During the usual recovery procedure after the planned and announced cycling of the SASE1 VAC loop yesterday, we observed a serious mistake by somebody:

The gatevalve(s) of the DP section in XTD9 were opened before the related turbo pumps were (fully) operating.
This caused a pressure increase on the UHV-side to briefly 1E-2mbar (!) and for about 30min to 1E-3mbar before this was cured.
Essentially the prevacuum side gases entered the UHV-side through the DP-turbos, that's not good at all.
Especially it would be tragic, if we had the XGM high voltages on during such a mistake (which was luckily not the case)
Below is the pressure record of the XGM UHV vacuum gauge.

This must not happen again ! Therefore please observe the following points:
1) after PLC reboots, these valves shall only be opened by the experts who know the correct sequence
2) the pressures and TP operation must be verified before opening these valves.
3) WP74 (e.g. Jan or Theo) and VAC (e.g. Raul) must be informed about a planned recycling of the VAC loop (this is an established scheme and always worked very well, also yesterday)

Explanations to graph:
13h30 the preparation of the cycling started with closing the XGM vatterfly valves by WP74
14h00 apparently the gate valves of the entire gas section closed at the PLC reboot which increases slightly the pressure at the XGM
around 14h18 the pressure shoots up although nothing changed at the XGM, and it is found that DP gatevalves are open without full operation of the associated turbos
around 14h50 (after some cross-checking and phone calls) the concerned gate valves were closed and the vatterfly valves at the XGM were opened to bring the XGM (and the entire gas section) down to about 1E-7mbar