
1 3Vickers by Danfoss Target-Pro 2 Analyzer and Sampler Operation Manual V-PP-MC- 2-E July 2 23
Ta r g e t C l e a n l i n e s s L e v e l s
You can use cleanliness levels to establish bench-
marks. If you have no com onent failures over a
rolonged testing eriod, the average level meas-
ured during that time may be an acce table goal. If
you need to reduce equi ment failures, want to
increase com onent life, or ex ect conditions to
change considerably, you can establish a higher
benchmark and use testing to hel reach it.
An acce table level of cleanliness de ends on
three features: 1. the contamination sensitivity of
com onents; 2. the o erational conditions of the
system; 3. and the required reliability and life
ex ectancy.
NAS [National Aerospace Standard] 1638 Cleanliness Code System
Maximum Contamination Limits (per 1 ml)
Size Range Classes (in microns)
1234567891 1112
5–15 125 25 5 1 2 4 8 16 32 64 128 256 512 1 24
15–25 22 44 89 178 356 712 1425 285 57 114 228 456 912 1824
25–5 4 8 16 32 63 126 253 5 6 1 12 2 25 4 5 81 162 324
5 –1 1 2 3 6 11 22 45 9 18 36 72 144 288 576
Over 1 1 1 2 4 8 16 32 64 128 256 512 1 24
Cleanliness Code Chart (with 100mL sam le volume)
H y d r a u l i c C o m p o n e n t M a n u f a c t u r e r s ’
R e c o m m e n d a t i o n s
Manufacturers know the effects of contamination. They issue
maximum ermissible contamination levels, and
remind users that cleaner fluids will im rove erformance
and increase com onent life. But no one hasestablished a
single standard for the cleanliness of hydraulic fluid, in art
because working conditions are different for any two a li-
cations. As a result, even trusted sources of information on
cleanliness levels give varying recommendations.
The table below should hel you get started. It gives a
selection of maximum contamination levels that arety ical-
ly issued by com onent manufacturers. These relate to the
use of the correct viscosity mineral fluid. An even cleaner
level may be needed if the o eration is severe, such as high
frequency fluctuations in loading, high tem erature or high
failure risk.
Note: The recommendations in this table should be viewed as
starting levels; adjust them as needed to reflect o era-
tional ex eriences or user requirements.
U N I T T Y P E I S O 4 4 6 C O D E
Pump Piston (slow speed, in-line) 22/ 2 / 1 6
Piston (high speed, variable) 17/ 1 5/13
Gear 19 / 17/ 1 5
Vane 18/16/14
Motor Axial piston 18 /1 6/ 13
Radial piston 19 /17/13
Gear 2 /1 8/15
Vane 19/17/14
Valve Directional (solenoid) 2 /18/15
Pressure control (modulating) 19/17/14
Flow control 19 /1 7/1 4
Check valve 2 /1 8/1 5
Cartridge valve 2 /1 8/1 5
Proportional 18/16/13
Servo valve 16/14/11
Actuator 2 /18/15
Ty ical Manufacturer Recommendations for Com onent Cleanliness (ISO 4406)
The NAS system was develo ed in 1964 to define classes
of contamination in aircraft com onents.This standard was
extended to industrial hydraulic systems sim ly because
nothing else existed at the time.
The coding system defines the maximum numbers ermit-
ted of 100ml volume at various size intervals (differential
counts) rather than using cumulative counts as in ISO 4406.
Although the standard rovides no guidance for quoting lev-
els, most industrial users quote the highest code recorded
in all sizes; this convention is used on the Target-Pro 2.
Contamination Level Classes according to NAS 1638
(January 1964)
Each contamination class is defined by a number from 00 to
12 that indicates the maximum articles er 100 ml, counted
on a differential basis, in a given size bracket.
Contamination Correspondent Recommended Typical
Codes Codes Filtration Applications
ISO4406 NAS1638 Degree
4µm(c) 6µm(c) 14µm(c) Bx ≥200
14 12 9 3 3 High precision and
laboratory servo-systems
17 15 11 6 3–6 Robotic and
servo-systems
18 16 13 7 1 –12 Very sensitive–high
reliability systems
2 18 14 9 12–15 Sensitive–reliable systems
21 19 16 1 15–25 General equipment
of limited reliability
23 21 18 12 25–4 Low-pressure equipment
not in continuous service