ADVERTISERS’ INDEX
RS Page
810 Bug-O-Systems . . . . . . . . . . W13
www.bugo.com
811 Dynabrade ............... W9
www.dynabrade.com
812 ESAB Welding
& Cutting .............. W16
www.esab.com
813 Fabricators & Manufacturers
Assn., Intl. . . . . . . . . . . . . . . . W5
www.fmanet.org
815 FABTECH® International
& AWS Welding Show . . . W15
www.fmafabtech.com
816 Fischer Engineering . . . . . . . W14
www.fischerengr.com
814 P & J Mfg................. W2
419-227-8742
Radiographic Testing (RT). RT uses except on welds in vertical butt joints in
X-rays produced by an X-ray tube or gamma beams or girder webs as follows:
rays produced by a radioactive isotope to test • 1⁄ 6 of the web depth beginning at the
welds that can be accessed from both sides. point or point of maximum tension.
Though it is slow and expensive, it detects • 25 percent of the remainder of the
porosity, inclusions, cracks, and voids inside web depth needs to be tested.
the metal or welds. • If unacceptable discontinuities are
In this method, penetrating radiation is found in spot RT or UT, the entire
passed through a solid object onto photo- lengthshallbetested. Therequirements
graphic film, creating an image of the item’s for RT and UT shall apply equally to
internal structure. The amount of energy shop and field welds. MT of fillet
absorbed by the object depends on its thickness welds and partial-penetration groove
and density. Energy not absorbed by the object welds joining primary components of
causes exposure of the radiographic film. These main members shall be tested.
areas will be dark when When inspecting in-the film is developed. f rastructure, the certified
Therefore, areas of the NDT locates welding inspector needs
object where the thick- t o know the original re-ness has been changed bydiscontinuities or discontinuities or q uirements of the compo-discontinuities, such as n ent being examined. For
porosity or cracks, wil l defects in critical instance, the inspector has
appear as dark outlines t o make certain that the
on the film. Low-density s ize, length, and location
inclusions, such as slag , areas without o f all in-service welds con-will appear as dark areas f orm to the requirements
on the film, while high- causing structural o f the code and original
density inclusions, such d etail drawings, and that
as tungsten, will appear u nspecified welds have
as light areas. damage. n ot been added without
All discontinuities a pproval of the engineer.
are detected by viewing the weld shape and The expected quality of every in-service
variations in the density of the processed film. component is that every significant feature
This permanent film record of weld quality is continues to meet the original designer’s
easy to interpret by personnel who are prop- intent. NDT examinations provide reliable
erly trained. Only qualified personnel should confirmation of fitness-for-service quality in
conduct radiography and radiographic inter- accordance with the intent of the original
pretation because X-ray and gamma radiation designer. ■
can be hazardous.
Putting NDT to Work
During bridge fabrication, the American
Welding Society (AWS) has outlined the percentage of welds that must be tested (D1.5,
“Bridge Welding Code—2008, Section 6. 7”).
For existing bridges, in-service engineering examinations follow NDT guidelines provided
for new construction in the bridge code.
The code states that NDT (RT or UT) in
addition to VT is to be performed to comply
with the code by the following frequency
requirements:
• One hundred percent of each joint subject to calculated tension or reversal of stress,
Jesse A. Grantham owns Welding & Joining Management Group, 1070 W. 124th Ave., Suite 800,
Westminster, CO 80234, 303-451-6759,
www.wjmg.com. Andrew J. McGoldrick owns
Welding Professional Services Ltd., 237 Pin Oak
Court, Westerville, OH 43081, 614-794-2360,
www.wps-ndt.com.
References:
American Society for Nondestructive Testing,
www.asnt.org
American Institute of Steel Construction, www.aisc.org
American Society of Mechanical Engineers,
www.asme.org
ASTM International, www.astm.org
American Welding Society, www.aws.org
Form ore inform ation,use readerservice num ber816
W14 2009 WELDING UPDATE FOR INFRASTRUCTURE
