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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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Bart verlaat nikhef co 2 kick off meeting 9july 2009 nikhef

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


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


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


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


Ped classification 2
PED Classification (2)

Largest component determines the overall component category

(Thus a blow system is category IV!)



  • 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.



  • 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


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


Co 2 pumps 2
CO2 pumps (2)

Gather gear pump

Lewa membrane pump


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)


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)


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)


Orbital welding
Orbital welding

  • As many joints as possible by orbital welding.

  • Very reliable connection method.

  • Light weight



  • 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!





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


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


Thanks for your attention questions
Thanks for your attention:Questions?