Solids in Industrial Oils
Hydraulic, gear and other lubricating system fluids do not usually see the extent of contamination that an engine oil is exposed to. However, they do not last indefinitely. Eventually, particulate contaminants will degrade fluid performance and reduce useful life. If contaminant particles are not removed they will circulate and cause additional wear. This wear will continue and result in premature system component failure unless an adequate filtration system is applied or the oil is replaced with new product.
The electronic particle counter is used to determine the cleanliness of these fluids. It is a great deal more sensitive than the tests described in the solids section of this tutorial. Indeed if the total solids test shows any measurable amount of contamination this test would be inappropriate for that fluid. This test measures the size and quantity of the particles in the fluid. The contamination level is then reported as an ISO code. The ISO code represents the number of particles in three different size ranges.
- 4-6 microns
- 6-14 microns
- Greater than 14
The ISO code reports the three "R" or range numbers for above particle sizes. The "R" numbers come from the table below. The smallest (4-6 micron) is reported first and the largest (Greater than 14 microns) is reported last.
Example: ISO Cleanliness Code 21/15/12
This code indicates the following level of contamination.
21- between 10,000 and 20,000 particles per ml between 4 and 6 microns
15- between 160 and 320 particles per ml between 6 and 14 microns
12- between 20 and 40 particles per ml greater than 14 microns
| Number of Particles per mL |
R
Range Number |
| More than |
Up to and Including |
80,000
|
160,000
|
24 |
| 40,000 |
80,000 |
23 |
| 20,000 |
40,000 |
22 |
| 10,000 |
20,000 |
21 |
| 5,000 |
10,000 |
20 |
| 2,500 |
5,000 |
19 |
| 1,300 |
2,500 |
18 |
| 640 |
1,300 |
17 |
| 320 |
640 |
16 |
| 160 |
320 |
15 |
| 80 |
160 |
14 |
| 40 |
80 |
13 |
| 20 |
40 |
12 |
| 10 |
20 |
11 |
| 5 |
10 |
10 |
| 2.5 |
5 |
9 |
| 1.3 |
2.5 |
8 |
| 0.64 |
1.3 |
7 |
| 0.32 |
0.64 |
6 |
| 0.16 |
0.32 |
5 |
| 0.08 |
0.16 |
4 |
| 0.04 |
0.08 |
3 |
| 0.02 |
0.04 |
2 |
| 0.01 |
0.02 |
1 |
The maximum ISO Code recommended for a serviceable oil is dependant on the system. It is related to the clearances between critical moving parts in the system. Typical maximums for common lube systems are given in the following table.
| Pressure |
< 2000 |
2000-3000 |
> 3000 |
| System Component |
Recommended ISO Cleanliness Level |
| Hydraulic Gear |
20/18/15 |
19/17/15 |
18/16/13 |
| Hydraulic Vane |
20/18/15 |
19/17/15 |
18/16/13 |
| Hydraulic Piston |
19/17/15 |
18/16/14 |
17/15/13 |
| Hydraulic Servo |
16/14/12 |
16/14/11 |
15/13/10 |
| Journal Bearings |
17/16/13 |
|
|
| Roller Bearings |
17/15/12 |
|
|
| Ball Bearings |
17/15/12 |
|
|
| Gear Box |
18/16/14 |
|
|
| Transmission |
17/15/13 |
|
|
| Engine |
NA |
NA |
NA |
NA = Test Not Applicable for this system
