Lube-Tech Summary


A lubricant is selected for a target application and should perform these functions over the intended service life. However, when lubricants become mixed, performance may change, and depending on the degree of incompatibility, potentially lead to a catastrophic machine failure. Interactions between a fluid’s ingredients may occur and lead to a lack of additives solubility, a change in composition or a deterioration of performance.


The evaluation proposed in this article is a step-by- step approach. Firstly, a review based on information we have on Hydraulic Fluid (HF) components chemistry. Next there is an evaluation of some mixtures to check signs of visual incompatibilities before carrying out filterability tests and surface properties deterioration.


The last step is to check the long-term compatibility through laboratory performance tests, considering the fluids composition, the operating conditions, the materials, the seals, and the environment.


1. Introduction


Hydraulic fluid is a non-compressible fluid which is primarily used to transfer power within machinery and equipment. The heart of any hydraulic system is the pump, which draws fluid through its inlet and forces the fluid through its outlet, usually against


Most hydraulic fluids consist of a mineral or synthetic base fluid and a combination of additives; they are classified according to ISO 6743-4 in 15 categories based on their base fluid type, applications and composition & properties.


LUBE MAGAZINE NO.166 DECEMBER 2021 23


PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE


No.137 page 1


How to check the compatibility of hydraulic fluids through laboratory testing


Vincent Bouillon, BFB OIL RESEARCH S.A – IESPM Group – Eurofins network; Les Isnes (Gembloux); BELGIUM


pressure created by valves, plumbing, and actuators downstream of the pump. Pumps, actuators, and other system components have surfaces that move relative to one another, often at high speeds, pressures, and temperatures. These components require cooling and lubrication for efficient performance and durability.


Hydraulic systems are most commonly found in construction and industrial vehicles, such as excavators or fork-lift trucks, but these fluids are used in many other applications like log splitters, lifts, snow plows, aircraft, air tools, tractors, ships and others.


Hydraulic systems are being optimised to become more compact and operate in more severe conditions than in the past. The smaller oil quantity, higher pressure and temperature as well as mechanical constraints require the additives and lubricants manufacturers to create better performance lubricants. The need for oxidation and corrosion resistance, thermal stability, good surface and anti-wear properties make the formulation more complex, using more advanced chemistries.


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