Findings

• During April 2025 safety walk ID: 2796 , it was noted that the oil level in NHC window oil expansion tank was below the indicator range.
• previous safety walks from July, October, Jan 2024 did not show any issues, but this was not a recorded item, only to check for leaks 
• No visible leaks from the exterior can be seen. 
• No air gap can be seen inside the window, so it is completely filled
• Last fill date September 28, 2022, no notes of finding a leak prior to, or after the fill
  •  ID: 2369 Entry time: Wednesday, September 28, 2022, 13:15

NHC Window Oil Filling

• Oil used was from a separate pail labeled Hot Cell Window Oil, believed to have come from the 55gal mother pail containing Penreco Drakeol 10 B LT Mineral Oil NF
• Nitrogen supply needle valve was closed to prevent oil from blocking this line
• Oil was filled from the removed pressure relief valve position which deviates from the procedure previously used ( ID: 2369 )
  
  • This was done to avoid oil from entering nitrogen supply line and limit oil from entering pressure gauge 
  • Valve from previous fill location (alleged old accumulator location) was also open to encourage better breathing
• ~1,775mL added via squeeze bottle before oil was seen in the indicator tube. Another ~1100mL was added via squeeze bottle to bring oil fill indicator to the previous 2022 fill mark that is about halfway up the tube. 2,875mL Total
  • This is considerably more oil added than in 2022 (1.5L)
  • Location of oil level and fill date marked on indicator tube and on reservoir  with blue Sharpie 
• Accumulator valve closed, Pressure relieve valve re-installed, nitrogen supply line valve opened 
  • 1.8 inH2O reached in ~10 minutes. 2.2inH2O was indicated the next morning 

Notes

• Oil level check on quarterly safety walks will be added
• Increased checking interval during the first quarter will be performed 
• Unrelated NHC entries in 2024 did not note any oil leaks, so not sure where 2.5L+ of oil has gone in 2.5 years
• SHC window oil level has remained about halfway up the indicator tube.