If we talk about petroleum refinery and processing, the casing inspection is one of the important factors to be done once in certain period. A casing inspection is the process to observe the integrity of the casing or tubing to find holes, cracks, or corroded spots and fluid entry or exit points that should not be there. This process is also meant to scale bacteria buildup, which can influence the flow of hydrocarbons from the wellbore. Casing inspections is very important, moreover to the industry related to oil and gas, energy, process and chemical sectors. Storage tanks hold the raw materials which is essential to these industries processes and operations, and the material itself often has less than ideal properties, such a high reactivity.
The general method of inspection utilize the field of non destructive testing, so that they can conduct the analysis of the status of the materials, without changing or alter it in any way. The alternative could involve cutting some sections of material to be analysed at a lab. This method could alter the structure and unnecessarily weaken the tank, besides, this is impractical method to inspect the entire area of the container tanks.
Non destructive casing inspection has several methods and levels of tank inspection depending on the thoroughness and level of inspection that is needed for a particular tank or tanks. There is more to the simple inspections, dye penetrant inspection, ultrasonic testing and magnetic particle inspection are all general methods that can usually be done by an NDT technician with certifications in relevant field. These techniques could be tried and tested while more thorough inspections are carried out by inspecting with a schema developed by EEMUA (Engineering Equipment and Material Users Association), such as EEMUA 159, which forms the standards for casing inspection. It is the recommended way to do Inspections which fulfills the standards such as these. In most cases, the inspection is regulated by safety concerns and tight legislation. Inspecting using a standard such as EEMUA 159, will ensure both of these targets are achieved thoroughly.
There is also more approaches using advanced techniques such as electromagnetics. The newer technology that has been used frequently because of its convenience is LFET (Low Frequency Electromagnetic Technique). This method uses electromagnetic coils to generate an electromagnetic field within the container tanks, which then will be disturbed if there is any defects in the material. LFET is a great method due to its ability to rapidly scan areas and distinguish between top and bottom side defects such as during the inspection of a tank floor.
Generally all areas of a tank will need to be inspected, the floor will use a technique such as LFET, the welds uses MPI (Magnetic Particle Inspection), dye penetrant or preferably eddy current testing, which has the ability to inspect linings thoroughly, making it especially useful. The shell will be inspected as well with ultrasonics, and any other components that needs inspection according to the reports. Visual inspections, and the other additional checks and measurements will use EEMUA as the standard like any other inspections.