1. Cryogenics – The Basics
Lesson 4
Torus 4K Operation and Recovery
D. Kashy

2. Lesson 4 - Topics Supply from ESR
Main Compressors
Cold Box
Valve Box
Hall B Distribution can for Helium Supply
Torus flow paths and controls
4K Supercritical Gas
Liquid Helium and Cold return
Lead flow
Back pressure control
Return gas to ESR
Off normal operation
ESR shutdown
Quench or Fast Dump of Torus
What to look for if called in and what to do next
Questions

3. Special NOTES
The slides in this presentation are a snapshot in time. They give general principles of operation.
The PID control loop settings may not be up to date so the operators must use the relevant spread sheets to verify recent and most proper settings.
M:\hallb_eng\CLAS12\Magnets\Operations\Cryogenic Operations

4. ESR Compressors High Pressure Flow rate (g/s)
The rest of the flow returns at the medium pressure
Low Pressure Flow rate (g/s)

5. ESR Cold Box The rest of the flow returns at the medium pressure
Super Critical Helium Flow to Valve Box
Low Pressure Flow 4.5K return from Valve Box

6. ESR Valve Box (part 2) and 10,000 liter Dewar
Helium Dewar With HX to cool the 4.5K supply
CTD672 Warm return temperature from All 3 Halls (Important upon CD or Recovery)
Small Polishing HX in the VB

7. ESR Valve Box (part 1)
Nitrogen Sub-cooler to send 4atm liquid at 77K (subcooled liquid)
4K supply flow meter (note sometimes reads about double actual flow, normal is ~6-7g/s)
4K Return Line with Cold Return Valve
CEV6721B (must be shut upon long ESR outages to facilitate Hall B magnet recovery

8. Hall B Torus Operation

9. Hall B Distribution Box (DBX)
Blue line is 4K supply, it feeds Torus, Solenoid and Buffer Dewar
No Control PID’s are presently being used on 4K supply in the DBX. All valves are in Manual mode

10. Hall B Torus Main Control Screen DBX/ESR items Supply flow valves
Coils and Recoolers
Down Stream Hex Beam Temps
Liquid Level Probes (DP and SC)
Lead flow controllers
Cool down Parameters

11. Supply Controls – EV8115JT Min is 40% to assure flow through Coils
Max is 65% to keep from dropping the pressure below supercritical as shown on PT8115

12. Supply Controls – EV8111CD

13. Return Controls
The cold return valve (PV8522TR) is used to back pressure the helium reservoir to drive the lead flow
The higher the pressure the warmer the coils

14. PLC Cryogenic Controls
There are several PLC based controls that are programed and not user changeable
Vapor Cooled Lead Flow
Vapor Cooled Lead Flow Venting
Reservoir Liquid Heater

15. PLC Control – Lead flow
The lead flow rate in standard liters per minute is shown on the main screen. The amount is programed to be 88slm at 0 Amps and 110slm (0.3g/s) each lead at full field, this flow returns to warm compressors (recovery or ESR 1st stage)

16. PLC Control – Lead flow
In the event that the lead flow stops due to high return pressure (PT8571 about the same as PT8120) then the PLC opens SV8122 and starts the magnet rampdown. This happens only if the magnet is powered! And it shuts after the magnet reaches 0 current.

17. Heater 8120 interlock
This heater can not be turned on if the helium level is less than 20% on LL8120SC

18. Other controls Lead heaters
There are two different sets of VCL heaters
The ones displayed on the Torus Helium Screen are PLC controlled
The second set is local controllers that have manual inputs and are on the vacuum rack on level 3

19. Additional screens/info for Torus Overview
Coil Temperatures
Relief Valve Temperatures
Cool Down Parameters
Interlocks

20. Coil Temps
These buttons give details on each coil temperature. Most of these are on the Copper cooling sheets that surround the coil. One is on the coil case itself

21. Relief Valve Temps
Relief Valve temperatures on all 4K circuit relief valves help to show if there is a relief valve that has not re-sealed and is leaking

22. Cool down Parameters
This screen shows lots of parameters that are calculated and are used to assure safe cool down

23. Cool down Interlocks
This screen shows interlocks for warm gas supply valves and heaters

24. Recovery after Cryo glitches or Fast Dumps
We have set up the system to try to recover both the Torus and Solenoid as quickly as possible with goals of:
Minimum intervention
Often no intervention for short ESR outs
Often no intervention for Solenoid Fast Dumps
System protection
Priority to Lead reservoirs so that magnets can stay on cold return
If magnets need to go to warm return the conversion back to cold return can be managed by the cryogenics group in most cases reducing the likelihood of an ESR trip

25. Supply During Recovery
Because both the EV8115JT and EV8111CD valves are programed to control Helium level LL8120SC they will both open to their Max allowed position to attempt to cool and refill the magnet.
As long as the magnet is below 100K there is no limit to cooldown rate
If the magnet is above 100K then an expert must be involved

26. Return During Recovery (empty reservoir and warmed coils >~7K)
If the ESR goes down and both magnets warm up and all reservoirs empty then ESR must shut the cold return valve CEV6721B
This will cause our magnet pressures to rise until our warm return valves PV8522TCD and SCD open because of their PID control loops
Once the Torus reservoir and Solenoid Lead reservoir have >50% helium level cryo can slowly open their cold return valve our PID loops will automatically close our TCD and SCD valves
If the Torus is the only load to warm up then the TCD valve may be opened and the TR valve closed, to allow solenoid and buffer dewar to remain on cold return. (This should be done by an expert operator)

27. What to look for if (when) called in
Most likely the helium level (LL8120SC/DP for the Torus) will be low or empty
The question is: Why?
Look at the helium supply pressure and temperature in the DBX
Look at the supply flow from the ESR
Check our valves to see their status
Check vacuum in the DBX and Torus
Go to Hall B and walk around look for ice or sweat on U-tubes
Contact Cryo to see status of ESR

28. Distribution Box - Normal
TD8512 < 7K
PT8512 > 2.7 atm
If these are off there may be an ESR issue OR
We could have warm gas returning from a magnet or the Buffer Dewar
Check our systems further then contact Cyro
ALSO
TC8500DC < 5.0E-2 torr
PT8563 < 2.0 atm
Call Hall B cryo expert and or Hall B Vacuum expert

29. Torus Helium- Normal TD8111 < 6K PT8111 > 2.6 atm
CFI6711B > 5g/s
If these are off there may be an ESR issue OR
We could have warm gas returning from a magnet or the Buffer Dewar
ALSO
PT8120 < 1.6 atm
Contact Cryo to see if they are having an issue and look more into our system then contact Hall B cyro expert

30. Torus Vacuum- Normal Both Turbo pumps at ~100%
Both Main and Secondary gate valves open
Roots gate valve closed
TC8103<9E-4
CG8103<9E-5
ESR down should NOT be lit (may need to be removed from this screen…)
IF these conditions are not met call in both Torus and Vacuum Experts

31. Questions?