Pump Failure and Spill - Lessons Learned
Hey all. So yesterday I was running an eVOLVER experiment overnight. The next morning, I received a text from a colleague in lab. “Hey Santi! Apparently the evolver overflowed (?) last night. Facilities came by and wants you to give them a call.” I came into lab and saw a completely empty bottle of media, some absorbent pads on the floor in front of our eVOLVER, and a small puddle on the bench underneath the unit. Notably, it was still running. After cleaning up, inspecting everything (pumps, lines, sleeves, etc.), and pulling the OD and temperature data, here are my observations:
Vial 3 of our unit overflowed and dumped an entire 1L bottle of media onto the top of the machine spill tray.
Efflux pump 3 could not move any liquid when tested. Upon closer inspection, a fine white dust was seen accumulated around the top of the pump, the metal shaft was turning, but the plastic rollers (white colored, like the aforementioned dust) were not. When disassembled, one of the plastic rollers in Efflux pump 3 showed scoring and abrasions, likely indicating that the metal shaft had been grinding against it. After cleaning and reassembly, the pump appeared to be working adequately (rollers were spinning, liquid was moving).
Sleeve 3 had media at the bottom of the sleeve.
The vacuum line to the spill tray was not turned on, I had forgotten the day before.
The OD and temperature traces for the vial that overflowed (vial 3) both show large aberrations occurring at the same time, likely due to media in the sleeve and therefore indicating the actual time of overflow. Interestingly, the OD reading begins to show extreme noise prior to the overflow event itself.
So, what happened here? This is what I think:
The cultures were growing normally (as seen in the other vial’s trace) and vial 3 successfully completed 1 dilution event at about hour 7.75. After this dilution event, vial 3’s OD reading began to suffer from increased noise. At hour 9.4, the OD reading began to show extreme noise (the reason for which I’m still unsure, any suggestions are welcome). This extreme noise eventually triggered a dilution event at hour 11.25. At this point, efflux pump 3 was not working. The vial began to overflow into the sleeve. The culture now filling sleeve 3 occluded the OD sensor, leading to an even higher OD reading, and the continued pumping of media into the vial until the bottle was empty. Eventually, the media drained out of the sleeve, revealing the OD sensor, and leading to the drop in measured OD at hour 14.5. It was only at this point, I believe, that influx pump 3 stopped running.
Moving forward I will certainly remember to turn on the vacuum line in case of something like this, and only a media bottle of sufficient volume to get through the night, but I definitely do not have much confidence in these pumps. The lack of a true mechanical connection between the shaft and the lobes (relying on only friction to actually make the pump function), makes it seem as if these pumps could fail at any time without warning. While I’m aware of the trick to put adhesive on the shaft to make it grip the rollers better, perhaps future iterations of the eVOLVER platform could benefit from more robust pumps. Additionally, perhaps some creative software safeguards could be implemented to prevent this kind of ‘overflow --> higher OD reading --> continual overflow’ cycle in the event of efflux pump failure (maybe using the huge temperature spike observed, or based on some kind of timing safeguard).
Anything I missed? Looking forward to hearing people’s thoughts. Thanks.