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Insulators in the ESP
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.
|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
precipitator has no purge blower system and the ring heaters were
|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.
|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.
insulator in this bus duct has failed due to a hole in the duct
overhead which allowed water to penetrate.
||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.
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.
||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.
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For more information contact: TRK Engineering Services - 95 Clarks Farm Road - Carlisle,
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