Betz Engineering & Technology Zone was primarily established to provide Non-destructive testing services, Failure Analysis and Metallurgical tests to the industry sectors as Power, Automobile, Foundry, Manufacturing and Fabrication.Betz over the five years of incorporation has gained reputable experience in the following test and service categories, and is equipped with the latest set of equipments and well trained and dedicated staff on board
Failure is an unacceptable difference between expected and observed performance. Failures do not happen, and they are caused.
The consequences of failures are Fatalities, injuries to personnel, Damage to property, Shutdown of plant, Loss of production, Ecological problems and Litigations.
Failure analysis is to establish the causes leading to a failure. From the results of a failure analysis, gets initiated the remedial action towards preventing such causes. The overall benefits of the said action will be improved reliability and highest adherence to safety.
In failure investigation routine analysis is recommended to ensure that the material is the one that was specified. Slight deviations from specified compositions are not likely to be of major importance in failures result from unsuitable or defective material. In specific investigations, particularly where corrosion and stress corrosion are involved, chemical analysis of any deposit, scale or corrosion product, or the medium with which the affected material has been in contact is required to assist in establishing the primary cause of failure. Where analysis shows that the content of a particular element is slightly greater than that require in the specifications, it should not be concluded that such deviation is responsible for the failure.It is often doubtful whether such a deviation has played even a contributory role is failure. The various tools and technique available for different types of chemical analysis are:
The detailed examination of component and fracture surfaces at magnifications ranging from 1 to 100X is generally considered as macro examination. The amount of information that can be obtained from examination of a fracture surfaces at low power magnification is surprisingly extensive. Consideration of the configuration of the fracture surfaces may give an indication of the stress system that produced failure. Fracture in monotonic tension produces a flat fracture normal to the maximum tensile stress under plane-strain conditions and a slant (shear) fracture at about 45 degree if plan stress conditions are ideal situations that seldom occur service, Many fractures are flat at the center but surrounded by a picture fracture of a slant fracture. The slant fracture occurs because conditions approximating plane structure operate at the center of the specimen but relax toward plane stress near free surfaces. Macroscopic examination can usually determine the direction of crack growth and therefore the orgin of failure. With brittle flat structures determination depends largely upon the fracture surface exhibiting chevron marks. Chevron marks occur because nearly all cracks are stepped at an early stage in their development, and as the crack front expands , the traces of the steps form chevron marks. In plate and sheet, chevron marks may result from the nucleation of new cracks ahead of a main crack front.
Where fracture surfaces show both flat and slant fractures it may be generally concluded that the flat fracture occurred first. Low power examination of fracture surface often reveals regions having a texture different from the region of final fracture. Fatigue, stress corrosion, and hydrogen embittlerment may all show this feature. The various tools available for macroscopic examination are unaided eye, hand lens, low-power optical microscope and SEM at low magnification.
This is a detailed examination of a fracture and polished section at magnification >100x. The microscopic examination of fractured surfaces can be carried out using an optical microscope, a transmission electron microscope, and/or a scanning electron microscope. Optical microscope is used extensively for low-magnification (<100x) fractographs, but it has for less application for microfractography. This is dur to its limited resolution (~10-6m)and depth of field (cannot not focus on rough surface)
Because the specimens for transmission electron microscope (ETM) must be thin enough to permit the transmission of electron beams, replicas of the fracture surface must be obtained. The use of scanning electron microscope (SEM) with resolutions below 3nm has consoiderably diminished the need for replication techniques. However, direct replication is still used in material since for special problems, such as examining the surface of a large component without cutting it, studying, radioactive material that cannot be placed as an ordinary unshielded microscope, or studying extremely fine Fatigue striations. Many problems involving the determination of the composition, crystal structure , or orientation of small second-phase particles are simplified if the particles are extracted from their matrix, and then supported in the microscope using a replica. The microscopic examination is a detailed observation of fracture and polished section at magnifications >100X. The typical features that can be observed by microscopic examination are:
The hardness tester EQUOTIP 3 comprises an indicating device and an impact device. It is based on the rebound hardness testing method according to leeb.It is for testing the hardness of all material surfaces over a large range of hardness quickly and independently.
