Industrial Radiography: Buying and Evaluation Guide

Requests for quotation often arrive with a single line: "digital X-ray system for welds". No serious supplier can price anything comparable from that. The thicknesses are missing, and so are the product standard, the testing class and the annual volume. Above all, the figure that decides whether the investment makes sense is missing: what each exposure costs today, from loading the film to the signed report.

Anyone buying an industrial radiography system, or upgrading a room that still runs on film, needs to reach the supplier with those numbers in hand. They drive the choice between film, computed radiography (CR) and digital detector arrays (DR), the sizing of the source and, before the order is signed, a realistic picture of the radiation protection work ahead. Without them, people buy on list price. In radiography, the list price tells you very little.

Film, CR or DR: three different ways of running the room

Film is still the historical reference for resolution and for acceptance in specifications, but it brings chemical processing, spent-bath disposal, waiting time and a physical archive that grows every year. CR replaces film with reusable photostimulable phosphor plates that a scanner reads after exposure: very little changes in the exposure room, while the darkroom and the chemistry disappear. DR uses flat-panel arrays, mostly a scintillator coupled to amorphous silicon or CMOS readout as described in ASTM E2698-26, which deliver the image within seconds with no read-out step. It costs more. And a rigid, fixed-format panel copes less well with curved geometries.

The standards run in parallel. For welds, ISO 17636-1:2022 covers the film technique and ISO 17636-2:2022 the technique with digital detectors, both CR and DDA; for metallic materials in general, ISO 5579:2013 sets the basic rules, but for film only. The digital part of ISO 17636 calls for images whose detection sensitivity is equivalent to film. So the move to digital is justified by volumes, reporting time and archiving. Never by accepting lower image quality for convenience.

When going digital pays back, and when it's worth waiting

The signs repeat from one company to the next. Film volume is steady and predictable, customers want the report the same day, the film, chemistry and disposal line keeps growing, and someone starts asking for images in electronic form, perhaps in DICONDE, the interchange standard described in ASTM E2339-21. When two or three of these conditions stack up, the conversion deserves a proper calculation.

CR is often the least disruptive first step, because it leaves most of the operators' working method and positioning fixtures untouched. DR becomes the stronger choice when productivity per shift is the constraint: repetitive parts, series castings, in-line inspection. The reverse holds just as firmly. With low, irregular volumes, film or an outside laboratory can remain the more rational option for a few more years.

A typical case: a fabrication shop moving from film to CR

Take a shop inspecting butt welds on steel pipe from 6 to 20 mm wall thickness, with a portable X-ray tube already in use and already licensed, one shift a day and about 30 exposures a day over 220 working days. These are our assumptions, chosen to keep the arithmetic readable, and they add up to roughly 6,600 exposures a year. At that volume, every euro saved on a single exposure, across film, chemistry, disposal and darkroom minutes, is worth about 6,600 euros a year to set against the annual share of the investment. At 1,500 exposures the same euro is worth less than a quarter of that. The picture can then flip.

Some things stay where they are. The source is the same, so the licensing regime normally doesn't change just because the detector does; it's still wise to involve the radiation protection expert, since exposure times and geometries will shift. The testing class required by the specification and the operators' certification also stay, although operators need training on screen reading and plate handling. What changes is how the system is checked: with CR, beyond the IQIs on each image, the scanner needs periodic performance and stability tests such as those in ASTM E2445/E2445M-20. Plate life depends heavily on handling, so ask the supplier for it in writing, together with the conditions it refers to.

The requirements that set the configuration, before you ask for a quote

Before comparing two offers, fix the application requirements, because they determine the configuration. The table lists the ones that move a quote the most.

If the table is filled in with precise values, two offers can be compared line by line. If cells stay empty, the supplier will fill them with assumptions of its own, and the comparison slides back to price.

X-ray tube or gamma source: thickness, logistics, licensing

An X-ray tube emits only when powered, lets you adjust voltage and current to the part, and suits fixed stations, shielded enclosures and production lines. Gamma sources use sealed radioisotopes; they are compact and need no power, so they work well on site and in tight spaces, but they emit continuously and come with strict rules for custody, transport and storage. They also decay. IAEA guide SSG-11 (2011) gives half-lives of about 74 days for iridium-192, 120 days for selenium-75 and 5.3 years for cobalt-60, with typical steel thickness ranges of 12-70 mm, 8-30 mm and 50-120 mm. An iridium source therefore has to be replaced periodically, often more than once a year, and that recurring cost belongs in the calculation.

