Portable Digital Radiography in NDT: Criteria and limits in the field

Industrial radiography has been, for decades, one of the most established techniques within non-destructive testing (NDT) for the evaluation of welds, critical components, and structures subjected to high mechanical integrity requirements. Traditionally, the use of radiographic film dominated inspection processes, offering high levels of resolution and reliability, albeit with evident operational limitations in field environments: prolonged development times, dependence on controlled conditions, and complex logistics for the management of consumables and waste.

Evolution of industrial radiography in the industrial field

The transition toward digital technologies, particularly computed radiography (CR) and direct digital radiography (DR), has transformed this scenario. These solutions enable the shortening of inspection cycles, enhance information traceability, and facilitate interpretation through advanced image processing tools.In contexts where asset availability is critical, such as pipe inspection campaigns in operating facilities, weld evaluation in process lines, or the control of components in service, the portability of digital systems has become a decisive operational factor for field NDT projects.

Portable digital radiography has expanded the scope of radiographic inspection in the field, integrating more effectively into maintenance programs, risk-based inspection strategies, and mechanical integrity schemes.

This advance responds to the technological maturation of the sector and to the contribution of different actors that have driven the development of detectors, acquisition systems, and image management platforms; within this ecosystem, specialized companies such as CARESTREAM NDT have contributed to bringing digital radiography from controlled environments to real applications in demanding industrial settings.

However, the adoption of these technologies raises key questions about their real scope, their operational limits in the field, and the technical criteria for selecting the most appropriate solution in each industrial scenario. Precisely, this article addresses these challenges with a practical approach, aimed at supporting technical decision-making in radiographic inspection projects under real operating conditions.

What is digital radiography in NDT?

Physical principles of digital radiography

Digital radiography in non-destructive testing is based on the same physical principles as conventional radiography: the use of ionizing radiation to generate an internal image of the inspected component without altering its integrity. The radiation is produced by X-ray sources or gamma emitters, whose energy is selected according to the thickness, density, and composition of the material to be evaluated. An inadequate selection of energy can compromise sensitivity to discontinuities or generate images with low contrast.

As the radiation beam passes through the material, it undergoes differential attenuation due to phenomena such as photoelectric absorption and Compton scattering. Local variations in density, thickness, or the presence of discontinuities (porosity, lack of fusion, inclusions) modify the attenuation pattern, creating radiographic contrast that constitutes the basis for detection. In digital radiography, this information is not recorded on chemical film, but on an electronic medium that converts the radiation into quantifiable electrical signals.

The formation of the digital image involves the capture of these signals by the detector, their analog-to-digital conversion, and subsequent processing through algorithms that make it possible to optimize contrast, sharpness, and the visualization of relevant indications. This post-acquisition adjustment capability is one of the main operational differences compared to film, where image quality is essentially defined at the moment of exposure.

Components of a portable digital radiography system

A portable digital radiography system integrates three essential elements. First, the radiation source, which may be a portable X-ray generator or an encapsulated gamma source, selected according to field constraints and penetration requirements. Second, the image acquisition systems, which may be based on Digital Detector Array (DDA) for direct digital radiography or on imaging plates in the case of computed radiography (CR), each with different implications for resolution, robustness, and workflow.

Finally, the processing and visualization station, composed of specialized hardware and software, enables technical interpretation, image storage, result traceability, and integration into inspection and mechanical integrity management systems.

Digital radiography technologies applied in the field

Computed Radiography (CR)

Computed radiography (CR) uses imaging plates or photostimulable phosphor plates as the medium for recording radiation. During exposure, the plate stores the energy of the beam attenuated by the inspected component; subsequently, the latent image is read by a laser scanner that converts this information into a digital image. This approach maintains a certain operational continuity with conventional radiography, which facilitates the transition from film in many industrial environments.

In the field, the typical operational workflow of CR includes placing the plate in the cassette, performing the radiographic exposure, transporting the plate to the reader, and subsequently visualizing and processing the image. This sequence introduces additional time compared to DR, but it is compatible with scenarios where access is limited, or environmental conditions require greater detector tolerance.

