Eddy current method of control
The scope of application of eddy current control is the control of the quality of electrically conductive objects: metals, alloys, graphite, semiconductors etc. Eddy current proved itself to be practically safe and reliable method which is admissible for production where high requirements to the control of the quality of the equipment condition shall be met within the restrictions of norms and conditions.
In Ukraine as well as abroad they widely apply heat exchangers with a large number of tubes in a tube bundle in technological processes of chemical, petrochemical, pharmaceutical and other enterprises. At present, the control of the condition of tube bundles is carried out, as a rule, by hydraulic testing. Another method consists in testing of the tube exterior with help of portable ultrasound or eddy current non-destructive inspection instruments. In both cases the procedure of testing requires considerable time efforts and as a rule does not provide a full and true picture of the tube condition.
The efficient solution of this problem is the use of eddy current method using the sensors moving inside a tube. Thus, in nuclear industry they have applied for a long time eddy current method of control with an internal moving sensor. Such equipment is used at Kolskyy, Khmelnitskiy, Rovenskiy, Novovoronezhskiy NPS, Hydropress and other enterprises.
On testing heat exchangers a sensor is input in a tube with help of a push bar allowing to develop the speed up to 8 m/s. The device allows a consequent generation of different frequencies. The control of tube condition on several frequencies considerable enlarges the resolution capability and the range of the use of the method providing for the possibility to discover various defects from surface cracks to nonhomogenity of material in deeper areas with high speed and reliability.