The XT V 160 is an open-tube design so that replacement of the electron beam-producing filament can be scheduled a couple of times per year for a cost of a few pounds. Filament replacement takes minutes, so downtime is short. A sealed tube, on the other hand, will last for a couple of years but can stop working without warning, perhaps at the worst possible time for the user. The manufacturer then has to be called in to renew the tube at a cost of many thousands of pounds and the machine is down for days.
With one or two products per batch to be X-rayed for QA, the machine will be in constant use once the process has been finally established.