Testing of Boiler Tubes

Applications of NDT (Non Destructive Testing) extend to just about any mechanical system you could think of, from testing parts during the production process, to the inspection of long standing structures such as pipelines and process columns. Boiler tubes are no exception, with regular inspection being performed internationally.
Boiler tubes are no exception, with regular inspection being performed internationally.

Methods of Inspection

Several methods for  water Boiler tube (also known as ” ท่อน้ำหม้อน้ำ ”  in Thai language ) inspection exist, one of the primary technologies is UT (Ultrasonic Testing), and this is often done via compression wave in several locations on each boiler tube in order to determine remaining wall thickness, and wear rates.

Dye penetrant is another commonly applied technique; this can be used to look for cracking in at risk areas, generally less widely used than ultrasonics.

Eddy current is a third technique that is used for the inspection of industrial boilers, eddy current is especially useful for surface and slightly subsurface cracking, and in particular weld inspection.

For the inspection of the surface area of the tube LFET (Low Frequency Electromagnetic Technique) is another option, instead of, or in conjunction with ultrasonics. LFET covers a 130 degree section of the tube in a single pass, and is capable of scanning 10ft per minute. This is great for screening the tubes at a fast pace for tubes with low remaining wall thickness.

Inspection Frequency

Depending on the type of   pipe valve (also known as ” ท่อน้ำหม้อน้ำ ”  in Thai language ) being run, the frequency of inspection can vary, for harsher environments within the boiler, such as i waste to energy boilers, more regular inspection is recommended, yearly inspections being commonplace. Generally the first few inspections will occur more regularly, and then as a good idea of the corrosion rate is established, a sensible inspection timetable can be devised.

Preventing Problems

The main problem that arises from a lack of inspection is the blow out of boiler tubes. Generally tubes with low remaining wall thickness are either replaced, monitored or treated to prolong their life. One technology that is being utilised is Inconel overlay. This can extend the life of the tubes by coating them with a layer of Inconel several millimeters thick.

A major driving force in the regular inspection of boiler tubes is the ever increasing regulation and safety conscious culture that is growing within the industry. Preventing deaths, injury and increasingly more common, preventing natural disasters and environmental damage, are concerns that drive the increasing pressures that spur new regulations and increasingly tight regulation for industries such as those involved with industrial boilers.

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