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.

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.

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 . 

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

 

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

Dadri stage 1 High energy drains

 

DADRI - COAL
High Energy Drain Valve Passing
[ STAGE - I ]
	Date	31.08.2025
S. No	Details of Passing Valve & Tag No	Unit-1
1	MAL-11(UPSTREAM OF HP TURBINE CONTROL VALVE)
2	Mal-26(UPSTREAM OF IP TURBINE CONTROL VALVE)
3	MAL-15(DN STREAM OF HP TURBINE CONTROL VALVE)
4	MAL-16(DN STREAM OF HP TURBINE CONTROL VALVE)
5	MAL-22(HP TURBINE CASING DRAIN VALVE)
6	MAL-31(DN STREAM OFIP TURBINE CONTROL VALVE)
7	MAL-32(DN STREAM OF IP TURBINE CONTROL VALVE)
8	MAL-65(CRH NRV UP STREAM)
9	MAL-66(CRH NRV UP STREAM)
10	MAL-12(UPSTREAM OF HP TURBINE CONTROL VALVE)
11	MAL-27(UPSTREAM OF IP TURBINE CONTROL VALVE)
12	MAL-47(HPH-5 EXTRACTION NRV UP STREAM)
13	MAL-51(DA EXTRACTION NRV UP STREAM)
14	MAL-54(LPH-3 EXTRACTION NRV UP STREAM)
15	MAL-81(DRAIN FROM GLAND SEAL STEAM HEATER)
16	MAL-55(LPH-2 EXTRACTION NRV UP STREAM)
17	HRH-101(HRH LINE STRAINER DRAIN HP DRAIN FLASH BOX)
18	HRH-102(HRH LINE STRAINER DRAIN TO HP DRAIN FLASH BOX)
19	HRH-103(HRH LINE STRAINER DRAIN TO IBD TANK)
20	HRH-104(HRH LINE STRAINER DRAIN TO IBD TANK)
21	HRH-105 (LP BYPASS WARM UP LINE)
22	HRH-106(LP BYPASS WARM UP LINE)
23	MS-101(MS LINE STRAINER DRAIN HP DRAIN FLASH BOX)
24	MS-102(MS LINE STRAINER DRAIN HP DRAIN FLASH BOX)
25	MS-103(MS LINE STRAINER DRAIN TO IBD TANK)
26	MS-104(MS LINE STRAINER DRAIN TO IBD TANK)
27	CRH-101 (CRH LINE NRV DRAIN)
28	CRH-102 (CRH LINE NRV DRAIN)
29	BFP-1A
30	BFP-1B
31	BFP-1C