Analysing and interpreting the results of radiographic tests
Overview
This standard identifies the competences you need to analyse and interpret radiographs generated from radiographic testing, in accordance with approved procedures and techniques. This will require you to obtain all relevant information about the test areas of the products/components, the acceptance criteria and radiographic technique to be followed, to ensure a valid outcome. You must ensure that image viewing conditions are correct, and you will be expected to check the image quality and to interpret the radiographic images against the background of the information obtained. You will identify the types of defect/flaws present, their location and relevant dimensions. You will then need to compare your findings with the acceptance criteria, and draw appropriate conclusions as to the condition of the products/components. The term radiography is used in this standard and can include real time radiography or computed tomography (CT scanning) methods. Also the term radiographic testing can mean using either photographic film or digital detectors.
Your responsibilities will require you to comply with organisational policy and procedures for the radiographic analysis and interpretation activities undertaken, and to report any problems with these activities or with the equipment in use that you cannot personally resolve, or are outside your permitted authority, to the relevant people. You will be expected to work with a minimum of supervision, taking personal responsibility for your actions and for the quality and accuracy of the work that you undertake.
Your underpinning knowledge will show a good understanding of your work, and will provide an informed approach to the inspection of products/components using radiographic testing techniques. You will have a sound understanding of radiographic principles, the nature and characteristics of ionising radiation. Also your knowledge will include the use of digital and computer radiography methods. Image formation on radiographic film/detectors and the effect of product/component geometry, radiographic practice and image processing on a range of image media and quality will all be key issues. You will understand the principles and practice of the interpretation process, in particular the appearance of defects/flaws on the image and the safe storage/archiving requirements of the radiography images in use. You will have an understanding of the product/component manufacturing process, especially that related to the incidence of defects/flaws. You will know the criteria of acceptance for the products/components, the influence of the defects/flaws on the products/components in service, and the consequences of their failure.
As you may be required to work in controlled areas, an understanding of radiographic practice will be a key feature, with special reference to hazards and safe working practice. You will be required to demonstrate safe working practices throughout, and will understand the responsibility you owe to yourself and others in the workplace
Performance criteria
You must be able to:
- work safely at all times, complying with health and safety legislation and other relevant regulations, directives and guidelines
- ensure that you have the necessary test data on which to conduct the analysis
- resolve promptly any inconsistencies in the data
- analyse the data using approved methods and procedures
- check that the data analysis is accurate and thorough and takes account of the test conditions
- compare the analysis against the product or asset specification and identify any faults or variations from specification
- record the results of the analysis, and complete test documentation in the appropriate format
Knowledge and Understanding
You need to know and understand:
- the specific safety precautions to be taken when working in radiographic Controlled Zones
- the regulations and codes of practice to be followed when working in radiographic testing areas
- the type(s) of personal protective equipment (PPE) to be used, and how to obtain it (such as protective clothing, personal dosimeters, radiation survey meters, barriers and screens, warning signals, visual indicators and alarm systems)
- procedures to be adopted in the case of accident and emergency/incidents involving radioactive sources
- the set-up and requirements of a Controlled Test Zone (such as the identification and marking of boundary exclusion zones, the erection of physical barriers, warning lights and visual signs to restrict unauthorised entrance, the siting of radiation survey meters, the positioning of appropriate radiation screens)
- the basic principles of radiographic testing (including the use of X-ray and gamma radiation as a penetrating agent; shadow effect and projection, and the capture of the image; developing, accruement, fixing, storing and the equipment used to view the images)
- the sources of radiation used in radiographic testing activities (to include the X-ray tube (generator) and the use of radioactive isotopes)
- the principles of real time radiography, computed tomography and digital processing of X-rays
- image formation (including rectilinear propagation; the geometry of shadow projection, inverse square law, focal spot, formation of penumbra and image quality indicators (IQIs))
- the types and selection of radiographic films or digital detectors and the image processing/manipulation systems
- processing faults, characteristic curves, and the effect of developing conditions on the finished image quality
- the storage/archiving facilities for the radiograph images both photographic and digital
- radiographic image quality (to include sensitivity, density, contrast and definition and the effect of scattered radiation on the image)
- the response of product/component defects/flaws to penetrative radiation, and the resulting image density
- the types of defect/flaws that are detectable using radiographic testing methods
- how to interpret the images and the appearance of various defects/flaws; spurious images and their cause and effect; assessment of defect/flaw size and location
- the conditions in which the images should be viewed (to include ambient conditions, use of appropriate light box or digital projection)
- acceptance criteria to be used for the product/component, and the level of defects/flaws that are acceptable
- the influence of defects/flaws on service and performance; the risks and consequences of product/component failure
- why it is critical that records of radiographic testing on the products/components are accurate, comprehensive and maintained legibly
the person that you need to pass the inspection records to
the extent of your own responsibility, and whom you should report to if you have problems that you cannot resolve
Scope/range
Ensure that you have the necessary test data on which to conduct the analysis, to include obtaining all of the following:
- relevant product/component information
- material of construction
- acceptance criteria to be used
- area of product/component being examined (geometries and thickness)
- radiographic parameters and testing conditions
- type of image quality indicator (IQI) to be used
- film/detector type
- processing conditions
Ensure the viewing area has the correct conditions, to include all of the following:
- appropriate subdued internal light
- correct ambient conditions
- suitable light box for viewing or digital projectors
Ensure that the radiographic image quality meets specified image quality indicator (IQI) requirements, to include all of the following:
- image quality
- sensitivity
- contrast
- density
Interpret the radiographs from one of the following product groups:
- welded joints
- castings
- wrought products or materials (such as forged, rolled, extruded)
- cold formed products (such as by bending, pressing, rolling)
- heat treated components
- structures (such as airframes, lifting beams, pressure vessels)
- other specific products
Interpret the radiographs and identify all of the following, as appropriate:
- defect/flaw type
- location of the defect/flaw
- dimensional size of the defect/flaw
Compare the analysis with the acceptance criteria, and record all of the following in the NDT report:
- personal data (such as details of radiographer, date of test)
- product identification
- material of construction
- geometry, thickness and surface condition in the test area
- test area identification (where indications are found)
- test equipment settings and parameters
- film/detector processing systems
- ambient testing conditions
- defects/flaws identified
- comparisons with acceptance criteria
- conclusions reached
Follow the correct procedure to deal with products which fall into three of the following categories:
- components, materials or structures which meet the specification
- components, materials or structures with identified defects/flaws
- components, materials or structures requiring further investigation
- components, materials or structures requiring other inspection methods
Complete the radiographic testing activities, to include carrying out all of the following:
- marking up defective/flawed products/components with all relevant information
- recording all the required details of the test in the appropriate format
- handing over the test details / NDT report to the appropriate people
Scope Performance
Scope Knowledge
Values
Behaviours
Skills
Glossary
Discontinuity – Any imperfection in the material / component / structure
Flaw – A significant discontinuity to be recorded but within specified limits and tolerances
Defect – A flaw outside specified limits and tolerances causing the material / component / structure to be non-compliant and rejected