the exterior surface of the test specimen at a minimum rate of 5.0 US gal/ft2-hr. The acceptable tolerance for the device ranges from 4-10 US gal/ft2-hr. Improved Portability and Usability The ease of use of the water penetration testing device relies upon required manpower, setup time, and transportation. The device should be assembled, transported, and operated by one person unless it is being used in suspension which would require two people. The assembly or disassembly of the spray device should take a maximum of 5 minutes. Most of the parts need to be stock and easily replaceable in case they break or malfunction. Finally, it is important that the device is able to be transported via a compact passenger car, eliminating the need for a truck/utility vehicle. Structural Integrity The structural integrity of the water penetration testing device maintains that it will withstand the stresses acting on it during operation. The spray device must be structurally sound when standing on the ground or in suspension. This ensures the safety of the users and other individuals within the proximity of the device during operation. The device also needs to withstand the rough handling and abuse of a construction environment while maintaining functionality. Because the device will be regularly exposed to water, all the device parts need to be corrosion resistant. Aesthetics The water penetration testing device should have a neat and professional appearance. Other key details include hardware that is consistent in appearance throughout the rack. Top-Level Alternative Conceptual Solutions After brainstorming possible design ideas, the team evaluated three final design solutions. A circular rack, flexible tubing rack, and a square modular rack were compared to the current Morrison Hershfield model in the scoring matrix in Table 1 below. The square modular rack accumulated the highest score. Table 1: Decision matrix for 3 possible design solutions. PDS Criteria Morrison Hershfield Square Modular Rack Flexible Tubing Rack Circular Rack Portability 3 4 5 5 Ease of Use 3 4 3 4 Maintenance 2 4 2 4 Durability 2 4 2 2
top corners fell below 0.25 liters/min-ft2, but the center test areas did not. This is largely due to the fact that there is minimal spray nozzle overlap at the outermost sample areas. At an 18 inch rack-surface separation, the spray rack effectively covered 61% more surface area, but the required internal pressure of the system rose to 30 psi. When the pressure of this system fell below 30 psi, it behaved almost identically to that of the 12 inch rack-wall separation system. Portability The portability of the new spray rack system has fully satisfied the requirements of the PDS. The rack can be assembled/ disassembled on site by one person in approximately 5 minutes, which minimizes the additional time needed to improve portability. Disassembled and bundled with Velcro straps shown in Figure 11, the rack’s dimensions are 6 ft. long, with its largest diameter equal to about 9 inches. The spray rack stand, used for mounting at ground level applications, is a 6.5 ft long, which intersects perpendicularly at one end with a 3 ft section of tube. Figure 11: The spray rack disassembled and bundled with Velcro straps. The spray rack and stand were tested and easily fit into a compact sedan (Nissan 200SX) by one person. Rubber caps were also attached to the ends of each member, shown in Figure 12, so that forces of impact from transportation and industrial handling will be more effectively absorbed. Maintenance Although the spray rack has not required any maintenance after the fabrication was completed, the team does not foresee many instances where potential problems could not be easily maintained and serviced in the field or at the Morrison Hershfield facility. Copper was chosen as the piping material with soldered joints. If a section of piping, or pressure gage were to be irreparably damaged, the affected area can be cut out if needed, and replaced with parts commonly found at most hardware stores. If leaks occur, the joints can be heated and re-soldered. Brass nozzles and bushings, shown in Figure 12, were chosen with simple designs to minimize corrosion, to be easily cleaned of clogs, and easily replaced. These parts were
purchased online at the popular website McMaster-Carr, where in the event a nozzle or bushing becomes damaged, the part can be replaced within a couple of business days at minimum cost. Figure 12: Rubber caps and brass nozzles and bushings were used in the final design, which require little maintenance, and are easily replaceable. The setup and operation constraints of the PDS were satisfied, maintaining or improving upon the current spray rack used by Morrison Hershfield. As mentioned previously, assembling the rack can be routinely performed in about 5 minutes by one worker. The ground level stand is a single telescoping tube, which can be controlled by one person. Once assembled, the rack (without water) weighs 24.3 lbs, which is far below the PDS constraint of 50lbs, allowing one person, instead of two for the current spray rack, to setup and mount the spray rack at ground level applications. The total setup of the rack or mounting of the rack to the installation at ground level takes no more than 15 minutes, which satisfies the PDS requirement. The team was unable to test the suspension mounting time, due to limited resources. Although it is conceivable that the spray rack be setup and mounted onto roof-suspended applications by a single worker, the new design was intended to be operated by two workers; which is also required for Morrison Hershfield’s current spray rack. This is due to the increased degree and quantity of risk inherent to suspending a spray device of this size from a large building. Two workers can ensure more stability and accuracy in suspending this device, and can monitor each other as well to ensure there are no crucial oversights that may result in injury or even death of people below. The simplicity of operating the rack is maintained, where only the internal pressure of the system needs to be monitored. The coverage area and expandability however are improved. The current design used by the project sponsor has a relatively small, fixed coverage area. With the new design, the spray rack has a larger coverage area, which can also be expanded if necessary. CONCLUSION The team has designed, fabricated, and tested a water penetration testing device that
APPENDIX D: PRODUCT DATA SPECIFICATIONS TABLE Requirements Customer Metric Target Target Verification Notes Priority Performance Reliability MH cycles ≥ 1000 cost effective testing 3 tests/week □□ Portability to site MH vehicle size required to transport pickup truck easier/more cost effective to transport end user feedback □□□ Portability to test subject MH dimensions average person can carry efficiency end user feedback □□□ Ease of Operation MH - - - end user feedback easy to operate consistently with minimal training □□□ Weight (heaviest component) MH lbs < 50 portability/ fatigue end user feedback □□ Service Life MH years ≥ 5 MH testing □□ Durability MH shock loading 10G SELF Abaqus withstand industrial stresses, impact, handling, transport □□□ Environment MH surface treatment corrosion resistant SELF end user feedback □ Operation Temperature MH degrees °F 35-105 SELF testing □□ Suspension forces SELF factor of safety 10G consistent operation end user feedback □□ Safety Frame Integrity MH factor of safety 10G SELF Abaqus □□□ Handling MH - - - - □□□ MH = Morrison Hershfield □ Low □□ Medium □□□ High MH = Morrison Hershfield □ Low □□ Medium □□□ High Requirements Customer Metric Target Target Basis Verification Notes Priority