XYZ Limited, a constituent of the Reliance – Anil Dhirubhai Ambani Group, company operates 500 MW coal based Thermal Power Plant at Dahanu (Maharashtra), commissioned in 1995, DTPS has beer  recognized as the best performing coal based power station in the country for its Operational excellence, Environment Management,Quality, Safety & Corporate Social responsibility.

DTPS has adopted modern power station O&M practices to make the power station highly reliable, efficient through system approach in all its activities.‘ Integrated management system (IMS) for Quality, Environment and OSHAS, Information Security ISO 27001 and Social Accountability SA 8000.

DTPS has over the period developed competency in measurement, monitoring, evaluation and control of various parameters related to plant performance and also implemented numerous improvement programs (IMP).

The plant undertook Six Sigma initiative, use techniques like Five-S, FMEA, COPQ, Pareto chart, control chart and 8-D analysis etc which has directly resulted in considerable improvement in various process performances at DTPS.

DTPS has consistently improved its environmental performance through concerted efforts and today it is considered as one of the best and cleanest power station In the country. Environment Management Programs (EMP) like Installation of Flue ga s Desulphurization plant, effective utilization of fly ash are the unique for this coal based power plant.

As a resp onsible corporate citizen DTPS has undertaken various social responsibility initiatives in and around Dahanu Taluka, a predominantly tribal area. These are focused activities in the field of Education, Health and other community needs.


Project scope was to identify root causes for CW pump tripping due to Electrical, C&l, Mechanical, Operation and Civil system / equipment problems. Project boundaries were limited from pump suction to the pump discharge valve. Scope excludes tripping of pumps due external causes like grid disturbances and natural calamities like floods, Tsunami etc.The project was executed using Six Sigma DMAIC model. Cross functional team of various departments worked jointly for this project.


Existing process sigma level is 4.2.
Total 36 causes were identified which can cause CW pump tripping.
Out of which 31 causes were identified as Direct improvements.
Remaining 05 nos. fall under controllable category which were further analyzed in depth by FMEA tool and validated with historical ‘data. The following major counteractions are suggested for the same.
1.Existing HT power supply cable is to be replaced by new high quality cable suitable for marine application
2Auto Fast changeover scheme is to be implemented for HT switchgear

3.New comon MCC for Hydraulic Power Packs ad Bearing /Cooling Tower Pumps

4.Laying new fire hydrant line from Main plant fire system to CW Pump House

5.Provision to sound Fire warning Alarm in Fire Station for any fire at CWPH

6.Providing additional smoke detectors in CW Pump House area.

7.Extension of 0N cable culvert.

8.Training of 0&M personnel on CW eiectrical system.
On implementation of project, process sigma level will improve from 4.2 to 4.5.
On complete implementation tangible & intangible savings achieved at Rs. 233.8 Lac P.A.
On implementation of project, process sigma level has improved much more than expected level.


Four nos. of CW pumps at Dahanu thermal power plant (DTPS) provide cooling water to condensers in plant. CW pumps on an average of 4 times in a year trip, causing direct generation loss of 1.0 MU per annum. Apart from above losses other intangible losses like reduction of plant /equipment life, inconvenience to, consumers and adverse effect on company’s image are occu rring on account of above problem.


Stretched targets are given by top management for better plant perfonnance. To achieve these targets, generation loss & unit tripping reasons were identified & prioritized on the basis of data available with Operation & efficiency Department. As problem in CW Pump area affects generation loss or tripping of both units simultaneously, this pain was taken on high priority to resolve the same through six sigma approach.To identify the pain area in CW Pump, Voice of Customer (VOC) carried out through site visits with questionnaires and that data was prioritized by Nominal Group Technique analysis of VOC Data Tripping of CW pumps may results in generation loss or tripping of both generating units. This leads to power failure to customers at Mumbai. Tripping of CW Pumps leads to average generation loss of 1.0 MU / annum and trend is reported increasing.

