Engineering Mechanics and Design
SIB-96-177

Case Study: Leaking Flange Connection
At a chemical plant, the connection between two heat exchangers was leaking to the point that disassembly would have been required to stop the leakage. SI designed a weld repair that fully met the requirements of ASME Code Section VIII. This permanent repair was implemented, eliminating the need for a lengthy repair outage.

Case Study: Valve Wall Thinning
At an operating nuclear power plant, internal valve wall thinning was discovered during an outage. To determine the required wall thickness for the next outage, SI utilized wall thickness measurements of the existing valve and performed finite element stress analyses. This analysis allowed the utility to continue operation without extending the outage to procure and install a new valve.

Case Study: Nozzle Post-Weld Heat Treatment
For several nuclear power plants, SI has assisted in developing post-weld heat treatment procedures for reactor and steam generator pressure vessels. In one case, SI performed heat transfer analysis to determine acceptable heater power levels and resulting nozzle temperature distributions. By simulating external heating blankets, the optimum placement of heating blankets on the nozzles was determined to minimize detrimental residual stresses that would contribute to in-service cracking.

Case Study: Trapped Fluid Between Isolation Valves
For one utility client, overpressurization of a valve connection and local piping system occurred due to heating of trapped fluid between dual isolation valves.

In this case, SI developed software that simulated transient heat transfer, pressurization, and wall flexibility to determine whether system modification was required to meet ASME Code Section III pressure limitations.

Case Study: Feedwater Nozzle Cracking
Feedwater nozzles in steam generators of pressurized water reactors (PWRs) have experienced cracking during low temperature auxiliary feedwater injection. For a PWR plant, SI developed a unique replacement feedwater nozzle safe-end design that offered a long term solution to the cracking problem. In addition, SI acted as prime contractor for replacement of these safe-ends.

SI provides innovative and economical solutions to complex engineering mechanics and design problems, including inspection and evaluation services to justify continued operation. In the event that continued operation cannot be justified, SI can provide creative design repair alternatives that can be employed for rapid return to service.

If you would like to obtain more information regarding SI's capabilities in the area engineering mechanics and design, please contact SI.