What Are The Advantages of Magnetic Particle Inspection?

NDT training institute in Hyderabad, is a reputed institute which prepares students for different kinds of training related to engineering services. Here the students pursue courses in different backgrounds like ultrasonic testing, radiography testing and magnetic particle testing. They prepare students to get on the job oriented training programs in industries such as, fabrication, manufacturing, fabrication,  automobile, aerospace, power plants, oil and gas sector and inspection companies. They also offer courses in organizational behavior and communication skills. Both NDT institutes in Hyderabad and NDT institute in Vishakhapatnam provide students a sound knowledge of core engineering sector.

BASIC PRINCIPLE OF MAGNETIC PARTICLE INSPECTION –

NDT training in Hyderabad opens up an enormous scope for students to get NDT jobs in Hyderabad. Out of all the premier courses offered at NDT training institute in Hyderabad, is the magnetic particle inspection. It is a practical training course that could be pursued by engineering students as well as working candidates. Magnetic particle testing is used mostly in inspection of mechanically welded heavy metals which is used in various sectors like automobiles, aviation, maintenance, power plants and hydroelectricity. It is used to detect discontinuities and leakage in ferromagnetic substances of the heavy metals manufacturing sector. .

 It has a wide scope of knowledge and usage as of today. Let’s learn in details about this valuable course and its functionality.

The magnetic particle inspection (MPI) is a relatively simple concept. The main principle behind this magnetic particle inspection is magnetic flux leakage.

For example take a bar magnet. It has a magnetic field in and around the bar magnet. Any place that a magnetic line of force exits or enters the magnet is called a pole. A pole where a magnetic line of force exits the magnet is called a north pole and a pole where a line of force enters the magnet is called a south pole. If we break the bar magnet at the centre, it will result in two bar magnets, with north and south poles on each end of the magnets. There is no isolated pole in the magnets.

If the magnet is just cracked but not broken completely in two, a north and south pole will form at each edge of the crack. The magnetic field exits the North Pole and reenters into the South Pole. The magnetic field spreads out when it encounters the small air gap created by the crack, because the air cannot support as much magnetic field per unit volume as the magnet can. When the field spreads out, it appears to leak out of the material and, thus, it is called a flux leakage field.

If iron particles are sprinkled on a cracked magnet, the particles will be attracted to and cluster not only at the poles but also at the edges of the crack. This cluster of particles is much easier to see than the actual crack and this is the basis for magnetic particle inspection.

The first step in a magnetic particle inspection is to magnetize the component that is to be inspected. If any defects on or near the surface are present, the defects will create a leakage magnetic field. After the component has been magnetized, iron particles are applied to the surface of the magnetized part. The particles will be attracted and cluster at the flux leakage fields, thus forming a visible indication that the inspector can detect.

Advantages and Disadvantages

The primary advantages and disadvantages when compared to other NDT methods are:

Advantages-

·         High sensitivity (small discontinuities can be detected).

·         Indications are produced directly on the surface of the part and constitute a visual representation of the flaw.

·         Minimal surface preparation (no need for paint removal)

·         Portable (materials are available in aerosol spray cans)

·         Low cost (materials and associated equipment are relatively inexpensive)

Disadvantages-

·         Only surface and near surface defects can be detected.

·         Only applicable to ferromagnetic materials.

·         Relatively small area can be inspected at a time.

·         Only materials with a relatively nonporous surface can be inspected.

·         The inspector must have direct access to the surface being inspected.

Magnetic particle inspection is a process used in almost all heavy manufacturing industries like, graphite, iron and steel, automobiles, energy, defense and transportation. It is an important non-destructive testing method used in the manufacturing sector of heavy industries, during final inspection, process inspection, quality control, receiving inspection, maintenance and overhaul. The NDT training institute in Hyderabad and NDT institutes in Vishakhapatnam offer this valuable course for endless job opportunities in the engineering sector all over the world.

Basic Principles of Liquid Penetrant Inspection

Welcome to NDT institute Vijayawada, a premium institute which offers courses in various engineering platforms like welding, piping, quality audit, liquid penetrant testing and international inspection techniques and certification. NDT institute in Vijayawada gives an in-depth training to students from various backgrounds like refineries, petrochemical industries, power plants and fabrication industries. It also gives on the job training o methods like, radioactive testing, ultrasonic testing and liquid penetrant testing. One of these techniques taught here is the Liquid Penetrant Testing which has a great deal of scope for students to find NDT jobs in India and NDT jobs abroad.

 Liquid Penetrant Testing

Principle of LPT:

The basic principle of liquid penetrating testing is capillary action.

Capillary Action: The rise or fall of liquid in a narrow opening is called capillary action. Capillary action is action by which surface of liquid, where it is in contact with solid is elevated or depressed.

