Leonard E. Bensch

Overcoming the electrostatic discharge in hydraulic, lubricating and fuel-filtration applications by incorporating novel synthetic filter media

Electrostatic charge generation occurs in fluid systems as a result of friction between the fluid and system components. The magnitude of charge generated by each component will depend on many interrelated factors, including environmental ones. It can occur during filtration of hydraulic and lubricating oils as well as diesel and gasoline fuels. This effect manifests itself in several ways, the most noticeable effect being an audible noise (clicking sound) as the discharge of electrostatic charge accumulation causes sparking internally within the system. Less-apparent effects involve migration of the electrical charge downstream of the filter, causing damage to system components and the filter itself when the charge dissipates by discharging itself to a grounded surface. Several methods have been investigated to overcome the aforementioned behavior and prevent the damage that can occur if the electrostatic discharge continues to operate unchecked. One of these methods involved adding an antistatic additive to the liquid, but this is restricted to fuel applications. Other methods involved surface modifications carried out directly on the filter media or the use of conducting materials such as meshes made from suitably selected conducting materials that can be incorporated into the construction of filter cartridges. The main aim of these modifications is to affect a discharge from the filter cartridge, before a hazardous potential accrues on the filter media, by lowering the voltage gap. Although this approach eliminates direct damage to the filter cartridge, it does not prevent charge migration into the oil where it subsequently accumulates. The approach we took involves designing the filter material to be electrostatic dissipative, which offers the advantage of eliminating filter damage entirely and significantly reducing migration of charge into the fluid.