RLI Sipat Case Study Booklet 4

P REGIONAL LEARNING

INSTITUTE(RLI),SIPAT
क्षेत्रीय ज्ञानार्जन संस्थान,सीपत

CASE STUDY
PUBLICATION

Volume IV
MAY 2022

REGIONAL LEARNING INSTITUTE (RLI), NTPC SIPAT
UJJAWAL NAGAR, BILASPUR, CHHATTISGARH-495555
E-mail ID - [email protected]

Index

MESSAGE FROM 01 
(1) RED (WR-II & USSC) 02
03
(2) CGM (SIPAT)
04
(3) GM (O&M) SIPAT 06 

PREFACE
01. Excessive High Voltage Output Issue of 220V Battery

Charger of Switchyard

02. Mechanism to Verify Indigenously Manufactured 09
Solar Cells

03. Modification of Generator Transformer (GT) Cooler 12
Scheme

04. Compressor Control Supply Modification 17

05. Pre Dispatch Inspection Issues of Conveyor 20
Structures

06. Smart Access to Information for O&M 22
26
07. Critical Drive Power Supply 29

08. Surface Defects During Casting Of Concrete
Shell of 275 M Chimney of BIFPCL- Bangladesh

09. Peaceful Transfer of Patratu Thermal Power Station 34

10. Assessment of Cold End Corrosion & Fouling 39
in APH Due to High Sulphur Content in Coal

11. Modifications Done in Stage-III Dry Ash 45
Handling System 50

12. Stage New Compressor System Motor Bearing
Modification

13. Strategy to Mitigate Fire Hazard Associated with LDO 55
Firing in Boiler

14. Generator Tripping on Bus Duct Fault 59

MESSAGE FROM RED (WR-II &USSC)

It is my great pleasure to learn I am happy to see that this fourth
that Regional Learning Institute edition (May 2022) has fourteen
(RLI) Sipat has undertaken regular interesting case studies including
publication of Case Study one case from our international
Booklets containing variety of operations and one from the
cases collected from all across experience of takeover of a plant
NTPC. by NTPC. I am sure readers will
find them interesting and will
NTPC takes pride in being a benefit from the wisdom shared
learning organisation. A learning through the cases.
organisation creates wealth of
knowledge through sharing of I appreciate and compliment RLI
experiences. In this context, case Sipat for the enormous effort
studies provide opportunity to being made to collect, edit,
learn from the wealth of previous compile and publish the case
experiences of others, and result studies completely in-house. I
in saving of precious time and wish that this series becomes a
resources. For a company like reference series for people
NTPC, which has vast seeking solutions to problems
geographical presence, and faced in different domains across
operates large fleet of machines, the company.
it is all the more important to
collect and share such knowledge AK Pandey
spread across the company. This RED (WR-II & USSC)
publication is an excellent way of
doing it.

Page
01

MESSAGE FROM HOP (SIPAT)

I am very happy to know that RLI- Case study compilation is a great
Sipat is coming up with yet way of documenting and sharing
another compilation of case such solutions across the
studies in digital format. company. These booklets will also
be of immense benefit to
In the challenging times of Covid, executives who get rotated on job
where physical learning systems and face new problems in new
roles.
got severely affected, digital
learning solutions emerged as a I would like to congratulate RLI
great resource of Knowledge Sipat for their continuous effort in
Management. In this context, the publishing these digital Case
digital Case Study Booklets of RLI Study Booklets. I am sure they will
Sipat are excellent learning be a valuable reference
resources which contain wealth of documents for our colleagues and
knowledge that can be easily will go a long way in augmenting
disseminated. company wide culture of sharing
and learning.
Due to complex and
geographically spread nature of Ghanshyam Prajapati
business of NTPC, our employees CGM & HOP (SIPAT)
handle diverse equipment and
diverse problems. Faced with
such problems, they come out
with unique solutions, which are
worth implementing at other
locations also.

Page
02

MESSAGE FROM GM(O&M) (SIPAT)

It's my great pleasure to see that Case studies are great avenue of
RLI Sipat is making consistent sharing of learning because they
efforts to release a series of Case
Study Booklets. It is also provide insights into actual
heartening to note that this problems faced and solved. In this
publication has come up to context, this effort by RLI Sipat is
really commendable.
pan- NTPC level and the cases
are being contributed by I wish that this series of case
colleagues from all across NTPC. study booklets become worth
collecting and sharing across the
As the business gets more and company.

more complex, the rate of Kudlu Sujai Naik
GM (O&M), SIPAT
learning of our employees needs

to become faster. This becomes

even more important due to

relocation and job rotation of

employees, who gather

experiences, create innovative

solutions to problems, and then

move on to take other

responsibilities. The knowledge

aquired by them needs to be

shared with others. Fast sharing

of such knowledge is therefore

critical for success of our

company.

