LHCbVELO Microchannel fracture safety system and evaporator concept

LHCb-VELO Microchannel fracture safety system and evaporator concept 26 June 2015 Bart Verlaat 1

Microchannel volume (1) • The minimum volume which we can shut-off is 1 u-channel including the in and outlet pipes. • The worst case is a filling of cold liquid – T-30ºC liquid (1076 kg/m 3) used in analyses – Under normal circumstances vapor is present and less CO 2 is present. • Assuming a 0. 5 mm inlet and 1. 2 mm outlet (1 m long) – See quick Co. Bra analyses 2

Microchannel volume (2) • Module volumes and CO 2 content @ -30ºC liquid (1076 kg/m 3): – Inlet: D 0. 5 mm x 1 m = 0. 2 ml • 0. 21 gram – μ-channel: 19 x (60μm*30 mm+120μm*200μm*267 mm) = 0. 12 ml • 0. 13 gram – Outlet: D 1. 2 mm x 1 m = 1. 1 ml • 1. 2 gram – Total module volume: • 1. 6 gram CO 2 total • Vacuum volumes (Eddy Jans memo, 5 November 2009) : – Secondary: 450 liter – Primary: 1715 liter – Maximum d. P=10 mbar • Loosing 1. 6 gram of CO 2 in the secondary volume gives a density of 1. 6 g / 450 l = 3. 5 g/m 3 – 3. 5 g/m 3 density after warming up to 20’C gives a pressure of 1. 9 mbar – Direct expansion without heat pick-up is • Conclusion: 1 μ-channel leak is not critical! But a proper module shut-off mechanism is needed 3

Venting CO 2 in vacuum Condition of -30⁰C liquid Condition of +20⁰C low pressure gas 285 m 3/kg 3. 5 g/m 3 => v= Far off scale Ca 350 k. J/kg*1. 6 g = 560 J to heat it up to ambient. 4

How can we isolate 1 μ -channel? • 3 module shut-off options: – Place no-return valves at each module inlet and outlet • • Will add the inlet manifold volume to the leaking volume 1 critical active common inlet valve No risk of liquid trapping Need a reliable miniature no return valve – Place a shut-off valve at the inlet and protect the outlet return flow with a no-return valve • No risk of liquid trapping • Need a reliable miniature no return valve • Many active valves in the vacuum – Place shut-off valves at each module inlet and outlet • Risk of liquid trap • Many active valves in the vacuum • For safe operation: – A relieve: risk of leak or an atmospheric back flow. – A safety gas volume: need a small heat source to keep it filled with gas (might be ambient) 5

No return valve option 1 Active NC valve needed and many miniature no return valves Ambient Tertiary vacuum Secondary Vacuum Red volume will leak in vacuum Green volume can stay pressurized. An additional pressure relieve can be included • • • Valve is NC and actuated when a pressure increase in the Velo is detected. Eg. 1 e-3 mbar This concept requires small passive no return valves. Actuator can be out of the tertiary vacuum Inlet manifold will be leaked into the vacuum as well: – – – Assuming a 4 x 0. 7 tube & 1 m long Extra Volume: 5. 3 ml = 5. 7 gram Pressure in secondary vacuum @ 20’C = 8. 9 mbar 6

Individual inlet shut-off 26 Active NC valves needed in vacuum and 26 miniature no return valves Ambient Tertiary vacuum Secondary Vacuum Red volume will leak in vacuum Green volume can stay pressurized. An additional pressure relieve can be included • • This concept requires small passive no return valves. 26 actuators in the tertiary vacuum – – Valves are NC and actuated when a pressure increase in the Velo is detected. Eg. 1 e-3 mbar • Pneumatic valves very complex in a vacuum Electrical valves NC have a constant heat load on the CO 2 inlet Small volume leaked into vacuum – Pressure in secondary vacuum @ 20’C = 1. 9 mbar 7

