11.0 Plant Residual Life Assessment

 Residual Life assessment (RLA) study

As per IBR regulation 391 A, the residual life of a running Boiler is assessed by ND tests.

For Boilers:-

1.	Operating above creep temperature (400 °C)	After 100000 Hrs of operation or 13.4 Years
2.	Operating below creep temperature	After 25 years of operation

 

Objective of RLA study as follows:

v  Prediction of impending failure of critical plant components resulting in enhanced safety, operation reliability, availability and maintainability.

v  Establishing life prediction, approach to enable repair, up gradation, replacement of necessary components and extension of remaining component life.

Types of tests:

A	Non Destructive Test
I	Visual Examination
II	Dimensional Measurement
III	Dye Penetration Test
IV	Magnetic Particle Inspection using wet non fluorescent method	Detection of surface and sub surface cracks/ discontinuity.
V	Ultrasonic Examination	Detection of sub surface cracks, loose bonding, material defects of any kind of discontinuity.
VI	Metallographic Replication by portable optical microscope	Assess the present micro structure condition of components.
VII	Hardness Measurement
VIII	Fibroscopic Inspection by means of miniature color video camera	Pitting or crack indication, scale of deposits, debris or loose parts.
B	Destructive Test	Metallurgical testing of tubes.

 

Test conducted at 10 MW thermal power plant:

	BOILER
1	Steam drum and Mud drum	Visual, UT, MPT, LPI, Replication, Hardness, DIM, Deposit analysis
2	Water wall top and bottom header, Economizer I/L O/L header	Visual, UT, LPI, Hardness, DIM, Fibro optics inspection
3	Primary Super heater header	Visual, UT, LPI, Replication, Hardness, DIM
4	Final Super heater header	Visual, UT, LPI, Hardness, DIM, Fibro optics inspection, In situ metallography
5	Attemperator Header	Visual, UT, LPI, Replication, Hardness, DIM, Fibro optics inspection
6	Main steam pipe lines	Visual, UT, LPI, Replication, Hardness, DIM
7	Economizer tubes	Visual, DIM, Destructive test, Micro structure analysis
8	Prim. & Final super heater coils	Visual, DIM, Destructive test, Micro structure analysis, Hardness, Oxide scale thickness
9	Boiler bank tubes and water wall tubes	Visual, DIM, Destructive test, Micro structure analysis
10	Tubular Air Preheater	DIM
11	ID, FD and SA Fan	DPT
12	Feed water lines	Visual, UT, DPT, DIM

 

	TURBINE
1	ESV	Visual, UT, MPI, DPT, Replication, Hardness
2	Throttle Valve	Visual, UT, MPI, DPT
3	Turbine casing, flange ligaments & inlet nozzle chamber	Visual, DIM, UT, MPI, DPT, Replication, Hardness
4	Diaphragm and stationary blade	Visual, DIM, MPI, DPT, Replication, Hardness
5	Parting plane fastners	Visual, MPI, DIM, Replication, Hardness
6	Gland casing	Visual, DIM, MPI
7	Turbine rotor forging, HP gland area, Journal, Disc	Visual, MPI, DPT, Replication, Hardness
8	Rotating blade, shrouds, Lacing wire & attachment	Visual, MPI, DPT, Replication, Hardness
9	Bearings	Visual, DIM, UT, DPT
10	Coupling Bolts	Visual, DIM, DPT
11	Condenser	Visual, UT, DPT
12	Generator shaft	UT, DPT

 

	ELECTRICAL SYSTEM
1	Generator rotor winding	DCR, IR, PI, HI-POT, Step Voltage Test. TDT, CT, PD, ELCID
2	Generator stater bus duct and 11KV cable	IR, HVT, TDT, PD
3	Generator Rotor	IR, RIT, WRT, PI
4	LT motor	IR, DCR
5	Power Transformer	IR, PI, ECT, DCR, MBT, TDT, PD
6	Transformer Oil	BDV, Resistivity, Acidity, PPM, DGA,PSM
7	Bushing	TDT, CT
8	Auxiliary transformer	IR, PI, DCR
9	Current Transformer	IR, PI, DCR
10	Potential transformer 11 KV	IR, PI
11	LV Switch gear/ MCC	IR, HVT, CRT, Breaker open/close time, PRT
12	LV cables	IR
13	MV Switch gear	IR, CRT, Breaker open/close time, PRT
14	MV motors	IR, PI, TDT, WRT

 

	ABBREVIATION
DCR	DC Resistance
IR	Insulation Resistance
PI	Polarization Index
TDT	Tan Delta Test
CT	Capacitance Test
CRT	Contact Resistance Test
RIT	Rotor Impedance Test
HVT	High Voltage Test
BDV	Break Down Voltage
MBT	Magnetic Balance Test
ECT	Excitation Current Test
PRT	Protective Relay Test
DGA	Dissolved Gas Analysis
PSM	Particle Size Measurement
MCR	Measurement of Contact Resistance
PD	Partial Discharge
HSVT	Hi-pot Step Voltage Test
WRT	Winding Resistance Test