Vision of Organization

To be amongst the world class power plants, delivering reliable generation of Electricity at competitive cost, with International standard

1.To provide affordable, quality, reliable and clean power to customers

2.To earn the trust and confidence of customers and stake holders and by exceeding their expectations, make the company a respected household name.
3.This project will increase the reliability of generating units at DTPS, which is our main business mission and itwould also save revenue loss of rupees 58.5 Lacs per annum on recurring basis thus reducing the cost of generation.
4.Reduction in tripping of CW pumps will enhance the availability and reliability of DTPS generating station by which fulfilling the mission to provide uninterrupted power supply to customers at Mumbai.

5.Project will improve the overall business performance of DTPS and help to enrich the company image among customers and stake holders.

Voice of Customer (VOC) carried out by walk through survey. (Refer slide 7)
VOC Analysis carried out using Nominal Group Technique. (Refer slide 7)


Elaborative process mappingwas done inclusive of all direct and indirectly involved functional process.


a.To find out the total nos. of C.W. Pump tripping since January 1999

b.To calculate the number of running hours of CW pump lost due to tripping.

c.To calculate the annual generation loss on account of CW pumps tripping.

d.To find out total no of unit tripping on account of CW pump tripping.

Data to be collected

a.Total number of CW pumps tripping since January 1999.

b.Average running hours of each CW pump since January 1999.

c.Total running hours lost due to CW pump tripping.

d. Total generation loss in million units (MUS) since January 1999.

COOLING WATER (C.W.) – Seawater used for steam cooling in condensers.

C.W. PUMP – The equipment driven by electric motor, used for lifting seawater from intake channel.

C.W. MOTOR -The 6.6 KV rated electric motor used to drive the CW Pump.

TRIPPING — Stoppage of C.W. Pump due to any type of abnormal operational conditions or loss of Electric supply.

GENERATION — Production of electricity using 2x250MW generators.

PCR — Plant Control Room,

PTW – Permit to Work, issued by authorized operation person to carry out the maintenance activities.

ISA — 6.6KV switchgear at CW PH for supplying electricity to all the Pumps & aux.

CIRCUIT BREAKER —- Electrical equipment used to switch ON or switch OFF electric supply under No Load, Load or faulty

conditions. – MIODULE / FEEDER- Arrangement of Electrical components in cubicle to supply and control low tension / High— tension electrical supply to any auxiliary.

PROTECT lON- Measures incorporated in the system to detect abnormal operating conditions and to isolate the equipment for minimizing the damage.

PLC – Programmable Logic Controller unit, used to carry out automatic operation of C.W. Pump system.

UPS — Uninterrupted Power Supply source, provided to PLC panels.

PARAMETERS -All Process variables, events measured & displayed for monitoring and control purpose.

BFV — Hydraulically operated Butterfly valve at discharge line of C.W. Pump

LINE UP — To check and carry out essential activities in predefined steps before starting, stopping or isolating any equipment.

Since data is collected from automated computerized record, hence error of reproducibility and repeatability do not occur ‘As per established system under ISO 9001, 0&E section collects and maintains all the operational and computer generated tripping event data of DTPS.

Tripping events related to CW Pumps to be collected as per prescribed format.

Following records to be referred for data collection:

  1. Local operator’s Log Book
  2. PCR 1 & 2 Unit controller’s Log Book.
  3. Event Analysis Report
  4. Equipment Running Hours record ‘

Summary of CW pump tripping data from year 1999-2005 (Refer slide 9)
CW pumps runninfg hour’s data from year 1999-2005 (Refer slide 9)

For calculating the base line performance of the existing process, previous five year data of pump tripping incidents collected

Total 21 nos. of pump tripping incidents observed with an average of 4 pumps tripping per annum.

Total number of pump running hours lost were 574 with an average of 115 hours per year

Total electricity generation loss was 5.0 Million Units (MU) with an average of T! .0 MU per annum.

