HYDRAULIC OIL FORMULATION AND METHOD TO IMPROVE SEAL SWELL

摘要

In one embodiment, a hydraulic oil with favorable seal swell is disclosed. The hydraulic oil comprises, a major amount of base stock, an antiwear additive, a phosphorous containing additive wherein the phosphorous comprises at least 10 ppm and less than 2500 ppm of the hydraulic oil, the hydraulic oil contains less than 200 ppm zinc and less than 100 ppm sulfur, wherein the ratio of phosphorous to metal ratio is chosen to obtain a favorable seal swell performance with at least a ratio of 0.5 and less than 20. In a second embodiment, a method to improve seal swell is disclosed. In a third embodiment, a method of formulating an oil to improve seal swell performance is disclosed. In a fourth embodiment, a method of improving seal swell is disclosed. The method uses a system cleaner for hydraulic systems comprising CaSo4.