Readiness Review of SCH

Cryogenic System

Hongyu BaiNov. 4, 2015

National High Magnetic Field Laboratory

1

Outlines

1. Status of Cryogenic System

2. Critical Events and Actions Document (CrEADo)

3. Safety in the cryogenic system

Cryogenic Controls (interlocks) and test, cooldown (By M. Barrios)

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He storage tanks

750 W Coldbox

Central Distribution Box

SCHMagnet

Recovery compressors

Main compressor

LN2 Tank

Purifiers

LHe Dewar

45 T Magnet

Cell 16 Magnet

80 KColdbox

Gas bags

Status of the cryogenic system

45 T Supply Cryostat

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4

Unloaded mode (Low pressure): Extra refrigeration: ~ 250 W (4.5 K)Loaded mode (Full pressure): Extra refrigeration capacity: ~ 600W (4.5 K)

Capacity testP=13 barI=8 kA

Pressure=10 barI=0 A

Heater power

LHe level

Refrigeration capacity test with 45T hybrid (03/13/2014)

5

Liquefaction rate with 45T hybrid

~ 120 liter/hr in the 3000 L dewar.

LHe level in 3000L dewar

6

SCH Cryostat Cold Test (Dec. 10, 2014)

The system was tested successfully with a dummy load of 500 W, with an inlet temperature of ~ 4.7 K in the cryostat. The cryogenic valves and flow meters worked properly.

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CONDITION SIGNALINTERL

OCKWAR

NPause ramp

Slow ramp down (500s)

"FAST RAMP down” (20 s)

MONITOR

COMMENTS

Controller, computer, UPSDCS power failure (FCS103)

             DCS will go down. All controls will default to the fail position.

One of the UPS or the house PS fails (FGPA power)

              Dual power supplies provide redundancy.

DCS processor failure              

The DCS Field Control Station processor has dual - redundant power supplies and processors. If one fails, the other will take over without delay

OPS server for temperature

    X      OPC

server & DCS

Two types of failure detection: One that looks for a watchdog switching on the OPC server, and a second that looks for no change in values that could indicate a crycon failure

DCS restart          If DCS has an unplanned restart (once in 20 years), the magnets would trip because the magnet cooling water would stop.

FPGA restart         X     will go to fail position

Critical Events and Actions Document (CrEADo) - Cryogenics

8DCS: for the control of cryogenic system; OPS server: for temperature data communicationFPGA: for the control of active venting valves

CONDITION SIGNALINTERLOCK

WARN

Pause ramp

Slow ramp down (500s)

"FAST RAMP down” (20 s)

MONITOR

COMMENTS

SCH cryostat and magnet

Vacuum in SCH cryostat

Relay from vacuum gauge setpoint

  X   X   DCS operator decision, Cryo beeper, audible alarm

Excessive temperature difference during cooldown

ABS(aver. Tout - aver. Tin) > 40 K

  X       DCSCryo Beeper: Too big temperature difference during cooldown!

Excessive temperature difference during cooldown

ABS(aver. Tout - aver. Tin) > 50 K

X X       DCSCryo Beeper: Too big temperature difference during cooldown! The cooldown will be shut down.

High inlet temperatureInlet temp. > 6.0 K

  X X     DCS Cryo Beeper: high inlet temperature!

High outlet temperature

> 8.0 K   X       DCS Operator decision

Shield temperature high

> 95 K   X       DCS Operator decision

High inlet pressure in SCH after cooldown

> 6 bara X X       FPGA FPGA opens the valves for venting & close valves for isolating. May be switched to quench signal if it does not work fast enough.

High outlet pressure in SCH after cooldown

> 5 bara X X       FPGA

Coil mass flow low < 3 g/s each   X       DCS Operator decisionBusline outlet temperaure High

Inlet Temp. > 7 K

  X       DCS Operator decision

Low LN2 level in SCH < 20%   X       DCS Operator decisionHigh LN2 level in SCH >90%   X        DCS Operator decisionLow N2 gas flow of CL < 0.5 g/s   X       DCS Operator decisionHigh return temp. of CL> 320 K   X       DCS Operator decision

Critical Events and Actions Document (CrEADo)

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CONDITION SIGNALINTERLOCK

WARN

Pause ramp

Slow ramp down (500s)

"FAST RAMP down” (20 s)

MONITOR

COMMENTS

CDB and transfer line

Bad vacuum in CDBvacuum transducer

  X       DCSoperator decision, Cryo beeper, audible alarm. Bad vacuum will cause temperature rise and finally quench the outsert

bad vacuum in transfer line

vacuum gauge   -       - Operator decision

Low LHe level in CDB < 40%   X  X     DCS Operator decision, stop ramping upLow LHe level in CDB [1]