Page
03

PREFACE and wide, transgressing all kinds
of physical boundaries. Based on
We are delighted to bring out this analysis of data from best of the
fourth edition of Case Study organisations, we feel that for a
Digital Booklet - May 2022 company like ours, the optimum
edition. This booklet is a great blend of physical Vs digital modes
learning resource containing of learning should be 60 % - 40 %.
twelve carefully selected cases In line with this philosophy, we
contributed by colleagues from have been making consistent
ten different locations across the efforts to bring in relevant
company. We are also very happy programs in physical, digital and
to see that our Case Study blended modes, based on type of
Booklets are being widely read by training and learning
colleagues. In these booklets, we effectiveness. In the year 2021-22,
make efforts to ensure that we we have conducted more than
present selected cases in concise, 300 high quality programs
easy- to-read, digital format. through various modes.

During the Covid 19 pandemic, As a result of our efforts, RLI Sipat
digital platforms for learning have has got the world-acclaimed,
in fact, created a silent revolution Brandon Hall Award in Gold
in the domain of learning and Category twice in succession for
development. This trend is here 2020 and 2021.
to stay. While the physical forms
of learning do have their strong Taking forward the digital learning
merits, the digital modes also revolution, we are extremely
have their own merits like easy happy to bring before Contd...
access, anywhere anytime
learning and ability to reach far

Page
04

you this fourth Case Study We request colleagues from
Booklet. We are delighted to get across the company to contribute
very enthusiastic response from their case studies in the format as
our colleagues in contributing the compiled here in this booklet.
cases. Cases may be sent in MS Word
In this booklet, we have featured format by email to
cases from locations like [email protected]. We shall be
grateful for your contribution and
Nabinagar, Ramagundam, RIO- shall be pleased to publish
WR1-HQ, Solapur, Vindhyanchal, selected studies. Honorarium will
Singrauli, Gadarwara, Sipat, also be paid to the published case
BIFPCL Bangladesh and Talaipalli. studies as per company policy.

We are making efforts to enrich With great humanity and
pleasure, we are handing over
the publication with cases from this fourth Case Study Booklet
May 2022 edition to all of you.
different domains. Besides having May this treasure of knowledge
get enriched with contributions
cases from O&M, this booklet also from across the company.

contains a case from Wish you Happy Reading, Happy
Learning and Happy Sharing!!
Management area dealing with
A K Tripathi
takeover of Partratu Project. GM, RLI Sipat

There is one case from our

international operations

(Bangladesh) also.

We wish that this publication
becomes a much sought after

journal in the company on which
our employees depend for
seeking innovative solutions to
problems faced by them.

Page
05

CEOXHUCATEPRSUGSTEIRIVSEOS FUHSEIGWOHFITV2CO2HL0YTVAABRGADETTERY

Name of the authors - 

Adil Qumar, Emp. No.:- 009088
DGM(EMD), BRBCL Nabinagar
Sanjeev Ranjan, Emp.No.:- 103260
Manager(EMD), BRBCL Nabinagar

Background of the case

Two nos. of 220 V DC sources along with charger and associated battery
banks had been in service for providing power to protection, control and
monitoring devices of switchyard equipment as per the envisaged
scheme.
DC Voltage of Source-2 of this DC system of switchyard was being
observed to be more than 260 V continuously.This was a matter of
concern. The protection relays and control devices of the switchyard are


designed to operate reliably and safely up to a voltage of 250 V. Higher

voltage may impair the life of protective and monitoring devices in
course of time.

Page
06

What was done

For rectification of the problem, systematic troubleshooting was done.
During checking, high AC voltage was found in the charger’s DC output.
Hence, the problem was identified in the battery charger. On further
investigation of the battery charger, 06 nos. 3300MFD capacitors used
in smoothing circuit of output DC to eliminate high-frequency ripples
were found to have failed.

Since similar rating spare capacitors were not available at the station,
capacitors of different MFD ratings were used to prepare equivalent
capacitance near to the original value and it was connected for
smoothing circuit of output DC of the charger. Subsequent to it, the
high output voltage problem was rectified and the system became
normal.

Major Learning

As DC systems are very critical for protection, control, and monitoring
devices of electrical systems & other emergency DC drives, standard
practices of DC systems' health monitoring should be adopted as per
guidelines & recommendations. Any abnormality should be
investigated thoroughly.

Page
07

1) Along with voltage measurements of battery chargers & cells, DC
output, AC voltage content in charger’s voltage output should also be
recorded during Preventive Maintenance.
2) Sufficient no. of spares for battery chargers (cards, capacitors, etc)
should be maintained at the site.
3) SOP for DC system monitoring & maintenance, including battery
bank &
the charger should be prepared & adhered to.
4) In case of exigencies equivalent capacitance can be created using
different rating capacitors.

