Thomas R. Hay, Ph.D., P.E, ASNT Level #107162
498 Meckley Rd.
State College, PA 16801
June 30, 2020
The rope access technician (RAT) certification process is structured in a similar manner to non-destructive testing technicians. Where NDT technicians are certified through various central certifications programs like the American Society for Non-destructive Testing (ASNT) Central Certification Program (ACCP), rope access technicians are certifiable through Industrial Rope Access Trade Association (IRATA) and Society of Professional Rope Access Technicians (SPRAT). Similar to non-destructive testing personnel certification levels, there are comparable rope access technician levels. For example, a Level 1 technician is qualified to work while suspended from ropes under the supervision of a Level 3 RAT. A level 2 rope access technician may perform some limited rigging work and planning under the supervision of the Level 3. Finally, the Level 3 technician is responsible to the project rigging, equipment safety, rescue plans and project execution. This article discusses some of the more common non-destructive testing applications that are converging to rope access and provides some example NDT applications.
Advanced Non-destructive Testing Techniques
Non-destructive testing techniques can be broadly classified into conventional and advanced NDT techniques. Conventional NDT techniques include visual inspection (VT), liquid penetrant testing (PT), magnetic particle testing (MT), and some disciplines of ultrasonic testing (UT), eddy-current testing (ET), and radiographic testing (RT). Some important advanced NDT methods include acoustic emission testing (AE), phased array ultrasonic testing (PAUT), time-of-flight diffraction (TOFD), alternating current field measurement (ACFM), total focusing method / full matrix capture (TFM/FMC), guided wave ultrasonic testing (GWUT), and some disciplines of magnetic flux leakage (MFL) and eddy-current testing.
Safety and Access to Fracture Critical Structures
The number one goal for any project that requires NDT support is to ensure the safety of the NDT inspector and support crew while providing access to the fracture critical assets to perform the inspection in accordance with the contractual obligations. This section contrasts two different approaches to undertake an NDT inspection at a hydroelectric dam spillway. The spillway’s tainter gates control the spillway flow and contain many complete joint penetration (CJP) welded joints that are considered fracture critical. In order to perform non-destructive testing on the tainter gates, the gates must be shut completely so that the ground surface is relatively dry. Staging the spillway platform for non-destructive testing is an expensive proposition. While the tainter gates are accessible via a man-lift from the spillway runoff, a large crane is typically required to lower the man-lift down to the spill way at the start of the project and to extract the man-lift at the end of the project. An 80-ft manlift can require 140-ton crane, detailed crane lift plan, permitting, and significant transportation costs. The cost of simply delivering and extracting the man-lift can easily exceed the NDT inspection costs for some projects.
Figure 1 shows a TECHKNOSERV CORP. rope access ultrasonic testing level 2 technician performing phased array testing on a tainter gate fracture critical member. In this scenario, a two-man team accesses the gate using rope from the roadway or walkway above the gates. Significant cost savings are realized through elimination of heavy machinery rental, transportation, and traffic control.