Normally can we repair CP and will it affect mA, kV or sparking?

If there is a crack and/or hole on CP, it will be repaired by using dummy plate to weld on CP. If there is a bent CP, it could be adjusted manually by using special tools and/or heating. Nevertheless, it is very difficult to expect the perfect results from repairing; especially, if the length of CP is ≥10 meter.

However, results after repairing the broken CP will show some improvement on kV and mA value (~10-20%), but the performance improvement will not be as significant as comparing with replacing with the new CP.

What is the benefit of rigid discharge electrodes (RDE)?

  • Minimal maintenance and longer lifetime
  • Superior corona generation area
  • Higher efficiency of ESP for the same process parameter
  • Lower ‘corona onset voltage’
  • Stiffness & stability for best rapping efficiency & cleaning effect
  • Reliable & Stable ESP PerformanceEase of installation
  • Can be installed in the original DE frame, thus lowering the cost
  • Shorter downtime of the ESP for the modification of DE

RDE Installation

Why should I change to RDE?

The invention of RDE is to help improve the performance of the existing DE, which can help leading ESP to better operating efficiency because RDE can generate higher aggressive current and overcome the below drawbacks from each type of DE.

  • Wire type DE: this type of DE can be broken easily, in which it can cause a field trip off, affecting the operation.
  • The strap type DE: this type of DE is subject to the aging of the material and loosening. Under a certain tension, long term corona discharge and abrasion of the DE will lead to the thinning of the DE and thereby causing the loosening and deformation of the DE, which will lead to the sparking / arcing and thus the breakage of the DE.
  • Spring DE: it has thin surface and less electrical force to generate corona thoroughly. Therefore, it is not suitable to be used with large dust particles. Also, its design causes it to have more tendencies to face with dust accumulation problem.

Why is Tai & Chyun’s RDE better than others?

  • It is produced from a single piece of fabricated metal without any joint to prevent the problem about detachment of spikes.
  • Our RDE is thicker. Therefore, it is harder to be broken.
  • Tai & Chyun uses steel supplied by the best steel supplier in Taiwan to ensure the superior quality of RDE material in order to lead to performance conformity.
  • RDE design of Tai & Chyun emphasizes on the spikes which makes it able to consistently generate corona leading to the stable performance of ESP.


Does the CP material quality contribute to problem of worn out or damage part?

The quality of steel material is important since better quality will provide better durability and mechanical properties. Tai & Chyun always emphasize on the product quality. Accordingly, we can provide material test certificate such as chemical composition of the steel in order to ensure customer about the quality of the steel used.

Broken CP

Dust Build Up CP

Deformed CP

What are the root causes of CP failure?

The reasons of CP failure are as follows:

  • Crack of CP in the bottom: Improper rapping force
  • Holes on the CP: Arcs erosion occurred
  • Thinning: Aged CP
  • Loose or detached hook of CP suspension system: Improper Installation

How does air leakage has an effect on CP performance?

Air leakage will make it easy for CP to be corroded from the moisture that occurs. Therefore, it causes sticky dust that can lead to dust build up problem on CP.

What are the main factors that cause CP to bend?

Severe hopper full up until reaching the rapping bar

Bent rapping bar

Detached CP interlock

High temperature due to process Issue

Poor product quality

Incorrect erection installation

Incorrect packing, transportation and loading

What is the allowable level of thickness for dust deposited on CP before CP retrofit is required?

The tolerance level of dust accumulation on CP surface should be maintained in the range of 0.8 to 12.7 mm. If it exceeds that level, it will be categorized as dust build-up problem.

The thickness of dust layer affects the strength of the electrical field. For instance, it will lead to heavy sparking, thus suppressing voltage and current.

As a result, the kV and mA values will exhibit the low number followed by high sparking. Therefore, replacement of CP is necessary to provide better ESP performance. 

If some of the missing CP founded, what is the suggested action while waiting for the process of changing new CP?

It depends on how much percentage of missing CP. If the quantity of missing CP is more than 10% from the total amount of CP in each field, it will affect ESP condition and performance, causing high outlet emission. Therefore, CP replacement is expected to be implemented urgently. In case that missing CPs cause a huge decreases in ESP collecting efficiency, new CP then should be replaced immediately.