Page
08

SMINOEDLCIAGHREANCNOEISLUMLSSLTYOMVAENRIUFFYACTURED

Name of the author -

Dileep Kumar Dixit, Emp No.:- 006948
AGM (FQA), Ramagundam

Background of the case

In year 2010, Government launched Jawaharlal Nehru National Solar
Mission to promote Solar Projects with the strict mandate of Domestic
Content requirement (DCR) which means mandate to use indigenously
manufactured Solar Cells and Solar Modules only.
In the same period, NTPC ventured into installations of Solar Projects
and there was no such foolproof mechanism to distinguish between
imported and indigenously manufactured Solar Cells/Solar modules. It
was a challenge for NTPC to develop a mechanism to comply to this
mandate as Chinese made solar cells and solar modules were very
popular due to being cheaper and were being imported in abundance.

Page
09

What was done

A methodology was thought out where in a proprietary identification
mark was supposed to be embossed on Solar Cell by each individual
Indian Solar Cell manufacturer during manufacturing of Solar Cell and
that mark may be subjected to verification by NTPC during Solar
Cells/Module inspection.
For this purpose, meeting was held with all the enlisted Indian Solar
Cell manufacturers. Initially all the manufacturers were resistant to do
the same, stating that printing the mark on front side of solar cell is not
possible and if done somehow, will reduce solar cell output.
However with lots of technical detailing and deliberations, ultimately all
enlisted solar cell manufacturers agreed upon the point that printing
the identification mark on Solar Cell is possible and won’t affect its
output.
Finally, each Solar Cell manufacturer decided their kind of proprietary
identification mark and after due approval by NTPC, they started
printing that mark on their Solar Cells, for all NTPC orders.
Subsequently this proprietary identification mark became the tool for
NTPC to verify the indigenously manufacturing Solar Cells and Solar
Modules.
Further to this, now all enlisted Solar Cell manufacturers have made
this their standard practice to manufacture the Solar Cells with their
mark as their brand logo.

Page
10

Major learning

There's always a possibility for change, no matter how difficult it might
appear in the beginning.

Solar Cell without any Solar Cell with identification
identification mark

Page
11

TSMRCOAHDNEIFSMIFCEOARTMIOENRO(GFTG)ECNOEORLAETROR

Name of the author -

Minal Kataria, Emp. No.:- 009074
Sr. Manager, NTPC Limited, RIO WR1- HQ

Background of the case

a) Nature of Problem: Failure of Cooler MCB & its input terminal
leading to tripping of Generator Transformer (GT).
b) Identification: 200 MVA, 1-phase, 21/420 KV GT, Jhajjar.
c) Case History:
Generator Transformer (GT) was provided with six coolers (5 running+1
standby). Each cooler bank consists of 2 Fan motors+1 Pump motor.
So, each GT was having total 18 nos. of motors. The maximum current
drawn by each motor was 2.5 Amp. All the motors were provided with
individual 4 Amp MCB. One Generator Transformer tripped due to
supply failure of cooler banks (3 nos.) which also lead to subsequent
tripping of Power Plant Unit. After physical inspection of marshalling
box (M. Box), it was found that one MCB input terminal box was burnt
which lead to disconnection of the input supply.




Page
12

From the above failure, it was not understood why failure of one MCB
of a cooler bank leads to complete failure of cooler bank, as standby
cooler bank was also available with auto mode. Later it was found that
failure of only 1 MCB of a cooler bank how caused supply
disconnection to 9 MCBs i.e. 3 Cooler banks.

What was done

i)Analysis:-
After physically tracing the cable connection, it was found that all 3
phase supply cables to each motor were connected with "Loop In-Loop
out" kind of arrangement in two parts. i.e. 9 motor in one "Loop In-
Loop out" arrangement and 9 motor in other "Loop In-Loop out"
arrangement. (refer below Pic-1)

Page
13

Because of "Loop In-Loop out" arrangement as per Fig.1, the actual
current drawn at the first junction (i.e. input terminal box of MCB-1 of
first motor) was 20-25 Amp. Because of such high current at the input
terminal of 4 Amp MCB, it got burnt and also lead to rupture of input
supply cable. Because of "Loop in-Loop out" arrangement of 3 cooler
banks (9 motors), these three cooler banks failed. Ultimately Generator
Transformer got tripped because of this.
ii) Corrective Action:-
There were three (3) probable solutions:- 
1) Supply to each cooler bank (3 motor groups) may be provided
individually with completely insulated sleeve busbar arrangement.
(refer below Pic-2)

Page
14

2) Supply to each cooler bank (3 motor group) may be provided
individually with the busbar arrangement with front shrouded or
sleeve insulated. (refer below Pic-3)

3) Supply to each cooler bank (3 motor group) may be provided
individually with the busbar arrangement with special Terminal blocks
with 1 input & multiple output.

