Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas RAMS ANALYSIS

1. Design, Manufacture, Transport and Integration on-site in Chile of ALMA Antennas • RAMS ANALYSIS • PM#03 Torino - April 5th- 6th, 2006

2. RAM aspects The RAM activity performed in the present phase is dedicated to the system requirement allocation process in order to provide inputs for the equipment specifications; it covers the following topics: - Refinement of the Antenna Reliability Block Diagram (RBD) according to all the available design information - Preliminary evaluation of the antenna equipment failure rate for which consistent design data are defined - Modification of the predicted equipment failure rates in order to satisfy the system level objective (MTBF3 years).

3. RELIABILITY BLOCK DIAGRAM The RBD is adequately defined for all the Antenna sections, except for: HVAC = The current modelization does not include any redundancy; however, considering the available MTTF figures in the technical literature (for not redundant HVAC) and the stringent Antenna MTBF requirement, it is supposed that some redundant units could be necessary to satisfy the preliminary allocated figure (MTTF125000 h). UPS & Power Supply = design under definition; the available information does not allow a preliminary modelization and evaluation of the failure rates of the involved units. The preliminary allocation process leads to MTTF40000 h. Smoke detectors and safety switches = The quantity of units and associated configuration under definition Metrology system = The units typologies and quantity are defined; the redundancy logic (if any) to be identified as result of the engineering analyses (thermal, structural, error budget, etc.)

4. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES This step of the RAM analysis is important to quantify the contribution of each unit to the overall antenna MTBF figure; the assessment takes into account all the available engineering information. The obtained figures constitute only the starting point for the apportionment process; they do not represent the Reliability performance of the antenna units (to be provided by suppliers). The table below lists the result of the prediction (at unit level) performed by the consortium.

5. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (cont’)

6. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (Cont’)

7. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (Cont’)

8. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (Cont’)

9. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (Cont’)

10. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (Cont’)

11. PRELIMINARY EVALUATION OF EQUIPMENT FAILURE RATES (Cont’)

12. RAM INPUTS FOR ANTENNA UNITS SPECIFICATIONS The preliminary failure rates obtained in the RAM assessment by the consortium, have been modified (reduced) in order to guarantee the system level requirement. The definition of these figures (that represent the reliability requirement at unit level) takes into account: - The expected practical limits for each unit typology (electronic, mechanical, electrical, etc.) in the ALMA operative environment. This is based mainly on engineering considerations. - The possibility to implement a complete or partial redundant configuration at unit level - The expected duty cycle (less than 100%) that allows to improve the effective unit failure rate for ALMA purposes. The table below lists the selected reference units MTTF (= 1/failure rate, assuming the exponential law for the time to failure of the units):

13. MTTF REQUIREMENTS

14. MTTF REQUIREMENTS (cont’)

15. MTTF REQUIREMENTS (cont’)

16. MTTF REQUIREMENTS (cont’)

17. SAFETY ACTIVITY • Hazard Analysis Preliminary Hazard trees, Hazard Matrix and Hazard list have been developed: • For each Hazard a preliminary list of possible causes has been developed • 9 Hazards in total. • 29 possible causes