Cement & Lime

A conditioning tower in a cement plant was at risk for structural failure due to interior corrosion and deterioration of the steel shell. Industrial Access was contracted for extensive inspection and repair work to identify most immediate problem areas as well as develop and carry out an interior reinforcement strategy to preserve the tower’s structural integrity.

A cement plant in the southeast of the US was experiencing severe degradation of their conditioning tower. This was a 162’ single wall carbon steel tower with 21’ diameter, exterior insulation and cladding supported on steel posts. The client was initially in need of inspection services for this structure to determine its condition and needs for further maintenance. During the inspection, areas of severe steel plate degradation were identified.

Because of the abrasive, corrosive environment inside of a concrete conditioning tower, steel surfaces deteriorate over time from corrosive and erosive attacks. This requires timely inspections and maintenance to prevent structural failure. In order to increase structure longevity, the client contracted Industrial Access (IA) to perform interior repair and reinforcement services over the following outage periods.

The technicians at IA are highly trained in rope access rigging and techniques to deliver services at maximized efficiency and safety. For this inspection, interior drops through the existing spray nozzle points were performed using expert rope access techniques. During the repair and reinforcement stages, a custom-built temporary swing stage was installed inside the tower to carry out the work safely and effectively. In addition, two access doors were installed in the sides of the tower at the top and bottom to accommodate the installation of the interior working platform and to carry in repair materials.

The first stage of services for this client was a condition assessment inspection of the conditioning tower interior. An evaluation was performed of the significance of any detected deterioration, damage or anomalies, and eleven sets of Ultrasonic Thickness (UT) readings were taken on a vertical line at 10’ intervals.

IA determined that the tower steel shell was in very poor condition. Multiple areas throughout the structure displayed excessive buildup, oxidation, delamination, failed patch plates, buckling and holes in the steel shell. Several of the previously installed patches had buckled or curled due to what appeared to be corrosion at the point of the welds. This had exposed the exterior insulation and cladding, and buildup material had filled the void. UT readings revealed substantial steel plate thickness loss – approx. 28% of loss across the board. The determined condition of the structure was a concern that could affect the structural integrity of the tower. Therefore, the team concluded that the heavily thinning, failing steel must be repaired and reinforced as soon as possible to allow the client more time to prepare for the future partial or complete replacement of their compromised tower.

During the following two outages, per client’s request, IA performed interior reinforcement services for the conditioning tower. After performing a washdown, the crew installed an almost complete set of new vertical stiffeners, HSS vertical stiffener extensions and flat plate circumferential rings in the conditioning tower interior. All vertical stiffeners were welded to the plate rings. Bolted end plate connections were used to splice HSS members, and knife plates were used to provide lateral connection between the tower and the members. Corroded and separated sections of the tower wall were repaired by welding new plate sections on the interior of the structure. All reinforcement work was done from 109’ to 40’ el. where the structural degradation was the most critical.

The conditioning tower interior reinforcement work was completed safely and successfully, strengthening the steel shell plate of the tower to preserve its structural integrity and prevent further buckling of plating. Since other unattended areas of the tower below 40’ el. are also showing signs of rapid deterioration, further reinforcement work is projected for a scheduled shutdown in the future. Regular inspections and timely maintenance work are crucial in preventing extensive future repairs and maximizing the potential lifespan of a structure.