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| # CSH2 Cryogenic Pump — Operational Context Knowledge | |
| # Practical knowledge that operators have but specifications don't document. | |
| # Derived from maintenance_log.xlsx, Technical PDF, and data analysis. | |
| sensor_trustworthiness: | |
| TT110: | |
| notes: > | |
| TT110 reads pipe wall temperature, not fluid temperature. After cooldown, | |
| it needs 10-15 minutes to equilibrate with the flowing cryogen. During | |
| transients (pump start/stop, flow changes), TT110 lags the actual fluid | |
| temperature by 5-30 seconds depending on flow rate. | |
| workaround: > | |
| For precise inlet temperature, use virtual T_inlet back-calculated from | |
| discharge state via ThermoProps (physics/thermo.py). The virtual sensor | |
| uses PT110 + TT130 + isentropic relations to infer inlet conditions. | |
| known_faults: | |
| - "Jul 16, 2025: 0-32K readings are sensor fault, not real cryo temps" | |
| - "Filter out readings during known warm periods where TT110 < 50K" | |
| FT140: | |
| notes: > | |
| FT140 is a Coriolis mass flow meter calibrated for LN2. When running LH2, | |
| the density difference (LN2: 808 kg/m³ vs LH2: 70.8 kg/m³) causes the | |
| raw reading to be 100-200x too high. The FT140Calibrator applies a density | |
| correction factor of approximately 11.4x. | |
| workaround: > | |
| Always apply FT140Calibrator (physics/ft140_calibration.py) density correction | |
| before interpreting flow readings. Near-zero flow at low pump speeds is | |
| expected and not a fault — the meter has a low-flow cutoff. | |
| known_faults: | |
| - "Raw FT140 reads ~100-200x too high for LH2 — apply correction" | |
| - "Near-zero flow at idle is expected, not a sensor fault" | |
| PT100: | |
| notes: > | |
| PT100 is stuck at -14.86 bar in the current dataset. This is not a | |
| physical pressure — it's a sensor fault. | |
| workaround: > | |
| Use default_when_invalid=2.0 barg for any calculations requiring PT100 | |
| (e.g., Psat estimation). This is the saturation pressure approximation. | |
| known_faults: | |
| - "Stuck at -14.86 bar — use 2.0 barg default" | |
| CalcMass: | |
| notes: > | |
| CalcMass is stuck at 0.18 kg in the current dataset. The PLC calculation | |
| is not updating. | |
| workaround: > | |
| Use FT140 integration (corrected) for actual dispensed mass calculation. | |
| Integrate corrected FT140 over the fill duration. | |
| known_faults: | |
| - "Stuck at 0.18 kg — use FT140 integration instead" | |
| M130_Speed_vs_MC130: | |
| notes: > | |
| Tag 68 (M130_Speed) replaces tag 13 (MC130_VFD_Speed) after May 28, 2025. | |
| Both map to motor speed percentage but are different register addresses. | |
| TAG_ALIASES in config.py handles this mapping. | |
| workaround: > | |
| Check TAG_ALIASES. Use tag 68 for post-May data, tag 13 for pre-May. | |
| Both are valid speed readings. | |
| post_maintenance_expectations: | |
| hp_seal_replacement: | |
| description: "After HP seal replacement or energizer work" | |
| expected_behavior: | |
| - "Initial friction: 7-9 kgf (from Jul 18 maintenance entry)" | |
| - "Break-in period: ~1000 cycles to reach 4-5 kgf steady state" | |
| - "Motor current will be higher initially — this is normal" | |
| - "Volumetric efficiency may be slightly higher initially (tighter seal)" | |
| timeline: "1000 cycles (~2-3 days at normal testing rate)" | |
| ref: "2025-07-18 maintenance event" | |
| icv_replacement: | |
| description: "After ICV replacement or reseating" | |
| expected_behavior: | |
| - "Immediate improvement in pressure build if ICV was the issue" | |
