Tubular Heat Exchangers – Non Destructive Testing on Heat Exchangers and Its Role Within Industry

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Heat exchangers are prevalent in many industries, helping to rapidly transport heat away from one medium to another. They are used in a broad range of scopes from space heating, refrigeration, air conditioning, chemical plants, power plants, petrochemical, and petroleum amongst many others. Heat exchangers are often used in industry to siphon otherwise waste heat from one part of a process to another, rather than introducing a new external heat source. This practice increases efficiency, and saves many industries large amounts of money, as well as helping to protect the environment.

Because industries involving the use of heat exchangers almost by definition involve high temperatures, pressures and large quantities of potentially harmful fluids, it’s important to keep the equipment involved serviced to a high standard. Not only because of the safety implications but also to maintain the finely calibrated processes in effect, and maintain cost efficiency. Contamination of fluids, or temperature drops could cause PH changes in fluids, or inefficiencies in processes that cause lost efficiency and ultimately loss in revenue. As well as contamination and minor flaws, major flaws can cause failures leading to unscheduled shutdowns and massive amounts of lost revenue.

So what’s the answer? Non Destructive Testing or NDT as it’s more commonly known is the answer. Its role is to analyse materials and parts using techniques which don’t damage the materials involved. Using techniques such as ultrasound, radio and magnetism, parts can be inspected without the need to be taken apart, or damaged.

In the case of heat exchangers, NDT provides many different methods for their inspection. Different techniques are used for different applications depending on needs, such as time, cost and thoroughness. Some of the main technologies involved include; Remote Field Electromagnetic Technique (RFET), IRIS (Internal Rotary Inspection System), Eddy Current Testing (ECT), MagWave and Remote Visual Inspection (RVI).

RFET is one of the main inspection methods, and is used to test carbon steel tubes. A probe is inserted in one end and pushed up through the tube, the probe is then pulled back slowly, and a steady rate, which outputs data to be analysed. Typical flaws and defects found include general erosion/corrosion, pitting and baffle cutting (support plate fretting).

RFET is capable of testing 300-500 tubes/shift and tolerates low fill factors. It can detect ID (Internal Diameter) and OD (Outer Diameter) flaws, and supports a wide variety of probe sizes, all the way down to.250″ (6.35mm), although custom probes can be produced for almost any situation. Bends can be inspected and access can be gained through either boiler drum.

NDT is recommended as part of a WSE (Written Scheme of Examination) as required by HSE in the UK. For NDT’s comparatively small cost it’s frequent use can help prevent accidents, deaths and unexpected downtime and in turn large loss of revenue, making it essential for the a savvy and efficient plant.

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Source by Zul S Sadiq