In the meantime, it will be better to control the ESP process and operating data such as the temperature control, uniform gas distribution, and maintaining kV and mA in proper value. Moreover, others ESP parts such as DE, CP rapping system, DE rapping system, insulator, etc. must be kept in the good working condition. Regularly checking and maintenance is always necessary to be aware of ESP condition is in the suitable tolerance or not.

What is the normal cycle time of ash handling?

The cycle time depends on the following factors:

  • Blow Tank size
  • Ash Capacity
  • Distance to storage silo

Components of Ash Handling System

What are the causes of Elbow Pipe Leakage?

Due to centrifugal force and inertia, when the fly ashes are delivered through the elbow pipe, it impacts the wall outer elbow. It causes the friction that leads to wear and broken elbow pipe. As a result, elbow pipe will become leakage.

Therefore, the elbow’s wearing problem has become the primary consideration for pneumatic conveying system, while the wear problem of the straight pipe is much smaller.

How to solve Elbow Pipe Leakage Problem?


  • – Using high hardness & wearing endurable material likes ceramic liner bend pipe
  • – The bend radius must be 5 x pipe diameter (R5D) or greater.
  • – The bend must be smooth bore with no step or ledges.


What is the maximum conveying distance for pneumatic system?

The maximum conveying distance is at 1500 meters with vertical lifts of 50 meters.

What is the maximum conveyor line pressure?

The maximum conveyor line pressure is 0.4 Mpa (4kg/cm2).

What is the maximum conveying capacity for DEPAC?

The maximum conveying capacity for DEPAC is 250 TPH.

When should you use a bottom discharge or top discharge?

A top discharge would be the most appropriate to use where there is a fine particle such as fly ash. A bottom discharge would be appropriate where there is coarse material or material that does not fluidize well.

DEPAC System

Is it okay to install ash handling system without shutdown?

Yes, it is. However, the slide gate valve must be closed between the ESP hopper and transmitter.

How to check and inspect ash handling during shut down ash handling system?

1. Close the slide gate valve between the hopper and transmitter

2. Change over to “LOCAL” the operation mode selector switch on the local control panel

3. Pressure Gauge: Check operation pressure

4. Slide Gate Valve: Check leakage from gland

5. Inlet Valve: Check smooth action

6. Air Inlet Valve: Check smooth action and leakage from flange

7. Transmitter: Check operation cycle

Is it possible to perform water washing inside the ESP and what is the advantage & disadvantage?

Yes. It is possible to perform ESP water washing. ESP water washing has both advantages and disadvantages as listed below


  • A fast way of cleaning ESP
  • It can clean heavy dust build up on CP, DE, GD screen, inner walkway and inner wall of hopper.
  • It can solve poor operating values due to heavy dust build-up.
  • The operating values will be significantly improved.


  • CE and DE corrode easily if the the mechanical parts don’t dry up.
  • It needs to build a temporary precipitate tank for waste water.

What’s the procedure of ESP water washing?

Before ESP Water Washing

  • CE and DE rapping must be operated continuously for a period of time.
  • Turn on the ash conveying system for few hours in order to clear off the dust.
  • If there is too much dust in the ESP, the dust must be removed by manual cleaning first.

Preparation of ESP Water Washing

  • Dismantle the ash conveyer cylinder’s fluidized tank.
  • Build a temporary precipitate tank.
  • Prepare waster source and pipes.

Performing ESP Water Washing

  • Pour water from the top to bottom.
  • Use huge amount of water to clean the dust.
  • Water pressure should be controlled so that the mechanical parts in ESP won’t be deformed.

After ESP Water Washing

  • Access doors should be kept open in order to allow the ESP internal parts to dry up faster.
  • ID fan and heaters must be turned on few hours to dry up.

Water washing is suitable or not suitable for what kind of dust?

Water washing can generally be performed in various type of ESP. Tai & Chyun has experiences in performing water washing for ESP from different industries including petrochemical, power, glass, etc. However, we do not recommend ESP water washing for the type of ash which is acid or causticity.

