DISCHARGE ELECTRODE REPLACEMENT
USE OF DIFFERENT DISCHARGE ELECTRODE
STYLES IN THE SAME ELECTRICAL SECTION
We recently visited several Plants where the original electrodes had been partially replaced. In most cases this was to replace randomly failed or damaged discharge electrodes. We generally advise against the replacement of individual discharge electrodes that have failed unless they are concentrated in one area, or represent a large percentage of the total number, and their absence would adversely affect ESP performance. Different styles of electrodes should never be mixed in the same electrical section. No failed discharge electrode should be replaced without first addressing the cause of failure.
Some Plants habitually replace a failed wire electrode with a new one. We advise against this in most instances. A new wire, installed in place of the old one, will develop different electrical characteristics when energized than the older wires which have been in operation for an extended period. Since the electrodes in a common bus section are energized by the same source (Transformer Rectifier), this can adversely affect the overall power to that section. A small number of randomly missing wires, less than 5% of the total, will not adversely affect the performance of the precipitator.
Another practice to avoid, for the same reason, is the replacement of random discharge electrodes with a different style of electrode. We have seen instances where barbed wire electrodes were installed randomly in a field where the other electrodes were straight wire, because that was all that was readily available. At another location, where a double chamber ESP shares transformers across chambers, the Plant installed new straight wires in one ESP chamber, but left the old barbed wire electrodes in the other chamber. Still another location installed a different style rigid discharge electrode to replace fire damaged electrodes within a field. The electrodes are designed to produce differing voltage / current characteristics and one design will govern, the one with the earliest corona onset. Mixing designs within a common electrical section can adversely affect precipitator power levels and hence, performance.
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Last updated: May 10, 2009.
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For more information contact: TRK Engineering Services - 95 Clarks Farm Road - Carlisle, MA 01741 - Telephone: 978-287-0550 - Fax: 978-287-0569 - email: email@example.com