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1 Bremerton Safety Council Camera Hazard List Frank O’Neill Safety Support August 18, 2015
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2 Corner Rafts/Science Rafts/Sensors
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16 Corner Raft
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23 Corner Rafts/Science Rafts/Sensors
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24 Cryostat
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25 Cryostat
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26 Cryostat
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27 Cryostat
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28 Filter Exchange System
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29 Filter Exchange System
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30 Filter Exchange System
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47 L3
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48 L3
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49 L3
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51 L3
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52 L1/L2
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53 L1/L2
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54 L1/L2
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55 L1/L2
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201558 LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 2015 Cryostat Final Design Review Safety-Hazards J. Langton Subsystem Engineering Manager June 9-10, 2015
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201559 Cryostat Hazard Analysis Report The Camera has drafted a Hazard Analysis Report (LCA-0014) –LCA -0014 explores and explains, in detail, the integrated camera and individual subsystems design and function and identifies potential hazards. The cryostat chapter of the HAR evaluates the associated hazards in detail. –Cryostat HAR provides the cryostat physical description and function. –Cryostat HAR evaluates each hazard area in detail and provides definition and explanation of the related controls and mitigations. Cryostat hazard areas: –Thermal and Cryogenic –Pressure and Vacuum –Structural –Electrical –Control –Environmental –Fire –Materials and Substances
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201560 Cryostat Hazard Analysis The camera has a drafted a hazard lists (LCA-15 & O&SHA) –Operating and support hazard analysis tabluate hazards associsted with camera operations phase. –Lists tabulate all of our identified hazards, plans to mitigate them, and plans to verify that the mitigation is, in fact, operating as required. –The Hazard List uses a semi-quantitative analysis to rank hazards by probability of occurrence and severity of impact. The cryostat system carries: –A total of 24 hazards –No “High” hazards –3 “Serious” hazards (unmitigated) Cryostat vacuum-pressure failure. Overpressure failure of cryostat. Asphyxiation due to release of refrigerant –All hazards are medium and Low assessment after mitigation Why not all hazards mitigated to “low”? Because, with very few exceptions, the severity of a hazard cannot be reduced. Only the probability of a hazard occurring can be addressed by mitigation and that sets a certain lower bound for any specific hazard.
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201561 Hazard Definition & Assessment Methodology Hazards can be defined as a failure of a component, system or function that could lead to personal injury or damage to hardware. –Hazards are NOT risks.
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201562 Cryostat Hazard List How are you protecting against the failure? What’s the failure & mode? How are you assuring protections work? Hazard assessment before protection Hazard assessment after protection
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201563 Cryostat Hazards Detail Hazard DescriptionMitigationVerification #021-Asphyxiation due to release of refrigerant1-provide ventilation of room suffcient to remove limiited refrigerant quantity of system charge 2-employ oxygen deficiency monitor in utility room 1-test ventilation system for adequate (as designed) performance for air change rate 2-Test ODM periodically, verify alarm set point. 3-Ensure training is adequate and retraining frequency is consistent with needs. #001-Failure of a vacuum seal in the cryostat leads to uncontrolled venting of the cryostat, possibly introducing contaminants and water vapor into the cryostat which could damage the detectors 1-Use double O-ring seals with an intermediate vacuum groove at all bolted joints. Failure of one seal can be detected. 2-use of all metal seals wherever possible 3-ensure all valve are normally closed / fail to safe configuration 4-ensure redundant valve for all critical locations, 5- implement control system with valve sequencing ensuring proper operation 6-test and verification of vacuum control system with double check function confirmation to ensure no unintended vent. 1-Test vacuum-tightness of each of the double O-ring seals 2-design reviews of system to ensure proper component selection #010-Cryo or Cold Plate exceed their max operating limits 1-design hardware to survive maximum possible temperature with heaters on / refrig lower cooling capacity 2- Temp sensors on Cryo and Cold plates provide feedback; over-temp switches cut power to heaters and RCM power supplies 1-Test montiring feedback control and over-temp switches Cryostat hazards are loosely grouped as follows: Personnel injury due to unplanned release or venting of gases or fluids. Mechanical failure—failure of a component due to improper system design or usage. Control or operations failure—damage due to incorrect operation or loss of transducer.
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201564 Hazard Mitigations and Verification There are 6 ways to mitigate a hazard –Eliminate hazard: Remove the hazard altogether –Control hazard: Change design/manufacturing plans to reduce risk of mishap –Safety feature: Incorporate passive or static interveners to prevent a mishap –Safety device: Add active device or monitor to interrupt mishap sequence –Warning device: Incorporate monitors and warning of incipient mishap –Procedure, training: Invoke special procedures, PPE, dedicated equipment And 5 ways to verify those mitigations: –Test: Functional test of installed system verifies mitigation functions correctly –Inspection: Visual inspection or measurement verifies mitigation is applied as-req'd –Process control: Control parts/mat'l selection; qual/proof test; fab/ass'y process controls –Audit: Check of in situ mitigations verifies that they are being used –Review: Review or analysis of mitigation plans indicates that they will reduce hazard level
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201565 Cryostat Hazard Reports The Camera Safety officer reviews the hazard analysis. Specific hazards identified as “High” or “Serious,” or with causes that are particularly complex are flagged and Hazard Reports completed. LCA-10742 reports on the cryostat housing hazard of structural failure due to overpressure. The reports details the hazard: –...If these gas supplies are not properly engineered and operated there could be a hazard buildup of pressure in the cryostat vacuum …. The controls / actions: –1-Design cryostat for overpressure loads with recommended safety factors –2-Include burst disk and / or pressure relief valve on cryostat vacuum system –3-Restrict…….. The effects: –1-ensure if an over pressure condition develops the structural integrity…….. –2- ensure if fault or failure occurs and uncontrolled supply of gas….. –3-ensure that the total pressure…… The verifications required: –1-Proof test cryostat to maximum expected overpressure…….. –2-Proof test pressure relief valve……… –3-Verify that burst disk……….
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LSST CRYOSTAT FDR SLAC, Menlo Park, CA June 9-10, 201566 Summary Affect on CD-2 readiness –We have identified mitigations for all 18 hazards. –The mitigations reduce hazard assessments to the lowest level achievable. –Verifications requirements for mitigations established and documented. Hazard reports and assessments have been reviewed and updated in preparation for FDR Cryostat hazard definition and assessment is mature. Mitigations are identified and integrated into the project execution and / or system designs. Hazard assessments and mitigations consistent with CD-3 readiness.
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