OUR ACHEIVEMENTS .

Eco Bypass duct total ash was evacuated through the system , thus avoiding

ash dumping outside .

Both sources ( Fdr - 1 & 2) for Marshaling Box of Start Up XFMR -2 ,

UAT-3A/3B were fed from one section of Station ACDB . Now they are provided

from both sections I.e source - 1 from sec - A & source-2 from sec -B.

During boiler hydro-test the temp. of TB of MDBFP was going high after a

prolonged period of operation on recirculation . The FST temp was also going

high due to operation of the pump on recirculation . The TB temp was

brought under control by reducing the FST temp as fresh makeup was taken

to the system & hot water was drained .

MAJOR PTW'S ISSUED DURING THE PERIOD .

APRDS from Unit- 2 to Unit- 4 was isolated for attending the AS 169 valve

passing problem . During this time steam to St- II FOPH was not available ( 36

hrs)

St- II HFO temp had dropped From 90 deg C to 60-65 deg C ( For operating

Units 4/5/6 )

During 3UA 11 Kv bus Shutdown all the 9 compressor’s control supply were

fed from one Service Water XFMR .

Similarly 4 Compressors out of 9 compressors were fed from one Transfomer

during 3UA/3UB 11 kv bus isolation for O/H job .

During US SWGR- Sec B isolation the Power supply to 220 V DCDB is fed

through the DG set via EMCC via Ch- 2. Incase of problem in DG set the

DCDB is fed from Batteries Only .

Bat Ch- 1 is from USS Sec- B

Bat Ch- 2 is from EMCC/ USS Sec- B

Hence to avoid the above problem Bat Ch - 1 source to be changed to

USS Sec- A.

MAJOR PROBLEMS EXPERIENCED DURING RECOMMISSIONING .

AREA : BOILER & AUXILIARIES

During APH water washing the Zero meter area got flooded as the Hopper

Drains are not provided for the above purpose .

Also the duct & other equipment are getting damaged due to falling of acidic

water from the APH .

The Drain Back side of PA/FD fan is getting clogged with CHP coal as the

reject chute of CHP is just above the drain .

Operation of dampers at ESP inlet & outlet , ID fan inlet are unsafe as vertical

ladders are not provided with cage .

Mechanical isolation of HAG was difficult as they were not properly approachable .

AREA : TG & AUXILIARIES

CW water box vent/drain are connected to the same funnel causing problem

during draining .

Duct draining took more time as gravity draining facility is not there .

There is no valve provided for duct draining .

CW duct was drained by loosening the dummy flanges

Portable dewatering pump was not available from the beginning .

AOP starting during Oil flushing got delayed as it was tripping on Fire

protection .

TG ECW system drained thrice to attend the H2 cooler & other valves

problem .

Exciter Cooler Valve passing problem has caused water falling on the

Generator bus duct continuously . To avoid such problem proper dummy of the

line is to be done after removal of exciter cooler .

After Synchronisation of the unit even though the drain valves got closed on

torque setting & Close LS feedback has come , it was observed that the drain

temp. were maintaining HI . They were manually further tightened & torque

setting was increased .

While cleaning PHE of TG ECW/SGECW the water was falling directly on the

equipment's / panels at TG “0”0 Mtr as there is no proper drain provision .

AREA : ELECTRICAL SYSTEMS

Difficulty was experienced in Heating the water for CO2 filling by wood

burning .

TG Hall EOT crane was having only one power source from Unit- 3 SSSWGR -

Sec- A . When PTW issued on this section the entire day EOT crane was not

available . This has happened as the 2nd source envisaged was not

commissioned .

The SWGRS which O/H job can be planned in normal time were planned during

O/H period .

(Ex- ACMCC-5 /EACMCC-5 etc)

The Breaker /Equipment Module indication lamps were not made available due

to shortage of lamps .

MDBFP- C suction flow transmitters were behaving erratically causing tripping

of BFP in 2 occasions .

SUGGESTION FOR IMPROVEMENT .

All the pending defects of the unit before shutdown are to be compiled

system/equipment wise & to be included in the Maintenance job plan for their

liquidation during the overhauling .

Such points are to be closely monitored in the daily overhauling meeting .

Standby supply source for critical systems & equipment are to be identified

earlier & to be provided for issuing PTW on the respective SWGR .

Ex - Boiler Lift / EOT Crane /TG hall Lift /Lighting at various places .

Boiler inside lighting AC/DC to be taken from the source provided by EMD .

PM PTWs can be avoided during overhauling .

To Minimise Isolation & Normalisation the Elect PTW/ Mech PTW are to be

clubbed together as far as possible .

With in EMD the different groups can take the PTW simultaneously (

SWGR/XFMR/Relay testing etc)

PTW on equipment's to be taken on Sec wise such as LHS / RHS Ex -

ID/FD/PA fans - A first & then - B . Also the LOP’s to be cleared by all the

Dept , So that The recommissioning activities can start in a phased manner.

Temporary dewatering pumps in condenser pit to be commissioned before unit

S/D.

Proper Approach to CT area Riser main valves & lighting to be provided to do

the necessary isolation & normalization in the Night

Proper Approach / illumination for SW Blow-down / Chlorination Plant water line

valves near CW ICV are to be provided to carry out the operation in the

Night .

MODIFICATIONS REQUIRED FOR IMPROVEMENT .

Gravity draining facility for CW duct as well as water box ( ref the sketch). This will reduce the drain timings of duct to a larger extent .

The sump pit pump discharge is to be staggered to avoid the overflow of drain at “A” Row .

Permanent power supply source for temporary dewatering pump in the Condenser pit .

BA I/O panel 3rd supply source to be provided for giving PTW on Bus coupler panels , (BAMCC/BMCC etc).

If Unit-3 BA I/O panel supply fails then the other units 4,5,6 PLC communication also fails .

ARV at end of Riser Main hdr at CT Area for duct charging & Draining .

Separate Drain system for Eco Ash Hopper during 2nd pass water washing . ( As discussed for APH Hopper system)

Tapping points from FH line at Eco bypass Hopper area for hopper & duct cleaning.

Power supply for Unit- 3 Lift & inside lighting are from different source ,to be provided from same source /same swgr .

2nd source for Chimney /Aviation Lighting (Now from Unit- 3 ESP Board - C) Permanent Dewatering power supply source for the CT Basins from

the Adjacent Units so that Cold Basin dewatering & subsequent cleaning will not be affected when CTMCC goes under PTW.

To avoid wood burning & heating the water for CO2 purge any one of the following may be provided .

Hot water header having connection from all the units . Provision of steam heating .

APH water wash line strainers are located in an inaccessible location , to be modified .

CONDENSER

Water Box Drain

Condenser Inlet side

Drain

Condenser Outlet side

Drain

Existing “C “ Row Drain

Existing “A “ Row Drain

VentVent

Floor Level

-ve Mtr Floor

Proposed Modification

PAPH-A HOPPER-1

PAPH-A HOPPER-2

Proposed drain hdr to boiler "0" mtr Drain

line with gradient .

150 nb Botterfly valve

Proposed APH hopper drain

line