NDT Film Processors
Our NDT film processor is designed to provide high quality processing of your NDT film. We can operate with film from all leading suppliers such as Kodak, Fuji and Agfa.
- Framework in pure aluminium to give a robust machine
- Tanks in stainless steel to prevent cracks – even in harsh conditions
- Double overflow in each side of the tanks to prevent spills and splashes in mobile conditions
- Automatic refilling system for the processing tanks
- Cascade fixer replinishing unit to reduce silver waste in the water tank (on request)
- Easy-to-use control panel that can store up to 6 different pre-programmed development jobs
Please see the following video to get a step by step instruction to the different functionalities that our NDT film developer offers:
What is the purpose of an NDT film processor?
It is imperative to process an X-ray film after it has been exposed, in order to procure a visibly permanent radiographic image that can be kept for years without deterioration. Processing forms a visible image from a latent image. Processing incorporates myriad procedures to form a permanent image, such as developing, rinsing, fixing, washing and drying procedures.
Many people employ set exposure factors to reach the desired density on a radiograph, and only adjust the development time to make up for over or under exposed images. However, with the advancement of technology, the development settings can easily be changed in the build-in control panel on our EG430NDT film processor. You may use an NDT exposure calculator to determine the correct factors, depending on the situation.
You can garner higher productivity and better consistency in the developer by decreasing the processing variables. NDT films provide a relatively stable speed and a stable contrast over a greater range of developer temperatures, as opposed to older film technologies that provide variable speed, relative to immersion time and developer temperature.
Timer and Thermometer
The Thermometer and timer are absolutely vital instruments. They must be in top-notch condition and highly accurate to begin with.
Handling of Film
The film should never be bent. When carrying, the film should only be handled at the edges to avert abrasions and finger prints.
Our NDT film processing equipment can develop films from any manufacturer, so we do not give recommendations as such. However, we have written this article about film development on the basis of KODAK INDUSTREX Single-Part Replenisher and Developer. The purpose is to give an introduction to the complexity of this area and to give a better understanding of the importance of using high-quality equipment in the stage where you process the xray/radiographic film.
Use KODAK Indicator Stop Bath or any acetic acid stop bath mixed at a 3% solution (mix KODAK 28% Acetic Acid at 110 ML/L). The stop bath should be used for 30 seconds. The stop bath controls development by thwarting most streaking or spotting, and thus protracts the life of the fixing bath.
“KODAK Rapid Fixer” or “KODAK INDUSTREX LO Fixer and Replenisher” is a viable option.
LATENT IMAGE FORMATION
The latent image is formed by the ionization of the exposed silver bromide crystals before the processing occurs. The bromide crystals interact with Campton, and the photoelectric interaction knocks out the electrons. After the film is exposed, a physical change occurs. Within the emulsion, the X-ray photons hit the silver bromide crystals. As a result, minute traces of silver ions are formed on the surface of the crystal. The bromine gas is emitted and is absorbed by the gelatin.
Crystals are purposely constructed with electron traps (sensitivity specks) consisting of sulfur impurities but also because of the addition of silver iodide. Electrons are trapped by the sulfur in the sensitivity specks giving it a negative charge. When this situation is created a latent image is produced in the film emulsion.
As a result, Silver bromide Silver ions + Bromine ions are formed. The deposition of free (ionized) silver ions forms the latent image. These free ions cannot be detected or seen by any physical test devised as yet. It remains in the emulsion of the X-ray film until it is changed into a visible silver image by chemical processing procedures. The free electrons move through the crystal until they are attracted to a sensitivity site where they become trapped and impart a negative charge to the site.
PROCESSING THE EXPOSED FILM
Exposed radiographs incorporating a latent image are highly sensitive to light energy, and should be processed as quickly as possible. The film packets should be opened only under safe-light conditions or in a darkroom. The first solution in the film processing is the developer solution. The developer precipitates metallic silver in the emulsion layer, removes the halides, and donates electrons, to chemically diminish the presence of energized ionized silver bromide crystals. The positively charged silver ions are attracted by the negative charge, and are reduced to black metallic atoms. The black areas on the radiograph correspond to the precipitation. The concentration of the developer consequently weakens with the time by oxidation of the developer by exposure to air and the numbers of films processed.
