[Chris, Corey, Dave, Jim, Mark, Nicole, Randy, Rodney, Steve, Zak]
After a late morning start, we commenced taking the BSC4 Dome at around 10:30am, and finished this around 11:40. After lunch, on O2 sensor reading was taken of the BSC4 chamber, Jim accessed the chamber via HAM10 (Zak & I acted as "spotters" to keep an eye on him while he was in a non-permit confined space), Jim disconnedted the Support Tube Bolts & the cabling from inside the chamber. Platforms were then installed and the Seismic Stack was pulled out from the chamber and laid down near the Large Roll-Up door. The Down Tube was rotated and laid down on the top of the Optics Table (we can de-stack this assembly tomorrow). Note: 8' straps don't allow for easy twisting of the Down Tube.
The other theater of SEI work in the LVEA was the cutting of the BSC8 Down Tube. The Down Tube was cut so the Support Table could be pulled out. The Support Table will be used as a hard fixture to maintain Support Tube rotation and position for the Mid-Station Chambers that get moved to the End Stations. (photos of the hacked Down Tube are attached)
Forgot to make mention of this in the elog from yesterday, but while inspecting the seismic stack for BSC4, just before lifting it out, we found an oddity: a rogue aluminum part. For the BSC Seismic Isolation stack, the Optics Table and Down Tube fit through a hole in the Support Table. There is a gap here between 0.5-0.75". But yesterday it was discovered there was a loose part closing this big gaps to just millimeters (see the 4th & 5th photos from the elog above). This part was loosely laying on the Support Table. It wasn't contacting the Down Tube, but perhaps during a big enough seismic event, this could cause a "seismic short" between the "ground" and the isolated Optics Table.
Attached is another photo of this mysterious part.
Wanted to write up a little something from the recent BSC4 work--especially while it's still fresh in my brain. This is mainly with regards to Safety related items.
The De-Install of an iLIGO PISI (Passive Internal Seismic Isolation) system is a major site activity encompassing several different and unique safety situations. Some of the issues have been documented and are familiar, but there are also other issues we need to be aware of or address in the future. Mark Hankel has brought up several points while observing our recent de-install, which will be helpful for next time. Below, I've bulleted some safety-related notes to keep in mind for this (and similar) activities.
Working From Elevation
Fair amount of work requires personnel to work at high elevations within a Clean Room (i.e. on top of Beam Tubes, Cross Beams, etc.). When one needs to work from these high elevations and can't work from a platform ladder, they must first connect to a Deceleration Device. On our BSC Cleanrooms the Deceleration Devices will be left connected to the recently-installed Anchoring Brackets on the Clean Room. We need to also leave a "tag line" connected to the Carabiner of the Deceleratin Device so one can pull it to one's person and attach it to their harness for high elevation work.
On a related note, there was some work/observation from the nearby Mezanine. We want to make sure personnel do not climb on the railing; the railing is the designed fall protection for the Mezanine. If viewing is an issue, perhaps the manlift can be used. Or simply rely on the hand signals of the person directing the craning activity.
Something to consider with all of this safety rigging: we now have much more combersome straps and gear on us. It does make walking around a little tougher than what we are used to. Sometimes it feels like there is a potential for the fall protection to actually cause a fall. The other issue is our Deceleration Device Anchors. We only have two Anchoring brackets in our cleanroom. It would be nice to have another pair of anchors available such that we don't have to extend the Deceleration Devices to their limits (this is what happened during Platform installation).
Mark has mentioned that our Fall Protection rigging should be all purchased from the same vendor. Mixing different componenets may nullify their ratings.
The ring at the back of our harness can be hard to access. An extension proved to make connecting the Deceleration Device easier. (we only have one on site as of now)
Non-Permit Confined Space
Mark et. al. have classified our Dome-less BSC2 & BSC4 (with an adjacent HAM Chamber door removed) as Non-Permit Confined Spaces. With this space, we decided an O2 reading should be taken of the chamber before occupying it. The cover was partially removed from the top of the chamber and an O2 Sensor wand with ~6' of tubing was dropped into the chamber to take readings. This is a dirty device, so did our best to not contact/contaminate in-vacuum surfaces. Readings were taken outside the chamber (20.8% O2), ground-level within the chamber (20.9% O2), and chest-level within the chamber (20.9% O2). We used an OXOR III O2 Sensor. After we saw adequate levels, entry was made, and a "spotter" was located at the HAM10 door entry the entire time someone was inside BSC4.
Critical/Heavy Loads
For this work we have several lifts of heavy loads. During these activities we do not want anyone under a load under a load. The toughest action related to this is draping covers under the Dome and over the BSC Chamber while the Dome is suspended inside the Clean Room. It is possible to walk a cover from one side to the other without needing to put a hand under the load; it was helpful to have spring clamps to help hold the initial end of the cover on the flange.
When handling the individual Leg Element masses it is acceptable to pull stuck Viton Spring Seats off from underneath the masses by hand, but using a tool could also be an option here.
Without the crane, the other tough loads to handle are the BSC Chamber Platforms. These need to be kept clean and taken up to the top of the BSC Chamber by hand. This can be a cumbersome task.
Discussing/Talking Out Activity Before Starting Work
We currently meet and go over the procedure and hazardous analysis for activities such as this amongst all people who will be involved with the work and Mike Landry. This has been a one-time occurrence at the beginning of the first time one is involved with the procedure. It may be beneficial to have more of a "before work" talk about the work. Here we can go over what we're doing, safety issues, input from people to make it go smoother, etc.