Page
15

The 3rd solution appeared to be fastest & easiest as the unit was under
operation. Hence so the same was adopted and cabling was modified.
Since then transformer has not faced any problem.

Major learning

Not to use "Loop In-loop Out" arrangement for critical Power
Transformers.
As per good engineering practice, manufacturers to adopt proper
individual supply distribution to coolers preferably as proposed in
1st solution. This shall ensure proper functioning & availability of
supply to each cooler bank.
It is recommended to specify power supply distribution at
marshalling box. Generally, panels (marshalling box) are bought out
items by most transformer manufacturers, so it is suggested that
transformer manufacturers review complete panel drawings before
releasing them for manufacturing and also ensure quality checks at
vendors.
Finally, it should also be ensured that marshalling box is not too
compact, adequate clearance is being provided at marshalling box
for cabling & termination of cables. Marshalling box shall also have
sufficient space between accessories, terminal blocks, and gland
plate.

Page
16

CMOOMDPIFRICEASTSIOORNCAOTNNTTRPOCLSSOULPAPPLUYR

Name of the author -

V H Rao Maddipatla, Emp. No.:-009020
DGM (O&M), NTPC Solapur

Background of the case

NTPC Solapur Main plant Instrument air compressor (IAC) and plant air
compressors(PAC) are having three different supply sources.

230V single-phase AC supply from UPS for PLC and control circuit
power supply.
415V three-phase supply from Unit Emergency Switchgear(UES) for
power supply of Compressor motor cooling fans and compressor oil
pump.
3.3kV power supply for running Compressor drive motor.

Page
17

As per engineering scheme, 415V three-phase supply from UES is a
single source. 2 IAC and one PAC control supplies are given from U#1
UES. One IAC and one PAC are from U#2 UES.
3.3KV supply 2 IAC and one PAC are given from U#1. One IAC and one
PAC are from U#2.
230V Single phase AC supply is from UPS PDB which is present in
compressor house which is fed from U#1 and U#2 UPS with auto
changeover scheme.
Issue Identified:-
In case of disturbance in control supply from UES, IAC/PAC used to trip
on protection acting from motor cooling fans and compressor oil
pressure. Although UPS and 3.3KV supplies are healthy, compressor is
not available for running.

Page
18

What was done

Modification:-
As we all know for a power plant IAC and PAC are critical, so we
proposed and implemented standby source for this three-phase 415V
power supply to compressor with auto changeover (Power contact
changeover type) scheme with the help of electrical maintenance dept.
 
In case of supply disturbance in UES, the second source from
Compressor Service Switchgear (which is fed from station
transformer) will take over, resulting in better compressor
availability.

Major learning

This modification of providing a stand by source with auto changeover
in-turn increased the compressor availability and led to better
operating conditions in NTPC Solapur.

Page
19

PORFECDOINSVPEAYTOCRHSINTSRPUECCTTUIROENSISSUES

Name of the author -

Ummer Farooque, Emp. No.:- 102653
Manager Business Devlp , Noida
A. Siva Kumar, Emp. No.:- 007128
DGM FQA, NTPC Singrauli

Background of the case

NTECL is facing severe corrosion damages in CHP structure because
the installation is near to sea coastal /marine environment.
Replacement of structures started in a phased manner in 5 years of
installation. NTECL had placed an order for 27 nos. of pipe conveyor
gantry structures to OEM for supply and replacement with improved
painting systems. The ordered items were delivered to site after Pre-
despatch inspection(PDI) by NTECL . During PDI on 26-07-19, it was
found that I) GI coating was not maintained(>100 microns) by Hot Dip
Galvanising(HDG) ii) Large variation were there in DFT measurements.
This resulted in rejection of the ordered items.

What was done

Root cause analysis for not achieving the required GI coating.
Revisit of contract specifications, MQP and approved procedures and
sub vendors capabilities.

Page
20

Developed spot DFT measurement procedure with OEM.
Discussion with vendor and insisted on sand blasting before HDG
process to achieve >100 micron thickness.
Ensured sufficient Zinc length and depth were maintained during
HDG process.
Monitored dipping time charts to ensure sufficient dipping time was
given.

Major learning

Blast cleaning before HDG is a must to get more than 100micron
DFT.
Maintaining Zinc bath dimensions and dipping time during HDG is
essential requirement to get desired results
Methodology of DFT Measurement also plays vital role in getting
uniform thickness
Internal DFT measurement records should be reviewed before going
for PDI.