Among its practical advantages are geometric flexibility, adaptability to curved surfaces, and superior mechanical robustness against moderate impacts. Its limitations include lower image immediacy, possible progressive degradation of plates with use, and effective resolution conditioned by the pixel size of the reading system.

Direct Digital Radiography (DR)

Direct digital radiography is based on Digital Detector Arrays (DDA) or flat panel detectors that convert incident radiation into electrical signals in a virtually instantaneous manner. This technology enables real-time or near real-time visualization of the image, optimizing inspection times and facilitating immediate verification of exposure parameters and positioning. In field applications, DR provides a clear advantage when high productivity or rapid adjustments of the radiographic setup are required.

However, DDA detectors present more demanding conditions of use in industrial environments: sensitivity to impacts, vibrations, and extreme temperature or humidity conditions, as well as higher requirements for physical protection and stable electrical power supply. Their optimal performance depends on proper management of the operating environment and strict protocols.

Technical comparison between DR and CR

From a technical standpoint, DR generally offers higher effective spatial resolution and a more uniform detector response, while CR provides adequate contrast sensitivity for a wide range of industrial applications, although dependent on the reading system. In terms of portability and field logistics, CR tends to be more tolerant of adverse conditions and complex geometries, whereas DR stands out for its operational speed and immediate control of image quality. The selection between both technologies should be based on a balance between quality requirements, inspection environment, and logistical constraints of the project.

Field application of portable digital radiography (DR) using flat-panel detectors for weld and pipe inspection, enabling a streamlined digital workflow within asset integrity programs. Courtesy of Inspenet TV:

Technical selection criteria

The selection between direct digital radiography (DR), computed radiography (CR), and conventional film radiography must be based on the image quality requirements demanded by the applicable code or project specification. In general terms, DR offers a more linear detector response, a better signal-to-noise ratio, and greater repeatability, which translates into consistent image quality for the detection of fine discontinuities.

CR, in turn, provides adequate performance for most industrial applications, including routine weld inspection in piping systems, although its effective resolution is conditioned by the plate reading system. Film continues to be a historical reference in spatial resolution, but with clear limitations in traceability and post-acquisition image control.

Material thickness and the type of discontinuities to be detected are determining factors. In thicker components or high-density materials, the stability of DR response facilitates the optimization of exposure parameters, while CR offers greater geometric flexibility in inspections of circumferential welds and piping.

For volumetric discontinuities (porosity, inclusions), both digital technologies are fully competitive; for critical planar indications, the contrast consistency of DR may provide advantages. In all cases, applicability according to ISO 17636-2 must be verified to ensure that the selected technique meets the image class, sensitivity, and traceability requirements demanded by the standard.

Operational criteria

From a field perspective, inspection times directly influence the technological choice. DR allows immediate image validation, reducing rework due to positioning or exposure errors. CR introduces additional time associated with plate reading, although it maintains acceptable operability in scenarios with complex access.

Accessibility to the component is also key: the physical flexibility of CR plates facilitates placement in restrictive geometries, while DR detectors require greater care in positioning and protection. The availability of electrical power may limit the use of DR in remote locations, where CR or even film may be more viable.

Economic and productivity criteria

In terms of operating costs, digital radiography reduces recurring expenses associated with chemical consumables and film waste management, although it involves higher initial investment in equipment. The impact on plant shutdowns is usually lower with DR, as it enables faster decisions and minimizes downtime during in-line inspections.

Finally, productivity in pipe inspection and weld inspection is favored by technologies that combine rapid acquisition, result repeatability, and ease of integration into digital workflows—areas in which DR and CR solutions clearly outperform conventional radiography in most current industrial scenarios.

