7/31/2019 GNDC ESP

1/66

Vietnam Guang Ning Thermal

Power Station ESP Training

Shanghai Metallurgical & Mining

Machine Manufactory

Technical Department Wu HUifeng

2009.03

7/31/2019 GNDC ESP

2/66

ESP Introduction

Electrostatic Precipitator (ESP) is highly sufficient dust-removal, whichcharactered by its reliable operation, easy maintenance, and low power-

consumption, etc. The products we manufactured are wildly used in power

station,chemical, metallurgical, constrction and paper-making, civil fields for

flue gas dedusting, gas capacity is104~106/m3. Our factory designed and

manufactured first ESP unit for 600MW thermal power station.

Our factory has huge and strong technological strenth and manufacturingcapacity in more than 40 years of designing and manufacturing of ESP for

short periodic time, reliable quanlity and excellent performance. In 1982 we

introced advanced exclusive patent of design and manufacture of ESP from

well-known Sweden ABB Co., meanwhile adopting CAD/CAM computer

system for designing,which realizing design on basis of computer

parameters and enhancing the ESP design level and fabrication ability.

The main characteristics of our products are following:

7/31/2019 GNDC ESP

3/66

Advanced Technology. Controlled by microprocessor with various methods

in spark-tracking, high-peak power supply, interval power supply, which is

suitable for flying dust collection.

Compact structure. More lightweight of main boby and highly accurate

calculation.

Welldone In Complete Set. In addtion of main body, verious auxiliary

equipents, such as agas flue, supporting, top ceiling, air door, expansion

joint, hoisting machine,which making easy for maintenance.

Complete Product Series. Application in 5MW~600MW station.

In 1986, we adopting advanced technology to designed and manufactured

225m2 ESP for first set of 600MW power station in domestic which fill the

blank in this field. In 1988, after operated successfully in 6000hrs and tested

by National Invironment Protection Bureau,Machine & Elecricity Bureau,

Power Department and related Designing institute, all performance indexs

achieved high-class standard, got an exclusive medal in this field by

national approval in 1990-1991.

7/31/2019 GNDC ESP

4/66

Our factory designed and manufactured first ESP unit for 600MW

themal power station in our country

2600MW ESP for Wujin Power station

7/31/2019 GNDC ESP

5/66

Separation principle of ESP

1 Gas flowionizingHigh voltage DC is applied through over two apecific electrodes to set up aelectric field which make voltage of electrodes system exceeds critical

voltage, then the gas is get ionized to form electrode corona dischaging.

The small area electric field surrounding discharging electrode is strong

enough to ionized the gas. Two areas formed in electric field. One is electric

corona area nearby and far from electric field 2-3mm in where producing

large amount of electric particles and positive ions. When negative electric

corona discharging come from negative voltage, particales go to collector

plate while positive ions go to discharging electrode itself. The other is non-

electric corona area where ocupied most space but without gas ionizing.

7/31/2019 GNDC ESP

6/66

Charged dust particleAs ion or particle from the electric corona to non-electric corona, andcollided with neutral particle, so dust particle be charged and its energy isrelated to particle diameter, electric field intension, thermal energy of ionand remaining time. Usually we thought charged dust particle has twomechanics:one is the elecric field charged particle which means ion iscollided with dust particle in the influence of electric field and the other isdiffused charged particle which means ion is collided and sticked withdust particle result from irregular thermal motio of ion with gas disffusion.

CollectionAfter be charged, dust particle will move to and settled on the surface ofits opposite polarity leave from its own polarity in the effect of electric field.Usually we regard the motion velocity of dust particle vertical to electrodeas migration velocity which related to dust particle electric quantity, the

electric field velocity, and gas feature. Negative charged dust particle willlose its electron and turn to be neutral particle and stick to surface ofelectrode when contact with collection electrode. Then dusts get off fromthe rapped collection electrode due to rapping device and down intohopper where in the bottom of ESP.

7/31/2019 GNDC ESP

7/66

7/31/2019 GNDC ESP

8/66

FLAKT Electrostatic Precipitator

Inlet gas distribution screen

Discharging rapping

Collecting rapping

Hopper

HV power

Casing

Insulation

Bent plate

Discharging wire

Collecting plate

7/31/2019 GNDC ESP

9/66

Casing

The casing is very important part of ESP and the resonable design is closely related

to the whole equipment charges,installation time and base working.

The casing all uses pressure-tight welding structures,including casing side

plates,gables and roof prefabricated plates.The side plates are horizontal or self-

supporting structure. The roof loads, that means the main loads go from roof beam

through roof plates to the column, then directly to the base along column. This king of

side plate design reduces the supporting points to minimum.

For the huge ESP,install the inner central column to directly transmit the top load to

the base. All the inner columns are respectively installed on the inspection channelsofall electric fields . The purpose of this kind of space girder design is to scatter the

load so that to keep the structure firm and electrode straight and guarantee the

excellent efficiency on the operation condition. Meanwhile,they can be fabricated in

the workshop to guarantee the quality.

7/31/2019 GNDC ESP

10/66

7/31/2019 GNDC ESP

11/66

Hopper

When the dust particles fallen down into the bottom pyramid hopper, heat

the hopper bottom (about 30%~50% height) to avoid condensation and the

installed baffles plate can prevent the gas flow leaking from the electric field.

