3 ms·

They say thermal imaging could have identified the issue, does that mean that it was actually a low voltage power line, not a signal line? Do they have cameras

They say thermal imaging could have identified the issue, does that mean that it was actually a low voltage power line, not a signal line? Do they have cameras that can see the heat from sub-mA connections? I wonder what kind of diagnostics and logging they have for their power distribution?

mikewarot 11mo ago
> Do they have cameras that can see the heat from sub-mA connections? If it was hooked to a circuit breaker, it wasn't a sub milliamp connection. A thermal camera might have been able to see the heat from arcing at the connection point. It could have caused a hot spot visible on thermal imaging.
- eternityforest 11mo ago
  The article claims it's a "low voltage signal wire", but perhaps they meant to say a low voltage power wire?
  - mikewarot 11mo ago
    According to the report, on page 7[1], it was connected to a WAGO terminal block 280-681 connector. Looking that up on Digikey[2,3] finds that it's a connector suitable for 28 through 12 AWG, up to 800 volts and 24 amps.(UL 20 Amps) According to "3 - ENGINEERING - DALI - ENGINEERING FACTUAL REPORT"[5], page 20, the circuit was DC, 110 volts, going to a circuit breaker's "under voltage release" terminal. It was 17 AWG, according to page 23. It apparently goes to a solenoid, and if [6] is in any way typical, it's only 2-6 watts of power in normal operation. This yields a current of 20-50 milliAmps. Here's a nice animation of the connection failure on that wire.[4] [1] https://www.ntsb.gov/investigations/Documents/Board%20Summary%20Contact%20of%20Containership%20Dali%20with%20Francis%20Scott%20Key%20Bridge.pdf https://www.ntsb.gov/investigations/Documents/Board%20Summar... [2] https://www.digikey.com/en/products/detail/wago-corporation/280-681/13549659 https://www.digikey.com/en/products/detail/wago-corporation/... [3] https://wago.priintcloud.com/datasheets/280-681/en_GG/d41d8cd98f00b204e9800998ecf8427e?attempt=1&signature=d4308f072daccce5371849c553978cc3_1iespcbe7 https://wago.priintcloud.com/datasheets/280-681/en_GG/d41d8c... [4] https://www.youtube.com/watch?v=bu7PJoxaMZg https://www.youtube.com/watch?v=bu7PJoxaMZg [5] https://data.ntsb.gov/Docket/Document/docBLOB?ID=19228257&FileExtension=pdf&FileName=DALI%20-%20DCA24MM031%20-%20Engineering%20-%20Factual%20Report%20-%20FINAL-Rel.pdf https://data.ntsb.gov/Docket/Document/docBLOB?ID=19228257&Fi... [6] https://abbsales.com/pdfs/tmax_techspecs.pdf https://abbsales.com/pdfs/tmax_techspecs.pdf
    - eternityforest 11mo ago
      Wow, that's a lot of amazing information, so many details that just get glossed over if you don't read the full report!

mikewarot 11mo ago

> Do they have cameras that can see the heat from sub-mA connections? If it was hooked to a circuit breaker, it wasn't a sub milliamp connection. A thermal camera might have been able to see the heat from arcing at the connection point. It could have caused a hot spot visible on thermal imaging.

eternityforest 11mo ago
The article claims it's a "low voltage signal wire", but perhaps they meant to say a low voltage power wire?
- mikewarot 11mo ago
  According to the report, on page 7[1], it was connected to a WAGO terminal block 280-681 connector. Looking that up on Digikey[2,3] finds that it's a connector suitable for 28 through 12 AWG, up to 800 volts and 24 amps.(UL 20 Amps) According to "3 - ENGINEERING - DALI - ENGINEERING FACTUAL REPORT"[5], page 20, the circuit was DC, 110 volts, going to a circuit breaker's "under voltage release" terminal. It was 17 AWG, according to page 23. It apparently goes to a solenoid, and if [6] is in any way typical, it's only 2-6 watts of power in normal operation. This yields a current of 20-50 milliAmps. Here's a nice animation of the connection failure on that wire.[4] [1] https://www.ntsb.gov/investigations/Documents/Board%20Summary%20Contact%20of%20Containership%20Dali%20with%20Francis%20Scott%20Key%20Bridge.pdf https://www.ntsb.gov/investigations/Documents/Board%20Summar... [2] https://www.digikey.com/en/products/detail/wago-corporation/280-681/13549659 https://www.digikey.com/en/products/detail/wago-corporation/... [3] https://wago.priintcloud.com/datasheets/280-681/en_GG/d41d8cd98f00b204e9800998ecf8427e?attempt=1&signature=d4308f072daccce5371849c553978cc3_1iespcbe7 https://wago.priintcloud.com/datasheets/280-681/en_GG/d41d8c... [4] https://www.youtube.com/watch?v=bu7PJoxaMZg https://www.youtube.com/watch?v=bu7PJoxaMZg [5] https://data.ntsb.gov/Docket/Document/docBLOB?ID=19228257&FileExtension=pdf&FileName=DALI%20-%20DCA24MM031%20-%20Engineering%20-%20Factual%20Report%20-%20FINAL-Rel.pdf https://data.ntsb.gov/Docket/Document/docBLOB?ID=19228257&Fi... [6] https://abbsales.com/pdfs/tmax_techspecs.pdf https://abbsales.com/pdfs/tmax_techspecs.pdf
  - eternityforest 11mo ago
    Wow, that's a lot of amazing information, so many details that just get glossed over if you don't read the full report!