< 30%   X X     DCS Operator decision

High pressure in CDB buffer

> 1.4 bara   X       DCS Operator decision

High pressure in CDB buffer

> 1.7 bara X X     X DCSDCS closes all return valves from SCH and 45T hybrid, Refrigerator stops

High supply pressure in CDB

> 13 bara X X       DCSOpen CV708, close CV702, CV705, CV712, CV703, CV707

High return pressure in CDB

> 12 bara X X       DCSOpen CV709, close CV702, CV705, CV712, CV703, CV707

Helium refrigeratorColdbox stops PLC signal   X     X DCS operator decision, Cryo BeeperMain compressor stops PLC signal   X     X DCS operator decision, Cryo BeeperInstrument airair pressure low gauge   -       - operator decision

Between 45T magnet and SCH

45T quenchesQuench detection

  X        May cause LHe buffer pressure high and shut down LR280. If the pressure is too high, the other magnet will be discharged as the set ramping rate.

SCH quenchesQuench detection

  X        

Critical Events and Actions Document (CrEADo)

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Cryogenic hazards fall into these general categories:

• Cold burns (frostbite): low temperatureAll the cold pipes or vessels are insulated.The safety issue on the user platform: Cantrell’s talk.

• Oxygen deficiency hazard (ODH): Kynoch’s talk.

• High Pressure: Special attention is paid for the venting in the event of quenches. This talk is mainly on the cryogenics for the SCH.

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Loca-

tion

Equipment P-max

( barg )

P-min

(barg)

T-max

(K)

T – low

(K)

Voltage*

max (V)

He

(Nm3)

N2

(Nm3)

[1] Compressor & ORS

15 0 373 283 480 15 0

[2]

Coldbox and PLC cabinet

15 -1 343 4.2 480 15 13

CDB and 80K CBX

15 -1 300 4.2 120 380 7

LHe dewars 0.7 -1 300 4.2 / 4000 0

[2] [3] Transfer lines 15 -1 300 4.2 0 15 7

[3]

SCH Magnet ~ 100* -1 300 4.2 2 k 80 0

Cryostat vessel 0.5 -1 300 4.2 / / 20

Shield 15 -1 300 77 / / 15

[1,2,3,5] DCS Control cabinets

/ / 313 273 120 / /

Outside LN2 vessel 5 - 1 300 77 / / 6400

Outside He gas vessels 16 0 310 260 / 7000 /

Cryogenic System

[1] Compressor room; [2] Cell 16; [3] Cell 14; [5] Mezzanine * Safety on electricity is not covered in this presentation.

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From Iain Dixon, “SCH Outsert design for HZB”, 200913

Helium pressure venting:

Pressure rise is caused by warm up of low temperature gas or boil-off of cryogenic liquid. The reasons include: -Vacuum break in the coldbox, CDB, transfer line jacket, and cryostat jacket-PS trip-Open breakers-Quench

Pressure venting device for SCH: -Actively controlled valves: fast reaction-Safety valves (Passive)-Burst disks (Passive): Burst disks will act as the final protection and they acts extremely fast than spring loaded valves.

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To prevent overpressure in the cryogenic equipment (pipes, vessels, heat exchangers, flanges, valves) and in the magnet (CICC, insulation breakers).

SectionCryostat CDB

Inlet of outsertOutlet

SCH supply

SCH return

LHe buffer

Layer 1-4

Layer 5-10

Layer 11-18

Safety valves 15 bargDN25

15 bargDN25

15 bargDN25

10 bargDN25

15 bargDN15

/ 2 bargDN25

Burst disks 20.5 bargDN50

20.5 barg

DN50

20.5 bargDN50

20.5 barg

DN50

/ / 3 bargDN40

Active controlled

valves

DN20 DN20 DN20 DN25 DN15 DN25 /

Pipe 23.4 mm

23.4 mm 23.4 mm 30 mm 23.4 mm 30 mm 40 mm

Pressure venting for SCH

The flow paths are shown in the following figures.

• The helium safety valves are supplied by Anderson Greenwood Valves.  The nitrogen relief valve is supplied by Cash Valves. 

• The burst disks are from BS&B Safety Systems. 15

1. Active venting valves: CV771, CV772, CV773, CV775. The open of the two valves is based on the coil inlet pressure and outlet pressure.