7/31/2019 GNDC ESP

12/66

Supporting bearing

In order to avoid producing irregular load because of casing hot expansion, install the

supporting bearing between the casing column and steel supporting structure. And

this kind of supporting bearing sliding surface is made of the material with minimum

friction coefficient. The bottom is connected with spherical surface so that no heavy

load will be produced when sliding or rotating on any horizontal directions.

7/31/2019 GNDC ESP

13/66

Discharging system The discharging system is very important part of ESP, taking as the heart of ESP.

The effect of discharging wires is to produce the corona phenomenon necessary for fluegas dust particle charging. In order to realize this purpose, the discharging wires must beinstalled on the symmetry positions in the electric field to avoid too much flashover and

short circuit. The discharging system should be of easy maintenance and can keep ESPnormal operating without being influenced by temperature.

The discharging wires are suspended between the frames, the upper, middle and downframes are closely connected with the suspension beam. The whole frame are suspendedon 4 supporting insulators which are installed in the roof insulating room, to isolate the fluegas from outside.

The frame design should be very firm, permitting the maintenance personnel walking on itwithout distortion. No need to install the stabilizing device as the frame will not swing. Theinstalled middle frame reduces the length of discharging wires , so the wires swing little andmake the effective vibration after rapping.

The standard discharging wires are made of high-tension steel less spiral wires. The spiralwires are coiled into circles with hooks at both ends and then delivered to site. Wheninstalling, evenly stretch the spiral wires by the special tool to the hooks on the frame.

The main characters of discharging system design:

The rigid and firm frame can keep the discharging wires straight. The spiral wires operatestably and install, maintenance easily. The spira wires can fasten by itself, no need to addfasteners and lowers wires broken rate. The kind of wires will produce even currentdistribution on the collecting electrode. The wires fasten easily, swing little with reasonablelength. This kind of discharging wires transmit rapping as well as ground surface withoutdust accumulation.

Another king of discharging wires is the new type RS rolled tubing pipe with spiked emitter.

7/31/2019 GNDC ESP

14/66

Rig Frame Design of Discharging System

7/31/2019 GNDC ESP

15/66

BS discharging wire

7/31/2019 GNDC ESP

16/66

Discharging Suspension The supporting insulators on the casing roof are installed in the seal insulating room

and the inspection hole on the top is easy for maintenance in the insulating room.

The HV rectiformer is installed on the ESP roof and connected with discharging

system by conducting wire. The steel structure rain-proof ceiling and monorail is set

up on the roof for easy maintenance on site, for example, if the transformer is burnedout, then lift the whole transformer to the ground for correction by monorail.

7/31/2019 GNDC ESP

17/66

Discharging Rapping

During de-dusting process, a small amount of dust particles will be attached on the

discharging frame and wires . If not cleared immediately, the corona will be closed

and de-dusting efficiency will be lowered with dust accumulating, so the accumulated

dust on the discharging system must be cleared by effective rapping. Use thetumbling hammer installed on the horizontal shaft to shock the frame and the hammer

raps the special shocking bar in sequence which connects the middle frames, as the

frame is very stong so that the rapping force is scattered to the frames and wires.

The tumbling hammer is of high mechanical strength without breakdown when

working in flue gas.

One set of rapping device is installed on every bus bar. When the rapping driving isinstalled on the ESP roof, taken as top driving, when installed directly on rapping

shaft then throuth casing side plates, taken as side driving. For the top driving, the

driving device is installed in the insulating room and the insulators are in the

insulating room with heaters and the inspection door is set on the insulating room for

insulators maintenance and cleaning. The top driving is transmitted to side driving by

pin wheel. This kind of pin wheel can work in any kind of flue gas without dust

particles blocking and any adjustment & maintenance.

The operation of rapping device is controlled by programmable motor or PC, and the

programmable motor or PC can program the best rapping frequency to control

charging operation and prohibiting reentrainment. The following rapping frequency

table is recommended and can be adjusted according to the operation actual

condition.

7/31/2019 GNDC ESP

18/66

Rotating Type Hammer Design Discharging Rapping Top Drive

7/31/2019 GNDC ESP

19/66

Discharging Rapping Side Drive Discharging Rapping Top Drive

7/31/2019 GNDC ESP

20/66

Collecting System

The collecting system is another important part of ESP, FLAKT company uses the

GS3-480C type collecting plate which is 480mm wide and is continuously rolled withhigh process requirement. The special from of collecting plate make the plates to

reach sufficiently current scattering and high rigid. The edge design of this collecting

plate has improved the regid and deleted the possibility of spikes, comparing with

traditional plate. This plate is completely seamless welded and designed the strength

hole on the top for suspending.

The collecting bottom is firmly connected with shocking bar by high tension bolts. The

shocking bar is a piece of angle steel without any welding seams. The rapping anvil

made of special material is also connected by high tension bolts, while the collecting

plate shocking bar is correctly guided on the side.

7/31/2019 GNDC ESP

21/66

Average pitch 200mm

7/31/2019 GNDC ESP

22/66

Collecting rapping

A single rapping tumbling hammer is for every row of collecting plates, like

discharging rapping. The rapping force is distributed to every plate through shocking

bar. The rigid and the design of shocking bar guarantee that the rapping force will be

distributed on every plate in best without concentrating on one point. The rappingacceleration is not more larger more better, and a minimum acceleration value is set

to guarantee the even rapping acceleration.