Customer - Specific conversion.
SEM Fractrographic study
Non destructive testing is used to assess the integrity of a system or component without compromising its performance. The purpose of inspection is to determine whether the components, systems or products confirm to given specifications.The choice of a specific NDT method is done based on many factors that include availability ,accessibility, sensitivity and cost etc.The selection of Inspection points is of paramount importance as failure/corrosion factors to be considered are related to the operating condition, geometry and environment of systems, materials of construction, external factors and historical records. A brief discussion on various NDT methods used for RLA/CA of the boiler and its components of ISPAT INDUSTRIES LTD., are given below.
Visual inspection is the oldest and most common form of NDT used to detect various forms of which include surface corrosion,pitting and intergrannular corrosion when proper access to the inspection area is obtained.Visual inspection is a quick and economical method of detecting various types of defects before they cause failure.Its reliability depends upon the ability and experience of the inspector.Visual methods can provide a simple and speedy way to assess questionable components and can help in deciding what to do next.The disadvantage of visual inspection is that the surface to be inspected must be relativelyclean and accessible to either the naked eye or to an optical aid.
Penetrant inspection is used to reveal surface breaking flaws by bleed-out of a colored or fluorescent liquid dye from the flaw. The technique is based on the ability of a liquid to be drawn into a clean surface breaking flaw by capillary action.After a period of time called dwell excess surface penetrant is removed and a developer applied.This acts a blotter.It draws the penetrant from the flaw to reveal its presence.Coloured penetrants require good white light while fluorescent penetrants need to be used in darkened condition with an ultraviolet black light. Advantage of this test method is that indications are produced directly on the surface of the part and constitute a visual representation of the flaw. The disadvantage of this method is that it cannot be applied on porous materials.
Magnetic particle inspection is used for testing materials that can be easily magnetized(ferro magnetic materials).This method is capable of detecting flaws open-to-surface and that just below the surface.When a specimen is magnetized wherever there is a flawthat interrupts the flow of magnetic lines of force,some of these lines exit out and re-enters the specimen.The points of exit and re-entry form opposite magnetic poles and when minute magnetic particles are sprinkled over the surface of the specimen the particles are attracted by local magnetic poles.The presence of magnetic particles creates a visual indication approximating the size and shape of the flaw. The limitations of this test method are that it can detect only surface opening and sub-surface defects in ferro magnetic materials.
This is an expensive technique compared to the other non destructive techniques and is predominantly used to detect internal flaws in casting and weldments. Automated systems are available for identification of the exact location of the flaw and the size of the defect.
Inspection using ultrasound is one of the most widely used and reliable non destructive test methods to monitor materials deterioration and corrosion damage on components. This method can be applied with one side accessibility which makes it useful to apply during service. Ultrasonic test techniques are used to measure the wall thickness and presence of flaws in the components. For flaw detection applications standard ultrasonic flaw detector is used whereas for thickness measurement a pulse-echo ultrasonic thickness can be used. The ultrasonic thickness gauge determines the thickness of a part by accurately measuring the time required for a short ultrasonic pulse generated by a transducer to travel through the thickness of the material reflect from the back or inside surface and be returned to the transducer. In most applications this time interval is only a few microseconds or less. The measured two way transit time is divided by two to account for the down and back travel path and then multiplied by the velocity of sound in the test material.The result is expressed in the well known relationship.
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|Betz is proud to be one of the international agents hand picked to conduct AWS/CWI, SCWI and other exams on behalf of the American Welding Society, USA. Right now BETZ is conducting its seminars and certification events in India and to be specific, Coimbatore and Chennai.|