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Pictures Insulators in the ESP Back to

Insulators are used in numerous locations in the precipitator high voltage system.  Common types of insulators and usage include support insulators which support and isolate the discharge electrode system, standoff, post and through bushing insulators to support and isolate the high voltage bus, insulated rapper rods to transmit rapping energy to and isolate the high voltage discharge electrode frames, and anti-sway insulators to prevent movement of the discharge electrode frames.  Failure of an insulator can cause grounding and other ESP operational problems.  Failure is usually of an electrical, mechanical or thermal nature.

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The high voltage support insulator is badly damaged.  Failure is likely attributable to a combination of thermal stress and electrical arc-over due to contamination of the insulator surfaces.  This precipitator has no purge blower system and the ring heaters were inoperative.

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It is important to maintain cleanliness of the inside and outside surfaces of HV support insulator.  The inside surface of this insulator is contaminated due to ineffective introduction of purge air.  The elbows at the top of the photo are installed incorrectly.  They are designed to be oriented either all clockwise or all counter-clockwise to swirl air flow tangentially around the inside surface of the insulator to maintain cleanliness.  Here the elbows are not oriented correctly.

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Note the burn marks from electrical tracking on these sections of failed support insulators.  These will produce a high resistance or dead short condition in the associated bus section and will detract from ESP operation.

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The standoff insulator in this bus duct has failed due to a hole in the duct overhead which allowed water to penetrate.



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This HV rapper rod insulator is damaged due to high intensity rapping and loose coupling bolts.  Another frequent cause of failure is water penetration due to damaged rapper boot seals.

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Electrical tracking on the internal selector switch post insulator for a transformer rectifier.  Cause of failure is the result of changing switch positions while the transformer was energized.



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Anti-sway insulators are installed in some ESPs to prevent on-line movement (swinging) of the lower discharge electrode frames.  It is important that they be oriented so as to avoid material buildup and installed to maximize tracking distances.  They are designed to maintain the collecting plate to discharge electrode alignment, not to obtain it.  The anti-sway insulator in this photo needs to be lowered to optimize tracking distances.

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Last updated: May 27, 2011.
Copyright 1997 TRK Engineering Services, Inc. All rights reserved.
For more information contact: TRK Engineering Services - 95 Clarks Farm Road - Carlisle, MA 01741 - Telephone: 978-287-0550 - Fax: 978-287-0569 - email: trkeng@apcnetwork.com