The purpose of setting a reasonable acceleration is to make the dust particles fall

down into the hopper by reasonable rapping, and to reduct the reentrainment to

minimum.

The rapping frequency also should be as low as possible to short the time of loweringdedusting efficiency in minimum because of by rapping.

7/31/2019 GNDC ESP

23/66

Steel Supporting

The steel supporting is composed of columns, bracings and diagonals.

There are three kinds of columns: the first is a frame made of channel steel, which is

of large amount of working, compound structure, bad painting quality and lower cost,

the second is adopting H steel with simple structure and excellent painting quality,

and the third uses big aperture steel with simple structure andgood painting quality

which is especially suitable for coast of high anti-corrosion requirement.

7/31/2019 GNDC ESP

24/66

ESP Operation and Maintenance

7/31/2019 GNDC ESP

25/66

Operation of ESP As for ESP, special personnel on duty should be arranged, personnel on duty should

have the basic knowledge of elementary electrician and ESP worker. After passing

safety regulations and operation procedure test, they are qualified for work.

The main responsibility of ESP personnel on duty is to regularly know the equipment

load, inspect the flue gas temperature, as well as whether the heating system of the

insulting room is normal. They should also inspect the rising temperature of the motor,

the lubrication of the gearbox, the hopper situation, as well as whether different kinds

of rapping devices can work normally. Furthermore, they should inspect or adjustsecondary voltage and current value in the operation cabin so as to make them work

in the best way. Field voltage, current and other related parameters should be

recorded according to the time requirement. Different bugs happening on the

equipment should be analyzed and eliminated.

In terms of high temperature, high dew point ESP containing flue gas clearing, in

order to prevent dewing and corrosion, we should pay particular attention to whethertheres something wrong with the heat insulating layer of the equipment, whether the

manhole door is tight. In the meantime, the electrode and insulator should be kept

clean.

7/31/2019 GNDC ESP

26/66

Test and inspection before commissioning Before putting into use, according to related standards and regulations, test and inspection

should be conducted on newly-installed or overhauled ESP. The inspection mainly includes:

Go through all the procedures of the work bill and remove the safety facilities concerningthe inspection. Guard bars and index plates should remain.

The equipment and components are complete and the symbols are clear and correct. Tight

faying surfaces, complete insulation and ample lighting should be available.

The motors are wired, the earthing wire is fixedly connected. The safety hood should be

installed and has no collision, as well as contact with the rotation part.

Discharging and collecting rapping devices, dust discharging valve, screw dust discharging

machine and other rotation equipment work normally. The oil quality of the gear box isqualified and the oil position is normal. Oil should be added to the driving chain so that

chains can move flexibly.

All the meters, switches, protection devices, regulation devices, temperature test devices,

alarm signals and indicating lamps are intact, complete and normal.

The heating device of high voltage insulation bushing room and hopper heating device are

intact. The high voltage rectifier device is clean, it is the same with insulation parts. Theres no oil

leakage in the rectifier transformer and resistor. The oil quality is qualified and the oil

position is normal. The lead wire of the rectifier device has a good contact ability and the

buffer resistance is intact. The rectifying control cabinet and the automatic regulation

device are intact. The adjustment button or knob is complete and the instruction is correct.

7/31/2019 GNDC ESP

27/66

High voltage isolating disconnecting link should have a good contact ability.

The operation mechanism is flexible and can be earthed reliably. The

disconnecting link is in the earthing position.

ESPs high voltage cable lead-in cabin is clean. Lead-in wires have good

contact ability and the buffer resistance is complete.

All the switches and disconnecting links of the low voltage distributor work

normally. All the power insurance and operation insurance are intact.

When confirming that silicon controlled plates, heating and rapping devicesswitch off, we will power the above equipment. As for the breakdown or

failure, generally, we will inspect the rotation part or the failure part. After

confirming that it is normal, it can be put into use.

7/31/2019 GNDC ESP

28/66

Switch on ESP Before switching on the ESP, we should confirm that theres no person in

the ESP. The manhole door is closed and theres no person in the highvoltage area. High voltage isolating disconnecting link is put in the operation

position.

Switch on the heating device 4-8 hours in advance. Heat the porcelain

through insulator, column insulator and electromagnetic shaft so as to

prevent dewing and creepage. Switch on the hopper heating equipment and remove the moisture on the

inner wall of the hopper.

Switch on the rapping device of the ESP collection electrode and

discharging electrode. Remove the dust particle attached on the electrode.

Switch on the main blower fan to preheat and dry the electrode system of

the field.

Switch off the earthing device and put high-voltage power in.

Refer to drawing one for the operation procedure of ESP.

7/31/2019 GNDC ESP

29/66

7/31/2019 GNDC ESP

30/66

Operation and inspection of ESP ESP works under high temperature and poor process condition full of corrosive gas.

Sometimes the flow, pressure and concentration of flue gas fluctuate, flue gas

contains sticky tar substance. Under such kind of conditions, in order to prevent thedecline of de-dusting efficiency, we must often inspect the equipment operation

condition and solve problems in time.

After the newly-installed or overhauled ESPs are put into use, a characteristic test

under the load condition will be given. Record the primary and secondary voltage,

current, conduction angle and flash situation. Draw C-V characteristic and determine

the optimum parameter, make some adjustments until it can work under the bestcondition.

During the operation process of ESP, we should monitor whether the HV rectifier

control cabinet, the meter of the console, as well as the indicating lamp are normal. In

the operation, every 2 hours, we record primary and secondary voltage, current and

conduction angle. On each shift, we conduct 2 regular checks and make records.