Summary technical comparison between DR, CR, and film in field NDT

Technical/operational criterion	DR (Direct Digital Radiography)	CR (Computed Radiography)	Film (Conventional Radiography)
Effective spatial resolution	High and consistent	Medium–high (dependent on the reader)	Very high (historical reference)
Contrast sensitivity	Very high, linear response	High, dependent on the scanner	High, fixed at development
Image immediacy	Immediate / real-time	Delayed (requires reading)	Delayed (chemical processing)
Repeatability and quality control	Very high, reproducible parameters	High, conditioned by plate condition	Variable, process-dependent
Geometric flexibility in the field	Medium (limited by detector rigidity)	High (flexible plates)	High (flexible film)
Robustness in industrial environments	Medium (requires protection)	High	High
Tolerance to vibrations and impacts	Low–medium	Medium–high	High
Electrical power requirements	Medium–high	Medium	Low
System portability	Medium	High	High
Logistics in remote locations	Medium	High	High
Recurring operating costs	Low	Low	High (consumables and chemicals)
Environmental management (waste)	Very favorable	Favorable	Unfavorable
Digital integration and traceability	Excellent	Very good	Limited
Productivity in pipe and weld inspection	Very high	High	Medium
Regulatory compliance (ISO 17636-2)	Applicable according to technique class	Applicable according to technique class	Referenced in classical standards

Critical applications of portable digital radiography

Pipe inspection

Portable digital radiography has become a key tool in pipe inspection, especially for the evaluation of circumferential welds during construction, maintenance, and repair stages. Its ability to produce high-quality images on site makes it possible to verify the integrity of the weld bead by identifying internal discontinuities that are not accessible through surface methods.

Among the most common indications assessed with this technique are lack of fusion, porosity, and inclusions, defects that can compromise the mechanical strength and in-service life of piping systems if they are not detected in time. In field conditions, its application is particularly valuable in hard-to-access sections, elevated lines, or environments where equipment mobility and fast verification are decisive to avoid delays in construction or commissioning.

Inspection of pressure vessels and structural components

In pressure vessels and structural components, portable digital radiography faces geometric limitations associated with thickness, curvature, and complex configurations of the inspected elements. Nevertheless, the possibility of flexible detector positioning, particularly with CR, makes it possible to adapt to curved surfaces and confined spaces, expanding the range of application in in-service inspections, nozzles, structural reinforcements, and critical geometric transition zones.

Integration into mechanical integrity programs

From a mechanical integrity perspective, portable digital radiography plays a strategic role within risk-based inspection (RBI) schemes and maintenance programs. Its integration with other techniques such as UT, PAUT, and surface methods enables a complementary assessment of damage mechanisms, combining volumetric and geometric information to support more robust decisions on fitness-for-service and the planning of interventions.

Limits of digital radiography in the field

Understanding the real limits of portable digital radiography in the field is just as important as knowing its advantages. In industrial environments, result quality does not depend solely on the technology, but on the interaction between the equipment, the operating environment, and project logistics. The following is a practical guide to identify and manage the main limitations.

Technical limitations

The relationship between resolution and the thickness of the inspected material defines the level of detail that can be achieved. For greater thickness or high-density materials, beam attenuation requires higher energies, which can reduce the contrast of fine discontinuities. In these scenarios, proper selection of the source, detector, and exposure geometry is critical to avoid compromising detectability.

Detector saturation is an operational risk, especially in DR, when the radiation dose exceeds the dynamic range of the system. This leads to information loss in high-exposure areas and can mask relevant indications. Strict control of exposure parameters and the use of filtering techniques help mitigate this effect.

Sensitivity to vibrations mainly affects rigid digital detectors. In structures subject to movement, wind, or nearby mechanical activity, even micro-vibrations can degrade image sharpness. Stabilizing the detector and planning inspection windows under controlled conditions are recommended practices.

Environmental limitations

Operating temperature conditions the electronic performance of detectors and battery stability. Extreme temperatures can introduce noise or intermittent failures. Humidity and the presence of dust or aggressive atmospheres pose risks to hardware integrity; therefore, the use of sealed enclosures, protective procedures, and equipment inspection routines before and after each campaign is recommended.

Logistical limitations

Physical access to the inspection point is often the main bottleneck in the field. Confined spaces, height, or complex geometries can limit optimal detector placement. System weight and ergonomics directly impact personnel safety and positioning repeatability. Finally, energy autonomy in remote locations requires prior planning of the power supply (batteries, generators), as the lack of stable power can compromise inspection continuity.

Best practice: Conducting a prior site survey that integrates technical, environmental, and logistical aspects makes it possible to select the most appropriate digital radiography configuration and reduce operational risks before deploying the equipment in the field.