Galvanised structures ready for DFT check

Page
21

FSOMRAOR&TMACCESS TO INFORMATION

Name of the author -

Rakesh Kashiv, Emp. No. :- 062072
Sr. Manager(Stores), NTPC Gadarwara

Background of the case

When it comes to access to information, it is always challenging to do
the same by an easy method. Many a times, we have all the details but
we are not able to produce it at right time. In our day-to-day
maintenance activities, we can miss opportunities and even find
ourselves in regulatory trouble if we do not monitor information, data,
etc. regularly.

Take a case of audit of lifting tools. Though we carry out testing and
have all the certificates for the same when auditors ask for it, we need
to contact the concerned person. It may also happen that we are not
able to present same to auditors.

What was done

A good way to ensure that information remains up-to-date and
accessible is to develop a shared system for the different information
categories by using the QR codes. The problem was sorted out up to a
great extent using this technique.

Page
22

QR code is a machine-readable optical label that contains information
about the item to which it is attached. These response codes can be
read and accessed through any smartphone. QR codes can support a
large range of media and data such as numbers, characters, pictures,
voice, business cards, videos, etc. They can be read in any direction.
Using these codes, there is no need for lining up perfectly. They can be
restored and read from the scanner or smartphone even if there is
some damage done to them. They can be read in many different
languages. QR codes can actually hold more information in a very small
amount of space compared to a normal barcode, which makes them
more compact and easier to scan.

Possible areas of Applications of QR Codes in O&M:-

To view different Certificates to comply with various statutory
norms.
To display SOP’s, LMI’s, Do’s & Don’ts, Technical Diary, etc.
To view information like equipment data sheet, drawings, BOM,
vibration records, PM history, breakdown history, etc.
Critical SOPs with more visuals steps or videos could be kept for
mistake-free operation.
Many safety videos could be linked to vulnerable places, so it will
increase safety awareness.
Effective usage in PTW system implementation.
Security enhancement in plant & township like Vehicle information,
etc.

Page
23

Major learning

Usage of QR codes results in
Time saving
Increase in efficiency
Increased safety
Increased accessibility of

Page
24

Page
25

CRITICAL DRIVE POWER SUPPLY

Name of the author -

V H Rao Maddipatla, Emp. No.:- 009020
DGM(Operation), NTPC Solapur

Background of the case

During commissioning of Solapur Unit-1, we identified many drives
with power supplies that are being fed from the same supply source as
per engineering schemes.
These include many critical drives like main turbine hydraulic oil
pumps and stator water pumps. Because of this, frequent system
tripping may happen. All these types of drives were identified and
listed as shown in next page.

Page
26

Page
27

What was done

As seen from above table, many critical drives like both stator water
pumps are fed from same section of different switchgears whose
supply is from same source. For example, in case of stator water
pumps, pump-1 is fed from TMCC 1.13R (from Section-1 of TMCC) and
Pump-2 is fed from UES 7.12F (from Section-1 of UES). These two
switchgear section is fed from USS section-1. In case of disturbance in
USS section-1, both stator water pumps will not be available and unit
will trip in absence of stator water flow. Similarly, the other drives listed
can also cause unit tripping/equipment failure.
 
The above list of issues identified were sent to electrical maintenance
and the same supplies were modified so that critical equipment
availability is improved.

Major learning

This process of identifying critical drive being supplied power from
same source, during commissioning phase itself led to resolution of
the issues, which if missed could have lead to unit tripping much later.
Same modifications were done in both units of Solapur. Similar process
can be followed in all projects and the issues if any to be identified and
rectifications to be done, otherwise, this type of small issue might
cause unit to trip in future.

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28

PRDCCREHOECOFINMEUJCCENRRTCREESTYETNDEOOCUFSFERHB2IOIEXNFLF6PGL6SCCO0ULAF-RMBS2FAWT7AIN5NCMGMEGLAOHAITFDERIEGESEHHT

Name of the author -

Sunil Murmu, Emp No.:-042132
Sr. Manager (FQA & COMMN.), BIFPCL Bangladesh

Background of the case

Slip Form method was used to do the casting of RCC shell of Chimney
in the 2X660 MW Maitree Project of BIFPCL Bangladesh. The vendor
was Simplex Infra Projects Ltd. from India which had an experienced
team at site for chimney erection.
A brief description of slip form method of casting-
Radial steel yokes, which have an inverted “U” at both ends, support
the slip form shutters all around the shell. Walers strengthen and keep
the shutters in place. The working deck and scaffolding is supported
from the walers and yokes. The yokes are supported on hydraulic jacks,
which move on jack rods embedded in the concrete.

