The combustion air system of an incinerator is a crucial component for its operation, consisting of a fan, two skids, interconnecting piping, and the incinerator itself. Dynaflow Research Group (DRG) was tasked with designing both the on-skid and off-skid piping systems, including those connecting the air fan and the incinerator. DRG’s scope also encompassed the design of all necessary pipe supports. This involved a comprehensive piping stress analysis, including a flange check and an evaluation of nozzle loads, all conducted in accordance with the ASME B31.3 design code.
Assessment
The entire combustion air system was meticulously modeled, incorporating recommended routing and restraining layouts. The client was kept informed throughout each stage of the design process, with feedback being integrated into the final design.
Design
To address varying system conditions, multiple temperature scenarios were investigated, including temperature differentials across a bypass line. A support layout was developed to minimize material stresses under different load cases. Pipe and flange stresses were assessed according to the ASME B31.3 piping code. Additionally, Finite Element Analyses (FEA) were conducted for the nozzles connecting to the burner and for a 38” section on one of the skids, which included several branches.
The piping connection to the air fan was designed to include two expansion joints. The maximum lateral displacement of the piping was calculated to ensure appropriate selection of these fabric bellows.
Results
The design process and subsequent analyses led to the following conclusions:
- The interconnecting piping routing was designed and approved by the client, allowing sufficient maintenance space around the incinerator and minimizing nozzle loads. The piping was kept as close to the ground as feasible to reduce the need for extensive support structures.
- All piping stresses met the ASME B31.3 code requirements. The load components on the incinerator nozzles adhered to the ASME Section VIII Div. 2 code.
- The outlet duct near the fan’s outlet nozzles required vertical support.
- The maximum lateral displacement at the bellows location was calculated and verified with the client.
- Isometric drawings were created for the interconnecting piping.
- Flange supports were recommended for the valves to ensure system stability during maintenance or replacement of the middle valve.
- DRG provided detailed designs for each support.
This comprehensive approach ensured that all components of the combustion air system were designed for optimal performance and compliance with relevant codes.
