{Kyle, Chandra}
Kyle vented the vertex at 8am (~ 2 hr vent) and then we both climbed on beam tube, each wearing a safety harness tied off to one single crane hook, to remove the 12" conflat flange blank and replace the leaky copper gasket on port located just before NEG #1. Chandra inspected the knife edges on blank and mating flange - all looked good. We noticed a discolored spot on both flanges about the size of a nickel outside of the knife edge on flat flange surface. We wiped it with iso-wipe. It is a cloudy gray color with hints of red/orange outlining - could be rust/corrosion. No photos taken because all four hands were needed and we didn't want to risk dropping anything inside the beam tube! Purge air was flowing strong while the blank was off (off for less than one minute). Old gasket came off with my gloved fingers. New gasket was torqued with flanges metal-to-metal, and we starting pumping down vertex at 10:50 am local.
Rough down pressure curve comparisons of EY and vertex. No surprise that vertex takes longer to pump given pump speed for given volume. We expect to be on turbo pump sometime tomorrow and will leak check either later in the day or Monday.
Measured dew point of vent air was -41C. I forgot to measure the dew point of the pressure equalization "blow down" air just prior to the start of the pump down.