Page
29

Slip Form structure MAITREE Chimney during erection

Problem faced during RCC Shell casting

It was observed that during upward movement of Slip form structure,
the concrete surface would repeatedly get damaged by the movement
of inverted “U” piece placed to support the shutters and keep distance
between reinforcement and MS shutters. Many experiments were
done to improve the surface finish of RCC shell such as reducing the
initial setting time of concrete to around 30 minutes. The concrete
slump was also kept at 120-150mm before start of each pouring. Still
no improvement was observed.

Before modification of Slip form shutters, the RCC shell surface

Page
30

What was done

Ultrasonic Pulse Velocity (UPV) ,Core strength, Rapid Chloride Ion
Penetration (RCPT) Test were performed by a team of experts from
Jadavpur University, Kolkata. They took a number of samples by core
cutting method from inside and outside surface of the Shell. The tested
strength of core samples was found adequate as per design
consideration of concrete grade C-30/37. Some localised surface
delamination of cover concrete was found at different locations.

Core cutting at outside and inside shell surface



Page
31

Suggestions given by Jadavpur University team

The Jadavpur University team suggested to use Solvent free epoxy
resin grout for pressure grauting of the affected areas of Chimney
Shell. Thermax Maxgrout E10 was used. For repair of core area,
Thermax BS 5F(B) Fiber reinforced Cementitious repair mortar was
used.
Moreover for modification of Slip Form structure the following steps
were taken.
It was decided to use GI sheets to cover the surface of slipform
shutters. So the vendor was persuaded to incur the additional cost of
purchasing of GI sheets to cover the entire surface area of the
shutters. And apply grease on the GI sheet surface which would come
in contact with the concrete. Considerable improvement was observed
in the surface finish of the RCC Shell after this exercise. The Slip Form
upward movement was also smoothened considerably. After that, the
entire 275Meter of Shell casting was done without major hindrance.

Surface finish after GI sheets were used



Page
32

Major learning

The initial setting time of fresh concrete may be chosen carefully as per
site condition. Floability of the concrete should be checked for each
Batch. The slump test of concrete may be done regularly and
temperature of the fresh concrete may be checked with each batch.
Regular inspection of Batching Plant should be done to ascertain the
quality of cement, aggregates, sand and the chemical admixture. Mix
Design Concrete to be used.

Periodic visual inspection should be undertaken for Slip Form
structure, the Yokes, Hydraulic Jack, Slip form shutters and the wooden
beams. Spare Jacks may be kept in case of jack replacement. If the GI
sheet covering the Shutters appears to be damaged, then they should
be replaced immediately. Speed of movement of Slip form structure
should be calibrated carefully.

Ultrasonic Pulse Velocity (UPV) ,Core strength test, Rapid Chloride Ion
Penetration (RCPT) Tests should be performed if there is any doubt
about the quality and strength of the concrete.

Page
33

PTHEAERCMEFAULLPTORWANERSFSETRAOTIFOPNATRATU

Name of the author -

Rohit Pal, Emp.No.:- 007397
AGM (HR), NTPC Talaipalli

Background of the case

Patratu Vidyut Utpadan Nigam Limited (PVUNL) was incorporated as a
subsidiary of NTPC in joint venture with JBVNL.
 
The original objective of PVUNL was the performance improvement
and capacity expansion of age-old PTPS power plant of 10 units having
total installed capacity of 840 MW, whose foundation stone laying was
done way back in 1963.
 
This PTPS plant was facing a lot of issues viz:  

30-50 years old units with out-of-date technology.    
Failed to comply to pollution guidelines and environmental norms. 
Only one unit was working, it was not a significant supplier of
electricity or a profit-making plant of Jharkhand.   
Unaddressed issues of land oustees and illegal encroachments. 
Unfulfilled expectations of development of the overall surrounding
area.
Page
34

Overall Environment before / prevailing during takeover was:
  

Patratu was once one of the most dreaded places in Jharkhand and
acted as a corridor for NAXALS (LWE).
The situation was highly unstable and sensitive as most political
parties, contract labour unions and PTPS employees were protesting
against this move and NTPC.  
The place had presence of all political parties (Major and regional)
and presence of Jharkhand tiger group (banned naxal outfit of the
then MLA-Barkagaon Shri Yogendra Sao).    
Being in the vicinity of coal bed there were widespread presence of
gang - lords and coal mafias. Another unit nearby had some vested
interests.

Despite above hurdles, initial Task Force team of NTPC started making
its inroads.  At the first instance, we started with the challenging task of
securing of plant boundary wall, removal and eviction of unauthorized
buildings/households inside our plant boundary, initiated processing
for obtaining necessary regulatory statutory registrations from various
statutory authorities, transfer of CISF, organizing of public hearings,
aligning ex PTPS employees and contract labours, building cordial
relations with local leaders, key opinion makers, people
representatives (MP, MLA, Mukhiya) etc., fostering effective liaison with
State and District

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authorities for management of law and order.