| - "New valve may need seating-in (initial performance varies)" | |
| - "Jul 22: orientation fix restored 700 bar immediately" | |
| - "Jul 14: polished ICV helped but didn't fully fix — surface not flat" | |
| timeline: "Immediate improvement expected" | |
| ref: "2025-07-01, 2025-07-14, 2025-07-22 events" | |
| dcv_polishing: | |
| description: "After DCV sealing surface polishing" | |
| expected_behavior: | |
| - "Immediate improvement in leak test results" | |
| - "Run PT130 decay test before and after to quantify improvement" | |
| - "Jul 1: polishing improved seal but some residual leakage" | |
| timeline: "Immediate improvement" | |
| ref: "2025-07-01 maintenance event" | |
| regime_caveats: | |
| ln2_vs_lh2: | |
| description: "LN2 and LH2 data are not directly comparable" | |
| details: > | |
| LN2 (77K, 808 kg/m³) and LH2 (20K, 70.8 kg/m³) have very different | |
| fluid properties that shift all performance curves. Compression ratios, | |
| volumetric efficiencies, heat transfer rates, and valve dynamics all | |
| change significantly between fluids. The SPEED_SCALE_FACTOR in config.py | |
| was calibrated for LN2 and needs adjustment for LH2. | |
| impact: | |
| - "Flow rate scales with density ratio" | |
| - "Pressure build rate changes with bulk modulus" | |
| - "Thermal effects are very different (77K vs 20K)" | |
| pressure_drift: | |
| description: "Discharge pressure drifts down during extended fills" | |
| details: > | |
| Documented in Technical PDF p.22. The pump operates at approximately | |
| fixed pressure ratio. As the small test cryotank depletes, inlet | |
| pressure (PT110) drops, and PT130 follows. This is NOT a fault — | |
| it's an expected consequence of the small tank size. | |
| impact: | |
| - "PT130 and flow rate decline over extended fills" | |
| - "Production tanks will be sized to maintain pressure" | |
| subcooling_sensitivity: | |
| description: "Pump performance is very sensitive to inlet subcooling" | |
| details: > | |
| From Technical PDF p.17: the pump is 169x more efficient with | |
| subcooled liquid than with gas. Even small amounts of flash gas | |
| at the inlet significantly reduce volumetric efficiency. Ensure | |
| adequate subcooling margin (>5K) before starting fills. | |
| impact: | |
| - "Inlet quality > 0 = reduced efficiency" | |
| - "Subcooling margin < 2K = risk zone" | |
| system_personality: | |
| recurring_issues: | |
| - priority: 1 | |
| description: "ICV sealing is the #1 recurring issue" | |
| details: "3 occurrences in July 2025. Check ICV first for any pressure build problem." | |
| refs: ["2025-07-01", "2025-07-14", "2025-07-22"] | |
| - priority: 2 | |
| description: "DCV sealing is the #2 issue" | |
| details: "1 occurrence. DCV polishing was effective but residual leakage remained." | |
| refs: ["2025-07-01"] | |
| - priority: 3 | |
| description: "Safety loop tuning needs attention at high pressures" | |
| details: "AOV141 hunting observed. PID tuning required." | |
| refs: ["2025-07-22"] | |
| strengths: | |
| - "HP seal life is excellent (8.2M cycle lower bound = 3+ months at 20 fills/day)" | |
| - "Phase 1B achieved 100% uptime across 6 fills" | |
| - "Specific energy of 0.26 kWh/kg matches target" | |
| - "Back-to-back fill capability demonstrated (4 consecutive fills)" | |
| known_limitations: | |
| - "Pump gas ratio 14.4% vs 2.7% target — efficiency gap exists" | |
| - "Peak pressure 370 bar vs 700 bar H70 target — further testing needed" | |
| - "Small test tank causes pressure drift during extended fills" | |
| - "FT140 requires density correction for LH2 — raw readings are wrong" | |