I'm translating a filling-and-capping line checklist (pharmaceutical production), and one of the points of the list goes like this:
Check the vacuum pump for operability. When the pump operates, one can hear the characteristic sound and witness the presence of vacuum in the stoppering unit.
Is there a better way to put it?
The Russian original text puts it quite bluntly:
Проверить работоспособность вакуумного насоса. При включённом насосе слышен характерный звук и присутствие вакуума в узле укупорки.
Check the vacuum pump for operability. When the pump operates, one can hear the characteristic sound and the stoppering unit has vacuum. (this does not look good in English).
The stoppering of a vial using vacuum looks like this - see this YouTube video - only that in my case the system is automated.