On one fine day in January 2017, due to fiscal liability, Patratu unit 10
was shutdown forever. The focus now shifted to construction of new
4000 MW power project. The earlier PTPS Plant was decommissioned
and all its units were deleted from all India database of CEA. This made
PTPS employees furthermore helpless and laborers were uncertain;
the whole economy at Patratu was at standstill and everyone was
apprehensive.
 
In the meanwhile, transfer scheme was issued by Govt of Jharkhand,
thereby all plant, machinery, civil and structural buildings and land were
transferred to JV Company-Patratu Vidyut Utpadan Nigam Limited with
all rights liabilities and ownership, free from all encumbrances. This
taking over of assets put us in a tight situation for all of us facing the ire
from PTPS employees and laborers.

What was done

In addition to the steps taken earlier,following additional steps were

taken

Speedy implementation of CD (Community Developement) activities

in the area was undertaken.

Building of credibility and fulfilling social aspirations by preferential

engagement of local youths in contractual jobs and tie up with OP

JINDAL ITI for skill development of local unemployed youths.

Due to timely Intervention, Govt of Jharkhand transferred all PTPS

personnel ( who were reluctant to continue with JV) to other sites.

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There were land oustees of Ex PTPS, consisting of 25 villages in and
around PTPS plant who were time and again disrupting the peace by
forcing their demands, during interactions at various levels (Block,
District ). We made our message clear to them outlining their non-
admissibility as land oustees and our inability for considering their
demands as they were not related to us.

Major learning

Focus on building credibility:
i) Effective liaison with District Authorities, statutory bodies, people's

representatives, and opinion makers is very crucial and key.
ii) Showing sensitivity towards societal needs of the locals –

 Health care
 Skill development of unemployed youths
 Rural sports
Constant touch with stakeholders: building relationship of trust.
Being proactive to employee needs- strive to make happy
customers, happy stakeholders.
Educating and creating awareness of contractors/contract workers.
HR to act as strategic partner in project execution and
implementation.

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Posting of SDPO (sub division police officer) for Patratu was
requested for expeditious management of law and order issues.
All necessary Plant/ office / Hostel infrastructure was renovated/
revamped and built.
Associates like UPL(utility power tech)/ICH /township security
through DGR(directorate general resettlement) were tied up and
requisitioned.
OHC(Occupational Health Center) started with ACLS(advanced
cardiac life support) /BLS(basic life support) ambulance and
renovation of hospital building with recruitment of adhoc doctors.
Non-recognizing any contract labour unions and land oustees
morcha.
Building cordial relations with labour authorities and district
administration.
Proactive approach to redressal of contract labour problems,
Monthly ER clearance, timely wages, enrollment of labors in social
security schemes were implemented and regular interventions
through workshop for EIC / Contractors and laborers through
statutory authorities (ESI(employee state insurance) / LEO(Labour
Enforcement Officer), ALC(Assistant Labour Commissioner) /
PF(Provident Fund) were organized.

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ACDINSOUCSREOERTSAOOSLSHMIOIGENHN&TSFOUOFLUPCHLOIUNLRDGCEINONNDATPEHNT

Name of the author -

Prag Sood, Emp No:– 007756
DGM (Chemistry), BRBCL Nabinagar

Background of the case

At Mouda, coal is received from WCL mines. WCL coal mines are rich in
sulphur content and the coal carries significant amount of iron pyrites.
The presence of high sulphur content in coal poses significant
problems in the second pass of furnace wherein chances of cold end
corrosion & fouling on gas side are very high. The presence of high
sulphur in flue gas in the form of SO2 content lowers the sulphuric acid
dew point of flue gas resulting in condensation of the sulphuric acid
droplets if the flue gas exit temperature is lower than the acid dew
point temperature.

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The condensation of acid droplets not only results in cold end
corrosion issues in flue gas side path but also results in fouling /
deposition of iron sulphate deposits on the baskets of air preheaters.
Once the fouling / deposition initiates, it rapidly grows over a period
resulting in lowering of the heat exchange and also rise in differential
pressure across the APH. It was noticed that there is occasional build
up / deposits of ash in air preheaters which was also leading to high DP
across air preheaters in some of the units. Station adopted the practice
of carrying out hot air preheaters washing during every opportunity
shut down and good removal of fouling material / deposits was noticed
during the activity. Special care was also taken in neutralization of the
APH washing effluents, as the effluents were quite low in pH ( < 2.5).
However assessment of cold end corrosion & fouling in APH could
not be ascertained as there is no measurement of acid dew point in
the flue gas.

