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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)
2
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
3
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.
7
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)
9
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)
10
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.
11
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.
12
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.
14
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
17
3. N2 circuit, Safety valves: SP=0.5 barg Burst disks: SP=2.0 barg
18
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
20
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
21
* 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
22
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)
25
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.
26
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
27
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.
28