Dadri station Highlight April to Sep 25

 

SOP of CW charging after Condenser Water Box Cleaning

 

How to detect Boiler tube lkg in boiler

 **Detecting Boiler Tube Leakage in a 210 MW BHEL Boiler at NTPC Dadri**

Boiler tube leakage is a critical issue in power plants like NTPC Dadri’s 210 MW units, which use subcritical BHEL-designed boilers (Combustion Engineering type, commissioned 1991-1994). Early detection minimizes downtime, prevents secondary damage (e.g., to turbine or other tubes), and maintains efficiency. Dadri has a strong record for minimizing tube failures, ranking among NTPC’s top plants, but leaks can still occur due to aging (30+ years), erosion, corrosion, or thermal stresses in high-pressure zones (drum pressure ~155 bar, superheater ~535°C). Below is a detailed guide to detecting boiler tube leaks, tailored to Dadri’s 210 MW BHEL boilers, combining practical methods, NTPC practices, and industry standards.

Safety Valve float Test

 **Safety Valve Float Test in a Boiler (Specific to Power Plant Context like NTPC Dadri 210 MW Boiler)**

The safety valve float test, also known as the "popping test," is a critical procedure in a power plant boiler to verify that safety valves open at their designated set pressure to prevent overpressure conditions, ensuring boiler safety and compliance with regulations like the Indian Boiler Regulations (IBR) 1950. For a 210 MW boiler at NTPC Dadri, this involves testing drum and superheater safety valves (typically set at 155-160 bar for drum and 135-140 bar for superheater). Below is a concise, step-by-step guide to performing the safety valve float test, tailored to subcritical boilers like those at NTPC Dadri, with practical insights from thermal power plant operations.

Strategies to improve efficiency and reduce Heat rate

 ### Understanding Heat Rate in a 210 MW Boiler at NTPC Dadri

The heat rate of a thermal power plant, including the 210 MW coal-fired units at NTPC Dadri (commissioned between 1991-1994), measures the amount of heat energy (in kcal/kWh) required to generate one kilowatt-hour of electricity. It is inversely proportional to the plant's thermal efficiency: a lower heat rate indicates higher efficiency, reduced fuel consumption (coal), lower emissions, and cost savings. For subcritical 210 MW units like those at Dadri, typical operating heat rates range from 2,300-2,500 kcal/kWh, with opportunities for optimization to below 2,300 kcal/kWh through targeted improvements.

What is SOFA?

 ### SOFA in Power Plants

In the context of power plants—particularly coal-fired thermal power plants—**SOFA** stands for **Separated Overfire Air** (also sometimes written as Separated Over Fire Air). This is a combustion technology used in boiler systems to reduce nitrogen oxide (NOx) emissions, which are harmful pollutants formed during high-temperature fuel combustion.

Efficiency improvement in 210 MW boiler

 ### Understanding Boiler Efficiency in 210 MW BHEL Units

A 210 MW BHEL boiler is typically a coal-fired, subcritical unit common in thermal power stations, where efficiency (often around 80-85% on a higher heating value basis) is influenced by combustion, heat transfer, and auxiliary losses. Improving it can reduce fuel consumption, emissions, and operational costs. Based on thermal audits and BHEL-specific practices, here are proven methods, categorized for clarity. These draw from operational optimizations, retrofits, and maintenance strategies.

St-1 Vacuum Pulling checklist

 CHECK LIST-VACUUM PULLING UNIT: DATE: SL NO ITEM DESCRIPTION STATUS

 1. Fill Hot well up to normal level. 

2. Vacuum pumps are ready for operation. 

3. Turbine gland area is clean and loose debrises are removed.

 4. One gland seal steam exhauster is kept in service.

 5. One CEP is kept in service and condensate flow is established through GSC minimum recirculation.

 6. Gland steam pressure control valve and Leak off control valves operation checking is complete. Oil level is OK in hydraulic actuators. 

7. Charging of cooling water to condenser water boxes. 

8. Control oil is charged. 

ST-1 Shutdown

 ST-1 SHUTDOWN PROCEDURE

 (Note-Tie CB means CB for tie between station buses as applicable)

 1. Switch OFF SD bus I/C DC supply . 

2. Ensure SB/SD/UB-3B tie already closed at SB end.

 3. Tie CB to SB/UB-3B CB at SD end, take its selection in manual in CR-1 to check healthiness of “CB in manual “contact by EMD.

