A prototype provides the opportunity to test critical procedures, materials and equipment prior to production. While prototypes are generally contracted as proof of production readiness, they are also used to test the feasibility of a proposed design during the design development stage.
Prototypes can be fabricated at our weld lab under laboratory controlled conditions or at the client’s facility to duplicate the actual manufacturing environment and resources. A prototype provides valuable hands-on experience to the manufacturing team and allows for modifications in response to actual conditions at the individual manufacturing facility.
AAI is equipped to provide client companies with specialized manufacturing as a sub-contract resource. Under the controlled conditions of our lab, final product and component sub-assemblies, as well as specialized restoration and repair techniques, have shown consistent high quality results.
Half-pipe jacketing around the outside diameter of a vessel is a common welded arrangement in the industry for heating or cooling the contents of the vessel. Depending on code requirements, half-pipe welding may need to meet partial or full penetration design criteria. Full penetration welds may also be required to eliminate crevices, potential corrosion sites.
AAI provided a two part development program for these two applications in order to minimize welding times and distortion. Weld bevels were eliminated for vessel long and circumferential seams by qualifying full penetration square butt procedures. Half pipe procedures were then developed for both fillet and full penetration approaches.
For the vessel walls submerged arc welding tests were run to establish penetration trends and then verify controlled penetration over a range of conditions. The final procedure provided radiographic quality two pass butt welds in the half inch thick 316L vessel walls. Completion rate for the procedure was approximately one linear foot every 1.25 arc minutes.
Establishing single pass penetration profiles
Verifying penetration control over the established range of procedural conditions
Offset/mismatch testing for final verification of the production procedure.
Half pipe welding development evaluated both fillet and full penetration conditions with the gas metal arc process. Submerged arc welding was reserved for fillet weld conditions only. For the gas metal arc process a range of fillers, including metal core, flux cored and solid wires were run. Gas mixtures concentrated on argon with low percentages of either CO2 or O2 additions. Internal beveling of the half pipe promoted full penetration attachment conditions. Nitrogen purging of the half pipe was selected for cost as well as promoting an “austenitic skin” effect for corrosion resistance.
Full penetrations half pipe attachment trials.
In this full size prototype of a spent fuel canister, welding tests were made in a full size shell to develop as-welded root pass backside contours. The contours were developed to promote visual and dye penetrant inspection prior to completing the second side. AAI established weld procedures and contour control techniques with modified groove designs and promoted a single station setup which eliminated the standard multi-process approach and back-machining operations.
A program to develop, qualify and implement hot-wire joining of centrifugally cast alloy piping produced the required sequencing for continuous groove welding operations. Extensive procedure development combined with in-process cooling rate control provided non-stop sequencing for tacking, root melt and multi-pass fill. Active cooling and in-process procedure controls produced consistent weld quality in the crack sensitive material and significant reductions in weld completion rates on a three shift production basis.
This prototype was designed to prove manufacturability for mass flow meters. Sequencing included design of tooling fixtures, machining, welding and inspection techniques. Strict control of filler material chemistry produced consistent weld penetration and root melt contours. Fixture design, in-process cooling and weld sequencing were critical to this application in order to meet the tight tolerances required for dimensional stability.