Software maintains joint quality

Edited by the Engineeringtalk editorial team Sep 21, 2004

A novel fastener/joint design software package helps a leading HVAC manufacturer with Six Sigma process validation.

Scott McGrath is a Continuous Improvement Engineer and Six Sigma Black Belt at Aerco International, tasked with quality assurance in the design and production of the company's commercial water heaters and boiler systems.

The company's 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 is critically dependent on the integrity of these connections.

The ongoing quality inspection of these threaded connections using Six Sigma methodologies recently led McGrath to Sensor Products' fastener/joint analysis software package Boltfast.

"The threaded nut connections are essential to the product's longevity", McGrath says.

"Boltfast 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".

"We consider Boltfast a mission critical tool in our quality control and new product development toolset".

"The knowledge derived from the program is put into action throughout Aerco", McGrath notes.

"Its influence extends far beyond the product design team".

"Boltfast helps not only the brazing and assembly operation, but also influences materials storage, lubricant sourcing, as well as testing and inspections".

"The ultimate impact of Boltfast also extends to our customers; it is an integral tool we use to ensure that our products are designed well and manufactured with unprecedented precision and quality".

Boltfast software is the most comprehensive bolted joint analysis software package available.

By combining a large database of fastener and interface materials and their physical characteristics, 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.

As in Aerco's case, engineers can quickly, efficiently and accurately evaluate quality of a bolted joint or fastener assembly.

The software specifically evaluates joints, threads and torque.

The joint analysis program determines if a bolted joint can sustain the forces acting on 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.

A free trial version of Boltfast is available for evaluation from the Sensor Products website.