Practical table: limits of portable digital radiography in the field and how to manage them

Category	Field limitation	Technical or operational impact	Best mitigation practices
Technical	Resolution vs thickness	Loss of detectability in thick materials	Adjust energy and geometry, select the appropriate detector
Technical	Detector saturation	Burned areas, loss of information	Control exposure parameters, use filters
Technical	Sensitivity to vibrations	Blurred images, reduced sharpness	Stabilize the detector, schedule inspections during low-vibration windows
Environmental	Extreme temperature	Electronic noise, intermittent equipment failures	Operate within manufacturer limits, protect the equipment
Environmental	Humidity	Risk of condensation and electronic damage	Use sealed enclosures, control environmental exposure
Environmental	Dust / aggressive atmospheres	Contamination of the detector and connectors	Sealing, preventive cleaning, equipment maintenance
Logistical	Limited physical access	Difficulty achieving proper detector positioning	Prior site assessment, use of mounting accessories
Logistical	System weight and ergonomics	Operator fatigue, risk of accidents	Select portable equipment, use supports and fixtures

Radiation safety in portable digital radiography

Radiation safety in the field is not an operational add-on: it is a critical requirement that conditions the technical, legal, and reputational viability of any intervention using portable digital radiography. Poor management of radiological risk exposes personnel, third parties, and the organization to severe consequences. The following is a high-value practical guide for operating with robust safety criteria in real environments.

Management of controlled areas in the field

The delimitation of exclusion zones must be based on dose calculations and the actual exposure geometry, considering factors such as beam energy, exposure time, and the presence of reflective structures. In the field, these zones are dynamic and require re-evaluation each time the radiographic configuration is modified. Access control and signage must be visible, unambiguous, and adapted to the environment (construction sites, operating plants, open areas). The use of physical barriers, demarcation tapes, warning lights, and dedicated spotters reduces the risk of accidental intrusion during exposure.

Radiation protection of personnel

Individual dosimetry is mandatory for all occupationally exposed personnel. The use of passive dosimeters and, where applicable, electronic real-time dosimeters makes it possible to monitor accumulated dose and verify compliance with occupational limits. Safe operating procedures must be documented and applied systematically: prior area verification, control of exposure times, use of collimators and portable shielding, and validation of the absence of people in the controlled area before each exposure.

The training of certified personnel is a critical risk-control factor; technical competence in NDT alone is not sufficient without a clear understanding of radiation protection principles and individual responsibility for equipment and environmental safety. In this context, radiation safety certification (IRRSP) becomes a key requirement for operators and supervisors involved in industrial radiographic testing in field environments..

Regulatory compliance and area control

Compliance with applicable regulatory frameworks requires knowing and applying national and international radiation protection regulations, as well as the specific requirements of each jurisdiction for the use of radiation sources in the field. Permits, licenses, and audits are part of the normal operating cycle and must be managed proactively to avoid project interruptions. Finally, traceability and documentary evidence, exposure records, authorizations, equipment calibrations, and safety reports, are essential both for internal control and for demonstrating compliance to clients and authorities.

Regulatory requirements and applicable standards

In portable digital radiography, the value of a good image is not demonstrated “by eye,” but through verifiable regulatory compliance. In industrial projects, parameter traceability, the applied technique class, and evidence of image quality are what make a result acceptable and defensible before clients, audits, and regulators.

ISO 17636-2: digital radiography in welds

ISO 17636-2 is the central reference when digital radiography (DR and CR) is used for weld inspection. Its technical scope is aimed at standardizing how image quality is obtained and how it is demonstrated in digital systems, avoiding variability between equipment, operators, and field conditions.

One of its key contributions is the definition of image quality classes, which in practice function as “levels of stringency” for the radiographic technique. This not only impacts on the detectability of indications, but also the way compliance is documented (what to verify, how to record it, and what evidence to retain).

In digital radiography, the standard emphasizes parameters typical of the digital environment, such as quality verification using image quality indicators (IQI), control of sharpness/geometric unsharpness, and metrics associated with noise and contrast that make it possible to demonstrate that the system is within valid conditions for interpretation.

