Gammasafe™ Radiography

Introduction

Normal radiography methods require evacuation of personnel in a wide area to allow two personnel - the radiographers- to perform their work. The Gammasafe™ method eliminates this problem.

The radiation-controlled area barriers can be set at less than 2-3 metre away from the radioactive source, even with source activities in excess of 50 Curies. Because radiography can be carried out without interfering with other operations it means that schedules can be maintained or improved and therefore huge savings can be made.

PRETECT with the help of Gammasafe™ system for carrying out radiography that supersedes the traditional methods and overcomes the problems of disruption associated with radiography.

The SAFER Small Area for Exposure Radiography developed by Gammasafe™ does not require evacuation of any personnel. This allows continuous operations to be carried out in the immediate area where radiography is being performed.

The use of radiography as an inspection method has been on the decline for some time, mainly due to its disruptive effects on other activities in the area.

The traditional method for mobile radiography normally requires the exposure of a gamma radiation source, often Iridium-192. The source is generally driven from a shielded container into an unshielded guide tube. When the source is in the guide tube the radiation emitted requires all personnel in a wide area to be evacuated. This causes severe disruption to any ongoing work in the surrounding area. It can also trigger nucleonics type instruments used in petrochemical plants, causing them to malfunction and shut the plant down.

Application

PRETECT can provide our specialist radiographers to carry out radiography on new construction work without evacuating any of your construction personnel.

Our Gammasafe™ system can also be used for corrosion monitoring or thickness checks on the existing plant. This can be easily achieved without interfering with the running of the plant - no need to evacuate personnel or drain the plant.

Our technicians can work in very close proximity to nucleonics type instruments and level indicators without causing them to malfunction.

Flexible flowline radiography has been pioneered by Gammasafe™ - multiple layers can be examined for integrity checks.

All the advantages of SAFER radiography coupled with all the advantages of digital radiography from one source - Gammasafe™.

Using the latest in computer aided design and computer aided manufacturing technologies we can design and manufacture specialist equipment to overcome your particular radiation shielding problems. We have established a good record with our many Clients in offering them solutions that make carrying out radiography in the SAFER mode possible.

Benefits

The Gammasafe™ method overcomes all these problems and significant advantages are achieved by using this new method. These are:

• Cost savings due to continuous working
• No disruption to personnel
• Maximisation of plant and capital equipment
• Overall reduction in downtime compared with ‘traditional’ radiography
• Easier to monitor barriers
• Less risk of radiation incidents
• Improvements in radiographic quality

Radiography Testing

Introduction

Radiographic Testing (RT) is a Non-destructive Testing (NDT) technique which involves the use of either X-rays or gamma rays to view, the internal structure of a component and is widely used in a variety of industrial sector including oil & gas, power generation plants, construction, petroleum, chemical and automotive, and for all types of components and parts. The technique is commonly used on welded parts, castings, forgings, composites and is also used for corrosion mapping and the assessment of wall thickness.

Types of Radiography

There are several types of RT techniques including conventional radiography and multiple forms digital radiographic testing. Each works slightly differently and has its own set of advantages and disadvantages.

Conventional Radiography

Conventional radiography uses a Radiographic film which get expose to the emitted gamma /X-rays to record an image of the part being examined. This image can then be examined for evidence of damage or flaws. The biggest limitation to this technique is that films can only be used once and they take a long time to process and interpret.

Unlike conventional radiography, digital radiography doesn't require conventional film. Instead, it uses a digital detector to display radiographic images on a computer screen almost instantaneously. It allows for a much shorter exposure time so that the images can be interpreted more quickly. Furthermore, the digital images are much higher quality when compared to conventional radiographs. With the ability to capture highly quality images, the technology can be utilized to identify flaws in a material, foreign objects in a system, examine welds, and inspect for corrosion under insulation.

The four most commonly utilized digital radiography techniques in the oil & gas and chemical processing industries are computed radiography, direct radiography, real-time radiography, and computed tomography.

Computed Radiography

Computed radiography (CR) uses a phosphor imaging plate that replaces film in conventional radiography techniques. This technique is much quicker than film radiography but slower than direct radiography. CR requires several extra steps compared to direct radiography. First, it indirectly captures the image of a component on a phosphor plate, then converts the image into a digital signal that can be visualized on a computer monitor. Image quality is fair but can be enhanced using appropriate tools and techniques (i.e, adjusting contrast, brightness, etc. without compromising integrity). It's important to know how tools, such as adjusting contrast, effect the image. Care should also be taken to make sure minor defects are not hidden after enhancements are made.

Direct Radiography

Direct Radiography (DR) is also a form of digital radiography and very similar to computed radiography. The key difference lies in how the image is captured. In DR, a flat panel detector is used to directly capture an image and display that image on a computer screen. Although this technique is fast and produce higher quality images, it is more costly than computed radiography.

Real-Time Radiography

Real-time radiography (RTR), like it's name suggests, is a form of digital radiography that occurs in real time. RTR works by emitting radiation through an object. These rays then interact with either a special phosphor screen or flat panel detector containing micro-electronic sensors. The interaction between the panel and the radiation creates a digital image that can be viewed and analysed in real time.

The brighter areas on the image are a result of higher levels of radiation that contact the screen. This corresponds to the thinner or less dense section of the component. Conversely, darker areas are a result of less radiation interacting with the screen and indicate where the component is thicker.

Aside from being able to make the images available more quickly and analyse them in real time, RTR has several other advantages. One being that digital images don't require physical storage space and thus are easier to store, transfer, and archive than film.

On the other hand, this method has several disadvantages as well. Compared to conventional radiography, RTR has a lower contrast sensitivity and limited image resolution. Images created via RTR often suffer from uneven illumination, limited resolution, a lack of sharpness, and noise. These factors have a major impact on image quality.

Application

Industrial radiography is used in the inspection of new products and welds to ensure they meet the requirements of the relevant standards of construction. New pipelines (including bends and joints), storage containers and even insulated materials are routinely inspected using radiography.

Another common use for industrial radiography is the detection and measurement of internal flaws in existing plant. The early detection of internal flaws in pipelines and plant in the oil and gas sector, for example, is essential for maintaining production flow and for the prevention of potentially disastrous hydrocarbon spills.

Detection of Corrosion Under Insulation (CUI), is another common application for radiography. Operators can pinpoint any defects without the costly and time-consuming process of removing and replacing the insulation.

Benefits

Compared to other NDT techniques, radiography has several advantages.

• Radiography is an effective tool that requires minimal surface preparation
• It is highly reproducible, Permanent record of the inspection
• Ability to inspect assembled components
• Detection of both surface and subsurface defects
• Determination of crack growth, Corrosion monitoring
• can be used on a variety of materials, Inspection capability for many types of material with varying density
• data gathered can be stored for later analysis.
• Many radiographic systems are portable, that allows for use in the field and pipe racks.