Specifications

69
ISO code
numbers
Type of system
Typical
components
Sensitivity
23 / 21 / 17 Low pressure systems with large clearances Ram pumps Low
20 / 18 / 15 Typical cleanliness of new hydraulic oil straight
from the manufacturer.
Low pressure heavy industrial systems or
applications where long-life is not critical
Flow control valves
Cylinders
Average
19 / 17 / 14 General machinery and mobile systems
Medium pressure, medium capacity
Gear pumps/motors Important
18 / 16 / 13 World Wide Fuel Charter cleanliness standard for
diesel fuel delivered from the  lling station nozzle.
High quality reliable systems
General machine requirements
Valve and piston
pumps/motors
Directional and
pressure control valves
Very important
17 / 15 / 12 Highly sophisticated systems and hydrostatic
transmissions
Proportional valves Critical
16 / 14 / 11 Performance servo and high Pressure long-life
systems
e.g. Aircraft machine tools, etc.
Industrial servovalves Critical
15 / 13 / 09 Silt sensitive control system with very high
reliability
Laboratory or aerospace
High performance
servovalves
Super critical
NOTE: The three fi gures of the ISO code numbers represent ISO level contamination grades for
particles of >4μm(c), >6μm(c) and >14μm(c) respectively.
Suggested Acceptable Contamination
Codes