Summary of discussion on ST cooling issues

			March 12, 2004

                    Frank Lehner, Helge Voss



Yesterday we had a meeting with the people from the CERN-ST/CV cooling
division, who are going to design the cooling infrastructure for IT
and TT. The baseline requirements are C6F14 as cooling liquid, -15 C
coolant temperature at the detector input and a flow of maximum
3000l/h for each IT and TT. (designed for a maximum reasonable Beetle
power consumption of 0.86W (see Sven's transparancies)

The issues discussed were the following:

1) Temperature regulation/variation:
   We decided on a maxium temperature variation of the cooling liquid
   of +- 0.5C and a possible range of working points of -15 C to +15
   C. THis translates into a chiller capable of reaching -20C and
   we'ld like to understand the cost implications of a chiller being
   able to provide -30C... for additional safty)

2) Pumps:
   In order to reduce costs, the second redundant pump in each cooling
   cirquit should be dropped. One spare pump for TT and IT together
   however will be available. (typical lifetime of the pumps are many
   years)

3) Transfer lines:
   In the current design 3 transfer lines (from control / counting
   room) are foreseen for the IT and one for the TT. This will be a
   matter of debate in order to reduce cost at the next meeting, when
   the alternative design of only ONE transfer line for IT as well as
   for TT are evalutated. 

4) Manifolds/patch panel
   In addition we asked them to provide also the
   manifold/valves/flowmeters close to the detector stations (12
   coolig lines for IT and 6 for TT) and to include them in their
   control system. (IT wouldn't make sense to start designing an
   additional control system if we would split the responsibilities
   for the cooling up to close to the detector and "near" the
   detector)

5) One combined Chiller:
   In the next ST-meeting we should also discuss the possibility of using
   one chiller only for IT and TT togehter. The possible cost savings
   will be evaluated by the ST-group.


In the next meeting set for the 7th April, a clearer cost brakedown
should be avilable on which basis we then need to decide on the final
design which needs to be finished accoring to the current schedule by
end of May in order to start the invitation for tender in June.