The latest generation sintered neodymium iron boron magnetic material is used in the MFL2000 inspection system. After extensive mathematical modelling we have designed a magnet that not only gives an increased flux density within the plate but also reduces attractive force. This not only means it is easier for the operator to handle the unit, reducing physical stress and increasing productivity, but reduces wear and tear on the unit itself. The stronger more uniform field achieved across the magnet width, coupled with cut out carriage design allows inspection closer to the edge of the plate than before, allowing detection of corrosion at the edge of the heat affected zone. A further benefit from the mathematical modelling and the revised magnet construction is that we have been able to design the transit case so that the unit can be considered non hazardous (non-magnetic) for air transport.
The motorised scanner has an auto-stop system which ensures any defect above
the operator adjustable threshold is identified. All controls are situated in a
recess at the top of the unit allowing easy viewing and operation whilst being
protected against accidental adjustment.
How it Works
As the scanner passes over a corrosion pit the excess magnetic field is forced
out of the plate and is detected by 36 Hall Effect sensors mounted in the centre
of the magnet. The signal generated by the Hall Effect sensor is filtered and
passes through an alarm circuit. If the signal is greater than the operator
controllable alarm threshold, power to the motor is cut automatically the unit
stops.
The operator is able to determine the precise defect position by noting which
LED’s illuminate. Each LED is numbered and a corresponding number is displayed
across the rear of the magnet carriage. Once the auto-stop system has been
activated the scanner continues to move forward until the defect is just behind
the rear rollers.
This allows the operator to accurately mark the affected area of plate for
further examination by an alternative NDT technique (usually Ultrasonic) to
determine corrosion depth. Once the auto-stop has been triggered the scanner
will not operate until the operator presses the reset button ensuring that no
defect is missed as can be the case with non motorised systems.