Cooling Tower Replacement: When It Is Considered and What It Involves

What wears out on a cooling tower

The PNNL guide calls a cooling tower a specialized heat exchanger in which air and water are brought into direct contact to transfer heat. It names two basic types: direct or open, and indirect or closed. In a closed tower the water runs through tubes and does not touch the outside air. EPA describes warm water pumped to the top of the tower, where it is sprayed or dripped through internal fill, which is a labyrinth-like packing with a large surface area.

The PNNL guide says fill is typically packs of thin corrugated plastic sheets, or splash bars supported in a grid. Small fans may be driven directly by the motor, but most designs need a belt or reduction gears between them. The PNNL guide says drift eliminators remove carryover water droplets.

SPX lists what a thorough inspection should identify before any rebuild. The list covers deterioration in structural elements, clogging or damage to fill, missing nozzles or leaking pipes, and wear and corrosion of mechanical components. It also covers ladders, guardrails, drift eliminators and louvers. Routine care of those parts is covered on cooling tower maintenance.

Repair, rebuild or replace: the order the guides give

FEMP's cooling tower guidance says to get expert advice to help determine whether a replacement is appropriate. It says new tower designs and improved materials can significantly reduce water and energy requirements for cooling. EPA's guide says facilities should first carry out efficient operation and maintenance and any available retrofits.

SPX draws the line between components and structure. It says new heat transfer media or spot repairs in an older tower will boost capacity in the short term. Unless structural integrity is also addressed, it says, there will be no improvement in the tower's longevity or structural stability. Where the required restoration is relatively minor and improving capacity is not critical, SPX says competent maintenance and repair specialists will normally be satisfactory.

A rebuild can also change materials. SPX says clogged or ruined fill may be replaced with higher performing fill, such as polyvinyl chloride (PVC) film fill in place of splash fill, where water quality allows. It says replacing wood with fiberglass-reinforced plastic (FRP) is a good choice when lifespan is a top priority. Where the fill is sound and no added performance is sought, simply cleaning it may meet the goals.

SPX's economics paper says the restoring options must be analyzed against a complete replacement. It names fill media replacement, water distribution refurbishment and mechanical component upgrades as those options.

Measure the tower before you decide

SPX's first step is to compare the tower's existing thermal performance with its design performance. It says performance is shown by plotting outlet cold water temperature against inlet wet-bulb temperature at constant fan speed, water flow and heat load. The less temperature and flow data the installed instruments provide, SPX says, the more likely a formal performance test is needed.

SPX adds that design conditions are normally chosen conservatively and occur less than 200 hours a year. So operating data should show water colder than the design point on all but the hottest days. If it does not, SPX says, the tower's thermal performance may not be adequate.

For a formal test, SPX points to the Cooling Technology Institute (CTI), which publishes a thermal test code for measuring how a tower performs. It says full-scale performance testing may require an outside agency's assistance. A test before the work gives a starting point for capacity goals and a reference for judging the result.

The shortfall matters beyond the tower. The PNNL guide says a poorly maintained tower produces warmer water and higher condenser temperatures, which reduces the efficiency of the chiller. How the chiller uses that water is explained on chiller system.

Building the comparison

SPX's economics paper lists what the value comparison between tower options should generally include:

1. Capital costs for equipment and installation.
2. Electricity costs for fan and pump operation.
3. Water treatment costs.
4. Maintenance costs, which SPX calls especially important when comparing a new tower with a repair or rebuild.
5. Operating cost reductions from lower operating temperatures.

SPX calls simple payback a screening tool used mainly in constrained environments, and says it is rarely the primary measure for ranking capital spending. It says internal rate of return (IRR), net present value (NPV) and economic value added give more meaningful information on long-term value.

FEMP says the first resource for advice should be local or headquarters engineers. It adds that input from experienced contractors and other government agencies should not be overlooked. Our reading: bring the performance test, the repair history and the plant's load plans to that conversation. How a tower fits a longer equipment budget is covered on commercial capital planning.

What a replacement project involves

A BAC project report describes new towers configured to meet the capacity needed while occupying the same footprint as the old units. It says this allowed the existing steel to be reused. BAC's Series 3000 rigging instructions say its International Building Code (IBC) rating is certified only with standard anchorage locations. They add that alternate anchorage or alternate steel supports will void any IBC wind or seismic ratings.

The same instructions say the unit must be level for proper operation and that anchor bolts are provided by others. Each section's weight should be verified from the unit's certified drawing before rigging. Before a lift, they say to ensure no water, snow, ice or debris has collected in the basin or elsewhere in the unit. Piping must not be supported by the tower's inlet connections.

BAC says each unit should be placed to keep its discharge air out of the ventilation system of any building. The PNNL guide says the same about fresh air intake ducts.

SPX says towers carry hazards such as high voltage power, fall hazards and trip hazards. It calls for a full job safety analysis (JSA) before anyone accesses a tower, with a mitigation plan for each hazard. It names lockout/tagout (LOTO), personal protective equipment and fall protection among the controls. SPX also suggests asking bidders whether they can provide temporary cooling if it is needed, and who carries the overall warranty. Temporary plant options are covered on temporary chiller rental.

Startup, testing and Florida's license line

The PNNL guide lists what tower startup should include. Accumulated debris is removed, and water flow is balanced by the maker's procedure so hot water reaches all areas of the fill. Chemicals are added on the water treatment company's recommendations. It says galvanized steel towers need special passivation during the first weeks to prevent "white rust." BAC says to refer to the unit's operation and maintenance manual before startup.

SPX writes that, according to CTI, about half of newly built cooling towers passed their initial performance test in 2014. It advises always insisting on a performance test when buying a new tower. SPX says that, at a minimum, every cell should receive an annual professional inspection of items including gearboxes, fans, fill, distribution piping and nozzles, ladders and other safety components.

In Florida, the 2026 statutes limit a Class B air-conditioning contractor to 25 tons of cooling and 500,000 Btu of heating in any one system. Ask which license class the contractor holds and what it covers. The Florida HVAC contractor license page explains how to check a license number.