NONDESTRUCTIVE TEST METHODS FOR ACCIDENT DAMAGE INSULATED TANK CARS

THERE EXISTS A NEED FOR FIELD EVALUATION TECHNIQUES ON DAM- AGED RAIROAD TANK CARS, A LARGE PROPORTION OF WHICH ARE OF INSULATED DESIGN CONSISTING OF AN OUTER SHELL, AN INSULA- TION SPACE, AND AN INNER LINER. THESE CARS ARE USED TO HAULMANY POTENTIALLY HAZARDOUS MATERIALS AND CHEMICALS, AND THEREFORE, MUST BE CAREFULLY ASSESSED IN THE EVENT THAT THEYARE DAMAGED. A MAJOR DIFFICULTY ARISES IN ATTEMPTING TO IN-SPECT THE INNER LINER FROM THE EXTERIOR OF THE CAR. THE IN-SULATION GAP MAKES MANY OF THE STANDARD NDE TECHNIQUE USE- LESS FOR ASSESSING THE INTEGRITY OF THE LINER. THERE ARE A NUMBER OF TECHNIQUES PROPOSED HERE THAT OFFER A REASONABLE POTENTIAL FOR DETERMINING THE STATE OF A DAMAGED TANK CAR. A TECHNIQUE USING DEEP PENETRATING EDDY CURRENT MAY PROVIDE A PRACTICAL MEANS TO DETERMINE THE CONDITIONS OF THE INNER LINER WITH RESPECT TO THE OUTER SHELL. THIS TECHNIQUE IS PRESENTLY BEING USED TO QUICKLY EVALUATE THE OUTSIDE DIAM- ETER CONDITION OF THICK-WALLED BOILER TUBING FROM THE INSIDETHE TECHNIQUE WOULD USE VERY LOW FREQUENCY EDDY CURRENTS ON THE ORDER OF A FEW HERTZ, MULTIPLE EXCITATION FREQUENCIESAND STRONG BIASING MAGNETS TO BE ABLE TO 'SEE' THROUGH THE OUTER SHELL. THIS TECHNIQUE WILL BE EVALUATED ALONG WITH OTHER METHODS DESCRIBED IN THIS PROPOSAL TO MIGHT PROVIDE A QUICK ACCURATE ASSESSMENT OF TANK CARS IN THE FIELD.