With regard to minimum acquisition parameters, the practical approach is to: (1) ensure geometry and distance that control unsharpness, (2) select energy/time to achieve sufficient contrast without saturating the detector, (3) maintain traceability of the “setup” (source, detector, position, technique, identifications), and (4) record objective quality evidence before releasing the interpretation.

Integration with industrial codes

In the field, ISO 17636-2 rarely “lives alone.” Its application is usually integrated with industry codes and acceptance practices such as ASME (weld fabrication and evaluation), API (integrity of in-service equipment and piping), and formal mechanical integrity systems. The key is to understand the separation between:

• Technique / image quality standard (how you obtain a valid and demonstrable image: this is where ISO 17636-2 applies).
• Acceptance/rejection criteria (which indications are acceptable according to the applicable code and the service of the equipment: this is where ASME/API and client specifications apply).

The direct implication for industrial projects is clear: you may have a “nice-looking” image, but if it is not qualified, recorded, and aligned with the contractual code or acceptance criterion, the result can be challenged. Therefore, in portable digital radiography, a senior best practice is to ensure from the outset the documentary “map”: procedure, technique, evidence of image quality, traceability, and the acceptance criterion applicable to the asset and its service condition.

Role of technology providers in the adoption of digital radiography in NDT

Technological ecosystem and maturity of industrial digital radiography

The sustained adoption of digital radiography in NDT applications is not solely the result of a change in image format, but rather the consequence of the progressive maturity of a complete technological ecosystem that integrates hardware, software, and working methodologies.

Over the past two decades, digital detectors have evolved in terms of sensitivity, dynamic range, and operational stability, while acquisition and processing platforms have incorporated advanced capabilities for contrast management, noise reduction, traceability, and secure image archiving. This progress has enabled digital radiography to move from controlled laboratory environments to field operating scenarios, where conditions of temperature, humidity, vibrations, and accessibility impose additional demands on system performance.

In this context, the need for robust field-ready solutions has become a key selection criterion for industrial users. Detector reliability, software stability in the face of interruptions, ease of integration with inspection workflows, and the ability to withstand intensive duty cycles determine whether a technology is truly viable for construction, maintenance, or in-service inspection projects. Digital radiography applied in the field therefore requires not only metrological performance, but also design oriented toward real industrial operation.

CARESTREAM NDT as a technological player in industrial digital radiography

Within this ecosystem, CARESTREAM NDT is part of the group of technology players that have had a presence in the development and standardization of digital radiography solutions for industrial applications. Its historical participation in the field of radiographic imaging has contributed to the consolidation of platforms in both computed radiography (CR) and direct digital radiography (DR), facilitating the technological transition in sectors where conventional film radiography was the dominant standard.

The contribution to the advancement of CR and DR in demanding industrial environments is reflected in the sector’s emphasis on improving system robustness, acquisition stability, and interoperability with normative procedures. In line with current industry demands, the focus on operational reliability, digital traceability of results, and compatibility with technical standards has been an enabling factor for digital radiography to be today a technically defensible and operationally viable alternative for NDT field projects, beyond the controlled laboratory environment.

Critical factors for implementing portable digital radiography in industrial projects

The effective implementation of portable digital radiography in industrial projects does not depend solely on acquiring technology, but on aligning technical decisions, human capabilities, and information management with real operating conditions. When these factors are not addressed in an integrated manner, the potential of the technology is diluted, and the expected benefits do not materialize in terms of reliability, productivity, and regulatory compliance.

Selection of the appropriate system (DDA, CR, power)

The choice between DR with Digital Detector Array (DDA) and CR with imaging plates must respond to the specific demands of the project. In high-throughput inspections, where rapid image validation and the reduction of rework are critical, DR offers clear advantages due to its immediacy. In scenarios with limited accessibility, complex geometries, or aggressive environments, CR provides greater flexibility and mechanical tolerance.

The power and type of source (X-rays or gamma) must be selected according to the thickness, material, and type of expected discontinuity, avoiding oversizing the energy, which can compromise contrast or unnecessarily increase radiation safety requirements. A good practice is to perform qualification trials under representative conditions before full-scale field deployment.