Buffet Pool

Bags for collecting wet dust

ESP Water Washing

During shut down, what are the parts have to be inspected inside ESP? Is there any order of which parts should be inspected first?

It is strongly suggested to do inspection for the overall ESP parts, starting from the electrical parts such as transformer (terminal box, insulation testing, V-I curve, T/R set appearance), insulators, heaters, rapping motors, controller, and rapping testing, followed by mechanical parts for both external and internal ESP. For external part, it could start from the casing including cladding and insulation, access door and manholes. It might be having problems with leakage or deteriorated gasket seal. Then, we could inspect the expansion joint, inlet, and outlet nozzle. ESP structure is also necessary to be checked. For internal part, the order could be listed as below:

  • Gas distribution screen (turning vanes/guide vanes)
  • Collecting electrode (CE)
  • Discharge electrode (DE)
  • CE rapping system
  • DE rapping system
  • Protection conduit/corona shield
  • Baffle plates
  • Hopper
  • Penthouse

ESP Inspection Chart

ESP Inspection

Is it possible to do preliminary inspection to determine whether the problem comes from electrical or mechanical parts?

Yes, it is possible. From the first time, we can do the V-I curve testing by comparing the graph from inlet to the outlet field to evaluate and maintain ESP condition over period of time. Deviation from the normal or previous result can indicate that there are some ESP problems happening. Primary readings should be proportional to the secondary reading. If not, it should be expected that the problem may come from electrical.

Is it necessary to perform ESP inspection in every shutdown?

Performing ESP inspection during shutdown is necessary as part of ESP routine maintenance and performance monitoring, leading to a good ESP operation. ESP Inspection includes testing, measurement of ESP parameter, comparison of the parameters with the original design condition/ value, and keeping record of ESP performance. Accordingly, these data is useful for ESP performance evaluation and problem diagnosis. An analysis of the key parameter can help to identify many ESP problems; indicating the need for maintenance and/or replacing part with the new one. 

What are the causes of broken support insulator?

Electrical shock:

  • Sparks or arcs due to dust accumulation or moisture.

Uneven loading and misalignment:

  • Improper installation of insulators and DE system.

Exceeding the maximum voltage or temperature:

  • Maximum voltage: 85 ~ 120 kV
  • Operating temperature: 100˚C ~ 450˚

What materials do Tai & Chyun have for support insulator?

Most of the support insulators are made from alumina-oxide porcelain, in which it usually contains 50 % of alumina content and is typically made with glazed surface in order to reduce the deposits of dirt and dust.

Other materials of support insulator such as fiber glass or Teflon may not be suitable enough because of its poor thermal resistance and fragility.

What are the disadvantages of Chinese made insulators?

Easily crack or break

  • Dramatic temperature changes
  • Poor mechanical properties
  • Poor heat conduction due to its thicker

Easily cause sparks in ESP

  • Poor insulation or isolation leads to current leakage

How to order the right insulator?

You need to inform sales representative about the following details.

  • Size (OD, ID, height, thickness)
  • Photos or drawings
  • Operation kV and Temperature (°C)

If I plan to change the existing T/R set to PowerPlus, what are the minimum adjustments required on control system?

Removing the original controller and SCR

  • Installing GDU in replacement of old controller
  • Integrating the signal to PLC/DCS/CCR.


For more product detail and the installation preparation, please feel free to consult with our technical team at any time for your PowerPlus inquiry.

Can PowerPlus be put on the ground instead of the roof?

In general, it should be installed on ESP roof to lower the impedance between ESP and PowerPlus.  Since PowerPlus operates in high frequency, it could react faster than conventional 60Hz T/R set. However, to install Powerplus on the ground is also feasible by requiring specific type of cable, together with some cable modification, but it has some distance limit in order to avoid the noise problem.

How to avoid PowerPlus over-temperature?

In order to avoid over temperature problem, an ambient temperature must be kept not to exceed 45°C, while the PowerPlus has developed the function of temperature control to decrease the power automatically when the temperature is over 62°C in order to prevent the trip problem. However, it is recommended that heat exchanger fin should be cleaned regularly when performing PowerPlus maintenance to allow for an effective temperature control.

What is the proper distance between CP and DE?