Inspect the equipment in the low-voltage switchhouse. Its supposed to have nooverheating, discoloration, burning odor or oil leakage.

Oil colour and oil position of the rectifier transformer are normal and so is the oil

temperature of the transformer. The highest temperature shouldnt overpass 85C,

silicon gel doesnt change its colour.

7/31/2019 GNDC ESP

31/66

Buffer resistance is intact and theres no discharging phenomenon Theresno evident discharging on the top of HV rectifier transformer, high voltageisolation disconnecting link, DC HV lead-in wire, linking wire and ESP.

The temperature in HV cabinet cant overpass regulated temperature. If itdoes so, switch on silicon-controlled ventilator.

During operation, people are not allowed to enter the HV room withelectricity or open the high-voltage insulating room cover for inspection

ESP, pipe and manhole doors are tight

The hopper and hopper heating device work normally and no dust blockingor dust leakage happens. The rapping device and other rotation equipmentwork normally

The heating device of the HV insulating sleeve and the thermometer arenormal

All the protection covers and service platform lighting of the motion partsshould be kept in a good state

Oil should be added to the rotation equipment based on the time

requirement and the oil position is normal Refer to drawing 1 for the times of checking and checking position of ESP

7/31/2019 GNDC ESP

32/66

7/31/2019 GNDC ESP

33/66

Switching off of ESP

When the main frame is switched off, ESP temporarily stops andthe field HV isolating disconnecting link is placed on the earthingposition.

After the power cut of the field, the heating device and rappingmechanism will continue to work until the dust in the field iscleaned

The dust in the hopper should be cleared instead of beingemptied completely.

When ESP stops working because of long-term or middle-termoverhaul, we can treat it as temporary machine halting. Therapping device at least works for 4 hours and then the heatingsystem stops working. Empty the dust in the hopper. In the field,the earthing rod is added and the site is kept clean. Make records

of the machine halting. Refer to drawing 2 for the machine halting procedure

7/31/2019 GNDC ESP

34/66

Maintenance of ESP

7/31/2019 GNDC ESP

35/66

Maintenance of ESP With regard to the maintenance work of ESP, besides the regular inspection on

key parts, we must conduct careful maintenance based on the ESP equipmentand the instruction of other mechanical and electrical products. Furthermore,taking the opportunity of machine halting, well launch a thoroughgoing inspectionon the field and HV control room. Refer to table 2 for the inspection content. If

abnormal situation happens, treat it timely. Normal maintenance of ESP includes:

Clear the accumulated dust on the insulation parts;

Lubricate all the driving parts once every week;

Every 3 months, add sewing machine oil to silicon-controlled cooling fan for 1 time;

Timely clean HV control cabinet and the automatic voltage adjuster, inspectwhether the switch of the contact, coil of the relay, as well as the contactor are

reliable; Every 3 months we check the resistance and heating components, every 6

months, we check thermometric components for one time;

Once every year, the drier of the respirator in the rectifier transformer should bechanged;

Once every year, an oil pressure test of the rectifier transformer should beconducted . The average breakdown value is higher than 35KV/2.5mm;

The earthing resistance of ESP should be tested each year(not higher than4).The rectifier transformer earthing and electric control earthing resistance arenot larger than 1 ;

If ESP stops working for a long time, we need to take measures to prevent rust inthe field. The rapping device should be switched on often so as to prevent thehammerhead and connecting rod from rusting;

We should choose to inspect the case of ESP, case of rectifier transformer so asto guarantee that no loosing place or serious corrosion happens.

7/31/2019 GNDC ESP

36/66

7/31/2019 GNDC ESP

37/66

7/31/2019 GNDC ESP

38/66

Just like all the other production equipment, ESP should regularly be given

short-term, middle-term and long-term overhaul in a planned and systematic

manner. Although the motion components are few and the equipment life is long,

its inner components work with dust particle under high temperature and highvoltage. Therefore, abrasion and electric chemical corrosion loom large. Some

components should be changed regularly.

ESPs inspection plan should comply with the inspection period of production

equipment. In the meantime, according to the component life, bugs and bug-

happening frequency, we formulate regular or annual inspection plans, devise

equipment improvement schemes, change broken parts and know the back-upproduct quantity and expense budget.

Regular inspection should combine with daily check. If the daily inspection

proceeds well, we can decrease the daily inspection work and the time interval

is prolonged.

A prevention-oriented planned inspection should be conducted on the ESP, it is

vital to prolonging the equipment life, guaranteeing the stability and highlyefficient operation. When it comes to the planned inspection, we should adhere

to Quality First policy and implement the spirit of seeking truth from facts. We

should make sure the overhaul work is well done and the equipment are always

in perfect condition.

Refer to table 4 for long-term overhaul. Refer table 5 for short-term and mid-

term overhaul.

Inspection of ESP

7/31/2019 GNDC ESP

39/66

7/31/2019 GNDC ESP

40/66

7/31/2019 GNDC ESP

41/66

7/31/2019 GNDC ESP

42/66

Safety and technical regulations of ESP operation After the erection and overhaul of ESP, trial test work should be conducted.

Personnel responsible for the trial test should peruse the instruction and relatedtechnical information, get familiar with the equipment property, structure. This shouldbe done in a step-by-step manner.