Current Process Capability

  1. Total Running Hrs. of Pumps for last five years = 176011

2 No. Of Hrs. lost due to tripping and non availability = 574

  1. Total expected running hours for of Pumps = 176585 “

4 Proportion Defect ‘ = (S74/176585)
= 3.251 X 10-3

    1. PPM = 106 X (3.251 X 103)

= 3251

  1. Current process sigma level i = 4.225



All controllable potential causes are analyzed on its ‘Severity’, ‘Occurrences’, and ‘Detection’ points. From severity, occurrence and detection level, Risk Priority Number (RPN) is calculated.

RPN = Severity X Occurrences X Detection
Detailed FMEA report: Failure Mode Effect Analysis (Refer slide 13)
Validation of root causes carried out with historical pump tripping data (Refer slide 13)
Validation of root causes carried out with historical pump tripping data (Refer slide 13)


HT power lncomer cable failure.
Mal—operations in changeover of HT Switchgear
Mal operation of BFV.
Malfunctioning of PLC cards.
Faults caused due to ingress of rats, lizards etc.
Fire hazards.
Motor cable failure.
Malfunction of scanners and RTDs.
Failure in 220V DC supply.
Leakages in hydraulic power pack system.
Chocking of suction net and trash rack.
CW Motor winding failure.
Jamming of BFV.
Leakages in bearing cooling pump lines.
Failure of hydraulic circuit due to contamination of oil.
CW pumps impeller and bearing failure.
Mechanical seal failure of CW pump.
Wear tear of TWS due to continuous operation.
Silt accumulation in CW intake water.
Human error during operation.
Faults in control cables for PLC and field equipment.
Mal-operati on of electrical protection
Troubles in motor circuit breaker like SF6 gas leakages, etc.
CW pumps coupling failure.
Miscommu nication between local operator and PCR engineer.
Flooding of CW area.
Failure of U P5 to take required load.
Failure of MCC modules for auxiliaries like BFV motor, BC & Cr pump
Components Failures due to chlorine effect on pump parts.
Failure of In take channel guide bund.
Failure of BC & Cf pump
Failure of fiber optic cable.
Failure of telephone system
Malfunctions due to virus in SCADA PCs.
Faults in CW. Transfonner.
Faults in local push button/ junction boxes
Best solutions evaluated through evaluation matrix. (Refer slide 14)


Taking up Quality Plans under QMS system ISO 9001
Work orders through ERP system
Monthly Review of work progress by Apex Council
Cross Functional teams
Monthly review by APEX committee


Monthly update of Dash board (Refer slide 16)
Monthly MIS Report generation and Review in ORT meetings by Apex committee
Review of Work orders related to CW Pump houses on monthly basis
Project shared with all our business groups
Project taken up with Transmission division to “Reduction in line tripping in 220 KV transmission network”
Project taken up with Mumbai Distribution Division to “Reduction in Number of HT Cable Faults in Supply Division —Mumbai”


A. Tangible
1. Loss of generation per ann um on account of cw pump tripping. = 1.0 Mus.
2. Revenue loss = 1.0 Mus X Rs. 3.50 = Rs. 35 lacs
3. Cost of per Unit tripping on account of heat rate, fuel oil, ‘
DM water, aux. power, etc. = R5. 15 lacs
4. No of unit tripping per ann um on account of CW pump tripping = 1
5. Cost of tripping per annum = 1 x 15 lacs = 15 lacs
6. Total loss per annum = (15 +35) lacs = 50 Lacs
7. Expected savings per annum after project implementation is = 50 Lacs
B. Intangible
1. No. of incidents having potential of Unit trippings since Jan 99
(i.e. for six years) ’ = 8 nos.
2. Potential for loss of generation on account of
CW pump tripping/annum = (8/6) Mus.
Potential for Revenue loss ; (8/6) Mus X Rs. 3.50 = R5. 46.9 lacs
Potential Cost of Unit tripping on account of heat ‘rate, .
fuel oil, DM water, aux. power, etc. = Rs. 15 lacs
Potential Cost of tripping per annum = (8/6) x 15 lacs = 20 lacs
6. Potential total loss per ann um = 46.9 + 20 = 66.9 Lacs

C. Expected savings after project implementation

(A) + (B) = 116.9 Lacs