Test Oil Cleanliness

Posted on Friday, June 7, 2013 in UEA Blog


Clean oil is critical to keep hydraulic components running properly. Contaminated oil in the hydraulic system will cause hydraulic components to prematurely fail, and consequently greatly reduce the life of the hydraulic system. As a general guideline, the ISO 4406:1999 cleanliness code is used to quantify particulate contamination levels per milliliter of fluid at 3 different sizes 4µ (micrometer), 6µ and 14µ. One micrometer (µ) equals to 0.000001 meters, or 0.00003937 inches. The ISO 4406 cleanliness code is expressed in 3 numbers (for instance, codes 18/16/13, the first number “18” indicates the counts for particles size larger than 4µ per millimeter oil are greater than 1300 but less than 2500; the second number “16” indicates the counts for particles size larger than 6µ per millimeter oil are greater than 320 but less than 640; the third number “13” indicates the counts for particles size larger than 14µ per millimeter oil are greater than 40 but less than 80). For general industrial and mobile equipment at pressure up to 3000 psi, the ISO code is 20/18/14. ISO code 18/16/13 is common for directional solenoid valves, fixed gear pumps, fixed van pumps, and proportional control valves used at high operating pressure and high-cycle applications, pressure from 3000 up to 5000 psi. UEA set the target ISO cleanliness code as 18/16/13 for manufactured hydraulic swivels to meet high pressure and high performance hydraulic system requirement.ICMIn order to deliver high quality hydraulic swivels to our customers, UEA implements effective measures in swivel assembling procedures to assure the finished swivel assemblies meet cleanliness specifications. Prior to finally assembling, aggressive parts washing and cleaning is done using clean oil after deburring machined spools and housings. During the leakage detection test, the assembled hydraulic swivel must be protected in the test stand by filtration that catches the majority of contaminates and cleans the oil before reaching the swivel. The In-line Contamination Monitor (ICM) was installed in the hydraulic test system to monitor the cleanliness level of the test oil in real time. Time stamped oil cleanliness ISO 4406 codes are recoded and stored. This data is available to our customers upon request.

During recent tests on a few types of hydraulic swivels, the ICM displayed the ISO cleanliness codes as 14/11/8, 17/13/7, 15/11/5, respectively. We take pride in the fact that we are getting better oil cleanliness levels than our preset target. It also an indication our hydraulic power unit filtration system is functioning effectively.

With the ICM integrated into the swivel test system, we are confident to say UEA delivers clean and functioning hydraulic swivels to our customers. For our customers' usage, we suggest these hydraulic swivels run in clean oil conditioned to ISO 18/16/13 or better. This will maximize swivel reliability, minimize repair cost and extend swivel useful life. Monitor it, maintain it, and justifiable rewards will be yours.

Bo Li

Design Engineer, Certified Fluid Power Specialist

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