Electrostatic charge measurement in hydraulic circuits

Abstract

Electrostatic charging of hydraulic circuits is recently becoming an issue as low conducting hydraulic fluids are increasingly in use. Charge generation is more likely to accumulate and build up large voltages. These high charge accumulations are hazardous as they can damage system components such as filters, which can eventually lead to system failure. In order to develop appropriate counter measures, a precise knowledge of influencing parameters is strongly beneficial. In this paper the causes for charge generation are discussed. Furthermore, methods for charge measurement of hydraulic fluids are presented. As the researched measurement methods are considered inappropriate, a new charge measurement method is developed. The development based on the principles of Faraday-cup and Faraday-cage are discussed in detail. Moreover, the integration of the developed charge sensors into an also developed experimental setup is described. The test rig in combination with the charge sensor allows the quantitative measurement of charged fluid without influencing the fluid to be investigated. It also enables measurements under pressure, meaning that the fluid can be pressurised up to 140 bar. The experimental setup is destined to obtain a large data basis. This data basis allows the validation of a charging model for which the modelling approach is also presented in this paper. This will lay the basis for a charging model to predict the charging tendency of a hydraulic system.

The origin, measurement and control of fine particles in non‐aqueous hydraulic fluids and their effect on fluid and system performance

“…However, the phenomenon was only associated with industrial oils, principally turbine oils, in the last 25 years and even more recently with hydraulic oils — possibly as a result of a trend towards ashless hydraulic oils, which are less conductive . Indeed, the availability of electrostatic filtration equipment to remove particulate matter from these fluids was probably in widespread use before the applicability of charge generation to industrial fluids was appreciated and investigated …”

“…16,26 Indeed, the availability of electrostatic filtration equipment to remove particulate matter from these fluids 27 was probably in widespread use before the applicability of charge generation to industrial fluids was appreciated and investigated. 12,28 It is now understood that charge generation occurs in any moving liquid whether this is flow in pipes, into a reservoir or in a component such as a filter. It is highest when the fluid flow becomes two-phase (fluid/air) such as a spray or jet discharging into a reservoir.…”