Practical demonstration from a professional with 13 years experience

Radiographic Testing Practical Video

MISTRAS CAME TO OCEAN CORP TO GIVE US A RT DEMONSTRATION.

 Here is a calculated 2 MR/HR boundary for compliance with radiation safety therefore no one get overexposed with radiation
The roentgen (R, also röntgen) is an obsolete unit of measurement for the kerma of X-rays and gamma rays up to 3 MeV. It is named after the German physicist Wilhelm Röntgen, the man who discovered X-rays. Originating in 1908, this unit has been redefined and renamed over the years.^[1] It was last defined by the US National Institute of Standards and Technology (NIST) in 1998 as 2.58×10⁻⁴ C/kg, (1 C/kg = 3876 R,) with a recommendation that the definition be given in every document where the roentgen is used.^[2] One roentgen of air kerma deposits 0.00877 gray (0.877 rad) of absorbed dose in dry air, or 0.0096 gray (0.96 rad) in soft tissue.^[3] One roentgen (air kerma) of X-rays may deposit anywhere from 0.01 to more than 0.04 gray (1 to 4 rad) in bone depending on the beam energy.^[4] This tissue-dependent conversion from roentgen to rad is called the F-factor in radiotherapy contexts. The conversion depends on the ionizing energy of a standard medium, which is ambiguous in the latest NIST definition. Even where the standard medium is fully defined, the ionizing energy of the calibration and target mediums are often not precisely known.

Radiographic Testing (RT), or industrial radiography, is a nondestructive testing (NDT) method of inspecting materials for hidden flaws by using the ability of short wavelength electromagnetic radiation (high energy photons) to penetrate various materials.
 
The beam of radiation must be directed to the middle of the section under examination and must be normal to the material surface at that point, except in special techniques where known defects are best revealed by a different alignment of the beam. The length of weld under examination for each exposure shall be such that the thickness of the material at the diagnostic extremities, measured in the direction of the incident beam, does not exceed the actual thickness at that point by more than 6%. The specimen to be inspected is placed between the source of radiation and the detecting device, usually the film in a light tight holder or cassette, and the radiation is allowed to penetrate the part for the required length of time to be adequately recorded.
The result is a two-dimensional projection of the part onto the film, producing a latent image of varying densities according to the amount of radiation reaching each area. It is known as a radiograph, as distinct from a photograph produced by light. Because film is cumulative in its response (the exposure increasing as it absorbs more radiation), relatively weak radiation can be detected by prolonging the exposure until the film can record an image that will be visible after development. The radiograph is examined as a negative, without printing as a positive as in photography. This is because, in printing, some of the detail is always lost and no useful purpose is served.
Before commencing a radiographic examination, it is always advisable to examine the component with one's own eyes, to eliminate any possible external defects. If the surface of a weld is too irregular, it may be desirable to grind it to obtain a smooth finish, but this is likely to be limited to those cases in which the surface irregularities (which will be visible on the radiograph) may make detecting internal defects difficult.
After this visual examination, the operator will have a clear idea of the possibilities of access to the two faces of the weld, which is important both for the setting up of the equipment and for the choice of the most appropriate technique.
Defects such as delaminations and planar cracks are difficult to detect using radiography, which is why ultrasonics is the preferred method for detecting this type of discontinuity.

ROV UMBILICAL

Video Monitor or video suite including a video switcher, video recorders and monitors are connected to the Surface Control Unit. The ROV's camera(s) are routed to the monitor(s).

The Hand Controller used by the ROV pilot to 'fly' the ROV as he views the video monitor and other sensor information displayed on the video overlay, is connected to the Surface Control Unit by a 5 metre lead. All of the vehicle's control functions are incorporated in the Hand Control Unit. These include camera pan and/or tilt, autopilot functions, thruster trim controls, speed, direction, dive, surface and lighting intensity. Spare capacity for additional control functions is included.

An Umbilical connects between the Surface Control Unit and the ROV. For free swimming applications a tough, flexible, polyurethane sheathed umbilical is used. The umbilical contains power conductors to the ROV as well as control signal and video conductors. Spare conductors are provided for accessories such as sonar, survey sensors, CP probes and tools.

Launch and Recovery. The umbilical cable is designed to lift the ROV during the launch or recovery stages. It can be stored on a winch fitted with a slip ring for this purpose. However some operators save the cost of a dedicated winch and use a warping drum to take the weight of the vehicle during this process. The umbilical is coiled in a figure of eight to avoid any kinking and is then led to the warping drum from which it passes over an umbilical sheave to the ROV. When the ROV has been launched and sufficient umbilical has been deployed, the umbilical can be 'stopped' by taking a reverse turn on the warping drum.

The Umbilical Sheave can be fitted to a conveniently located ship's crane, davit or 'A' frame. In order to avoid damage to the umbilical, the sheave wheel must have a greater radius than the minimum bend radius of the umbilical.

ROV CONTROLS WITH VIDEO

ROVs range in size from that of a bread box to a small truck. Deployment and recovery operations range from simply dropping the ROV over the side of a small boat to complex deck operations involving large winches for lifting and A-frames to swing the ROV back onto the deck. Some even have “garages” that are lowered to the bottom. The cabled ROV then leaves the garage to explore, returning when the mission is completed. In most cases, however, ROV operations are simpler and safer to conduct than any type of occupied-submersible or diving operation.

Remotely Operated Vehicles (ROV)

Remotely operated underwater vehicles (ROVs) are unoccupied, highly maneuverable underwater robots operated by a person aboard a surface vessel. They are linked to the ship by a group of cables that carry electrical signals back and forth between the operator and the vehicle. Most are equipped with at least a video camera and lights. Additional equipment is commonly added to expand the vehicle’s capabilities. These may include a still camera, a manipulator or cutting arm, water samplers, and instruments that measure water clarity, light penetration, and temperature. First developed for industrial purposes, such as internal and external inspections of pipelines and the structural testing of offshore platforms, ROVs are now used for many applications, many of them scientific. They have proven extremely valuable in ocean exploration, and are also used for educational programs at aquaria and to link to scientific expeditions live via the internet.

ROV at work in an underwater oil and gas field. The ROV is operating a subsea torque tool (wrench) on a valve on the subsea structure.