(1).Before switching on the ESP, we must inspect different parts of ESP, afterconfirming that the equipment works well and theres no person in the field and eachmanhole door is closed, we can switch on the machine

(2).Four hours before ESP operates, all the insulation heating system and hopperinsulation system should be put into operation first.

(3). When the dust enters ESP, all the rapping device and dust discharging systemshould be put into use at the same time. When the flue gas temperature is higher

than the dew point temperature, it means the field is in normal state and we can offerthe field electricity.

(4). Before switching on the machine, we should enhance our inspection, if anyproblem occurs, we should handle them correctly.

(5). During the ESP operation, the automatic voltage adjustor is not allowed to havearc, as well as adjustment inefficiency, if the following deficiency happens, we shouldstop supplying electricity to the correspondent field. After the deficiency is tackled,we can reswitch on the ESP.

1) In the operation, primary current overpasses rated value; 2) Flashing phenomenon in the HV insulating component is serious;

3) Buffer resistance flash is frequent and sometimes it causes fire;

4) The rectifier transformer has temperature excursion alarm, oil gushing, oil leakageand abnormal sound;

5) The power supply device deviates greatly;

6) Th t li it i t f t l

7/31/2019 GNDC ESP

43/66

6) The current limit is out of control;

7) After 2 times trial use, the power supply equipment trips;

8)Controllable silicon radiation fin is over 60C;

9) Theres sth wrong with dust discharging valve, dust blocks up thehopper

10) Changes happen on the main engine and other situations that maybring harm to the equipment or endanger people

(6). We should record the following content in the operation

Every 12 hours, we record primary and secondary voltage, currentvalue and operation temperature value of ESP; 1) We record rectifiertransformer temperature twice on each shift; 2) Switch-on and switch-offrecord of all the ESP; 3) Abnormal situation and equipment deficiencyrecord; 4) Assembling and dissembling record of the earthing wire;5)record of warning plates

(7). During the operation of ESP, the following should be monitored daily,if any problems occur, we should handle them timely 1) At someparticular time each shift, the alarming device is tested. 2) Primaryand secondary voltage current value; 3) Rapping, electricity heatingand dust position control system; 4) Oil temperature, oil colour,discharging and leakage of the transformer; 5) Operation situation ofthe rapping system; 6) Operation situation of electric screen, cabinet,box and plate; 7) Controllable component cooling fan operation, noflash of baffle resistance; 8) Theres good sealing condition of themanhole door, no dislodging of the insulation layer.

(8).If ESP stops working, we should adjust the field voltage to the zero

7/31/2019 GNDC ESP

44/66

position, pull down the general disconnecting link and otherdisconnecting links. Then close the insulation room, conductcontinuous rapping on all the manual rapping system, stop rappingafter clearing the dust in the polar plate and frame. When we makesure that the hopper is emptied, we should close the dust-discharging

system, in the meantime, we stop the work of the hopper heatingsystem and dust transmitting system.

(9).One person is responsible for the operation and another forsupervision. The protection work should be conducted well.

(10).When the ESP is operating, the manhole door is not allowed to beopened. If entering the field is inevitable, we should cut off the power

first and turn down the air door or stop the induced draft.

(11).To prevent overvoltage, in the operation, HV isolation switch is notallowed to be opened, under the open-circuit circumstance, powertransmission is not allowed.

(12).When theres a fire on the electrical equipment, firstly, we should cut

off high and low power supply, water is not allowed to be used inextinguishing the fire. When a power accident happens, firstly, cut offthe power, then first aid is given, saving other people single-handedlyis prohibited

(13).If the flue gas temperature overpasses the set value of ESP due toabnormal process flow, we should stop the machine and takeemergent measures. Switch on the machine until the work conditionis normal.

I ti d f t l ti f ESP

7/31/2019 GNDC ESP

45/66

Stopping of ESP should be conducted based on the stopping procedure, after entering thefield and conducting the inspection, we should abide by the following regulations:

The control plate and operation plate switch of the HV power supply device should becut off;

An inspection plate should be hung on the operation plate so as to avoid switching onwrongly;

HV cut-off switch is connected on the earthing part, discharging electrode should alsobe earthed (in the inspection process, it should always be earthed)

Use a portable earthing rod to release residual electricity in the HV system

When theres no power in the field, the rapping device continues to operate and thedust adhering to the electrode is cleaned, the hopper dust discharging device alsocontinuously operates until the dust in the hopper is completely discharged

When the field cools off step by step,( the cooling time is not less than 8 hours), themanhole door is allowed to be opened, or the sudden entry of cold air easily leads tothe plate transformation under high temperature.

When there are some people working in the ESP, supplementary equipment(such asthe major exhaust blower, rapping system, dust discharging device) should be lockedor an inspection board should be hung;

Based on the field condition, inspection and maintenance personnel should wear dust-proof cover, dust-proof clothes, dust-proof shoes and corrosion-proof gloves, as wellas other protection devices to enter the field;

When the hopper is blocked by the dust, the hopper manhole door is not allowed to beopened and discharge dust

Personnel who enter the inspection and maintenance site should wear safety helmets.If the falling height is above 2-meter datum, construction personnel should wear safetybelts.

Before entering the field, CO and other toxic gases, treatment of accumulated dustand gas in the device should be inspected

Drawing 3 is the operation procedure and confirmation items from the safety perspective,its intention is to guarantee the safety by using forcible means.

