Impact of Contaminated Fluid on the Working Performances of Hydraulic Directional Control Valves

0 INTRODUCTION It is very difficult to predict and precisely determine the impact of fluid cleanliness on the system operation or its components, due to many factors and a variety of hydraulic system applications. The hydraulic fluid contamination is an issue that can shorten the working life of hydraulic components, which has a direct impact on maintenance costs [1] to [3]. Also, contamination can be considered as a hydraulic system “intruder”, which has a direct or indirect influence on system behaviour and parameters such as precision, response time, repeatability, controllability, etc. [4] and [5]. Many well-regarded companies and other institutions dealing with manufacturing, maintenance and testing of hydraulic systems and equipment, based on their own experience from practice and experimental research, claim that the working fluid contamination represents the main cause of failures in 70 % to 80 % cases [2] and [6] to [9]. Additionally, the requirements for more precise control and higher efficiency of hydraulic systems, have resulted in the decreased clearances between working elements of hydraulic components and the increased working pressure values [10]. Due to the decreased clearance size, the adverse impact of micron-size solid contaminants becomes evident. Although it is wellknown that solid contaminants are destructive to hydraulic system components, as well as to the working fluid itself, there was no internationally accepted method for objectively determination of contamination tolerance for systems or each component separately [11], until 2017. In 2013, was initiated and consequently published ISO 12669:2017 standard, developed for determining the required cleanliness level (RCL) for a system [12]. This standard is now under review for five years period. Due to the lack of a standard procedure, the RCL choice is based on the system designer experience or on the third person recommendation (such as components manufacturer) and his experience. This doesn’t mean that optimal cleanliness level was selected for the specific system operation. The RCL selection by this method is strongly subjective, for which reason it does not provide consistency. Consequently, many system designers, as well as the users of hydraulic systems, are unsure and confused about the appropriate cleanliness level Impact of Contaminated Fluid on the Working Performances of Hydraulic Directional Control Valves Karanović, V. – Jocanović, M. – Baloš, S. – Knežević, D. – Mačužić, I. Velibor Karanović1,* – Mitar Jocanović1 – Sebastian Baloš1 – Darko Knežević2 – Ivan Mačužić3 1University of Novi Sad, Faculty of Technical Sciences, Serbia 2University of Banja Luka, Faculty of Mechanical Engineering, Bosnia and Herzegovina 3University of Kragujevac, Faculty of Engineering, Serbia