How often should servo valves be serviced?

Servo valves are highly dirt sensitive and often many companies have inadequate maintenance standards. Always change filter elements when the dirt alarm switches or the pop up shows. Armageddon. Cleanliness is next to godliness when it comes to hydraulic fluid and servo valves, i.e. it should meet ISO 16/13/9 standards for most applications. Dirty hydraulic fluid is the often at the base of servo valve troubles and therefore servo valves can be used for long periods without being service if you ensure that the fluids used are in good conditions.