The distance between CP and CP or DE and DE can be varied from 250 – 450 mm. The old design uses 250mm, the common design usually uses 300 – 400 mm and the newest design tries to use 450mm.

The gap between CP and DE is too close and trip the system, how to solve this problem?

If the close gap was caused by bending, detached or broken CPs or DEs, those CPs and DEs should be removed to prevent ESP trip. However, the allowed quantity for CPs or DEs to be removed is 10 % of total quantity in each field. If there are more than 10% that are damaged, the whole field replacement is needed to be considered.

What is the ideal distance between CP and DE in order to have access for repairing damaged CP or DE?

There is no ideal distance between CP and DE for the repair works as long as the safety provisions can be met and the worker is able to fit and execute the repairing job safely. However, if the access is not possible, it should be discussed among the maintenance team and safety staff for considering about access modifications.

Can CP and DE deformation cause close clearance between CP and DE? And what are the solutions for this problem?

If CP and DE deforms, of course it will cause close clearance between CP and DE. In case that deformed CP or DE cause some serious disturbance to the ESP performance, it will be better to remove the deformed CP or DE out in order to prevent problem about close clearance between CP and DE. Water spray can also help to reduce the operating temperature to prevent the problem about CP and DE deformation. Apart from that, it is also necessary for the plant personnel to regularly address all the leakages inside ESP in order to prevent the moisture getting inside ESP to cause some corrosion as well as deformation.

What are possible causes of CP and DE misalignment?

  • The collapsed support insulators
  • Improper installation during erection of parts
  • Bent and Deformed CP & DE
  • Dust Accumulation on CP & DE

Close Clearance between CP &DE

Deformed DE

Good Alignment between CP & DE

Dust Build Up CP

What are the possible problems for MIGI Rapping?

  • Broken Rapping Insulator
  • Water Leakage
  • Broken Coil
  • Misaligned Rapper
  • Corroded Terminal
  • Damaged Boot Seal
  • Improper Height of the Plunger

Damaged Boot Seal

Water Leakage

Misaligned Rapper

Corroded Terminal

How to do maintenance of MIGI Rapping during ESP Shut Down?


  • Checking condition of the sealing around MIGI Rapper
  • Checking rapping insulators
  • Checking rapping alignment on plungers

Checking the space between the bottom of plunger and bottom of MIGI Rapper:


  • Checking the HV Insulation: Withstanding 1.5kV between live and earth for 1minute
  • Checking insulation resistance: Megger value exceeds 50MΩ

Checking the current when operating

What spare parts of MIGI Rapping that should be kept?

  • Coil
  • Seal
  • Plunger
  • Rubber cover

Can sonic horn be installed when existing design doesn’t have?

Yes, sonic horns are installed as supplementary equipment for dislodging the dust in order to help enhance dust collecting efficiency. It is functioned to help dislodge an excessive level of dust by using sound vibration to fluidize dust build-up inside ESP. Once the dust particle absorbs the sonic energy and vibrates, the adhesion force of the dust will be weaken to be collected easily. Mostly sonic horns are founded to be installed at the following location

On the roof:   to help dislodging dust on CE inside ESP

On the hopper: to help preventing the dust-build up in the hopper due to bridging or rate holing problems

How sonic horn help to dislodge dust?

Sonic horns use powerful sonic sound waves operating at frequencies between 60Hz to125 Hz and 140~150dB to dislodge the collected ash.

The way for sonic horn to produce the sound waves is illustrated as below:

What is the difference between hopper vibrator and air cannon application comparing to sonic horn regarding hopper dust accumulation prevention?



Compare to Sonic horns

Air cannon

A compressed air device to dislodge powdery material

  • Only work in one point(narrow localized)
  • uses more compressed air

Hopper Vibrator

Apply vibration to dust pile

  • As effective as sonic horn
  • Damage the hopper casing due to vibrate fatigue

Can sonic horn be applied in other equipment?

Sonic horn can be applied in any area where there is the dust that needed to be dislodged such as in bag house, economizer, silo, induced drag fan or heat exchanger, etc. You can consult for more detail with our sales representative for any specific location to suite with your requirement to help solve your dust build up problem.