Intake and Exhaust Stack Inspection: Project Brief

The inspection team from SVI Dynamics inspected the intake and exhaust stack at a power plant. After the thorough inspection, the team made recommendations for necessary maintenance and repairs.

What Type of Inspection Was Performed?

A visual and ultrasonic inspection was performed for the intake and exhaust stack for the plant’s unit #3. The goal of the inspection was to examine the components for their overall condition to determine if they needed repair, replacement, or future monitoring only.

 

What Did the Intake and Exhaust Stack Inspection Find?

On the exhaust stack, at the entrance region, there were three ceiling panels that were loose because most of the connection assemblies (plate washers, threaded rods, nuts) were not secured. A 3’ x 1’ plate was missing from the east side near mid-height. Regarding the floor plates, there were various cracks identified on previously installed patch plates, as well as several bulged regions. A crack was found in the west wall above the access hatch.

The diagonal member of the added pipe supports was completely cracked from the turning vane assembly, and the upper connection bolt at the linkage connection had shifted inward and was slightly skewed. No concerns were noted about any baffle when viewed from above or below. Most spacer panels did not span the full height of the baffles, and there were areas of heavy rust and scaling on surfaces in these regions.

On the upper extensions, there were several regions that were split open along vertical seams of inner panels, and cracks were identified in the channels at past welds in the upper corners and at welds at channel splice locations.

The concrete foundation pads had significant cracking and spalling on the southeast quadrant, with thin cracks in the other areas. There were no immediate concerns viewed with the steel supports or slide plates. There was no corrosion or deterioration in the anchor bolts and nuts. And the siding and attachment members were found to be in good overall condition.

The intake stacks also had inspection findings, including heavy deterioration with heavy levels of rust and scaled plate. There was surface deterioration visible, but no signs of cracked or bulged regions. All baffles appeared secure and in the proper position. The surfaces along the upper perimeter deteriorated due to moisture infiltration from the upper enclosure. Minor fit-up issues, connection weld, and painting issues were found in most regions. There was pitting in a plate local to the drain opening, and two holes were found in a plate in the northwest corner.

Read about SVI BREMCO’s capabilities in a similar project: Simple Cycle Combustion Turbine (CT) Exhaust Duct and Stack Thermography Analysis in Virginia.

What Intake and Exhaust Stack Solutions Were Offered?

Upon completion of the stack inspection, SVI Dynamics recommended that although there wasn’t one particular region or component of the exhaust stack that was in an excessively deteriorated state, the sheer number of defects found across all parts warrant the complete replacement of the stack. To assist with making the decision of repair or replacement, SVI suggested that the plant request cost estimates for the following list of repairs so a comparison can be made.

• Secure all ceiling plates and stiffeners in the entrance region.
• Replace missing side plate in entrance region.
• Repair the cracked side wall plate above the access hatch.
• Remove and replace all floor plating.
• Repair or replace the broken pipe of the turning vane support.
• Replace the displaced support bolt (upper east side of vanes).
• Exposed regions of plates above the spacers (between each
• baffle) to be cleaned and coated.
• All seams between the perforated plates in the upper enclosure are to be bridged with a stainless plate.
• Repair all cracks in the corners and splices of the enclosure.
• Perform concrete NDE for all four foundation pads to determine their structural integrity.

The intake stack also had recommended repairs. On the baffle enclosure, in the upper elevations, the exposed regions of the carbon steel plate between the 15 baffles require repair or replacement. If the baffles can be removed, this region should either be cleaned (sandblasted) and coated (painted) or have the carbon steel areas replaced. If the baffles cannot be removed, then a method to clean (wire brush or sandblast as much of each region as possible) and coat or possibly install a cover plate that will encase the deteriorated regions. The cover plate could be secured to the upper and lower elevations of the enclosure.

On the left side intake, floor plate holes need to be patched. Deteriorated welds and regions along angles and patch plates around the perimeter should be cleaned, repaired as necessary, and coated.

Does Your Plant’s Intake and Exhaust Stack Need This Type of Inspection?

The professionals at SVI Dynamics design and install advanced solutions for industrial power plants’ intake and exhaust stack systems. If your plant is in need of a comprehensive inspection, contact SVI to schedule a time for our team to come to your site.