Accumulator charging process

If the charging process continues after all the lead sulphate has been used up, then the charging voltage rises. Hydrogen is liberated from the lead electrode, and oxygen is liberated from the lead dioxide electrode. The accumulator is then said to be gassing . 

Static charge generation causes an ignition hazard only if the accumulated charges create an electric field sufficient to produce an electrical discharge in a flammable atmosphere. In most processes, this means that the electric field intensity at some location must reach the breakdown strength of air (nominally 3 X lO " V/m). The objective of static-control measures is to ensure that electric field intensities cannot reach this value. 

Mesh strainers finer than 100 mesh/inch (<150 /rm) should be treated as microfilters. Coarser strainers up to 50 mesh/inch (300 /rm) may generate significant static when fouled with accumulated debris, so should be treated as microfilters except in cases where fouling is not expected or may be rapidly identified by either periodic inspection or monitored pressure drop. Clean strainers should nevertheless be placed as far upstream as practical for nonconductive liquid service. A theoretical model for the charging process in strainers (screens) is given in [119-120]. Viscous nonconductive liquids (5-2.5.4) may produce unusually high charging currents in strainers. 

The energy of a spark discharge is a function of the accumulated charge (Q in coulombs) on the object, the capacitance of the object (C in farads), and the potential, or voltage (V in volts) of the object. These three variables are related by the expression C = Q/V. The actual energy (expressed in joules) associated with the discharge process is given by... 

The mode of coupling is resistive for those devices which have electrodes in direct contact with the ionized gas or plasma environment. In these devices the electrical field necessary to sustain the plasma is caused by positive and negative charge accumulations both within and at the boundaries (walls, electrodes, etc.) of the plasma region. A finite potential difference at the gas-electrode boundary always exists as a consequence of the accumulated charges. This potential supports a number of collision processes (ionization, excitation, electron emission or collection, etc.) which act to sustain the discharge. 

Equilibrium is disturbed when a net forward or backward reaction occurs, producing current in the external circuit. The current induces a potential change and causes polarization. Charge conservation requires the total rate of oxidation be equal to the total rate of reduction for any corrosion process. To avoid accumulation charge in the electrode, the sum of anodic currents must equal the sum of cathodic currents. 

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