From gkm@na47sun05Mon Feb 12 10:58:29 2001 Date: Wed, 7 Feb 2001 18:23:45 +0100 (MET) From: Gerhard Mallot To: Martin Davenport , Eric Weise , david.hay@cern.ch, jukka.lindroos@cern.ch, mauro.nonis@cern.ch, hans.taureg@cern.ch, jonathan.gulley@cern.ch Cc: Gerhard Mallot Subject: COMPASS ventilation summary Summary of Ventilation Meeting on February 6, 2001 Subject: Ventilation and Extraction in Gas Mixing Zone in Building 888 Present: Martyn Davenport EP/TA2, Jonathan Gulley TIS/GS, David Hay ST/AA, Jukka Lindroos ST/CV, Gerhard Mallot EP/TA2, Mauro Nonis ST/CV (part time), Eric Weise EP/COMPASS Concept: The ventilation concept depends on feasibility of the 3% LEL sensitivity catalytic sensor, the quality of the construction of the soft enclosure and, to an extent, the flow limit at 500 l/h for the CH4 lines. The flow to the gas mixing zone in 888 will be limited by calibrated orifices in building 908. Thus the maximal leak is 500 l/h in case of two methane lines and 1000 l/h for one methane line. With 3 % LEL sensitivity a 50 l/h methane leak can be detected even a 40 m3/h air extraction rate. Once a leak is detected (level 3) the flow into 888 will be stopped at 908 and the lines will also be closed at arrival in 888. A moderated air extraction prevents the accumulation of flammable gas from very small undetected leaks. Specifications: The following scheme was adopted for the ventilation and air extraction in the gas mixing zone in building 888: - the gas flow from 908 must be limited to 500 l/h in case of two methane lines and to 1000 l/h if only one line is available. 200 l/h for the other flammable gases. - four groups of 2 racks each with flammable gas are foreseen. Each such group will have a severate top hood with a damper to equilibrate the air flow for the groups. The hoods will be connected to a common air duct. - a second duct will extract air from the bottom of the racks (when necessary) - the nominal standard flow is 200 m^3/h in the top duct and 100 m^3 in the bottom duct. - the flow will be optimized for this standard flow, however the fan should allow to switch to 600 m^3/h. The fan should be explosion proof. - the ducts should be dimensioned for the higher flow of 600 m^3/h. - gas detectors with 3 % LEL sensitivity will be placed in the top hood calibrated for methane. In the primary rack and the DC rack an additional detector of heavy gas with be placed in the bottom of the rack, calibrated for ethane. - the gas racks will be closed on the back side and the two sides by flame retartant curtains, on the front side by transparent sliding doors. The installation of the curtains must we very well engineered. Air inlet should be protected by a dust filter and be arranged in the lower half of the sliding doors. All racks are standing in a heavy gas retention bac. If need be, one can cut away the sides of the existing bac and screw folded sections of Aluminuium sheet at the height and width needed to match the curtains etc. one can imagine that there will be a floor divider between each compartment. - electro valves should be placed at the primary inlet of flammable gases and must close at level 3 alarm. This avoids emptying of the small amount of flammable gas in the lines (about 300 l STP) to the gas building 908. The fan should switch to the 600 m^3/h speed. Actions: D. Hay: prices for 3 % LEL detector (4 needed), prices for infrared detectors J. Lindroos: offer for ducts, fans, dampers E. Weise: clarification of second methane line, orifices G. Mallot/E. Weise: follow up of design, order and installation check for curtain and door material with Tavlet and Nuttall. -------------------------------------------------------------------- Gerhard Mallot, CERN, EP-TA2, CH-1211 Geneve 23 Tel:+41 22 767 6423 Email: Gerhard.Mallot@cern.ch Fax:+41 22 767 7930 Mobile: +41 79 201 3425 --------------------------------------------------------------------