nas 1683and iso4406[1]清洁度标准

Particle contamination in oil is specified from particle count. Two basic standards the ISO and NAS systems are com-monly used as contamination reference. The two cleanliness standards can not be directly compared or converted, as the basic principles within the two systems differ to much. This is explained in the next pages.

However, the following tables gives some rough guidelines of common practice for setting targets of cleanliness levels in different systems. As seen both ISO 4406 and NAS 1638 are represented. These guidelines are minimum fluid cleanliness levels required for an acceptable lifetime of equipment and

components.

Many factors influence lifetime and demands to fluid quality. High reliability systems enhance demands to quality, and high pressure systems and heavy bearing load increase de-mands.

The last three columns of the tables indicate the range of the GreenOil filter system. Although the filters may be put into

service in many application, parameters as fluid volume and viscosity should be taken into consideration before expecta-tions to contamination limits are set. Working with ISO4406 and NAS 1638

GreenOil Standard

Date: 15-12-2005

T echnical Paper 004

Particle Contamination ISO4406 and NAS1638

Page 1 af 3

Saved as: Technical Paper 004

Hydraulic Equipment and Components Pressure Range GreenOil

Filter Inserts

ISO 4406 NAS 1638 H

T

M

Silt sensitive, aerospace, robots, High pressure 250-400 bar

14/12/9 4 ISO 10/6 NAS 3

Servo systems, injection moulding, High pressure 250-400 bar 16/14/11 5

Proportional and flow valves, High pressure 250-400 bar 17/15/12 6 Piston pumps and motors, Normal pressure 150-250 bar 18/16/13 7 Typical new hydraulic oil

18/16/13 7 Gear pump and motors,

Medium pressure 50-150 bar 19/17/14 8 Cylinders and Flow Control Low pressure 0-50 bar

20/18/15

9

Lubrication Oil

Equipment and Components

Ball bearings, turbine oils, Small and medium gearboxes 14/12/9 4

Roller bearings

Transmission gearboxes 16/14/11 5 ISO 14/11

NAS 5

Journal bearings

Industrial gearboxes

17/15/12 6

Mobile equipment and gearboxes Paper mill

18/16/13 7 ISO 16/12

NAS 7

Diesel engine lubrication

19/17/14 8 Heavy duty gearboxes

20/18/15 9 Typical new lubrication oil

20/18/15 9 Typical in-line filtration

21/19/15

10

Minimum

Class Requirement

Page 2 T echnical Paper 004 Introduction

Contamination in oil is specified from particle count. Two basic methods are used:

Laser based particle count analysis equipment gives directly information on particle sizes (micron= u) and figures within specified size ranges.

The other method utilize filtering an oil sample through an very fine mesh filter paper. The particles on the surface of the filter paper is then monitored in a microscope and com-pared to standard contamination pictures to indicate the de-gree of contamination.

Contamination classes

Instead of specifying particle counts contamination is sepa-rated into classes defined in two major systems ISO (International Standard Organisation) and NAS (National Air-space Standard). Each class defines a range of counts within an exponential scale.

Unfortunately, the two systems are not identical and can not be converted in simple mathematics. However, some simple guidelines can be given. First of all let’s look at the two sys-tems.

NAS1638

The NAS system divides particles in 5 ranges. Furthermore, the NAS system specify different counts within each particle range to score a specific class.

In practice oil samples will show up to gain almost same NAS class rating within the different particle ranges. The system is designed to match the most common found con-tamination which has really many small particles and fever big particles. The sidebar example shows a typical oil analy-sis with counts divided in the 5 classes. As seen the classes ranges from 3 to 6, however, the resulting NAS class is de-fined as the particle count with the highest (worse) score, and only this class is specified.

The sidebar example will be classified as “NAS1638 class 6”. Classes

5 to 15 15 to 25

25 to

50

50 to

100 > 100

00 125 22 4 1 0

0 250 44 8 2 0

1 500 89 16 3 1

2 1,000 178 32 6 1

3 2,000 356 63 11 2

4 4,000 712 126 22 4

5 8,000 1,425 253 45 8

6 16,000 2,850 506 90 16

7 32,000 5,700 1,012 180 32

8 64,000 11,400 2,025 360 64

9 128,000 22,800 4,050 720 128

10 256,000 45,600 8,100 1,440 256

11 512,000 91,200 16,200 2,880 512

12 1,024,000 182,400 32,400 5,760 1024

Particle Classes Size Range per 100 ml NAS 1638

Particle range Counts Class 5-15 u 8450 6

15-25 u 11982 5

25-50 u 312 6

50-100 u 46 6

>100 u 2 3 Resulting class 6

NAS analysis example