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 the "dwell," excess surface penetrant is removed and a developer applied. This acts as a blotter. It draws the penetrant from the flaw to reveal its presence. Colored (contrast) penetrant require good white light while fluorescent penetrants need to be used in darkened conditions with an ultraviolet "black light".

Steps of Liquid Penetrant Testing

The exact procedure for liquid penetrant testing can vary from case to case, depending on several factors such as the penetrant system being used, the size and material of the component being inspected, the type of discontinuities being expected in the component and the condition and environment under which the inspection is performed. However, the general steps can be summarized as follows:

1. Surface Preparation: One of the most critical steps of a liquid penetrant testing is the surface preparation. The surface must be free of oil, grease, water, or other contaminants that may prevent penetrant from entering flaws. The sample may also require etching if mechanical operations such as machining, sanding, or grit blasting have been performed. These and other mechanical operations can smear metal over the flaw opening and prevent the penetrant from entering.

2. Penetrant Application: Once the surface has been thoroughly cleaned and dried, the penetrant material is applied by spraying, brushing, or immersing the part in a penetrant bath.

3. Penetrant Dwell: The penetrant is left on the surface for a sufficient time to allow as much penetrant as possible, to be drawn from or to seep into a defect. Penetrant dwell time is the total time that the penetrant is in contact with the part surface. Dwell times are usually recommended by the penetrant producers

or required by the specification being followed. The times vary depending on the application, penetrant materials used, the material, the form of the material being inspected, and the type of discontinuity being inspected for.

Minimum dwell times typically range from five to 60 minutes. Generally, there is no harm in using a longer penetrant dwell time as long as the penetrant is not allowed to dry. The ideal dwell time is often determined by experimentation and may be very specific to a particular application.

4. Excess Penetrant Removal: This is the most delicate part of the inspection procedure, because the excess penetrant must be removed from the surface of the sample while removing as little penetrant as possible from defects. Depending on the penetrant system used, this step may involve cleaning with a solvent, direct rinsing with water, or first treating the part with an emulsifier and then rinsing with water.

5. Developer Application: A thin layer of developer is then applied to the sample to draw penetrant trapped in flaws back to the surface where it will be visible. Developers come in a variety of forms that may be applied by dusting (dry powders), dipping, or spraying (wet developers).

6. Indication Development: The developer is allowed to stand on the part surface for a period of time sufficient to permit the extraction of the trapped penetrant out of any surface flaws. This development time is usually a minimum of 10 minutes. Significantly longer times may be necessary for tight cracks.

7. Inspection: Inspection is then performed under appropriate lighting to detect indications from any flaws which may be present.

8. Clean Surface: The final step in the process is to thoroughly clean the part surface to remove the developer from the parts that were found to be acceptable.

Advantages &Capabilities:

·         Penetrant testing inspection is capable of examine the entire exterior surface in one operation even though object may have complex shape.

·         Penetrant inspection can detect very small discontinuities and penetrant bleed out magnifies apparent size of discontinuity making them easier to see.

·         Penetrant testing indications formed provide information on location, orientation and approximate length of discontinuity.

·         The process is relatively simple and rapid and can easily be automated where large volume of parts is to be inspected.

·         Penetrant testing inspection can be used on wide variety of materials including, ferrous and non- ferrous metals, ceramics, cements, glass and many types of plastics.

·         The process sensitivity can be varied by selection of materials and processing procedures. Aerosol spray cans make penetrant materials very portable. Penetrant materials and associated equipment are relatively inexpensive.

Disadvantages & Limitations:

·         Penetrant testing inspection will not reveal discontinuities that are not open to the surface. Subsurface discontinuities cannot be detected by penetrant inspection.

·         The part surface and interior of any discontinuities must be clean and free of contaminants, soils and moisture. If it is present organic or inorganic materials of the surface of the part or inside the discontinuities can interfere with penetrant entering and filling the discontinuity void.

·         Porous material or material with seeped-in penetrant that is not removed during post cleaning operations is difficult to inspect.

·         Penetrants usually contain petroleum based liquids that can soften, destruct or attack some non-metallic materials such as certain plastics and rubber.

·         Penetrants, emulsifier and developers contain chemicals that have wetting and detergent properties however they can dissolve and remove natural oil from human tissues if they come in contact with and remain on skin surfaces for a length of time. This causes drying and cracking which is a source for secondary infection.

Liquid penetrant testing taught in NDT institute Vijayawada is a very useful training, which helps lots of candidates to acquire NDT jobs in India  and  abroad.

Basics of Radiography Testing Procedure and Image Processing

Welcome to Future NDT. The world’s premier training institute for advanced courses in mechanical engineering and non-destructive training (NDT). Students from all over the world come to NDT training institute, to enroll themselves in various advanced courses like radiography, film processing, magnetic particle testing, Quality and Audit.

Here they also offer short term certification courses and training on Quality testing, ultrasonic testing, non-destructive training and range of other engineering skills.

