Charge relaxation in vessels with insulating liners

Abstract

Approximate analytical solutions for the relaxation of electrostatic charge in a lined cylindrical vessel containing charged powder or liquid are obtained. The transient solutions are for two distinct configurations of vessels with partial linings: T/B, where the dielectric lining is only on the top and the bottom inside conducting walls; and C, where the cylindrical side walls are lined. The results show that a significant fraction of the initial charge contained by the vessel can accumulate at the surface of the lining. If the liner is thin, this surface charge relaxes very slowly according to an extrinsic characteristic time dependent upon the geometry of the vessel and the capacitance per unit area of the liner. No solution for the case of a fully lined vessel is offered, but means to estimate the extrinsic time constant and the maximum surface potential on the liner are given. These approximations are useful in assessing the influence of liners on the electrostatic discharge ignition hazards associated with lined vessels and pipes.