Software helps improve product quality
Scott McGrath, Continuous Improvement Engineer, AERCO International, Inc., Northvale, NJ, ensures quality assurance in the design and production of the company’s commercial water heaters and boiler systems.
Scott McGrath, Continuous Improvement Engineer, AERCO International, Inc., Northvale, NJ, ensures quality assurance in the design and production of the company’s commercial water heaters and boiler systems. Its signature steam-fired product is a high-efficiency, self-descaling water heater that uses vertical stacks of helical coils, which share a common steam riser and condensate return pipe. To keep field repairs and coil replacements simple and cost-effective, each independent coil set is connected to the common pipes via a threaded nut connection. The longevity of the heat exchanger depends on the integrity of these connections.
McGrath needed a way to quickly, efficiently, and accurately evaluate the quality of a bolted joint or fastener assembly. The ongoing quality inspection of these threaded connections using Six Sigma methodologies led him to a fastener/joint analysis software package called BoltFAST by Sensor Products, Inc. East Hanover, NJ.
McGrath says, “The software program enables us to confirm the upper and lower torque values and the capabilities of our connection. It also helps us accurately quantify the effects of prevailing torque on the joint components caused by braze in the connector threads. The program facilitates our joint assembly analysis and confirms a very expensive finite element analysis performed by the company. As a result, we can quickly validate as many as 16 different dimensional aspects of our threaded connection design.”
McGrath says that the software not only helps the brazing and assembly operation, but also influences materials storage, lubricant sourcing, testing and inspections.
The program determines the fatigue endurance limit of a thread, the amount of embedding anticipated in a bolted joint, and the optimal tightening torque for given friction conditions by combining a large database of fastener and interface materials and their physical characteristics. It specifically evaluates joints, threads and torque. The joint analysis program determines if a bolted joint can sustain the forces acting upon it; the thread analysis program calculates the force necessary to fracture a fastener and strip the internal and external threads; the torque analysis program helps determine correct tightening torque and resulting anticipated clamp force for a threaded fastener.