Written by Scott Schreeg | Power Plants
SVI Dynamics recently completed an inspection of the exhaust systems for two units at a power plant in Virginia. A total of 15 high-frequency baffle sections and 16 low-frequency baffle sections were visually inspected, and multiple repairs were recommended.
What Type of Inspection Was Performed?
The SVI Dynamics inspection team did a visual inspection of the exhaust silencer and diffuser A042 duct, which included inspections of the exhaust silencer low and high-frequency baffles, the exhaust duct access doors, and the diffuser liner and flex seal.
What Did the Exhaust System Inspection Find?
The inspection found the silencer duct and baffles were in poor structural condition. Most of the low and high-frequency baffles had perforated sheet deterioration and cracks. The welds between the perforated sheets and baffle frames were broken and separated. Additionally, all the baffles had lost more than 50% of the acoustical insulation, which negatively affected the acoustical performance of the silencer.
The site inspection also found that many of the access doors had cracks in the plates and welds; typically, the door cap had cracks in the corners, and material had deteriorated.
The diffuser liner and flex seal were not without findings. There were multiple studs of the diffuser flex seal found missing, some of the welds between diffuser expansion joints and the silencer duct were cracked, and all four bleeder pipe rings in each unit were cracked, or part of the ring was missing.
What Exhaust System Solutions Were Offered?
The SVI Dynamics inspection team offered temporary repairs to prevent any safety issues that could result from baffle deterioration and perforated sheets breaking off. The temporary solution was to grind the cracked welds and reweld the perforated sheets to the baffle frames. When the perforated sheets become disconnected from the baffle frame, small parts of the sheets get ejected outside the stack during operation and cause safety issues. Additionally, SVI recommended replacing the existing baffles with new baffles within one year to prevent any major safety issues or emergency shutdown. SVI proposed a new silencer baffle design that would eliminate the high frequency set simplifying the system while maintaining acoustical performance, optimizing velocities, and reducing system pressure drop.
For the exhaust doors, the team recommended that the deteriorated and cracked door caps be removed and replaced.
Lastly, for the diffuser (A042 duct) liner and flex seal issues, SVI recommended that missing flex seal studs be replaced (welded in) and new nuts and washers installed, the cracked welds between the diffuser expansion joints and the silencer duct be rewelded, and that all cracked or missing bleeder pipe rings be replaced.