The tank sight glass marked up to show where an acceptable level is allowed and what point the low level alarm and cut out kicks in. The technicains and operators know that they do not need to top up until the oil gets close to the bottom of the green band. Previously they either were topping up too regularly is the system was losing oil through small leaks or they assumed that as long as there was oil in the sight glass it would be ok. An oil level close to the bottom of the sight glass kicks in the minimum level alarm and then the low level machine stop.
