This past June in the USA, we trained our customers local crew on the Trojan TDOS system they had recently purchased.
This was their first experience using an online, unattended filtering system anywhere on their network. Prior to this, any transformer that required moisture or gas removal was scheduled for an outage and an offline vacuum processor was brought in.
The inevitable conclusion was that the offline process did not provide the long term moisture reduction results they were seeking: extending the operational life of the transformer by halting the rate of paper degradation.
During our time onsite they commissioned the TDOS to an energised transformer.
The crew then set the TDOS in the desired treatment program, packed up and left the site.
In the intervening couple of months they had no need to visit the site to check on the unit: replacing site visits with remote communications to check on its operating status and download data.
This TDOS has since moved onto other transformers after achieving pretty awesome results on this first one. Not a single cent has been spent on consumables.