PUB – Impact of differing water contents on electrostratic charging


A paper on the „impact of relative humidity on electrostatic charging“ was published at the AFK Fluids 2019 conference in San Francisco, CA, USA.

  Charge density over relative humidity of different fluids

Hydraulic fluids evolved these past years and some of these changes resulted in hydraulic fluids with lower conductivity. Standards, such as ISO 11158, do not mention electric conductivity, thus resulting in little awareness of the potential complications associated with poor conductivity. Poor conductivity facilitates electrostatic charging in a system, which in turn may lead to a shortened service life of the hydraulic fluid and filter elements. Relative humidity has been seldomly considered in electrostatic charging of hydraulic fluids. In this paper a small scale test bench that integrates a Faraday’s cup into a Searle-viscometer is used to test three thydraulic fluids of the HLP 46 type at 20°C at varying relative humidities. The test results show that all fluids, independent of their initial conductivity, exhibit a larger charging tendency as the relative humidity increases.