Swollen and soft gelatin emulsion forms on the film after it is removed from the developer. This emulsion incorporates chemicals which must be removed by exposing the film to a water bath. Rinsing the film in moderate water thwarts the development reaction, removes any soluble chemicals, and diminishes the alkalinity of the residual developer. Because the unexposed silver halide crystals are water insoluble, they cannot be washed away and remain intact on the film.
It is prudent to match the temperature of the water bath to that of the fixer and developer to avert any uneven contraction and expansions of the emulsion layer, also known as reticulation. If the temperature was different, the film would retain the alkaline developer, which would neutralize the more acidic fixer. This would in turn impair the hardening and fixing action of the fixer and the radiograph would be contaminated with brown stains within a few weeks.
In addition, since the gelatin layer is soft when set, the film is prone to scratching. Thus, when locating the film from the developer tank first to the wash tank and later to the fixing tank, safe-light conditions must be ensured to avoid fogging. During automatic processing on equipment such as ours, the chemicals are removed from the film by squeegee rollers, and thus the film can be transferred from the developer tank directly in to the fixer, without passing through the rinsing stage.
The film appears milky when placed in the fixing solution due to the presence of residual silver bromide crystals. However, after both the film faces are completely rinsed by the solution, and are moderately agitated, the milky appearance would gradually alleviate. The acidifier within the fixer neutralizes any lingering alkaline developer and thwarts any on-going development action. However, because the gelatin is still porous and swollen, the clearing agent tries to dissolve any undeveloped silver bromide crystals, and leaves the developed silver image untouched. This is known as the clearing action.
After the clearing action abates, we move on to the hardening action. The hardening action is caused by the hardening and shrinking of the silver image containing gelatin emulsion. This action is highly imperative because it impedes any considerable swelling of the emulsion in the later washing stages. The processing room should be devoid of any white light until the film becomes entirely clear, since the presence of white light can clog and streak the film.
Several factors determine the duration of the fixing process, such as the emulsion thickness, number of films being fixed, the surface area of the film being fixed, the amount of film agitation, the temperature of the solution, and the nature and strength of the fixer. The film should at least remain in the fixing solution until it is cleared and hardened. Ideally for best results, the fixing time should be around 3 times as long as needed to clear and harden the film.
To eliminate any lingering fixer chemicals, such as silver salts and thiosulphate, from the film, a final wash is vital. If the film is not washed adequately in the NDT film processor, the unwashed residual chemicals can cause browning and spotting of the film, a few weeks down the road. Furthermore, if the temperature of the final wash exceeds that of the fixer or developer by more than 15 F, the emulsion layer becomes vulnerable to reticulation, or the uneven shrinkage and swelling of the layer. In addition, washing for more than the recommended time also softens the emulsion layer and makes it prone to scratching easily.
In some development studios where development is done manually, the professionals dry the films by hanging them in a darkroom on a rack, and catch the runoff water by using a drip tray, while others dry the films by placing them under fans. In our automatic film processor, the film is dryed automatically as part of the development process. This is done by a build-in cabinet dryer, equipped with heating elements and a fan.
The pulp, or the areas of the films with a lower density, allows a higher penetration of X-rays, and therefore more X-ray particles can reach that zone of the film. Thus these X-ray particles can energize a greater number of silver bromide crystals and would help to precipitate more silver, producing a radiolucent or black outline around the pulp. The thicker areas of the film, those that received considerably lesser rays, would be subjected to smaller amounts of radiation and would contain lesser silver precipitate. As a result, they appear less gray.
FINAL WORDS ABOUT PROCESSING NDT FILMS
As you can see, processing xray/NDT films is a complicated task, for which you need high-end equipment. At Echo Graphic, we produce processors specifically designed for development of NDT/xray films. Our machinery can work with radiographic film from any brand such as Kodak, Fuji and Agfa.