Inspection and safety regulations of ESP

7/31/2019 GNDC ESP

46/66

7/31/2019 GNDC ESP

47/66

Common factors of abnormal operation of ESP

When abnormal conditions happen in the operation of ESP and if certainrules can be used, its easy to make some judgement. Sometimes, its

complicated, in this respect, we need not only experience, but information

and data as well.

As the information of the equipment, on the one hand, ESP operation record

reflects the operation situation of ESP, on the other hand, it is the basis for

analysing the problem, because some general problems in the operation ofESP are formed on a step-by-step basis. During the operation process of

ESP, if theres sth wrong with the electrical parameter and dedusting

efficiency, staff on duty should analyse and make judgement based on

these circumstances, they should find possible causes and solve the

problem as soon as possible.

In the ESP operation, refer to table 6, 7, 8 for abnormal phenomenon and

possible cause.

7/31/2019 GNDC ESP

48/66

7/31/2019 GNDC ESP

49/66

7/31/2019 GNDC ESP

50/66

Problem happening on the ESP

There are few components on the ESP so it can operate reliably for a longtime. If we maintain the machine in an appropriate way, no problem will

appear in a relatively long period of time

The failure type of ESP has sth to do with the ESP structure and its way of

use. According to the research from related department, the most common

operation failure of ESP is the broken discharging wire, which accounts for

68% of the researched objects, the causes of the failure mostly aremechanical fatigue. It is caused by frequent local disruptive discharge or

corrosion. Another opt-happened failure is on the rapping part, standing at

40% of the researched objects. Furthermore, insulation failure and short

circuit failure account for 28% respectively, the hopper failure 24%,

transformer rectifier 20%.

The failure type and failure frequency vary because of different work

conditions, but the main component failure and its cause are as follows.

7/31/2019 GNDC ESP

51/66

Failure of the discharging electrode

Broken discharging wire. Broken discharging wires have multiple

causes. For instance, aging causes discharging electrode to haveno enough strength, electric corrosion, deficiency in the erection and

construction work and too much rapping force are also the culprit.

Because there are sth wrong with the flue gas and dust, the

supporting component of the discharging electrode is corroded and

then its usage life is shortened. High specific resistance leads to

inverse corona. When the rapping is conducted repeatedly and the

discharging electrode vibrates, the hammer and discharging

electrode are running and its contacting position will give rise to

electricity corrosion.

Broken electric wire means the collection electrode has burrs. The

discharging electrode vibrates and shortens the electrode distance,

which leads to the local field strength increase. The discharging wire

is broken because of the disruptive discharge. Electric corrosion will

happen after ESP is operated for years.

7/31/2019 GNDC ESP

52/66

Thickness of the discharging electrode. Outside dust particle

thickness of the discharging wire concerns the property,

concentration, vibration force and rapping mechanism of the dust

particle. In the field, positive electricity adheres to the dischargingwire and a membrane is formed. Because of inefficient rapping dust

clearing and accumulated dust, the discharging wire is thick. When

collecting high specific resistance dust particle, the corona current

will decrease, corona discharge diminishes and disruptive discharge

increases. Based on the above circumstance, we should adjust the rapping

force, readjust the rapping time and rapping period.

If the electrodes thickness is caused by the flue gas below the dew

temperature or frequent switching on or off the machine, please

improve the insulating measures and power supply. Before the fluetemperature falls down to the dew point, clear the dust of the

continuous electrode rapping. Continuous rapping is conducted

within several hours of stopping the machine.

Failure of the collection electrode

7/31/2019 GNDC ESP

53/66

Failure of the collection electrode(1).Dust accumulation of the collection electrode. Just like thethickness of the discharging electrode, local dust accumulation of thecollection electrode will reduce the discharging property and thecollection efficiency will be lowered. Local dust accumulation relatesto the nature of smoke, dust concentration, as well as rappingconditions. The major cause is no enough rapping force or unevenrapping force distribution. Sometimes, its because of the loosing ofthe connection bolt on the collection plate or inefficient rapping forcetransmission. And then we need to enter the field to ascertain thereason.

(2).Transformation of the electrode plate. Transformation of electrodeplate makes the electrode distance have some changes. The reasonis that the flue gas temperature is high, the electrode plate istransformed due to some limitation. Or accumulated high temperaturedust cause thermal storage and then transformation occurs; or theflue gas temperature overpasses regulated temperature value; or thebreakdown arc inside the electrode plate transforms the electrodeplate. If it is due to the redundant polar plate room or erectionproblem, when the electrode plate is transformed because of the flue

gas, its phenomenon is that the voltage can reach the rated value,when smoke appears, voltage will drop with the rise of temperature.When we stop providing flue gas, the voltage will rise little by little.This kind of failure will appear on the ESP which is newly put into use.If the local transformation is caused by thermal storage and arc, weneed to ascertain the reason and change transformed electrodeplates and solve the problem from adjusting the electrode distance or

improve the rapping system.

Failure of the rapping device

7/31/2019 GNDC ESP

54/66

Failure of the rapping device Use hammer rapping for ESP, the transmission part is on the outside of

ESP, the rapping hammer is in the field, the failure of the rapping partcan be judged according to the change of the secondary voltage or rthedecrease of the dust removing efficiency. As for the discharging electroderapping, if theres sth wrong with the insulation part, the whole field cantwork, this situation will immediately be detected, but if an individualhammer fails or breaks down, we cant find it until it is inspected.

