Low Pressure Composite Repairs at Base of Coal Ash Silos
Industry:
Power Generation
Date:
Feb 2024
The Challenge:
An engineer from a power plant in Florida contacted us to look at two of their coal ash silos that had two different type of failed external wrapping systems at the base of the silo (which was 90 foot off the ground, causing a cavity that could have allowed valuable coal ash to weep from the bottom of the silo and into the atmosphere.
Upon inspection, on Silo #1, the rubber liner was damaged in multiple locations and is leading to concrete deterioration and crevices.Corrosion. On Silo #2, there was a polymer liner that failed at the seam, thereby allowing ingress of moisture and escape of coal ash.
Each silo is 50 feet diameter. The repair included coating and sealing 16″ up onto the steel silo and 12 inches onto the concrete base.
Repair at Coal Ash Silo
The Solution offered:
Corrocoat’s Sales Engineer arrived on site within a week of the call. One week after that, we devised a specification that includes removal of each types of failed wrap using pneumatic tools, working a portion of the surface from 125 foot
manlifts.
The coating specification included for priming each respective substrate using Plasmet ZF for the Steel and Plasmet ECP for the concrete, followed by a layer of multiaxial fiberglass and finished off with an additional coat of Plasmet ZF and
a polyurethane topcoat for UV protection.
An unexpected problem that was encountered during the project was discovered while filling holes with the Corrofill E. (Note that there were there were hundreds of holes ranging from the size of a pinhead to the diameter of a walnut – see top right image.) Although the silo was said to be depressurized during the operation, the shape and size of the silo created a natural draft and therefore pressure on the silo.
After filling about 80% of the holes, the pressure increased on the remaining cavities to the point that pinholes formed in the Corrofill E once placed. It took several passes and significant skill and patience to finally stop all of the air from escaping and fashion the filler to a shape that would allow for effective fiberglass application.
Ultimately, Corrocoat was up to the challenge and we solved a dificultand potentially expensive problem that we expect should last for the life f the plant.
Product:
Plasmet ZF
Plasmet ECP
Corrocoat Epoxy Laminating
Resin (ELR)
Corrothane AP (PU topcoat)
*Note that Coal ash is a byproduct from burning coal used in thermal power plants. Coal ash is used in industry for a variety or commercial purposes, primarily as an additive in contentious concrete