Hydraulic oil cleanliness level corresponding table
September 18, 2022
At present, my country's lubricating oil manufacturers still control the particulate matter of hydraulic oil with "mechanical impurities" <0.005%, while foreign countries mostly use NAS 1638 of the National Aeronautics and Space Administration (NAS) and ISO 4406-1987 of the International Organization for Standardization (ISO). Cleanliness levels come constant. For example, hydraulic system requirements for oil cleanliness are as follows: Large clearance, low pressure hydraulic system: NAS 10～12 (approximately equivalent to ISO 19/16～21/18, allowable ≥5μ particle count/ml: about 5,000～20,000; ≥15μ: about 640～2,500 ) Medium and high pressure hydraulic system: NAS 7～9 (approximately equivalent to ISO 16/13～18/15, allow ≥5μ particle count/ml: about 640～2,500; ≥15μ: about 80～320) Sensitive and servo high pressure hydraulic system: NAS 4～6 (approximately equivalent to ISO 13/10～15/12, allowable ≥5μ particle count/ml: about 80～320; ≥15μ: about 10～40). At present, the hydraulic oil produced by ordinary processes in my country can generally only reach NAS 8 to 10.
What I want to share with you today is the "Corresponding Table of Hydraulic Oil Cleanliness Grades". Hydraulic oil cleanliness level corresponding table
The NAS1638 grade standard defines the allowable contamination levels of various hydraulic system fluids. At present, for hydraulic systems manufactured abroad, the oil pollution level at the beginning of use is controlled at NAS7 level or above. When the hydraulic system is lowered to NAS9 level after use, the hydraulic system generally does not fail. When the pollution level is reduced to NAS10~11 The hydraulic system will occasionally malfunction during the stage. When the contamination level of the oil drops below the NAS12 level, there will be frequent failures, and the hydraulic oil must be circulated and filtered. Note: NAS1638 is segment counted and has 5 size segments. Since the contamination levels of the actual oil sizes cannot be the same, the contamination level of the tested oil sample is determined according to the highest level, which causes a problem. For example, the measured pollution degree of 5~10μm may be grade 4, the pollution degree of 15~25μm particles may be grade 6, the pollution degree of 25~50μm may be grade 5, and the pollution degree of 50~100μm particles may be grade 8. When data is difficult to process, it often makes concepts unclear. If conservative, it will be judged as level 8 according to the regulations, and the system is considered to be dirty.
In fact, the new wear theory shows that only particles with a size comparable to the movement gap of the components will cause serious wear, that is to say, particles of 5~15μm are the most harmful, and 50~100μm can not enter the movement gap, which has an impact on wear and tear. But not big. NAS cleanliness level representation: NASX, X represents a number, the smaller the number, the higher the cleanliness level. Such as NAS8, which means NAS1638 standard, the abbreviation of 8-level pollution. NAS ratings are interchangeable with ISO ratings, but not absolute. The NAS level corresponding to ISO17/15/13 cleanliness level is basically around NAS6 level. ISO 4406 23/19/16 indicates the degree of contamination of hydraulic oil, Where 23/19/16 is the pollution degree code, The first code indicates the particle size greater than 4μm, The second code indicates the particle size greater than 6μm, The third code indicates the particle size greater than 14μm, Example: Code 23, indicating that the oil is larger than 4μm and the number of particles is in the range of 40000-80000 (the number of particles in 1ml). The specific number of particles can only be known through particle counting. There are also NAS standards. The following table is the ISO pollution degree registration code table:
