19 August 2022

RLA Test | Remament life assessment | IBR rule 391A talks about ageing of boilers |operation for 1,00,000hrs (One Lacks hours) for assessment of the remament life of the parts

RLA Test

1.)  Which IBR regulation talks about ageing of boiler?

IBR rule 391A talks about ageing of boilers.

2.) After how many hours of operation is RLA carried out?

The boilers which are operating at a temperature of 400*c and above including utility or industrial boilers and all boilers parts operating in the creep range of the boiler shall be non destructively tested after they are in operation for 1,00,000hrs (One Lacks hours) for assessment of the remament life of the parts.

3.) Tests with reason that are carried out under IBR regulation 391 A for RLA

Types of Non-destructive Test :

1. Shearography
2. Eddy Current test
3. Acoustic Emission
4. Thermo graphic
5. Ultrasonic Testing
6. Vis ual Inspection

1. Shearography

• The object under study is illuminated by laser light, and a camera produces two sheared images that interfere with each other, causing a speckle pattern.
• When the object is deformed (sheared), the speckle pattern changes.
•The two speckle patterns interfere to produce a fringe pattern that depicts the surface gradient of the deformed object.
• Though the images obtained are good, this method is time consuming.

2. Eddy Current Principle

• When an energized coil is brought near to the surface of a metal or conducting component, eddy currents are induced into the specimen. These currents set up magnetic field that tend to oppose the original magnetic field. The impedance of coil in close proximity to the specimen is affected by the presence of the induced eddy currents in the specimen.
• When the eddy currents in the specimen are distorted by the presence of the flaws or material variations, the impedance in the coil is altered. This change is measured and displayed in a manner that indicates the type of flaw or material condition.

3. Acoustic Emission Principle

• Sounds made by a material, structure, or machine in use or under load are heard and analyzed to determine its “state of health”.
• One or more ultrasonic microphones are attached to the object and the sounds are analyzed using computer based instruments.
• Noises may arise from:
– friction (including bearing wear)
– crack growth
– material changes (such as corrosion)

4. Thermographic Principle

• Heat flow in a material is altered by the presence of some types of anomalies.
• These changes in heat flow cause localized temperature differences in the material.
• Slow heating of part reveals these anomalies.

5. Ultrasonic Testing

• The use of ultrasonic waves to evaluate the condition of a material.
• Anomalies absorb or deflect the sound waves, which are then detected as changes in the waves.
– holes, delaminations, voids
– damage, debonds
– resin rich, poor areas

6. Visual Inspection

• Basic principle:
– illuminate the test specimen w ith light
– examine the specimen with the eye
• Used to:
– to magnify defects which can not be detected by the unaided eye
– to assist in the inspection of defects
– to permit visual checks of areas not accessible to unaided eye
• Most widely used of all t he nondestructive tests.
• Simple, easy to apply, quickly carried out and usually low in cost.

4.) RLA Study:-

The Residual life assessment through condition assessment followed by Non-destructive test consists of :

1. Interviewing of the operation and maintenance personnel of the plant,
2. Reviewing relevant design, operation, maintenance, outage, history and failure analysis and records available for the boiler components
3. Quantitative condition assessment and identification of critical component inspection are carried out on the base of history.
4. Inspection plan which include non-destructive evaluation procedure will be made on the basis of high and low temperature components.
5. The health assessment of various components is carried out using appropriate field testing like visual examination, dimensional measurement, in-situ metallography, hardness measurement, dye penetrant test, ultrasonic and magnetic particle test, video images copy, oxide scale measurement, hydrogen embritlement and any other specified tests.

Assessment of creep damage and other mechanical test will be done on post service samples of super heater tubes. The samples from various sections will be collected for various tests at laboratory including mechanical test. Findings requiring immediate attention of plant authorities to facilitate taking action are given at site itself for the repair. All the results are summarized to find the remaining life of the components. The study provides the information to take the decisions like repair/replace/run for further safe usefulness of the pressure part components of the boiler.

The following test methods are widely used on boiler pressure parts:

• Visual inspection
• Thickness & diameter measurement
• Dye penetrant test
• Ultrasonic flaw detection test
• Magnetic particle inspection test
• In-situ metallography/ replication
• Hardness measurement
• Fibroscopic inspection
• Oxide scale measurement
• Hydrogen embrittlement
• Material grade identification
• Tensile & Flattening test
• Radiography
• Accelerated Creep rupture test
• Deposit analysis
• Weight loss analysis for tubes
• Hanger inspection
• Hydraulic test

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