1. Summary of the second Hydrogen CEDAR Safety Meeting 24 November 2008 Present: J.Gulley/ SC-GS, A.Sharma/PH-FGSO, Augusto, Cristina, Lau, Niels

2. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting2 Reminder:  A first discussion with safety took place on 5 January 2005 See summary on web page of Beam WG  Since then studies concentrated on light detection  The agreed next step is to install a “standard” CEDAR on the new K12 beam and operate it with Hydrogen at 3.6 bar absolute pressure  The meeting concentrated on this option only.  Note that the volume of the counter is ~1.1 m 3 This corresponds to ~4 m 3 of gas at atmospheric pressure

3. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting3 Entrance and exit windows  The material and thickness of the entrance and exit windows (0.4 mm of Al, AFNOR=AZ5GU in the standard CEDAR, for Helium pressures up to 15 bars) must be discussed with Benoit Delille in SC/GS. It may well be that the safety factor is gas dependent. B.Delille explained that the safety factors for a group 1 gas (H2) are the same as for group 2 gases (e.g. He), but there is a more stringent quality control on the fabrication, e.g. radiography of welds. A risk analysis is needed and EN13445 resp CODAP norms must be respected. Note that the required thickness goes with Ø 2 !  Preliminary ANSYS calculations have been made by Ans Pardons to compare the windows of a standard CEDAR counter (for 15 bars of He of N2) with windows for 4 bars of Hydrogen.

4. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting4 ANSYS calculations (non-linear) with elastic Aluminium for several cases. A thickness of 0.2mm seems ok. Stress plots are attached. Not taking into account: Stress from clamping Stress from heating Stress in centre: (stress plots shown from center to 0.9* radius, to not show the stress concentration due to the clamping) Thickness=0.4mm & pressure= 15 bar: 520MPa (above plasticity limit of some aluminium grades) 0.2mm & pressure= 3bar: 275 MPa (heat-treated aluminium grades have yield limits around this value 0.1mm & pressure= 3bar: 430 MPa (above plasticity limit of some aluminium grades) Deflection in centre: Thickness=0.4mm & pressure= 15 bar: 5.4mm 0.2mm & pressure = 3bar: 4mm 0.1mm & pressure = 3bar: 5mm CEDAR WINDOW THICKNESS CALCULATIONS BY A.PARDONS

5. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting5

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8. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting8 Insulating material  Polyurethane is admitted in small quantities, whereas polystyrene is strictly forbidden. The material used in the CEDAR is polyurethane.  As it is very unlikely that the material specification can be found back 30 years later, and as the polyurethane has degraded over the last 30 years anyway, it is strongly suggested to replace the thermal insulation. Check with J.Gulley before purchase, supply data sheet.  If this is not done, a sample must be provided to S.Sgobba and S.Clement in TS/MME for analysis and a fire test. Check with J.Gulley which fire test is suitable.

9. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting9 Protection of motors and HV  The diaphragm motors, the PMTs and the control unit below the nose must be enclosed in a Nitrogen enclosure at slight overpressure. Inside this enclosure a Hydrogen detector must be placed (by David Hay in TS/ASE).  No special precaution is needed for the X/Y motors for the CEDAR alignment with the beam.  The small gap between the exit window and the beam vacuum will be put under Nitrogen.

10. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting10 Hydrogen bottles and transport  The Hydrogen bottle will be stored in a gas building outside the cavern.  Gas will be brought to the counter via a stainless tube of minimum diameter 6 mm (André Castel in TS/LEA). The gas pressure will be limited by a safety valve to a maximum of about 4 bars. This valve will be inspected regularly like all pressure valves.  The return tube must be stainless steel as well and of at least 8 mm diameter, to avoid the build up of local gas concentrations. It should be equipped with no-return valves. It should release the gas outside at a sufficient height (about 3 metres above ground level).

11. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting11 Pressure control  The CEDAR pressure pumps must be Hydrogen rated (“EX” norm).  Similarly the nearby pumps in the beam vacuum sections just upstream and downstream. Note that the vacuum window may be damaged by the Cedar entrance or exit windows in case they rupture.  Ferdi Hahn in PH/DT can be consulted concerning EX rated pressure gauges. The Hamilton gauges heat the gas to 40 o C and are not obviously EX-rated.

12. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting12 Dear Lau, I send you two links to Vega (our standard) and to Endress and Hauser (high pression). You have to choose the ATEX versions for a zone 2 application. Endress and Hauser can probably do the accuracy you need, Vega might not be as good (on paper)... As an alternative you could also consider to build a small reference pressure volume and measure relative pressure to increase the accuracy. …. Ferdi Vega: http://www.vegacontrols.co.uk/products.asp?fixedRangeID=10http://www.vegacontrols.co.uk/products.asp?fixedRangeID=10 Endress Hauser: http://www.uk.endress.com/http://www.uk.endress.com/

13. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting13 e.g. Endress and Hauser:

14. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting14 or:

15. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting15 Leak detection and alarms  Two domes shall be installed, one above the nose and control unit and one above the exit window. In case all purged Nitrogen enclosures are equipped with H 2 detectors, the domes are probably not necessary.  Both shall be equipped with Hydrogen detectors.  In case of rupture of one of the windows or Hydrogen detection by one of the detectors, a Level-3 alarm will be sent automatically to the Fire Brigade. And the Cedar pumps, motors and PMTs, as well as nearby beam vacuum pumps will be stopped. Sector valves will be closed in the nearby beam line vacuum sectors.

16. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting16 N2 enclosure

17. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting17 N2 enclosure (but not R.Malleyran, please…) H 2 detector

18. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting18 Procedures  Procedures will be made available that describe all steps in the normal operation of the CEDAR (empty before filling with Hydrogen, how to vent), as well in case of e.g. leak detection or window rupture.  This includes the technical intervention, but also whom to inform and what alarms to send where.

19. LG, 11-12-2008 Summary of Hydrogen CEDAR Safety meeting19 Final remark  The safety experts reacted very positively to the fact that we involved them from the start.  They came to our meeting, as well as to TCC8 and to a CEDAR in the COMPASS beam line to understand better.  Many thanks to them!