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Abstract
This report describes the second and final phase of a study to develop an ultrasonic NDE method for evaluating the integrity of seams of single ply roofing membranes. The results of the laboratory evaluation of a prototype pulse echo apparatus (the field scanner) were positive in that voids could be distinguised from well bonded sections of th speciment using the intensity of the echo from the adhesive layer. In the Phase 2 study, seams of existing EPDM single ply membranes were examined by roof top scanning to evaluate the performance of the field scanner in practice. This was followed by laboratory tests to confirm and explain observations made during the field tests of the seams. The field scanner was sensitive to micro-cavities, which could be generated in adhesive layers. This resulted in a number of "false positive" readings. The formation of the micro-cavities was attributed to the temperature-induced volatilization of residual solvent remaining in the adhesive layer after its application on the membrane material. It was concluded that the field scanner technique had limited applicability for assessing the condition of solvent-adhesive seams because it could not readily differentiate between the micro-cavities and voids and delaminations in the adhesive layer. The results also implied that the field scanner might be applicable to seams formed using other techniques and that the addition of data recording and processing equipment would enhance the operator's ability to interpret the pulse-echo data obtained.
This report describes the second and final phase of a study to develop an ultrasonic NDE method for evaluating the integrity of seams of single ply roofing membranes. The results of the laboratory evaluation of a prototype pulse echo apparatus (the field scanner) were positive in that voids could be distinguised from well bonded sections of th speciment using the intensity of the echo from the adhesive layer. In the Phase 2 study, seams of existing EPDM single ply membranes were examined by roof top scanning to evaluate the performance of the field scanner in practice. This was followed by laboratory tests to confirm and explain observations made during the field tests of the seams. The field scanner was sensitive to micro-cavities, which could be generated in adhesive layers. This resulted in a number of "false positive" readings. The formation of the micro-cavities was attributed to the temperature-induced volatilization of residual solvent remaining in the adhesive layer after its application on the membrane material. It was concluded that the field scanner technique had limited applicability for assessing the condition of solvent-adhesive seams because it could not readily differentiate between the micro-cavities and voids and delaminations in the adhesive layer. The results also implied that the field scanner might be applicable to seams formed using other techniques and that the addition of data recording and processing equipment would enhance the operator's ability to interpret the pulse-echo data obtained.
Date
11/1990
11/1990
Author(s)
H Watanabe; W Rossiter Jr.
H Watanabe; W Rossiter Jr.
Page(s)
41
41
Keyword(s)
adhesive bonding; EPDM; field inspection; nondestructive testing NDT; pulse echo; seams; ultrasonis; void
adhesive bonding; EPDM; field inspection; nondestructive testing NDT; pulse echo; seams; ultrasonis; void