 4. Remove tripping of SB end tie CB with help of EMD (otherwise on closing SD end breaker, SB end tie CB will open & fault appear in it in CR-1 . To avoid it, EMD will remove this tripping of SB end tie CB) 5. Close tie CB at SD end . Ensure SB end tie CB will not trip. 

6. Open SB bus I/C from ST-1 . 

Generator ATT

 

 

Guidelines RELATED TO GENERATOR AIR TIGHTNESS TEST

CRITERIA FOR THE ACCEPTANCE OF TEST:

·         The test pressure drop in the system should be monitored for a period of 24 hours. No break is allowed.

·         The gas system can be considered sufficiently tight when the pressure drop during a 24 hours test with compressed air does not exceed 0.15 bar or the loss of air is below 1.5m³/24 hrs (s.t.p).

·         If air loss is higher than 0.15 bar / 24 hrs, a search for leakages must be made.

·         The test pressure should correspond to the rated gas pressure of the generator (i.e. 3.5 bar) in normal cases, otherwise 4.0 Ksc if rotor is threaded out.

Biomass Co-firing Operating Procedure

 

1)    Mill Operating Parameters and Operation procedure: -

Ø  Maintain Mill outlet temperature-> 55C

Ø  Mill inlet temperature -> not more than 180 C

Ø  Observe all 4 coal pipe temperature of Mills with biomass regularly. In case of any deviation from rest of the pipes(any abrupt rise or fall), stop the mill and give PTW for inspection.

Ø  Pre start and post shutdown purging of mill is mandatory.

Ø  Continuous monitoring of mill parameters most importantly mills inlet air temperature, mill outlet temperature, mill current and mill DP.

station Source c/o Procedure stage 1 Dadri

 

 In stage 1 we have two station transformers (ST1 and ST2). In case of planned outage or emergency tripping of one station transformer the station bus of that  station transformers can be charged via available station  transformer

 

 

 

Case 1 : Charging of  station bus SC bus via station bus SA

 

1. Open Station transformer 1 & 2 scheme in station common OWS (fig (i))
2. See which breaker among CBE 213 and CBE 217 is in closed condition. In normal condition one breaker (CBE 213 or CBE 217) must be in closed condition.
3. If CBE 213 is in closed condition  then

a)      Select Breaker CBE 216 ( SC incomer from ST#2)  in SA-SC trip selector. (fig (i))

b)      Turn the common synchronizer  switch on common electrical  vertical panel  to check mode (fig (ii))

c)      Put Synchroscope (on common electrical  vertical panel  ) in ON mode (fig (iii))

d)     Select breaker CBE 217 (SC tie from SA) and check its permissive

e)      After ensuring all the permissive are coming , close  breaker CBE 217

f)       After closing of CBE 217(SC tie from SA)  breaker CBE 216 ( SC incomer from ST#2)  will open in auto and SC bus will get charged by SA bus

SD Bus isolation checklist

 

SC Bus Isolation checklist

 

SB Bus isolation checklist

 

SA Isolation checklist

 

Mill Ignition Permit

TG Oil Flushing Procedure

TG OIL FLUSHING PROCEDURE

PURPOSE:

• · This document is prepared to guide the operation personnel to line up  for Lub oil Flushing  and achieve desired oil Parameters
  

SCOPE:  

• · This shall be applicable to the MOT Lub oil system of Stage-1 (210 MW*4) & Stage-2 (490MW*2)
  

PRECONDITIONS OF STARTING TG LUB OIL FLUSHING

S No	ACTIVITY	Responsibility	Status
1.	Ensure MOT inspection & Pedestal closing clearance and Lub oil flushing Clearance from TMD and C&I.	Operation
2	MOT Drain, Coolers drains and filters drain and vents are closed	Operation
3	MOT  level is >Low and <High	Operation
4	All Instruments root valves are charged, & all instruments are healthy	C&I
5	No insulation work is to be carried out on TG module and on its bearings during flushing & bearings pedestal area is to be maintained clean.	TMD
6	Check one cooler, whose oil side as well as water side are lined up, in service	Operation
7	MOT centrifuge is in service with purifier mode	TMD/Operation
8	One VEF in service	Operation
9	Provision of line filters in lub oil lines	TMD
10	Clean baskets strainers are put in MOT.	TMD
11	Availability of Lub oil pumps with P&I in service	Operation
12.	First DCEOP to be started for filling/venting of lines. Then DCEOP to be stopped &  AOP to be srated. Check AOP discharge pr., current & MOT level.	Operation

