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.