Full active shut-off 52 Active NC valves needed in vacuum Ambient Tertiary vacuum Secondary Vacuum Safety volume always contains warm gas Red volume will leak in vacuum Green volume can stay pressurized. An additional pressure relieve can be included • This concept is very sensitive for trapping cold liquid – – – • Valves are NC and actuated when a pressure increase in the Velo is detected. Eg. 1 e-3 mbar 52 Actuators in the tertiary vacuum – – • Each line needs a relieve mechanism Open relieve mechanisms (Burst disc or safety valves) are a risk for the modules (sudden cool down when activated) A warm safety volume is an option Pneumatic valves very complex in a vacuum Electrical valves NC have a constant heat load on the CO 2 inlet Small volume leaked into vacuum – Pressure in secondary vacuum @ 20’C = 1. 9 mbar 8

Upgrade Velo cooling vs current Velo cooling Tertiary vacuum with manifolds and safety valves Cooling lines passing the module base on the side All inlet capillaries on 1 side Return common (Manifold inside) Cooling feed through with thermal stand-off Out of the way space for cooling connector and flexible part All Electronics crates Cable feedthrough 9

Safety system continued • The all no-return valve option seems optional and favorable (option 1) – Simplest from control point of view • No active parts in vacuum – Need to develop a reliable miniature no-return valve • A small leak rate still tolerable as the vacuum pump continues pumping (Ca. 10 mg/s allowed) • Other options require many active valves (26 or 52) all in vacuum. 10

CO 2 pumping in secondary vacuum Mass flow (g/s) ACP 28 pumping capacity for CO 2 A constant CO 2 leak of 10 mg/s is tolerable Pressure (mbar) At least 1 ACP 28 pump is active, sometimes 2 work in parallel 11

Concept Evaporator P&ID PT 30052 SA 30052 TT 30052 BD 30052 nc PV 35052 By-pass with dummy load Safety vent EH 39052 TT 39052 PV 30040 TT 30036 Pre-heater EH 30036 CV 39052 NV 30148 NV 30248 NV 30348 NV 30142 NV 30242 NV 30342 NV 35148 NV 35248 NV 35348 NV 35142 NV 35242 NV 35342 nc 36 52 38 CV 30038 PT 30038 TT 30038 PT 35052 SA 35052 TT 35052 BD 35052 nc PT 39058 TT 39058 BD 39058 PV 30050 nc 52 nc PV 35052 58 nc Safety vent PV 39060 60 nc TT 39032 PT 39032 BD 39032 PV 35040 Pre-heater PV 39030 PV 59054 nc nc TT 35036 nc 38 36 32 30 PV 35050 nc nc EH 35036 PV 59032 CV 35038 PT 35038 TT 35038 Ambient Vacuum PV 49060 To UT-Detector 60 12 30 PV 49030 PV 110

P&ID explained • Labelling (QQxyyzz) – QQ=component • • – PV=Pressure valve CV=Control Valve NV=No Return Valve TT=Temperature transmitter PT=Pressure Transmitter EH=Electrical Heater SA=Safety Accumulator x=System ID • • – • 1=Chiller A 2=Chiller B 3=CO 2 Velo 4=CO 2 UT 4=CO 2 Common 6=Dry-air 7=Tertiary Vacuum – – • • – – – – • • CV 30038 & CV 35038 are set constant for a certain evaporator flow The constant d. P allow the sharing of the UT Safety procedure – 00 = Aside common 01… 26 = Evaporator 1 to 26, A side 50 = C –side common 51 -76 = Evaporator 1 to 26, C side 90 = General (Inlet, By-pass & return) PV 59054 & PV 59032 open Close the PV 39030 & PV 39058 incase of Velo failure or visa versa Preheater EH 30036 & EH 35036 regulate TT 30036 & TT 35036 The Pressure difference (PT 39032 -PT 39058) is regulated constant with CV 39052 – yy=Branch ID • • • UT and Velo can be connected at the level of the accumulator If Pvacuum>10 -3 mbar, then close PV 30038, PV 35038, PV 30052 & , PV 35052 If PT 30038 < PT 39058 – 3 bar, then open PV 30040 & PV 30050; This means there is a leak in this section If PT 35038 < PT 39058 – 3 bar, then open PV 35040 & PV 35050; This means there is a leak in this section System remains running over by-pass, to stay active for safety control and UT operation The safety procedure is safe by default valve position (No venting), Venting is done in addition to be more safe. A safe vent action requires NO valves, but than there is a high risk of unwanted venting which is a hazard for the modules as a cool down is a result. A safety accumulator in the module section must prevent accidental liquid trap. The SA has always a gas filling. 13