Major failures of the rapping and transmission devices include thefollowing:

(1).Shaft locking. Main causes for shaft locking are:(1) the supportingshaft of the rapping shaft has a serious abrasion.(2) rapping shaft

bearing is not on the same line and it overpasses the compensationability of coupling and affects the concentricity of the rapping shaft.

(2).During the operation, the hammer and rapping anvil is not aligned.Besides the erection problem, most are caused by the heat inflationof the rapping shaft and ensuing rapping hammer dislocation

(3).The rapping and transmission porcelain shaft of the dischargingelectrode is broken. Firstly, its the porcelain shaft quality problem,

before erection, we should strictly inspect it. If the porcelain shaft hasno certificate, or has cracks on the surface, it shouldnt be used.During the trial run, we should timely re-inspect. Secondly, therapping shaft torsion is too big, furthermore, there are other factorsconcerning excessive leakage current or breaking of the unevenheating of porcelain shaft caused by the dust accumulation anddewing.

7/31/2019 GNDC ESP

55/66

HV insulator Mechanical failure easily happens on the HV insulator. Furthermore,

when HV insulator adheres to the conductive dust, it loses itsinsulation property and evokes the reduction of ESP efficiency. If dustadheres to the insulator in an all-round way, the leakage currentincreases, the corona current needed for dust removing will decrease.If the adhered dust is not distributed evenly, it will get hot because oflocal current increase and then, the insulator greatly lowers its

insulation ability and the inner part of the insulation bushing will havethe state of flashing. This is the main cause for the accident. Anotheraccident is dewing and creepage, it is caused by great humidity, lowtemperature of the dust, inappropriate heating , no heating facility, aswell as the accumulation of condensation water on the insulator.Thirdly, the erection of insulator is not level, then the wholedischarging electrode has uneven load and it may cause thebreaking of the insulator.

Analyse the failure based on the meter

7/31/2019 GNDC ESP

56/66

Analyse the failure based on the meter

The failure of the ESP is caused not only by itself, but also by the treatment of fluegas. The complexity of flue gas gives rise to the diversity of the ESP failure. Onthe surface, some failures looks exactly the same, but actually, they are quitedifferent, some failures of the same type vary due to the failure degree or workcondition. Recently, through long times observation and practice, Chinas ESPtechnical and management staff have summarized some methods in analyzing theESP failure.

Primary and secondary voltage meter and current meter have no indication

The major return circuit contactor cant work. The major reason is: safety

interlocking plate, contacting position of HV isolation switch block device isnt

closed, the starting return circuit is switched off, the control core of the return

circuit is broken or has poor contacting. The automatic voltage adjuster trips inside,the relay contacting point cant be released

Although the main return circuit cant operate, when manual or automatic is

conducted, theres no voltage but increase of current

Main reasons:

(1) The automatic voltage adjuster has no current. At this time, primary and

secondary current are both zero, but theres 50V primary current, 8kv secondaryvoltage( they are called starting leakage voltage). Controllable silicon conduction

angle has zero setting.

The most common reason why A type power supply device has no power is

because the supplementary power supply device has not a good contacting ability,

this contactor is designed according to the general low voltage control return

circuit. The actual connection and disconnection automatic voltage adjuster has a

work voltage of 23V, because of the low voltage, its easy to get bad contacting.

7/31/2019 GNDC ESP

57/66

D type power supply contactor is linked in the 220V control return circuit, whichmakes the automatic voltage adjuster greatly decrease its power failure

One simply way to adjust whether automatic voltage adjuster has no power is topress the flash button, it the adjuster has power, the flash indicator should light

The fuse or rapid fuse of the major return circuit is broken. Under this kind ofcircumstance, the primary and secondary current is zero, drain voltage cant beseen, controllable silicon conduction angle is 100%. Controllable siliconconduction angles indication comes from the number of trigger pulse input ofthe voltage adjuster, because the major return circuit switches off and nosecondary current is feedbacked on the automatic voltage adjuster, accordingto the principle of automatic spark tracking, the output pulse increases to theutmost. Understanding 100% conduction angle will contribute to our quick

judgment on the failure.

Secondary voltage is zero, secondary current has indication 1. In most cases, theres a short circuit in the field. Main characteristic of this is:

When it is used in the field, secondary current will rise following secondaryvoltage, theres no turning point of discharge inception voltage.

When it is started, the starting primary and secondary drain voltage dont exist. The field doesnt have flash, each voltage and current meter doesnt sway upand down

In secondary current, after short circuit, primary current decreases. As for thefield working in the state of flash, after the short circuit, secondary current risesand is limited to the current limit value, and then primary current rises.

F th fi ld ith l ti l littl d lt d t b f

7/31/2019 GNDC ESP

58/66

For the field with relatively little secondary voltage and current, because ofsecondary current increase and rectifier transformer high impedance feature,primary voltage rises, in the field where secondary voltage and current are great orcurrent limit value in the automatic voltage adjuster is relative little, primary voltagedecreases.

Use 2500VM meter to measure the insulation situation of the field, if it is below

10M or zero. Common causes of the complete short circuit of the field

The full hopper causes short circuit, metal short circuit in the field or the insulationcomponents are broken down.

