Analytical Model And Application For Pulsed Eddy Current Testing Of Equipments With Metallic Claddings

Pressure equipment with mental claddings,such as pipes and pressure vessels,is widely used in large complete sets of equipment of ten million tons of oil refining,one million tons of ethylene,etc.Local wall thinning is one of the threats,thus to guarantee the continued safe operation of the pressure equipment,non-destructive testing(NDT)methods are necessary.With advantages of strong penetration,low cost and good security,pulsed eddy current testing(PECT)has been applied in pressure equipment with mental claddings in recent years.However,electromagnetic shielding effect of mental claddings seriously affects the penetrability of pulsed eddy current and the detection performance,which becomes the bottleneck for the development of PECT.Therefore,how to remove the electromagnetic shielding effect is of great significance to improve the performance of PECT.The aim of this dissertation is to study the theory and method for PECT of pressure equipment with mental claddings.Firstly,the classical Truncated region eigenfunction expansion(TREE)method is optimized based on the directions of magnetic field lines in the equipment and the cladding,an analytical model of PECT for pressure equipment with mental claddings is proposed with Robin boundary conditions.Secondly,to expand the scope of this analytical model from the aspects of pressure equipment and sensors,analytical models of two PECT sensors for the plate with a Flat-Bottom Hole is established,including the coaxial sensor and the Transmitter-Receiver(TR)sensor.These analytical models expand the types of defects from the uniform wall thickness thinning to a Flat-Bottom Hole,which has the ability to solve two-dimensional problems instead of one-dimensional ones.They also expand the types of sensors from coaxial-type to TR-type,which gives theoretical supports for pressure equipment with more sensor optimization parameters for different testing conditions.Thirdly,methods of reducing the electromagnetic shielding effect is provided based on the proposed analytical models.In the aspect of sensors,according to distribution features of the electromagnetic shielding effect in mental claddings and coefficients of the sensor coil,the performance and applicability of the coaxial sensor and the TR sensor are discussed.In the aspect of signal processing,according to component features of analytical solutions,a parameter with no relationship of mental claddings is presented,namely a measurement characteristic of the normalized signal similarity.Finally,based on the above research work,a simulation evaluation software is developed with functions of PECT signal simulations,sensor performance evaluation and quantitative analysis of defects in pressure equipment and then used in the field testing.The study in this dissertation developed around the theory research of PECT,supported the development of international standard ?ISO 20669:2017 Non-destructive testing — Pulsed eddy current testing of ferromagnetic metallic components ?,and benefits for promoting the further development and application of PECT technology.