Objective:
The objective of this project is to demonstrate the following two technologies for controlling hazardous air pollutants (HAP), particularly hexavalent chromium (Cr6+), generated during certain welding operations: the use of a new chromium (Cr)-free consumable and the addition of tetramethylsilane (TMS) to the shield gas. Occupational exposures to Cr6+ and other metals also will be reduced using these technologies.
Technology Description:
This project includes a demonstration/validation and technology transfer effort for the two new welding technologies described below. While the technologies could complement each other in some welding operations, both technologies stand alone and will be tested separately. Both technologies have been evaluated in the laboratory and their feasibility for field applications demonstrated.
A new Cr-free welding consumable has been developed as a replacement for conventional stainless steel consumables such as Types 308, 309, and 316 for welding austenitic stainless steel base metal. This new consumable has comparable corrosion resistance and mechanical properties relative to the consumables it is designed to replace. The measured Cr6+ in the fume of this electrode when welding Type 304 stainless steel is virtually nil (0.02 wt%) and represents a 100-fold reduction in Cr6+ relative to a conventional Type 308 consumable.
The TMS process prevents the formation of Cr6+ by suppressing the oxidation of Cr species and by forming an insulating coating on Cr particles. This technology is not metal specific, and it is also effective for other toxic metals of concern such as manganese, nickel, and copper. Furthermore, it requires minimal modification to existing welding equipment.
Expected Benefits:
Using these technologies, the Department of Defense (DoD) can reduce the fugitive emissions generated during welding repair and maintenance operations throughout the Services at the depot and shipyard level, and limited welding at smaller intermediate operations. During these operations, DoD releases HAPs into the atmosphere. While these HAPs are usually not directly reported to the Environmental Protection Agency (EPA), facilities estimate the residual risk to public health and, in certain states, must report the findings to the public when cancer risk exceeds a threshold of one in a million. When the threshold is exceeded, the facility is also expected to initiate measures to reduce the fugitive emissions. (Anticipated Project Completion - 2012)
Principal Investigator:
Ms. Kathleen Paulson
NAVFAC Engineering Service Center
1100 23rd Avenue, OP421
Port Hueneme, CA 93043-4370
Telephone: (805) 982-4984
Fax: (805) 982-4832
E-mail: kathleen.paulson@navy.mil
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