2.Incomplete short circuit of the field. When the field increases its voltage,secondary voltage rises step by step, when it attains certain value, it is brokendown to zero, the current rapidly rises and is limited to the limit value of current. At

this time, the field parameter is like the complete short circuit of the field. Stopusing manual decrease, when primary voltage lowers to a certain value,secondary voltage resumes to a certain value. This field has started drain voltage,use 2500 VM to measure the insulation situation of the field, the data dependson the reason of breakdown, but it is not zero.

The common cause for incomplete short circuit of the field: There are foreignparticles existing between the discharging and collecting electrodes; Hot bloatingof the plate makes the distance of discharging and collecting electrode nearer. The

insulator is polluted seriously. Secondary voltage measures return circuit failure or the meter failure. The

parameter is different from that of the field short circuit, we can compare theparameter situation of the short circuit with the field in the same situation, analysewhether theres a real short circuit or false short circuit on the meter. If it belongsto the failure of secondary return circuit, D-type power supply device will tripbecause of the low voltage delay

Low secondary voltage

7/31/2019 GNDC ESP

59/66

Because of the decreased load, the field characteristic curve changes, inthe relative low voltage value, secondary current has attained the currentlimit value. When it is used in the first and second field, dustconcentration in the third field decreases and secondary voltage is limitedby the current limit. Under such kind of circumstance, low voltage is

normal. The cause for low voltage failure is: 1. Poor rapping. Bad rapping of discharging and collecting electrodes

cause the decrease of secondary voltage, decrease of secondary current,increase of the field flash. Common causes are:

(1)The rapping mechanism is locked, generally, it is caused by thehammer, besides the hammers being locked by inappropriateinstallation, the hammers not being reset after the inspection of thefield is one of the reasons.

(2)Broken fuse

(3)In rapping, the control return circuit fails or rapping period cant bechosen correctly

(4)Rapping device cant be installed appropriately, the welding is notfastened and the rapping acceleration of the electrode decreases.

2. Reversed polarity change in the field. The causes are: There are metal pieces in the field Structure pieces are transformed in the field The polar plate is transformed by heat inflation, heat inflation enables

secondary voltage to have following characteristics when it decreases

Under the same voltage, if secondary current is high, the more crooked

7/31/2019 GNDC ESP

60/66

g , y g ,plates are, the more the current is

In cold position, the voltage rise is normal, in hot position, the voltagedecreases

With the increase of load, the voltage lowers step by step

Open the manhole door of the correspondent field, the voltage cancompletely or partially rise.

During the shutdown period, the sign of the hopper air deflectors being bentcan be seen.

(4) The insulation components are humid and polluted

(5) The power supply device has serious magnetic field deviation

Magnetic field deviation of the power supply device is that AC is inputtedinto the rectifier transformer through controllable silicon and the voltagecurve is not symmetrical, as for light field deviation, other parameters donthave evident changes except the slight increase of primary current, themost serious situation of magnetic field deviation is that there are onlypositive and negative curve, this voltage is like DC pulse voltage, at thistime, secondary voltage and current are low and primary current is high andit overpasses rated value. Primary voltage is 200V in the return circuit

induction function, controllable silicon conduction angle indication is 100%.Because of the field abnormity, there are abnormal vibration and soundinside the rectifier transformer, the increase of iron loss and copper lossenables the rectifier transformer to have a temperature rise. Light magneticdeviation is because two groups of trigger pulse have asymmetricalparameters, serious deviation is caused by one group of pulse output failureor one controllable silicon failure.

Secondary voltage is higher than the normal value

7/31/2019 GNDC ESP

61/66

y g g Secondary voltage relates to the erection quality in the field, size of ESP,

flue gas, dust concentration and equipment operation situation. Under thesame condition, the front and back field voltage are different, if weexclude these normal difference, secondary voltage increase will becaused by the following

1.High voltage return circuit has no good contacting, sometimes its linked

and sometimes its disconnected. At this time, the field parameter has

such characteristics: Frequent field flash, flash terminal voltage

sometimes is high, sometimes is normal, when the voltage is high, the

current is low or even no current at all. If this problem cant be solved,

it probablycause complete open circuit. Bad contacting is: After several operations, HV isolation switchs springleaf is concave, which makes the link loose or the switch cant be usedbecause of the operation mechanism corrosion; The work earthing line isloose or broken, buffer resistance is burnt but the broken area is shortand is broken down by high voltage electricity, buffer resistance anddischarging wall bushings linking position maybe are loose or burnt.

2.High voltage return circuit is complete open. The characteristic is(1)When the major contactor is closed, there are high primary and

secondary starting drain voltage

(2)When raising the voltage, primary and secondary voltage rapidly rise,secondary voltage is 85-100kw, primary voltage is 380V, secondarycurrent is zero, primary current is less than 10A.

7/31/2019 GNDC ESP

62/66

Secondary voltage and current are normal, primary current is high

The main reason is that there are problems existing in the primary current

measurement return circuit or there are problems existing inside the

rectifier transformer. Inside the rectifier transformer, the place where problems easily happen

is the breakdown of AC HV part or silicon series string. The most

common way to judge whether the transformer has problems is to use

power supply device when the transformer is in open circuit situation,

then, secondary current is zero, primary current will explode following the

rise of primary voltage.

Common problems and treatment

Refer to table 11 for common problems and treatment of ESP

7/31/2019 GNDC ESP

63/66

7/31/2019 GNDC ESP

64/66

7/31/2019 GNDC ESP

65/66

7/31/2019 GNDC ESP

66/66

The End