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Minutes of Flammable Gas Safety Meeting:
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date: 07.03.01 10:00 892-1-D20

subject: finalize flammable gas safety system and alarm actions for
	 bld 908, bld 888, bld 888 gas mixing zone, RICH tent and
	 RICH test area

participants: Silvia DALLA TORRE, Jonathan GULLEY, David HAY, 
	      Hans TAUREG, Martyn DAVENPORT, Eric WEISE, 
	      Gerhard MALLOT, Fulvio TESSAROTTO,  Iouri KHOKHLOV,
	      Bruno PICHLER

signs:  --  <=>  information
	->  <=>  recommended/prescribed action 

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open questions:
i) each group using gas, has to specify emergency actions in case of
   an gas alarm
ii) to Juan Gomez: does the main emergency switch (AUG) cut the power also
    for PT and RICH gas zone?

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gas supply: 
  -- second methane line from bld 908 to 888 availiable
     => the flow per line will be limited to 500 l/h	      


electrical zones:
(local emergency switches (LAV) cutting power in each region)
  1. beam-/experimental area (including barracks)
     -- includes gas mixing zone
  2. RICH radiator gas zone
     -- rack for methan supply of photon chamber is controlled by the 
	second PLC (orginally allocated for PLC in zone 2) wich is
supplied
	with power from zone 1)
     => danger of cross-connection between zone 1 and 2!
  3. PT (polarized target)


gas safety interlocks in case of L3 alarm (most simple strategy):

  bld 908     -> off gas

  mixing zone -> off gas in bld 908
	      -> off arrival gas from 908 (approx. 300 l stored in lines)
	      -> off 220V gas mixing zone
	      -> off flows to chambers (flammable and inert gases, to keep
up mixing ratio) 

  exp. area   -> off gas in bld 908                                      
	      -> off arrival gas from 908                                
	      -> off 220V gas mixing zone                                
	      -> off flows to chambers                                   

  -- possible division (not yet decided) in sub-areas (with seperate
supply lines from 908): 
       a) PT-SM1: MicroMegas, DC Saclay <=> isobutane C2H6
       b) tent: RICH <=> methane CH4, first line
       c) MW2 <=> methane CH4, second line
       => in  case of gas alarm, just stop flow in dedicated supply line
          Problem: in case of L3 alarm in one of the sub-areas and the
fire brigade ist 
	           automatically alarmed, there would be still flammable
gas flow in the area
		   (this is contrary to normal procedure !)

  -- number/position of detection head wich caused the alarm can be coded
in computer 
     generated alarm (software), normally there are just two hard-wired
alarm signals:
       L2 alarm - to TCR
       L3 alarm - to TCR and fire brigade

  -- L3-alarm precipitates interruption of gas supply in bld 908
     (procedure: detection head electronic transmitted signal to central
relais-logic, which
     switches electric valve in bld 908)

  -- separation of detection head electronic and intrinsic detection head
possible, but not 
     yet tested (no test facility availiable)


RICH photon chambers:

  -- passive emergency system: in case of power failure a bypass around
the Ar mass flowmeter
     wich is by default (without power) open, provides Ar flow

  -> normal total flow: 200 l/h CH4
     => should be reduced to the smallest possible flow

  -> seperate safety bottle for Ar supply recommended
     => should be stored outside the building 

  -> safety bublers:
     => exhausts leading outside bld 888 on jura-side
     => plastic tubes adequate 
     => no carrier gas needed
     => measurement of flow of returning gas would indicate leaks
	(installation foreseen) 


MW2:

  -- anticipated leak rate: 10 l/h for all 6 planes

  -> connection shielding boxes to be flushed by N2
     (one 4 meter box per plane => 8 N2-inlets per box)

  -> connection to gas tubes to be checked by TIS


mixing zone ventilation system:

  -- alarm level
     lower detection heads (standard type) on the floor:
     (neccessary in case of usage of iC4H10 for RICH) 
       L2 alarm  <=>  10% LEL         
       L3 alarm  <=>  20% LEL  
     upper detection heads (ICARE-heads; temperature drift compensated by
heating)
       L2 alarm  <=>   3% LEL
       L3 alarm  <=>   6% LEL (could be higher to avoid wrong alarms)  

  -> power for ventilation system and electronic for gas detection 
     should be provided by CERN's secure power network
     => not suspended by AUG 
	(diesel emergency power supply will be suspended bey AUG!)

  -> ventilation system will be installed by ST
     => interlock signal in case of L3-alarm
     => fan turned to high-speed in case of alarm in mixing zone

date of next meeting: 21.03.01