What was done

As it has got evident that sulphur rich WCL coal is having potential of
causing cold end corrosion / fouling issues in second pass of boiler and
flue gas path, hence it was suggested that we should have a
measurement facility which can predict about the chances of
occurrence of cold end corrosion / fouling in the flue gas path / APH.

This triggered to have an online / offline sulphuric acid dew point
analyzer to assess the operating range of flue gas exit temperature. As
online analyser will require four analyzers for four units, hence it was
decided to procure a portable sulphuric acid dew point analyzer which
can be handy in use with flexibility to be used as per requirements.

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Accordingly, station Chemistry department procured one no of LAND
make Amteke portable Sulphuric Acid analyzer and this instrument is
contributing significantly in assessing the Sulphuric Acid dew point
temperature of the flue gas and accordingly, we could assess whether
we are operating in safe zone.
The instrument is first of its kind to be procured at any NTPC station
and is a worth for station having high sulphur issues in coal. The
instrument is used for realtime sulphuric acid dew point temperature
at Air preheaters inlet. As a exemplary basis, the acid dew point
temperature measured in Unit # 2 at SAPH # B was found to be in the
range of 115 – 116 DegC. During this measurement the unit load was
465 MW and Sulphur content in feeder coal was 0.7 %. As WCL coal
mines sulphur content varies between 0.5 to 2.5 % , hence there is
every chance that when high sulphur content coal is burnt in furnace,
the acid dew point may be on lower side and hence the importance of
the portable sulphuric acid dew point meter will be evident.

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In due course, the instrument was used to measure ADT ( Acid
Dewpoint Temperature) at different load conditions and under
different input coal feed quality [ With Different Sulphur content] to
formulate a data base atlas that can be used as reference by operation
department while maintaining flue gas exit temperature under
different load conditions and different feed coal quality. A typical
portable acid dew point analyzer and the recorded ADT value along
with other parameters are shown in Exhibit – 1.0

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Exhibit – 1.0

Acid Dew Point Meter measures Acid Dew Point Temperature (ADT),
Minimum Metal Temperature (MMT), SO3 Concentration in ppm and
Sulphur Acid (H2SO4) concentration in ppm.

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Major learning

By using portable sulphuric acid dew point measurement analyser, we
were able to assess whether the flue gas temperature at APH outlet is
maintaining higher than the sulphuric acid dew point in the flue gas at
the time of measurement. In case the sulphuric acid dew point is on
lower side than the operating APH outlet temperature, then there will
be condensation of the sulphuric acid on the internals of the APH and
will lead to cold end corrosion & fouling related issues. Hence use of
state of art portable acid dew point meter has contributed significantly
in assessment and prevention of cold end corrosion & fouling in APH
due to high sulphur content in WCL coal. This is first of its kind
assessment of cold end corrosion & fouling in APH in NTPC using
portable sulphuric acid dew point meter.

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SSMTYOASDGTIEFEMI–CIAIITDIORYNSASDHONHEANINDLING

Name of the author -

Mr. Alok Kumar Srivastava, Emp No:- 100515
(DGM, AHM),Vindhyachal.

Background of the case

STG-III :
In Dry Ash Handling System, the Silo, telescopic chute, water sprinkling
system and TAC lines are among the major components. Any
improvement in these sub systems makes a major impact on the
overall performance of the complete dry ash handling system.

Following problems were identified in the existing system:
Frequent choking below rotary feeder.
Telescopic chute bag filter choking & damage.
High ash spillage during each loading
Frequent breakage in telescopic chute during ash filling truck
movement.
Frequent choking in the TAC lines of U#09.

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THE CHOKING PROBLEMS CAUSED FOLLOWING ISSUES:
Increased waiting time of trucks for ash filling
Ash had to be dumped during choking cleaning.
Increased water consumption for cleaning of silo area.
Man hours consumed in choking clearance. Further, a lot of ash
was going inside lungs of person involved in choking clearance.
Increased dust emission during choking clearance

What was done

MODIFICATION-1 & 2 FOR SILO CHOKING
1.The dead volume below rotary feeder has been reduced by insertion
of partition plate. The direct connection between rotary feeder
discharge and the inlet of chute has been made using a duct.
Therefore, no direct ash will enter into the bag filter through the
rotary feeder. Only air vent of the truck is filtered through the bag
filter.
2.Further, a fluidizing line connection has been provided in the bottom
area of the rotary feeder to improve the fluidization of ash.

These modifications have been done in the silo-1 and silo-2 of stg-III.

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Modification-1 Modification-2

Modification done

The above two modifications have been completed in both silo in 3rd
quarter of 2021.
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