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13.	MOT level will start dropping. Monitor the same and take necessary precautions.	Operation
14.	See oil flow through each bearing return oil pipe.	Operation
15.	Inspect all pedestals for oil leakages ( both external and from internal fittings, hoses , gauges,etc).	Operation
16.	Check for any oil leakage in MOT room, oil canal & pedestal area.	Operation
17.	Monitor choking of duplex filter.	Operation/TMD
19.	MOT coolers are filled and venting done.	Operation
20.	Stop AOP and clean the Oil line filters and MOT basket strainer after first four hours of oil flushing.	Operation/TMD
21.	Clean duplex filter when choked more than 50%	TMD
22	Collection samples from MOT tank, Centrifuge inlet & outlet	Chemistry
23.	When frequency of cleaning   of duplex filter reduces considerably and simultaneously clearance is received from chemistry department of mechanical impurities and moisture (both < 100 ppm) , oil flushing is stopped .	Operation/TMD/chemistry
24.	Basket strainer is removed, cleaned and put back in position.	TMD
25.	Remove oil line filters and replace with oil throttles.	TMD

Completion Criteria:  

• · Mechanical Impurities & Moisture Content in samples are less than 100ppm by weight
  
• · MOT strainer should remain clean after 24 hours of TG Oil flushing
  
• · There should not be any hard particle in line filters
  
• · Duplex filters are required to be cleaned after 12 hours of oil flushing
  

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CHECK LIST FOR PUTTING TG ON BARRING

Sr. No	ITEM DESCRIPTION	Responsibility	Status
1	Clearance from C&I, TMD, chemistry before putting on Barring	Operation
2	Oil vapour extractor Normalised & ON	Operation
3	Generator bearing chamber exhauster ON.	Operation
4	Check for local line up of lube oil and jacking oil systems.	Operation
5	All pipe connections are OK.	Operation/TMD
6	Check lift of rotor journals at all bearing pedestals.	TMD
7	Check hand barring is free prior to putting oil barring.	Operation/TMD

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Dadri St1 Hydrant pump Auto Cut in Pressure

 

Dadri St1 Turbine EHTC Characteristics

 

Dadri St1 Hotwell Level Control Logic

 

Dadri stage 1 Light Up/Turbine rolling checklist/Steps

 

