One of the GS13s of HAM-ISI unit #6 (Pod #94) appeared to be defective this week (see aLog 3183).
Greg and I opened it this morning. Two flexures were broken.
One can see wear on the non-broken side of D0901319-v4, s/n199 (Pic. 3,4). The pattern is very similar to what Jim reported in the SEI Log a few months ago.
We also found a small flexure debris. This debris was identified as being part of D0901318-v3 s/n 124 (see black line on pic. 5).
The pod was tested at reception on a leveled surface. Nothing abnormal could be seen on its response at that time. It was then installed in the ISI. No major event was reported (drop/shock/…). Spectra were taken with the ISI tilted and the pod appeared defective. Any spectra, even with the ISI leveled showed it defective after that.
As it already happened, it is possible that the shocks, endured by the instrument during its shipment, damaged the flexures. In these conditions, tilting the pod back and forth to install it, and/or tilting the ISI for testing purposes, could have lead to the breakage.
We have shockwatch data for this shipment. Greg will post it later on.
This shipping log was less eventful, especially as the threshold had been set higher, than the previous LHO-LLO. A big difference in this shipment was the large vertical shocks whereas the previous one had seen mostly horizontal. 3 of the 4 events also happened in Louisiana going by the time stamps.
It appears that pod #94 was already shiped back to LLO in March to be reworked after a pre-amp issue. see alog #2369.
Nothing was noticed on its flexures then. If the flexures were not changed at LLO, they saw at least 3 Livingston-Hanford trips .
In his aLog, Greg also mention a similar issue experienced on Pod #71: Working at reception. Stopped working afterwards. Opened and broken flexure found.
DCC document Q1100073 sensor issues tracking was updated.
I went through the history/time-series/spectra available for the Pod #94 (H1).
06/05 the batch of GS13s the Pod #94 belongs to, is sent from LLO.
06/12 Pod #94, and all the pods of that batch, are huddle tested OK (Plot 1). None of their spectra show partiicularities (H2 channel corresponds to the horizontal GS13 #58 which was already in the ISI).
06/13 Pod #94 is installed in HAM-ISI Unit #6 with the Pod #66(H) from the same batch. Interfaces chassis are turned ON. All instruments are tested OK (Plot 2).
06/14 Plot.3 shows that Pod #94 was functional, with no particularities on its spectra, until the interfaces chassis were turned OFF around 3.45 PM
06/19 Interfaces chassis are turned back ON around 10am. Pod #94 appears defective right away (Plot 4). It seems like the flexure breakage happened during the re-installation of the GS13s, even though no major event was reported (shock, drop, ...).
I can not notice any feature on spectra/time series that would have warned us of upcoming flexure breakages.
While talking about it at today's SEI call, we agreed on gently tilting the GS13s back and forth before huddle testing them at reception, so we can discard the GS13s with flexures that are about to break.
