Presentation on theme: "31/03/11FV 1 CEDAR from flammable gas safety point of view."— Presentation transcript:
31/03/11FV 1 CEDAR from flammable gas safety point of view
VF2 31/03/11 CEDAR – ČErenkov Differential counter with Achromatic Ring focus Pumping outlet Diaphragm motor and diaphragm opening potentiometer – inside of motor cover Motors and gas control unit – will be replaced 8 quartz windows
VF5 31/03/11 CEDAR – Vessel and gas Vessel: Geometry: Total length - 6.2m Main vessel length - 4.5m Inner diameter - 53.4cm Steel pipe Polyurethane foam thermal insulation – 10cm around the counter Gas: Volume -1.1m 3 Composition – 100% H 2 Operating pressure – between 2.5 and 3.5 bar absolute, up to 4 bar during a pressure scan
VF6 31/03/11 CEDAR – gas system, nitrogen enclosure H2H2 N2N2
VF7 31/03/11 Pumping outlet Diaphragm motor and diaphragm opening potentiometer – inside of motor cover Safety valve PT100 Big O-ring of the nose Entrance window
VF8 31/03/11 CEDAR – control unit below the nose
VF9 31/03/11 CEDAR – list of possible leaks (Jens Spanggaard) Entrance Window Quartz Windows Big o-ring for the noise Top vacuum valve Top safety valve Diaphragm motor axe feed-trough (on top of H2!) Gas pipe for pressure gauge (Should be Ex proof !) Gas pipe for servo regulator Gas pipe for inlet/outlet Big o-ring for end-cap End window
VF10 31/03/11 Entrance Window Quartz Windows Big o-ring for the noise Top vacuum and safety valves Diaphragm motor axe feed-trough Gas pipe for pressure gaugeBig o-ring of end cup Exit Window
VF11 31/03/11 CEDAR – other features Equipment inside of nitrogen enclosure 240 photomultipliers operating at high voltage Preamplifiers and signal-shaping electronics Heat exchangers Electrical equipment of CEDAR (all motors and end-switches are 24V) Diaphragm end-switches – inside the H2 volume ( !) Diaphragm motor and Diaphragm opening potentiometer – inside of motor cover, on top of the front flange Control unit below the nose Horizontal and Vertical Position motors with end-switches and position potentiometers – downstream support 4 PT100’s: entrance window, front and back flanges, air
VF13 31/03/11 From the minutes of H2 safety CEDAR meeting 24-11-2008 (Lau Gatignon) 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. No special precaution is required for the X/Y motors for the Cedar alignment. Quartz Windows 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. 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 meters above ground level). 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. Two domes shall be installed, one above the nose and control unit and one above the exit window. Both shall be equipped with Hydrogen detectors. In case all purged Nitrogen enclosures are equipped with Hydrogen detectors, the domes are probably not necessary. 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. 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.
Beam pipe connection VF15 31/03/11 The CEDAR must be connected to the vacuum beam pipe at both ends in such a way that a hydrogen leak is not accompanied by any admixture of air in order to prevent any risk of explosion. An important secondary consideration is that damage to sensitive detectors must be minimised by mitigating the effects of hydrogen leaks and the shock wave resulting from the potential rupture of the window at either end of the CEDAR
VF16 31/03/11 CEDAR – gas operation Before introducing any H 2 gas, the entire system (including the detector) is filled with clean and dry N 2 The detector is then pumped to vacuum using a dry membrane vacuum pump down to 5 mbar and willed with H 2 gas At the end of a physics run the Hydrogen is pumped out and the detector is refilled with nitrogen.