How it works:

The inspection method is an adapted RFT (Remote Field Technology) method which is a low frequency AC (electromagnetic) technique similar to remote field eddy current. In this technique a signal is sent from an exciter coil(s) to 15 detector coils. The signal passes through the tube wall at the crown of the tube near the exciter(s) and returns through the wall again near the detectors. The time of flight of this signal is directly related to the wall thickness of the tube near both the exciter(s) and detectors.

Features:

• Electromagnetic flaw detection for water wall tubes of boilers
• 2 parts: Tube Cat (crawler) and Vertiscan (equipment)
• Uses adapted Remote Field Technology
• Detection of metal loss, pitting, fatigue cracks, hydrogen damage
• Allows for 5 tubes to be tested at the same time
• 1.5 up to 3m/min; 6000 point readings/meter
• Detects defects from 5% wall loss
• 15 detector coils

For small boiler we can use the manual hand held E-Pit probe which is also RFT based technique.