• On Line – Continuous Periodic
• Off Line - M/c Assembled M/c Disassembled

Online condition monitoring is possible during running condition of equipment and it detects problems in their early stage so that rectification can be undertaken before severe fault. Off-line monitoring requires shut down which consumes time. It is recommended to carry out both on-line and off-line condition monitoring for finding the exact condition of equipment.

There are various techniques for different types of equipment and their components which can give precise information about their condition /health.

The EL CID equipment tests a core for faults by exciting the core using a toroidal winding to produce a ring flux up to 4% of its normal working level of excitation. A sensing head is then passed over the surface of the core to detect magnetically the presence of fault currents.

This technique gives information about stator, rotor winding health, and contamination in the windings.

• Motors : Off line & On line (> 1000 jobs)
• Generators : Off line & On line (> 75 jobs)
• Power Transformers : Off line & On line (> 350 jobs)

Visual examination is the simples and one of the most powerful techniques for assessing the condition of plant equipment. All components are visually examined before and after cleaning the surface by using aids such as illuminated magnifying glass, mirror, and if needed by portable optical microscope for detecting abnormalities such as misalignment, bow, sagging, ovality, deformation, breakage, cracking, porosity, abrasion, erosion, pitting, etc..

Dimensional measurements are essentially used to quantity changes in the present geometrical configuration of a component with its original reference design dimensions. As an example, outside diameter measurements are generally employed to determine swelling (bulging) due to creep. Thickness measurements, at critical locations, such as bends give accurate indication of thickness loss due to erosion and corrosion.

For dimensional measurements, the surface is first thoroughly cleaned by removing scale and corrosion products using appropriate tools such as wire brush, hand grinder, cotton cloth, etc. Subsequently, outside diameter measurements are made using digital vernier calipers, measure tapes, bow gauges, etc; while for thickness measurements, ultrasonic thickness meters are required.

Dye-penetrant examination using coloured dye is used for detection of surface cracks/ porosity / discontinuities. The components subjected to high stress and temperature are examined after thorough cleaning, by the dye-penetrant test. Extreme care is taken during surface preparation to avoid pre-mature closing of surface defects.

Magnetic particle inspection using wet fluorescent dye is employed for detection of surface and sub-surface defects. The examination is conducted using the continuous method i.e. the magnetizing field remains on while fluorescent iron powder particles are sprayed. The sprayed areas are examined visually and under ultra-violet light of appropriate intensity. Magnetization is done in at least two perpendicular directions to ensure high probability of crack detection. All relevant indications are recorded by identifying their location, nature, and size on a sketch and/or by a colored photograph.

All weld joints are examined by MPI to check for presence of surface and sub-surface defects. On completion of a given test, residual magnetism remaining in the component is removed by de-magnetization.

Ultrasonic Examination method is employed for detection of surface cracks, loose bonding, volume cracking and any other kind of defect to ensure internal soundness of the component. The examination is usually carried out on header butt joints, drum-weld joints, as well as on other joints deemed critical.

The ultrasonic test equipment is properly calibrated prior to use. The resolution & sensitivity level of the equipment is set to record the presence of the smallest possible defect size. It is to be noted that a typical advanced ultrasonic instrument (of the kind used by ERDA) has adequate sensitivity to detect even fine multi-branched cracks resulting as a consequence of stress corrosion cracking.

Metallographic examination by portable optical microscope and by surface replication technique is carried out to assess the micro-structural state of the plant component.

The replication technique is used at selected locations on the components to reproduce accurately metallographic features such as distribution, size, and morphology of the carbide precipitates as well as micro-cracks typical in case of stress corrosion and Hydrogen embrittlement.

The locations selected for examination are properly polished with a portable grinder and etched with suitable chemicals for examination under a portable microscope. The reverse image replicas of the metal surface are taken on a plastic replicating film for detailed laboratory examination under an optical microscope. The quality of the replicas is checked at site by a portable optical microscope before bringing these to the laboratory, for further analysis.

In-situ hardness testing is carried out on all components operating at high stress to determine the extent of micro-structural degradation. The locations for hardness measurements are selected based on results of various other tests including visual examination. The measurements are taken using a Portable Hardness Tester. Before using this device, its accuracy and reproducibility is checked using pre-calibrated standard test blocks.