Unit start up Checklist
1	IOM sent to CISF
2	Two ECW Pumps i/s
3	Written clearance from: PP,RM.C&I,TM,AHM,EM
4	Check Air, FG Pass dampers
5	2 Pass of ESP opened, All ACP i/s, Fields ready to be taken into service
6	BT 50%
7	IA, SA PR Adequate
8	Aux PRDS charged from station
9	LDO stations and AB, CD guns Normalised
10	APH Soot blowing started with SB 26
11	Mills ABCD normal
12	MS 1,2 Supply Normalised
13	FA, BA evacuation system ready, AHP Clearance
14	SH drains Manual Opened
15	SH Manual vents, SH start up vents & drum vents Open
16	MS lines drains u/s of HPBP @8.5m open
17	Open Eco R/c E20
18	open CBD manual valves
19	MS 203,204, HRH 203,204 CRH 203,204 open with manuals
20	MS, HRH strainer drain to IBD MS 103/104, HRH 103,104 open
21	MS, BD,SS,FW,HRH sampling line OK
22	start CEP
23	start BFP in r/c, wait for Chemistry clearance
24	Take FRS 30%line and fill drum upto +50 mm
25	Start APH, Scanner fan, ID fan, Fd fan put draft in auto, purge boiler
26	Pull Vacuum
27	Take AB13or AB24 and light up the Boiler
28	After 30 minutes, Take other pair of AB
29	Charge MOT cooler, LOTCV in auto with 45 Deg SP
30	Check for TG Lub Oil filter
31	Turbine SVs gagged removed
32	Governing rack Normal, EHC Normal
33	EHTC mimic: Speed SP<Turning speed,EHTC o/p:10%, Load controller ON
34	All MAL dranis And MS/CRH/HRH drains to HPFT open
35	Close Drum vents, SH Vents@2ksc
36	CBD open
37	Charge MS line @ 8ksc Drum Pr
38	Charge HP, LP Bypass @ 10 lsc, close MS line drains u/s of HPBP
39	close start up vents after HPLP Bypas charging
40	EHTC mimic: Load ref 20MW,PRmax 50 MW
41	Check X1, X2, X3 Before ESV opening
42	Reset turbine by lower SD to 0%, Reset GRP
43	Rolling: TG>>turbine all SGC>>turbine Seq>>Program ON>>startup
44	Advance upto 101 to 105 for SD to reach 42% i.e. ESV opening
44	For 540 rpm, check X4, X5, the advance upto 112 step, Then wait
45	start PA Fans, Charge SW, SO, H2 Gas Cooler @ 540 rpm
46	check Barring gear close@240rpm, JOP @ 540 rpm
47	Inform S/Y to close Isolator
48	For 3000 rp, X6 fulfills.
49	From Program , advance upto 116 step, Program OFF
50	DAVR: DAVR Reset, Close FCB, Excitation ON, make 16KV Gn TV
51	Then Sel GCB form OWS, and selction: ATRS from ECP, EHTC: Synchroniser ON
52	Open Speed Ref Pop-up for loading , As Unit sync, Load Turbine, Prmax:225 MW
53	close HP Bypass , the LP Bypass to avoid HP/IP Trim
54	check for GT Fans
55	take Mill A
56	close MS 101,102,103,104, HRH 1010,102,103,104
57	Put SLC Drains ON
58	@20% Load : Charge D/A, LPHs
59	@40% load: charge HPHs, Change over ST to UT
60	Take Mills B, C@ 30% and 40% load
61	Changeover FRS 30% to 100% @ 40% Load
62	Take Additional mill D, and withdraw oil support
63	Put Machine in CMC
64	Close E20 v/v
64	charge ESP Fields, and Normalise all Passes

Dadri stage 1 Important Drives Rating/Protections

 

MILL	1	SA Hdr PR <127mmWC for TD 1 Sec
	2	PA Hdr<500, FEDCBA trip with TD 15 sec
	3	Feeder capacity 49 tph
	4	Full Load current: 54.7 A
	5	O/L Current: 65.25 A with TD 6 Sec
PA Fan	1	LO Pr 0.4 ksc: 0.9 ksc(standby starts)
	2	HC Oil Pr: 0.8 ksc; 0.6 ksc(standby starts)
	3	Brg Temp: 90 Deg
	4	HC/ Return Oil Temp: 110/120
	5	Vibration: 9mm/sec
	6	F/L Current/ O/L Current: 113.5/130.5 A
FD Fan	1	LO Pr 0.5 ksc: 0.9 ksc(standby starts)
	2	Brg Temp: 100 Deg
	3	Vibration: 9mm/sec
	4	F/ L Current/ OL Current: 108/116.5 A
	5	Control Oil Pr: 8 ksc (standby starts)
ID Fan	1	LO Pr 0.7 ksc: 0.9 ksc(standby starts)
	2	Brg Temp: 90 Deg
	3	Vibration: 9mm/sec
	4	F/L Current: 157.8 A
	5	O/L Current: 191.88 A
Misc Prot	1	Furnace: +150/-180
	2	Drum: +225(TD 10 sec)/-225(TD 5sec)
	3	Vacuum : -0.7 ksc/515 mmHG
	4	Vac p/p: Autostart -0.85 ksc/630 mmHG
	5	LO Pr:1.88 ksc
	6	Fire Protetion.1/2: -50, -100
BFP	1	LO Pr: 0.5ksc/0.8ksc(AOP starts)
	2	D/A Level: <700 mm
	3	Brg & HC Temp: 95 Deg
	4	WO Temp: 130 Deg
	5	Suction Pr: <1.7 ksc
	6	Full Load Current: 356.5 A
	7	O/L current: 399.28 A