U.S. Department of Transportation
Federal Highway Administration
Preliminary visual inspection should be carried out as a supplement to the radiographic and ultrasonic inspection but is not to be considered a substitute for either.
The effectiveness of nondestructive testing depends upon the capabilities of the persons who are responsible for and who carry out the testing.
Those individuals who are assigned to, or who are engaged to carry out, the inspection work are required to have appropriate knowledge of the technical principles underlying the nondestructive tests they are to perform.
The minimum level of qualification required shall be equivalent to that expected of nondestructive testing personnel qualified and certified to NDT level II, which may be stated as follows:
The Level-II individual shall be qualified to direct and to carry out tests in the method certified. He must be able to set up and calibrate the equipment to be used, be able to read and to interpret indications, and to evaluate them with reference to applicable codes and specifications. He shall be thoroughly familiar with the scope and limitations of the method and shall have the ability to apply detailed techniques to products or to parts within his limit of qualifications. He shall be able to organize and report nondestructive testing results.
An NDT Level-III qualified individual should supervise the Level-II individual.
The Level-III individual shall be capable of establishing techniques, interpreting specifications and codes, designating the particular test method and techniques to be used, and interpreting the results. Further, he shall be capable of evaluating the results in terms of existing codes or specifications and also should have sufficient practical background in applicable materials technology to assist in establishing tests and acceptance criteria when none in otherwise available. It is desirable that he have general familiarity with all other commonly used NDT methods. He shall be responsible for conducting examinations of NDT Level-I and NDT Level-II personnel.
We again reiterate that our experience with electro-slag welding strongly indicates that NDT examination of these welds is of immediate urgency when they occur in nonredundant main load carrying tension members.
In conjunction with the nondestructive examination, the State should carry out a number of preliminary operations which will add to the success of the examination by the NDT team. The design, fabrication, and construction reports should be examined to determine the following pertinent information for each nonredundant main tension member:
(1) the design stress and the stress range,
(2) the garde of steel together with the mill test reports where available,
(3) the location and type of electro-slag welded joints in the member,
(4) the record of qualified welding procedure and associated test results,
(5) the as-built shop plans for the fabricated member,
(6) fabrication records which might reveal any repairs made to the electro-slag weld,
(7) any radiographs made during the fabrication of members, including radiographs of all rejected welds, together with the films of any repairs,
(8) any ultrasonic inspection reports,
(9)any construction records showing field changes and/or field repairs which might vary the location of, or the details of the shop or field weld as originally detailed, and
(10) any record of changes or difficulties observed since construction.
Review of the above data will assist in the evaluation of this inspection. The following additional considerations should not be overlooked:
(1) The scaffolding may be required to support not only the personnel making direct observation on the weld but possibly also the radiographic equipment, which in the case of thicker plates may involve shielding weighing over half a ton.
(2) The pertinent regulations pertaining to safety of the personnel or the public and the regulations pertaining to the use of radiographic materials and equipment should be examined and steps taken to conform with these requirements.
(3) Where repairs may have been made to an electro-slag weld, examination of the weld should involve the complete removal of paint on the weld by careful grinding, followed by etching of the weld to trace out the repair limits.
(4) Closed box girders, as in the tie girders of a tied arch, must be adequately ventilated by a blower system to eliminate foul and possibly toxic air.
The selection of the inspection team may be influenced by the factors mentioned above. It is our intent that the team members shall be individuals demonstrably competent carry out the examination required, to document, and to report the results of their findings. These reports will serve as a basis for determination by the State of the adequacy of these welds and the necessary remedial action. Weld repair of defective ES welds should not be permitted. A summary of the inspections made and copies of significant reports should be furnished to FHWA Washington Headquarters.