Personnel training and digital image interpretation

The transition to the digital environment requires a step change in NDT personnel competencies. Training is not limited to equipment operation, but includes understanding acquisition parameters, image quality control, management of digital artifacts, and responsible use of post-processing tools. The interpretation of digital images requires consistent criteria to avoid both underestimation of real indications and over-interpretation of noise or artifacts. Internal standardization of interpretation practices and cross-checking among inspectors help maintain technical consistency of results.

Data management, traceability, and reporting

Data management is a cornerstone of digital radiography. Structured image storage must ensure integrity, security, and long-term availability, with version control and backups. Integration into mechanical integrity management systems allows radiographic results to feed condition assessments, RBI analyses, and evidence-based maintenance decisions. Finally, traceability and reporting, records of exposure parameters, asset identification, evidence of image quality, and document control, are essential to respond to technical and regulatory audits, ensuring that each result is defensible from both a technical and regulatory standpoint.

Technological trends in digital radiography for field NDT

Digital radiography applied in the field is entering a phase of technological maturity marked by the comprehensive digitalization of processes, improvements in equipment robustness, and the progressive incorporation of software-assisted analysis tools. These trends not only affect how images are acquired, but also how they are managed, interpreted, and converted into operational decisions within asset integrity programs.

Digitalization of the inspection workflow

The digitalization of the inspection workflow goes beyond replacing film with a detector. It involves integrating image acquisition with data management platforms and structuring the entire digital workflow of inspection, including automatic traceability of exposure parameters, digital identification of components, and the generation of structured reports.

In the field, this translates into reduced manual errors, greater consistency in documentation, and the ability to make technical decisions in shorter timeframes, especially in projects with limited intervention windows. Connectivity between acquisition equipment and corporate management systems allows radiographic results to directly feed maintenance processes, risk-based inspection, and quality control.

Advances in more robust digital detectors

Digital detectors are evolving toward greater tolerance of real industrial conditions. Improvements are being seen in encapsulation, impact resistance, thermal stability, and protection against humidity and dust, factors that are critical for deployment in operating plants, construction sites, or remote locations. In parallel, parameters such as dynamic range, quantum efficiency, and noise reduction are being optimized, expanding the spectrum of viable field applications without compromising image quality. This increased robustness narrows the historical gap between laboratory performance and operational reliability in demanding industrial environments.

Integration with software-assisted analysis and automation

The incorporation of software-assisted analysis is transforming the interpretation stage. Tools for contrast enhancement, assisted indication detection, and image quality verification help standardize criteria and reduce exclusive dependence on individual experience.

In parallel, partial automation of workflows, from acquisition to preprocessing and report generation, contributes to improving productivity and result consistency. Although final interpretation remains the responsibility of certified personnel, these technologies act as technical support that strengthens the reliability of the radiographic inspection process in the field.

Conclusions

Portable digital radiography has moved beyond being a technological promise to become a strategic tool within modern inspection and mechanical integrity management programs, redefining how radiographic testing is executed in real field environments. Its ability to reduce inspection times, improve information traceability, and support on-site decision-making has transformed how welds, piping, and critical components are evaluated in real industrial environments. However, this potential is only realized when the balance between the technology’s technical capabilities and its operational limits in the field is properly understood and managed.

Proper technology selection, between DR, CR, or, in specific cases, film, is not a generic decision, but a contextual choice that must respond to material thickness, the type of expected discontinuities, environmental conditions, site logistics, and applicable regulatory requirements. Choosing the right technology for the wrong scenario can compromise both result quality and project efficiency.

From a mechanical integrity perspective, portable digital radiography delivers value when it is coherently integrated into RBI strategies, maintenance plans, and asset management systems, complementing other NDT techniques to build a more complete picture of equipment condition. Finally, operational reliability and regulatory compliance are the pillars that sustain the technical credibility of results: without qualified procedures, documentary traceability, and rigorous radiological control, even the best technology loses legitimacy. It is within this balance between technology, technical judgment, and operational discipline that the true impact of digital radiography in the field is defined.

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