Measurements– Performed on all components

• Five thermal cycles• Pressure tests: 22 bar @ 77 K, 15 bar @ RT• Cold and warm leak tests

Voltage isolators welded to test rig

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Manufacturing Procedures

• Travelers and work procedures are used in most of the fabrication tasks• Travelers include sign-offs and required inspections• Work procedures are continually updated for quality improvement

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Manufacturing Procedures

Risk Assessment, Equipment

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Equipment

Event Likelihood Consequence Risk

CICC Failure Very Unlikely Severe Medium

Quench Possible Minor Low Med

Unprotected Quench, Low Energy Possible Minor Low Med

Unprotected Quench, High Energy Very Unlikely Severe Medium

Plumbing/Isolator Rupture Unlikely Significant Medium

Short to Cryostat Very Unlikely Severe Medium

Offset from Insert Short Possible Minor Low Med

Risk Assessment, Personnel

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Personnel Hazards Present Controls

Event Likelihood Consequence Risk

CICC Failure Very Unlikely Negligible Low High voltage, cryogens Engineering design, contained in cryostat, venting, restricted access, electrical isolation

Quench Possible Negligible Low High voltage , cryogens Venting, restriced access, isolation, quench protection

Unprotected Quench, Low Energy Possible Negligible Low Moderate voltage Restricted access, electrical isolation

Unprotected Quench, High Energy Very Unlikely Negligible Low High voltage, cryogens Restricted access, electrical isolation, venting

Plumbing/Isolator Rupture Unlikely Negligible Low Cryogens Cryostat containment, venting, verification tests of every isolator

Short to Cryostat Very Unlikely Negligible Low High voltage Restricted access, electrical isolation, Paschen testing, grounding

Offset from Insert Short Possible Negligible Low Large forces Design criteria, contained in cryostat

CrEADo

CONDITION SIGNALINTERLOCK

WARN

OPERATOR CONTROL,

Can be aborted

Pause

Slow Ramp

Down, 50 A/s

"FAST RAMP

TO ZERO",

20 S Ramp Down

INHIBIT GATING

10 Second Rampdown

(when Breakers

Open)

OPEN BREAKERS2 Seconds

MONITOR

Outsert QuenchVoltage Taps differ

from neighbors, >100 mV for 100 ms

              MPS MPS

Outsert Quench - 2

Co-Wound Coil shows difference to magnet voltage > 200 mV for

100 ms

              MPS MPS

Joint QuenchJoint voltage > 20 mV

for 50 ms              MPS MPS

SC bus quench V > 20 mV for 50 ms               MPS MPS

Thank You!

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