Non Destructive Testing for Storage Tanks, Heat Exchangers, Condensers and Pipelines

 Non Destructive Testing (NDT) is the process of examining an asset in order to determine condition without the need for intrusive destructive processes that may be prohibitive due to operational needs, prohibitively expensive, or even impossible when the condition of an entire asset needs to be assessed.

Various techniques for the non destructive analysis exist, with distinct branches for similar assets, such as tube inspection for heat exchangers, coolers, condensers etc. Pipeline inspection for all sorts of piping, and tank inspection for various storage tanks, silos, and vessels.

Each distinct branch has its own methods and techniques however generally all rely on the same principles applied in different manners.

The most basic techniques consist of dye penetrant inspection (DPI) and magnetic particle inspection (MPI) which are both used for crack VERIFICA DI INTEGRITA' VENTENNALE STRUTTURALE ATTREZZATURE DI SOLLEVAMENTO detection - typically in plates, piping and welds. These are generic techniques that can be applied across a variety of branches and are low cost methods however limited in the fact they can only detect surface breaking defects and are vulnerable to operator error.

More sophisticated techniques such as eddy current testing (ECT) exist which can be used in welds, plating, piping etc. for crack analysis, and can detect sub surface cracks up to depths of typically around 10mm in the field. ECT requires more rigorous training however has many benefits such as sub surface crack detection and the ability to inspection through coatings, such as paint and other linings.

ECT can also be applied to tube inspection such as for heat exchangers and condensers, and typically looks for pitting, corrosion, baffle cutting, erosion, steam impingement and other wall losses. The process works via sending a probe down the inside of the tube and pulling it out ('pulling the tube') whilst analysing the data. Data can be saved and analysed later if required.

ECT is also applied to piping via techniques such as LFET (Low Frequency Electromagnetic Technique), in this instance low frequencies are used to gain deeper penetration into the tubes, typically around 5-10Hz. This technique generally looks for corrosion and other wall losses associated with pipework, such as hydrogen damage, corrosion cells, micro-biologically induced corrosion, flow accelerated corrosion etc.

Ultrasonics is another main branch of non destructive testing and makes up a large part of non destructive testing work - being a very versatile technique it's used almost everywhere in various forms such as very precise tube inspection, thickness measurements and crack sizing to name a few, across all types of assets. Ultrasonic testing (UT) is an established technique that is used heavily due to its precise nature.