aLIGO LHO Logbook

LHO VE

chandra.romel@LIGO.ORG - posted 17:10, Tuesday 27 February 2018 - last comment - 20:46, Tuesday 27 February 2018(40751)

CP4 bake commissioning

We tested the CP4 regen heater today and it works! We can adjust the P-I-D parameters in Beckhoff as needed, but "proportional gain" parameter alone does the job. Heated the GN2 to 30 deg. and verified that the "regen over temperature" interlock works and trips heater and does not reset automatically.

The bake enclosure contractor was on site today to program and hard wire thermocouples for heater over-temperature protection. Programmer will be back tomorrow morning to finish up. We are leaving the fan run overnight for testing.

Note that there was a pressure surge on PT-245 as a result of Kyle installing the N2 needle valve on CP4's turbo. It was quick enough to not cause alarms, but does show up on pressure trends.

Comments related to this report

kyle.ryan@LIGO.ORG - 19:21, Tuesday 27 February 2018 (40758)

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With the turbo purge port needle valve installed, we are now admitting UHP N2 and will be until the month long bake of CP4 is finished.  GN2 purge is intended to prevent water condensation accumulating in the positive displacement backing pump and flow has been adjusted so as to be the dominate gas load.  This has brought the foreline pressure up to 2.2 x 10-2 torr.  As a consequence, CP4's pressure has responded and flattened out at a value slightly higher than was seen with the lower foreline pressure - the compression ratio of the turbo being near constant at these pressures.

chandra.romel@LIGO.ORG - 20:46, Tuesday 27 February 2018 (40761)

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Worth noting too that the turbo gate valve was closed during the needle valve installation so pressure rise up to 0.7 Torr was seen only on turbo side and not in CP4 volume.