They also conduct frequent workshops and internships for candidates from refineries, power plants and fabrication industries. NDT training institute guarantees 100 % placements for candidates, in multinational companies through their campus selection procedure.

Radiographic Testing-

Radiography-NDT training institute in Hyderabad is one of the reputed training institutes, to pursue a course in radiography.Let's take a close look at radiography process in details- Radiography is used in a very wide range of applications including medicine, engineering, forensics, security etc. At NDT training institute in Hyderabad, radiography is a skilled craftsmanship, widely used and taught  to the future trainees. Radiography testing(RT) offers  a number of advantages over other NDT methods, however, one of its major disadvantages is the health risk associated with the radiation.

In general, RT is method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials. The intensity of the radiation that penetrates and passes through the material is either captured by a radiation sensitive film or by a planer array of radiation sensitive sensors (Real-time Radiography). Film radiography is the oldest approach, yet it is still the most widely used in Non-destructive testing (NDT). There are endless NDT jobs in India to pursue a career in radiographic testing.

Basic Principles-

In radiographic testing, the part to be inspected is placed between the radiation source and a piece of radiation sensitive film. The radiation source can either be an X-ray machine or a radioactive source (Ir-192, Co-60, or in rare cases Cs-137).

This part will absorb lighter radiation compared to the thicker and denser areas, which will absorb more of the radiation. The radiation that passes through the part will expose the film and form a shadowgraph of the part.

The darkness of film (density) will vary with the amount of radiation passing through the film through the test object. The darker areas indicate more exposure (higher radiation intensity) and lighter areas indicate less exposure (higher radiation intensity).

This variation in the image darkness can be used to determine thickness or composition of material and would also reveal the presence of any defects inside the material.

Advantages and Disadvantages

The primary advantages and disadvantages in comparison to other NDT methods are:

Advantages-

• Both surface and internal discontinuities can be detected.
• Significant variations in composition can be detected.
• It has a very few material limitations.
• Can be used for inspecting hidden areas (direct access to surface is not required)
• Very minimal or no advance preparation is required.
• Permanent test record is obtained.
• Good portability especially for gamma-ray sources.

Disadvantages -

• Hazardous to operators and other nearby personnel.
• High degree of skill and experience is required for exposure and interpretation.
• The equipment is relatively expensive (especially for x-ray sources).
• The process is generally slow.
• Highly directional (sensitive to flaw orientation).
• Depth of discontinuity is not indicated.
• It requires a two-sided access to the component.

Film Processing-

Film processing is yet another useful course at NDT training institute in Hyderabad, which draws a lot of students to learn this unique procedure. One can learn film processing at NDT institute Hyderabad and apply for NDT jobs abroad. Let's get a clearer picture of this process, to start with a preliminary focus on NDT jobs in India.

As mentioned previously, radiographic film consists of a transparent, blue-tinted base coated on both sides with an emulsion. The emulsion consists of gelatin containing microscopic, radiation sensitive silver halide crystals, such as silver bromide and silver chloride. When X-rays, gamma rays or light rays strike the crystals or grains, some of the Br- ions are liberated leaving the Ag+ ions. In this condition, the radiograph is said to contain a latent (hidden) image because the change in the grains is virtually undetectable, but the exposed grains are now more sensitive to reaction with the developer.

When the film is processed, it is exposed to several different chemical solutions for controlled periods of time. Film processing basically involves the following five steps:

Development:

The developing agent gives up electrons to convert the silver halide grains to metallic silver. Grains that have been exposed to the radiation develop more rapidly, but given enough time the developer will convert all the silver ions into silver metal. Proper temperature control is needed to convert exposed grains to pure silver while keeping unexposed grains as silver halide crystals.

Stopping the development-

The stop bath simply stops the development process by diluting and washing the developer away with water.

Fixing: Unexposed silver halide crystals are removed by the fixing bath. The fixer dissolves only silver halide crystals, leaving the silver metal behind.

Washing: The film is washed with water to remove all the processing chemicals.

Drying: The film is dried for viewing.

Film processing is a strict science governed by rigid rules of chemical concentration, temperature, time, and physical movement. Whether processing is done by hand or automatically by machine, excellent radiographs require a high degree of consistency and quality control.

Radiography and film processing is widely used in NDT units of aerospace, automobiles, shipbuilding, bridges, pipelines, storage tanks, power vessel and pressure vessels.

Non-destructive Testing (NDT) is used in a wide variety of settings, especially in industries where component failure could present a significant hazard or cause severe economic loss. Industries that use it have saved millions of rupees per year in cost savings or cost avoidance.

NDT methods are used to detect flaws, leaks, determine locations and measure stress in materials.

At Future NDT, the trainees find a whole new approach towards sharpening their engineering skills for future job prospects and are able to keep themselves updated with the latest challenges, by enrolling in different certification courses and on the job training facilities provided here.