Fibroscopy / Boroscopy / Videoscopy are optical visual examination techniques used for examining & recording visual/video images of internal condition of various components of boiler, turbine & auxiliaries such as headers, tubing, piping, rotor bores, etc., for determining the presence of internal defects such as internal cracks, corrosion and erosion, oxidation, deposits, pitting, blockages, choking, as well as presence of foreign objects such as left over welding consumables, steel pieces, cuttings, spattering, welding slag, refractory and insulating materials, etc. Fibroscopy, boroscopy, and videoscopy is carried out up to a length of eight meter inside each accessible component. Fig. 3 shows typical images obtained from fibroscopic and boroscopic examination of headers and heat exchangers. The image can be recorded using freeze frame digital photography or a continuous video record can be made.

The eddy current flaw detection technique is based on the principle that a time varying magnetic field induces a circulating current in the near surface regions of metallic/conducting material, when a probe in the form of a coil carrying a time varying current is brought near a conducting surface to be examined. The mutual inductance of the scanning coil - surface being examined changes in the presence of surface and sub-surface flaws. This translates into a change in the scanning coil impedance, based on which the presence of flaws can be detected.

Insitu chemical analysis is usually conducted on turbine components. However, insitu chemical analysis is also widely used for identifying & verifying pressure part chemistries in steam generators using advanced materials. Before the analysis, a wire brush and grinder are used to thoroughly clean the surface. A portable state of art instrument operating on the principle of spark emission /XRF spectroscopy is used for conducting this analysis.

The vibration energy associated with an engineering structure undergoing dynamical excitation under time varying externally applied forces is primarily concentrated at the characteristic frequencies (eigen-values) of the structure. Since concentration of excessive vibration energy can lead to excessive vibrational amplitudes with accompanying large time varying stresses, the vibrating structure becomes prone to failure by the process of fatigue. In a turbine, the components most prone to failure by this mechanism are the rotor blades. Among the various turbine stages, the blading associated with the low pressure stages - especially the last couple of stages – are the most prone to excessive vibrations excited by the various disturbing forces encountered in a turbine. It is thus important that the fundamental vibration frequencies of the low-pressure blading be accurately determined using a suitable technique.

The technique used to determine the natural frequencies of blading involves exciting of blade packets by hammering (to simulate an impulse load) with an instrumented tuned hammer and the resulting vibrations, as picked up by an accelerometer, are recorded using a digital storage oscilloscope and subsequently converted into a frequency domain transfer function record of the original signal using a Fast Fourier Transform (FFT) algorithm. The natural frequencies of the first three vibrational modes are subsequently extracted from this transfer function record.

Fibroscopic & Boroscopic Images of Headers and Heat Exchangers

• Thermography
• Acoustic Emission Analysis (AE)
• Vibration Measurement and Analysis
• Noise / Sound Measurement
• Shock Pulse Measurement (SPM)
• Ferrography Analysis

The Energy Management Section (EMS) of ERDA was established in the year 1995 with the objective of providing energy conservation services to the Nation. The energy audit studies undertaken by the EMS have covered Industries, Power Generation Utilities (GENCOs), Power Distribution Utilities (DISCOMs), Commercial Complexes, Hospitals, Dairies, Municipal Corporations, etc. EMS has carried out more than 250 energy audits until now and the benefits realized by our esteemed clients by implementing our recommendations are quite handsome. Over the years, EMS has specialized in energy conservation related to conventional fuels such as coal, oil & gas. These conventional fuels are limited and will be exhausted shortly and thus the need arises to reduce their consumption by efficient utilization. The supply and demand gap of electric power is increasing every year and is expected to increase even further due to the huge cost required in setting up of Thermal Power Stations as well as the associated environmental pollution.

Energy conservation is an optimal operational practice, which improves the efficiency of the equipment associated with both supply side and demand side i.e. at the user end. Since the industries account for a greater share of power consumption, energy conservation programs will benefit them by reducing their Specific Power Consumption and making them more competitive in the market. ‘Negawatt’ (a negative ‘Megawatt’), a term coined by the renowned energy analyst Amory Lovins, highlights the fact that a Negawatt produced by reducing energy need saves more than a Megawatt generated. Energy audits lead to the generation of “NEGAWATTS” and thus result in virtual augmentations to the installed power generation capacity of the Nation!