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Bart Verlaat Nikhef CO 2 Kick-off meeting 9July 2009 @ Nikhef - PowerPoint PPT Presentation

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Experiences with CO 2 cooling hardware and applied designs. Experiences from past CO 2 systems and philosophies for the future. Bart Verlaat Nikhef CO 2 Kick-off meeting 9July 2009 @ Nikhef. Scope of the presentation.

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Experiences with CO2 cooling hardware and applied designs.Experiences from past CO2 systems and philosophies for the future

Bart Verlaat Nikhef

CO2 Kick-off meeting

9July 2009 @ Nikhef

[email protected]

Scope of the presentation
Scope of the presentation

  • This presentation will summarize the design solutions as they were successfully applied in LHCb or other lab experiments.

  • As the presented technologies worked well, they can be used as a guideline for future CO2 systems.

  • Experiences from the past has set a standardization at NIKHEF for the design of the future plants

[email protected]

Pressure design issues
Pressure design issues

  • Within the EU pressure systems above 1.5 bar absolute must comply with the Pressure Equipment Directive (PED) for the design and fabrication.

  • Will CERN / ATLAS follow these PED regulations?

  • It is best to take any regulation into account during the design.

  • Nikhef is investigating these implications for the CO2 system design, since pressure systems designed and used at Nikhef must comply with the PED

[email protected]

Ped classification 1 pressure equipment directive
PED Classification (1)(Pressure Equipment Directive)

PED classification for CO2 systems.

MDP = Relieve pressure > (P @ TenvMax + 5 bar(start-up) + dPpump)x110%

PTP = 1.3 x MDP

MDP = Maximum design pressure, PTP = Proof Test Pressure

24ºC => (63 bar + 5bar +10bar)x110% = 86 bar => MDP= 90 bar => PTP = 120 bar

Components with non dangerous gasses

Tubing with non dangerous gasses

0.55 2.2 11.1 33.3

32 100 250

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Ped classification 2
PED Classification (2)

Largest component determines the overall component category

(Thus a blow system is category IV!)

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  • Heaters in an insulated cooling system are dangerous

    • (High power + failing cooling = burning insulation).

  • At Nikhef we always use 2 independent thermal switches to prevent overheating.

    • At least 1 hardware switch.

  • Long heaters (like cooling pipe dummies with heaters), an additional smoke detector as interlock is recommended, as the hotspot can be anywhere.

  • Good experience in LHCb with Watlow fire-rod heaters with epoxy seal.

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  • Good experience with Swagelok 43G ball valves. (2-way and 3-way)

    • -53ºC /172 bar

  • Nikhef has designed a handle extension for the 43G so warm panel mounting is possible. Ideal way of supporting the tubing structure.

  • 1 design for manual and automatic control

  • T-shape hole to avoid liquid trap

    • SS-43GHLVCR4

Electrical Control replaces manual knob

[email protected]

Co 2 pumps 1
CO2 pumps (1)



  • Good experience with the LEWA LDC1 metering pump in LHCb.

  • Modifications made for LHCb:

    • Spring loaded outlet valve (0.8 bar), normal for high viscous fluids

    • Heated oil bath to prevent moisture

      • (Toil=18ºC)

    • Dismountable isolation for easy access

  • LEWA pump gives pulsations

    • Gas damper

  • Gather gear pump under investigation for test plant

    • No pulsations

    • Smaller pump

    • First result: pumps well, but after 2 weeks in CO2 the gears got blocked due to swelling (PPP). New gear material under investigation.





Lewa pump in LHCb

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Co 2 pumps 2
CO2 pumps (2)

Gather gear pump

Lewa membrane pump

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Vtcs accumulator
VTCS Accumulator

Cooling spiral for pressure decrease


Thermo siphon heater for pressure increase


2pacl filling



Accumulator Liquid level

Over critical filling

Under critical filling

2PACL filling

2PACL Start-up

Decrease heater power near critical point to prevent dry-out. Higher vapor density cause less convection.

  • Single-phase cold operation is worst-case for minimum level

    • (Heater need to be submerged all the time)

  • Two-phase cold operation is worst-case for maximum level

    • (Significant part of the cooling coil need to be in vapor phase)

Accumulator for lab experiments
Accumulator for lab experiments

The easy way: Completely submerge a vessel in water-glycol controlled by a thermostatic bath. (The AMS-TTCS test set-up way)

[email protected]

Heat exchangers
Heat exchangers

The reinforced heat exchanger is now commercial on the market. (limited to -10ºC because of steel plates)

Reinforced heat exchangers in LHCb (135 bar)

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Connectors and tubing
Connectors and tubing

  • Swagelok VCR connectors

    • Easy to assemble and reassemble

    • Easy to leak test

    • Very reliable

  • All tubing is 316L and matching the Swagelok orbital weld connector series dimensions.

  • More choice in imperial units, so tubing is standardized imperial as well.

    • 1/8” x 0.028” (1/8” VCR-2 connector, 573 bar)

    • 1/4” x 0.035” (1/4” VCR-4 connector, 360 bar)

    • 3/8” x 0.035” (1/4” HVCR-4 connector, 240 bar)

    • 1/2” x 0.049” (1/2” VCR-8 connector, 180 bar)

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Orbital welding
Orbital welding

  • As many joints as possible by orbital welding.

  • Very reliable connection method.

  • Light weight

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  • ¼” VCR (1/4” tube) and HVCR (3/8” tube) have connector diameter 19mm

  • Most other hardware is selected to match ~19mm.

  • Tubing is isolated to ø18mm

  • The rest is insulated with Armaflex NH 25-018

  • Important: Air tight glued assembly to keep moisture out!




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Control and monitoring
Control and Monitoring

  • PLC control development (Siemens S7)

  • In house development of PVSS projects

    • Both for laboratory set-ups and for real slow control at experiments (LHCb)


PLC rack

LHCb-VTCS PVSS interface

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Safety relieve
Safety relieve

720 bar

  • Trapped cold liquid is a real danger in a liquid cooling system.

  • Every volume need a relieve

  • Swagelok SS-RDK-16-1900 (130 bar) miniature rupture discs works well.

  • Relief valve SS-4R3A, has decompression problems of o-ring. New o-rings under investigation

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