Electrostatic Precipitator


 

Electrostatic precipitator troubleshoot guide

Step 1

Electrostatic Precipitators are complex devices with many potential faults and problems. This guide seeks to help with the most likely causes and scenarios, however, should your problems not be resolved through this process, please contact our expert staff either via the telephone or by email.

The first step in diagnosing an operating ESP is to look at the data available; typically the electrical readings.
What are normal electrical readings?

It is normal for the electrical readings to vary from zone to zone within an operating ESP. In fact, it’s strange if they do not vary.

An ESP that is operating well will have th following pattern:
The first zone will have the highest secondary voltage (kV) reading, with each successive zone slightly lower. Similarly the first zone should spark more than each successive field.
The last zone will have the highest secondary current (mA) reading (typically close to the maximum transformer rectifier rating), whereas the first zone will have the lowest.

 

Electrostatic Precipitator

Electrostatic Precipitator

Are your ESP readings in this pattern?

 

Step 2 – Electrical Readings

The following section lists a number of potential meter states with likely explanations for each. This guide seeks to help with the most likely causes and senarios, however, should your problems not be resolved through this process, please contact our expert staff either via the telephone or by email.

Note: In each of the following, the dotted arrow represents the normal operating point and the red arrow represents the currently observed condition. In all cases, check signal integrity first.

 

Observed:
No secondary voltage, high/maximum secondary current and/or a transformer rectifier trip on “under voltage”

Likely cause:
A short circuit between the high voltage system and the earth system. This could be caused by many things including the following:
A broken discharge electrode touching a collecting plate
A broken (or detached) collecting plate touching a discharge electrode
An earth switch in the wrong position
A tracked, cracked or broken insulator
A foreign body touching both the discharge system and the collecting plates (welding rods, scaffolding tubes, tie wires etc.)

 

Observed:

No secondary current, high/maximum secondary voltage

Likely cause:
An open circuit between the high voltage system and the earth system. This could be caused by a limited number of things including the following:
A broken high voltage connection somwhere between the transformer rectifier and the connection with the ESP support insulator.
Observed:
Normal or above normal secondary voltage, but lower than normal secondary current.

Likely cause:
Typically these readings are caused by large amounts of dust. Check the following:
Is the dust load from the process to the ESP greater than normal? More dust between the discharge electrode and collecting plate will cause this.
Are the discharge electrode rapping systems functioning correctly? A broken discharge system rapper will allow dust to build up on the discharge electrodes causing this observation.
Are the collecting system rappers working correctly? A broken collecting system rapper will allow dust to build up on the collecting plates causing this observation.
Observed:
Below normal secondary voltage, lower than normal secondary current. Also, above average sparking.

Likely cause:
Typically this result is caused by a clearance issue between the high voltage system and the earth system. This can happen in many varied ways, the following is a brief highlight of a few of these areas:
Is there a bent discharge electrode?
Is there a bent collecting plate?
Is the zone correctly aligned between the discharge electrodes and the collecting plates?
Is there a tracked, cracked or broken insulator.
Are any of the high voltage links in the bus duct too close to the side wall?
Has the dielectric strength of the transformer rectifier oil broken down allowing sparking between windings?
Is the shielding on the kV signal intact?

Observed:
Below normal secondary voltage, high to maximum secondary current.

Likely cause:
Typically this phenomenom is caused by increased conductivity between the high voltage system and the earth system. Check the following:
Has there been a change in process conditions? Has the chemistry of the gas or dust changed? Is there more moisture in the gas stream?
Is there a conductive layer on the support insulators? Are the insulator heaters working?
Is the zone correctly aligned between the discharge electrodes and the collecting plates?
Is there a tracked, cracked or broken insulator?

 

Step 3 – Other issues

The following section lists a number of potential ESP issues that may not show up in the electrical readings with likely explanations for each. This guide seeks to help with the most likely causes and senarios, however, should your problems not be resolved through this process, please contact our expert staff either via the telephone or by email. Remember, we have the parts, personnel and experience to resolve any issue you may have.

Observed:
Higher than normal dust emissions but electrical readings are OK

Likely causes:
This could be caused by many things including the following:
A blockage or large hole in the gas distribution plate. This will require an internal inspection.
Poor gas distribution through the electrostatic precipitator. A full gas distribution analysis will need to be completed to dtermine if this is the cause.
Missing or broken wall sneakage plates
Missing, damaged or broken hopper baffles.
An open manhole through a hopper baffle
Leaking door seals or expansion joints
Holes in the casing, hopper or evase walls
Dust build up in the hoppers due to a blockage or faulty materials handling system.
Back corona caused by high resistivity dust. A VI-curve anaylsis will need to be completed to determine if this is an issue with your plant. Call us for help with this.
A change in your process conditions – has your gas composition changed? Has your dust chemistry changed? Have you changed feed material?

In most of the above cases, a detailed internal inspection is required to determine the exact cause of the problem. At EPS we regularly fly anywhere in the world to complete detailed inspections for our customers and to get them back to peak performance. Can we help you?