When thinking about where you can improve operational efficiency, facility managers rarely jump to cooling towers. This however, can be a hugely inefficient part of your operation. We find cooling tower maintenance is a great way to improve operational efficiency as well as extend the life of your equipment.
Cooling towers are heat exchangers that are commonly used to remove heat from water leaving the chiller or air conditioning condensers. There are many different styles of cooling towers, such as cross flow, counter flow, induced draft and forced draft. These units will have slightly different maintenance requirements so be sure to always follow your manufacturers recommendations.
Start-Up Cooling Tower Maintenance Checklist
For starting up a cooling tower in the spring time, follow these maintenance steps:
- Clean and remove any debris, such as leaves and dirt from the air inlets.
- Flush the cold water basin (with the strainer screens in place) to remove any sediment or dirt.
- Remove the strainer screen, clean and reinstall.
- Check mechanical float valve to see if it operates freely.
- Inspect water distribution system nozzles and clean as required. Check for proper orientation.
- Check to ensure drift eliminators are securely in place and in the proper orientation.
- Adjust fan belt tension as required.(Replace Belt Annually)
- Lubricate fan shaft bearings prior to seasonal start-up.
- Turn the fan(s) and pumps by hand to insure it turns freely without obstructions.
- Visually inspect the fan blades.
- Verify if any stagnant water remains in the system including “dead legs” in the piping.
- Manually fill the cold water basin up to the overflow connection.
- Adjust mechanical float valve as required to the proper water level.
- Unit basin should be filled to the proper operating level.
- Verify fan is rotating in proper direction.
- Measure voltage and current.
- Adjust bleed valve to proper flow rate.
- Sliding motor base – Inspect and grease as needed.
- Clean pan strainer.
- Clean and flush pan.
- Check bleed-off valve to make sure it is operational.
- Inspect operating level in pan and adjust float valve if necessary.
- Check water distribution system and spray pattern.
- Check drift eliminators.
- Inspect the fan blades for cracks, missing balancing weights & vibrations.
- Check sheaves, bushings, fan shafts and fan hubs for corrosion.
- Check fan screens, inlet louvers and fans. Remove any dirt or debris.
Cooling Tower Routine Maintenance Checklist
Here are a few maintenance tasks that should be completed in the summer.
- Clean pan strainer (summer)
- Clean and flush pan (summer)
- Check bleed-off valve to make sure it is operative (summer)
- Check operating level in pan and adjust float valve if necessary (summer)
- Inspect water distribution system and spray pattern (summer)
- Check drift eliminators (summer)
- Check the fan blades for cracks, missing balancing weights & vibrations (summer)
- Inspect sheaves, bushings, fan shafts and fan hubs for corrosion (summer)
- Lubricate fan shaft bearings (summer)
- Check belt tension and adjust (summer)
- Check fan screens, inlet louvers and fans. Remove any dirt or debris (summer)
Cooling Tower Fall Maintenance Checklist (Shutdown)
As you get ready to shut down your unit for the colder months, follow these steps.
- Drain the evaporative cooling unit cold water basin
- The cold water basin should be flushed and cleaned with the suction strainer screens in place.
- Clean and reinstall suction strainer screens.
- The cold water basin drain should be left open.
- Lubricate the fan shaft bearings and motor base adjusting screws.
- The water make up valve needs to be closed.
- All water make-up, overflow and drain piping needs to be drained.
- The finish of the unit should be inspected.
- Clean and refinish as required. Energize motor space heaters. (if equipped)
Cooling Tower Maintenance And Water Flow
We have encouraged a number of facilities to let us examine the flow rates on their cooling towers units. Fortunately and unfortunately for these facilities, we have a high success rate at finding issues. We often find some zones are overflowing, some zones are under flowing and air side velocities are all out-of-whack. This results in units that get nowhere near nameplate performance!
For organizations like ethanol plants and other industrial facilities where summer production is limited by cooling tower output, this can be a huge problem. By re-balancing flows to cooling towers, they will not only increase unit efficiency, but also production capabilities.
In large commercial buildings, inefficiencies in cooling tower performance results in increased cooling bills. This means small tweaks and improvements can result in BIG savings on energy bills.
To measure the water flow, you have to start by using an ultrasonic flow meter. Ultrasonic flow meters work by transmitting ultrasound between two sensors. These offset sensors measure the time it takes for sound to travel between them and determine flow speed. From there you can adjust the flow to meet the requirements of the entire system.
New factory units are sometimes set up to over amp. In fact, we see this in the field all the time! When you’re looking to increase efficiency, cooling tower flow rates are a surprisingly good place to start. We also recommend checking flow rates on any main unit AHU, pumps, cooling towers or chillers on a yearly basis. This will ensure you are getting the performance your unit is designed to achieve.
Legionnaires’ Disease And Maintenance
Legionnaires’ disease is a severe form of pneumonia and has a death rate of 1 in 10 according to the CDC. The disease is most commonly spreads through cooling towers, hot tubs, showers, faucets and water features. By performing routine cooling tower maintenance you can spot stagnant water, perform proper chemical bacterial treatment and help reduce the risk of this disease.
According to an article written by Chardon Laboratories,
“Microbial growth causes numerous problems for your system and your employees. In warm conditions, bacteria and algae proliferate in uncleaned water. Biofilm, a physical film filled with bacteria, can cause micro-biologically influenced corrosion. These mats of bacteria can also harbor disease-causing microbes, such as Legionella. In addition to ongoing use of a bio-dispersant to break up this biofilm layer, a cooling tower cleaning can protect your system from these problems.
OSHA recommends cleaning your cooling tower at least twice a year to prevent the growth of Legionella bacteria. Following this schedule is critical because most evaporative cooling towers maintain warm water at the ideal temperature for bacterial growth. (Between 68 degrees Fahrenheit and 122 degrees Fahrenheit.) Additionally, due to the evaporation of water into the air nearby, workers in the area could breathe in Legionella bacteria. Putting them at risk for the disease.”
COOLING TOWER INSTALLATION
We can help you with your next cooling tower install. We can install natural draft, mechanical draft, crossflow and counterflow cooling towers. Installation will vary depending on size and type but here are a few common installation practices:
- System Evaluation And Appropriate Cooling Tower Selection
- Site Prep And Demolition of Existing Tower (If Present)
- Offload Components of Cooling Tower
- Setting Basins Followed By Installing Sump Boxes
- Setting Uppers Followed By Installing Corner Brackets
- Install Cell Redirectors And Louver Panels
- Install Handrails, Ladders, Conduit And Wiring
- Finally Install System Piping