液压油污染度等级 ISO and NAS GB 02-10-07

Particle contamination in oil is specified from particle count. Two basic standards the ISO and NAS systems are commonly used as contamination reference. The two cleanliness stan-dards 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 dif-ferent systems. As seen both ISO 4406 and NAS 1638 are repre-sented. These guidelines are minimum fluid cleanliness levels required for an acceptable lifetime of equipment and compo-nents.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 demands. The last three columns of the tables indicate the range of the GreenOil filter system. Although the filters may be put into ser-vice in many application, parameters as fluid volume and vis-cosity should be taken into consideration before expectations to contamination limits are set.Hydraulic Equipment and Components Pressure Range GreenOil Filter InsertsISO 4406 NAS 1638HT M Silt sensitive, aerospace, robots, High pressure 250-400 bar14/12/9 4 ISO 10/6 NAS 3Servo systems, injection moulding, High pressure 250-400 bar 16/14/11 5Proportional and flow valves, High pressure 250-400 bar 17/15/12 6Piston pumps and motors, Normal pressure 150-250 bar 18/16/13 7Typical new hydraulic oil18/16/13 7Gear pump and motors, Medium pressure 50-150 bar 19/17/14 8Cylinders and Flow Control Low pressure 0-50 bar 20/18/159Lubrication OilEquipment and ComponentsBall bearings, turbine oils,Small and medium gearboxes 14/12/9 4Roller bearingsTransmission gearboxes 16/14/115ISO 14/11 NAS 5 Journal bearings Industrial gearboxes17/15/12 6Mobile equipment and gearboxes Paper mill18/16/137ISO 16/12 NAS 7Diesel engine lubrication19/17/14 8Heavy duty gearboxes20/18/159Typical new lubrication oil20/18/15 9Typical in-line filtration21/19/1510MinimumClass Requirement Page 1 of 3IntroductionContamination in oil is specified from particle count. Two basicmethods are used:Laser based particle count analysis equipment gives directlyinformation on particle sizes (micron= u) and figures withinspecified size ranges.The other method utilize filtering an oil sample through an veryfine mesh filter paper. The particles on the surface of the filterpaper is then monitored in a microscope and compared tostandard contamination pictures to indicate the degree of con-tamination.Contamination classesInstead 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 withinan exponential scale.Unfortunately, the two systems are not identical and can not beconverted in simple mathematics. However, some simpleguidelines can be given. First of all let’s look at the two systems.NAS1638The NAS system divides particles in 5 ranges.Furthermore, the NAS system specify different counts withineach particle range to score a specific class.In practice oil samples will show up to gain almost same NASclass rating within the different particle ranges. The system isdesigned to match the most common found contaminationwhich has really many small particles and fever big particles.The sidebar example shows a typical oil analysis with countsdivided in the 5 classes. As seen the classes ranges from 3 to 6,however, the resulting NAS class is defined as the particle countwith the highest (worse) score, and only this class is specified.The sidebar example will be classified as “NAS1638 class 6”.Classesu 5 to 15 15 to 25 25 to 50 50 to 100 > 10000 125 22 4 1 00 250 44 8 2 01 500 89 16 3 12 1.000 17832 6 13 2.000 356 63 11 24 4.000 71212622 45 8.000 1.425 253 45 86 16.000 2.85050690 167 32.000 5.700 1.012 180 328 64.00011.4002.025360649 128.000 22.800 4.050 720 12810 256.000 45.6008.1001.44025611 512.000 91.200 16.200 2.880 51212 1.024.000182.40032.4005.7601024Particle Classes Size Range per 100 mlNAS 1638Particle range Counts Class5-15 u 8450 615-25 u 11982 525-50 u 312 650-100 u 46 6>100 u 2 3Resulting Class 6NAS analysis exampleISO 4406The ISO system is not as practical orientated as the NAS system. First of all it consists of 2 or 3 figures. Each figure define a class within a size range. A typical ISO 4406 oil test will be indicated as:17/15/12Particles > 2 u Particles > 5 u Particles >15 uAs seen particles less than 2 u are omitted. The original ISO4406 operated with only two digits omitting counts below 5 u. This standard is still widely accepted, though it does not relieve the same information as the newer 3 digit ISO version.15/12Particles > 5 u Particles > 15 uThe cleanliness levels represent the particle counts as shown in the table.(Not to get stuck in mathematics: the class represents powers of the numeral 2. A cleanliness level 15 indicates counts between 214 (16,383) and 215 (32,768) for a sample of 100 ml fluid). As seen, each time the class is reduced one digit the particle count is halved.The sidebar example will be classified “ISO4406 17/15/12”NAS and ISOTo conclude: NAS and ISO can not be compared directly. As seen both NAS and ISO operates exponentially. In both sys-tems, the particle counts must be halved to reduce the class or cleanliness level one digit.In practice the great advantage of the NAS system is that con-tamination is identified by only one class number. For identify-ing contamination sources this could be a limitation which does not apply as much for the ISO system which is more open yet complicated.The NAS and ISO 2-digit systems does not take particles less than 5 u into consideration. The ISO 3-digit system monitors down to 2 u particles.The ISO system has the same class definition throughout the particle ranges. The NAS system has different definition of class within each particle range .Klasse nummerMere end Op til og med 24 8.000.000 16.000.000 23 4.000.000 8.000.00022 2.000.000 4.000.000 21 1.000.000 2.000.00020 500.000 1.000.000 19 250.000 500.00018 130.000 250.000 17 64.000 130.00016 32.000 64.000 15 16.000 32.00014 8.000 16.000 13 4.000 8.00012 2.000 4.000 11 1.000 2.00010 500 1.000 9 250 5008 130 250 7 64 1306 32 64 5 16 324 8 16 3 4 82 2 4 1 1 20.5100 0.25 0.5Antal partikler per 100 ml ISO 4406ISO analyse example: 17/15/12Partikel områdeTællinger Klasser <2 u 96.050 17 5-15 u 23.263 1515-25 u 3.150 25-50 u 256 50-100 u 16 >100 u312。