SCH cryostat PID 16

2. Safety valves: SP=15 barg Burst disks: SP=20.5 barg

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3. N2 circuit, Safety valves: SP=0.5 barg Burst disks: SP=2.0 barg

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4. Pressure venting in CDBFor supply line of SCHFor return line of SCH

Central Distribution Box PID 19

5. Pressure venting of LHe buffer in CDB Safety valve SP=2 barg

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No. Mode Expected maximum loads

Venting via

1 Protected Quench About 350 g/s at 27 K Active venting valve

or safety valve2 Loss of insulating

vacuum6 kW/m2 Safety valve or burst

disk3 Loss of insulating

vacuum and a protected quench

6 kW/m2 and maximum Joule heating of 180 kW

Safety valve or burst disk

4 Unprotected quench

About 1.23 kg/s at 137 K Burst disk

Pressure relief for different failure modes

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* Based on ASME Boiler and Pressure Vessel Code VIII and API recommended practice 520

Sizing of relief valves and burst disks

Size of venting valves:DN20, DN25

Size of safety valves:DN25

Size of Burst disks:DN50

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Pressure loss on the inlet pipe of safety valves (burst disks)

Safety valve ID of pipe

(mm)

Length of pipe

Inlet pressure loss (bar)

SV775 30 2 m <0.5 bar

SV771

At full flow

23.4 2 m <0.5 bar

SV772

At full flow

23.4 2 m <0.5 bar

SV773

At full flow

23.4 2 m <0.5 bar

Cryogenic isolators were tested at 15 bar at RT and 40 bar at 4 K, from “ Ceramic Voltage Isolator Test Summary NHMFL-MST-11-EM-949-002”.

23The solenoid valves for the active-venting valves are tested in magnetic field.

Check valve

Compare with pressure venting of HZB SCH

• The figures shows the pressure rise in the event of open-breakers at different current of HZB SCH.

• The active quench venting valve has to be opened quickly in the event of quenches to prevent opening of burst disks.

• The active control valves were opened when there is a “breaker opening” for HZB SCH. For NHMFL, we plan to use “pressure signals”.

• The size of the inlet pipes of safety valves is larger in TLH than in BER. (23.4 vs. 15.7 mm ID)

• Three active venting valves at the inlet (3 in TLH vs. 2 in BER)

• Back pressure downstream the control venting valves is lower in TLH than in BER. 24

Node Description: Magnet inlet

No. Guide Words Possible causes Consequences Safeguards Recommendations

1 General

2 Loss of Containment

Leakage of valves or pipes

Pressure loss during standstillHelium loss to vacuumHelium loss to ambient

Pressure, Vacuum measurementPressure and leak test of components

Check by operator

3 High flow n.a.

4 Low flow Valves closedBlockage of CICC

Not sufficient flow and Temperature risesQuench of magnet

Flow metersTemperature sensors

5 Zero flow/Empty

See above See above See above

6 Misdirected or reverse flow

Power supply trip or quench

Pressure increase at the inlet

Press. MeasurementQuench venting valvesSafety valves

Check during commissioning

HAZOP (Hazard and Operability Study)

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7 High Level n.a.

8 Low Level n.a.

9 High Pressure Power supply trip or quench

Pressure increase Press. measurementQuench venting valvesSafety valvesBurst disks

Check pressure at different current during commissioning

10 Low Pressure Evacuation of system Leaks

Pressure measurement

11 High Temperature

Low level in the LHe bufferBad vacuum

Magnet quench Temp./vacuum measurementQuench protection

12 Low Temperature

n.a.

13 Impurities Insufficient purging

Suction of air

Block of valve or pipe

Operation manual, training of personnel

14 Wrong media n.a.

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15 Mechanical vibrations

16 Failure of instruments

Inspection by operators

17 Utility Loss Loss of instrument airPower failure

Valves to their fail positionFailure of instruments

System shut off

18 Corrosion/Erosion

n.a.

19 Incomplete or improper start-up

Interlocks,

Training

20 Incomplete or improper Shutdown

Training

21 Inadequate personal safety

Follow safety rules

22 Inadequate of improper maintenance

Follow safety rules

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Summary

1. The cryogenic system has been installed and commissioned, showed a good reliability and efficiency in the past years.

2. The cryogenic system was connected to the 45 T hybrid and has been operated with the 45 T hybrid for ~ 2 years.

3. The tests with the 45 T hybrid and the SCH cryostat showed that the cryogenic system can provide sufficient refrigeration capacity, and required temperature, pressure and mass flow for the cooling of SCH.

4. HAZOP analysis was performed on the helium refrigerator and distribution system and was reviewed before.

5. Pressure venting in the event of quenches or open-breakers has been analyzed and designed. Based on the test results of the HZB SCH, the safety venting is adequate and the capacity is sufficient.

6. CrEAdo has been created for the SCH cryogenic system and will be implemented in the cryogenic controls.

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