The practical criterion starts from thickness and access to the part. Gamma makes sense on site, on pipework already installed, or on thicknesses a portable tube can't reach. For repetitive inspection in a controlled environment the tube is generally preferable, partly because adjustable energy helps contrast on medium and thin sections, and SSG-11 itself recommends radiography in shielded enclosures whenever reasonably practicable. Energy also matters for the detector: a DR panel must be chosen for the energy range it will work in, and ASTM E2698-26 notes that some of its tests may not apply above 450 kV.

Total cost of ownership is read per exposure

Purchase price is the most visible item, and often the least decisive. The right comparison is the full cost per exposure, over the same horizon the company uses to depreciate capital equipment: the annual share of the investment, maintenance and periodic checks, training, radiation protection duties, consumables and operator time per image.

Each technology spreads these costs differently. Film asks little up front and a lot per exposure, in sensitive material, processing chemistry and disposal. CR raises the investment and lowers consumables, but adds a scanner, plates that wear and need replacing, and system checks. DR concentrates spending on the panel and cuts variable cost and idle time, provided volumes keep it busy; a dropped or damaged panel, on the other hand, is a cost film never has. Break-even therefore depends almost entirely on annual exposures, and it's the typical case above, redone with the company's real numbers.

Radiation protection: what the employer must do before the first exposure

The employer carries the first obligation. In Italy the framework is Legislative Decree 101 of 31 July 2020, which transposes Directive 2013/59/Euratom and was later amended by corrective Decree 203/2022; elsewhere in the EU the same directive is transposed by national law, with its own procedures. The Italian decree requires the employer to ensure physical surveillance through a radiation protection expert (art. 128), who cannot be the employer or the person running the activity. The expert reviews the installation design in advance, performs its first verification and classifies areas and workers in a written report, with assessments at least once a year (arts. 130 and 131).

The licensing regime depends on the source, and this is where the purchase meets the paperwork. Prior authorisation (nulla osta) applies to practices using generators in which the maximum energy of accelerated particles exceeds 200 keV, and to radioactive materials above the activity thresholds set by the decree (art. 50), thresholds that gamma radiography sources normally exceed. A 160 kV system and a 225 kV system can therefore follow very different paths. Where no authorisation is needed and no exemption applies, the practice must be notified at least thirty days before it starts (art. 46). These lead times belong in the schedule before the order is signed.

Personnel qualification sits alongside radiation protection. ISO 9712:2021, adopted in Europe as EN ISO 9712:2022, defines three certification levels per method; in aerospace, qualification normally follows EN 4179. A certified operator who has always read film still needs training to interpret CR or DR images on screen, and that training belongs in the budget.

Buy, rent or use an outside laboratory

Buying isn't always the answer. With occasional inspections, seasonal peaks or pilot projects, a qualified outside laboratory can cost less and also takes most of the radiation protection duties off site; renting, by contrast, leaves them with whoever operates the equipment. Buying becomes the natural choice when volumes are steady, when in-house inspection genuinely shortens delivery times, or when component confidentiality argues against parts leaving the plant.

Here too the decision comes from comparing total cost of ownership with the cumulative cost of the alternative over the same years, with an exit condition that works both ways. If after twelve months of outsourcing exposures stay consistently above the calculated break-even, it's time to reopen the purchase file. If an in-house system runs well below it, the laboratory comes back into play.

From order to commissioning: where the months go

A well-run purchase follows a set order. It starts from the application requirements, which produce the configuration and the quote; then come layout and shielding, in parallel with the expert's design review, the notification or authorisation, and operator training. Before production use, image quality is verified with IQIs on the actual technique and the digital system's reference values are recorded, to be checked again at every periodic test.

The mistakes that stretch lead times nearly all share one root: decisions taken before the requirements are known. Technology gets chosen on purchase price rather than cost per exposure, the configuration is defined before thickness, material and testing class are fixed, and only after the order does someone find that the chosen generator needs authorisation or that the existing enclosure can't handle the new energy. Last, and often the most expensive, comes archiving: software that can't export to an open format ties the company to one supplier for years. Shielding, authorisations and qualifications can weigh on the schedule as much as hardware delivery. Planned from day one, they stop being surprises.

What to send the supplier for a quote you can compare

A useful evaluation needs only a few data points, as long as they are precise:

• minimum and maximum thicknesses, materials and part geometries;
• product standard, testing class (A or B) and required acceptance level;
• exposures per shift or per year, today and in three years;
• working environment: existing enclosure, site work or production line;
• source already in use and its licensing regime;
• archiving, data format and traceability requirements.

With these, the choice between film, CR and DR can be steered, the source sized and the regulatory duties estimated, leading to a coherent quote instead of a generic price list. Available technologies and configurations are described on the dedicated industrial radiography page, and the head-to-head between the two digital routes is covered in the CR and DR article. If your annual exposures sit close to break-even, the next step is sizing on real data, which PITECH prepares as a tailored quote within 24 hours.