Often tucked away in the back of a plant, industrial cooling towers are one of the most necessary, but under-appreciated pieces of equipment found in any processing plant.
Thermal demands from cooling towers are increasing every year as plants are producing more and more heat from their processes. Since plants cannot operate without cooling towers, many rebuilds are required to be completed on line. This means the cooling tower rebuild must be accomplished while it remains fully operational and without impacting plant production. Unfortunately, this leaves the structure in the cold water basin inaccessible until a full plant shutdown or outage occurs.
Since full plant shutdowns are extremely expensive, they are being pushed to ever-increasing intervals (four to seven years in some cases), and when they do occur, they are very short in duration (two to eight weeks). One of the key challenges of replacing industrial cooling towers during a short outage is upgrading a cooling tower's structural design to meet current wind speed requirements while also working with the existing concrete anchors.
Most cooling towers being replaced were designed in the '60s, '70s or '80s, and additional design and engineering is required to ensure the rebuild meets current ASCE-7 standards. These days, most areas of the Gulf Coast require design wind speeds of 145-155 mph. Additional bracing may be required, and there is always a concern over the condition of the existing anchor bolts in the basin. Further complicating the rebuild process is the fact that cooling tower basins are difficult to inspect while in operation. With many clients extending their outage intervals, current inspection data of the anchor bolts is not always available.
Ideally, all the anchor bolts would be replaced to ensure all connection points to the concrete are adequate. But with shortened shutdown durations, sometimes new anchor bolts are installed only where there's damage to existing bolts or new structural bracing is required.
Once it's determined which anchor bolts are damaged, replacing them or installing new ones is not always a simple task. The majority of the existing anchor bolts were cast in place when the basin was originally constructed. They either need to be drilled out with a coring machine or cut off, and the base anchors need to be moved and/or redesigned.
New anchor bolt and casting location.
Orginal unusable anchor bolt location.
New anchors need to be post-installed anchors (either mechanical wedge or epoxy type fasteners). Updates to the selection software for these anchors have reduced the allowable edge distances so much, that if the current base anchor is anchored to a pilaster, it will probably need to be moved to the basin floor. Once moved to the floor, if there is still water in the basin, different epoxies must be investigated to ensure the increased wind-load requirements can be achieved.
New engineering solutions and innovations are available to meet all of these challenges. However, it's critical that the solutions are planned prior to the outage to ensure no untimely delays are encountered once the outage is underway.
For more information, visit www.ictower.com or call (832) 780-6900.