Seasonal Overhauls for Chillers: Chapter 3
Cooling Tower Overhauls Part 1
As seasonal shutdown looms on the horizon, your cooling tower needs extra attention. Take a peek at our quick tips for your cooling tower seasonal overhaul so that you are prepared when the snow starts to fly. You should be able to handle all winter shutdown problems after going through this module. Skip to quiz!
Cooling Tower
Do you think overhauling only the main components of the chiller is sufficient to run them efficiently? No! Just like leaving your car unused for a while can degrade all of its components, winter shutdown can damage chiller components.
There are several components of the chiller system. The component on the building rooftop is a cooling tower. Recall that the chiller removes heat from the building. In the same way, a cooling tower is used to remove heat from the chiller.
Cooling Tower Components
Do you recall what all components a cooling tower has? The components of a cooling tower are:
Basins,
Fills,
Nozzles,
Drift eliminators, and
Fans
Ice or debris can form and collect on cooling towers during the winter shutdown. The image shows that the fan stops rotating due to ice collection on the blades. This will stop the circulation of air throughout the cooling tower.
Just like a car with deteriorated tires needs servicing, a cooling tower with obstructed components needs to be overhauled. The animation shows the overhauling of a cooling tower during a winter shutdown.
Recall that drift eliminators trap large water droplets from escaping. The drift eliminators should be free from mud or debris buildup to trap these water droplets. If they look dirty, we need to clean them during overhauling.
For cleaning drift eliminators, we need to remove them from the cooling tower. We can easily access them from the top of the cooling tower. Place them gently on an elevated platform or the ground.
Next, wash eliminators by spraying pressurized water until debris is removed. Insert the eliminators back into place in the cooling tower.
Water cleans eliminators effectively to remove all debris. While inserting eliminators back in place, we need to ensure they are oriented correctly.
The orientation of eliminators is critical. Just like our home roof tiles are oriented improperly or cracked, they will not seal the rooftop and need to be replaced. In the same way, if the drift eliminator is ruptured, we need to replace it. Next, let's look at overhauls of fill media.
Inspect the cooling tower fill media by removing pieces of fill media from all fill layers. Visually inspect the flute openings on the bottom side of the piece.
If the buildup of algae bacteria is significant, the fill media needs to be cleaned. Remove the fill media and clean it with water and mild detergent. This is similar to cleaning drift eliminators.
Like debris in the water tank can block our shower head, ice buildup or debris can block the nozzle. We need to inspect the water distribution pattern of the nozzle visually.
We should get a uniform square water pattern. We get a non-uniform pattern if sticks or large objects are stuck in the nozzle. We need to remove the blocked nozzle and pressure wash them.
Recall that improper lubrication leads to bearing failures. We should lubricate the bearings of a cooling tower fan motor during overhaul.
We need to pump grease into the bearing using a hand-operated grease gun. Pump it until new grease appears at the drain opening. This will remove old grease and contaminants inside the bearing.
Gearbox lubrication is commonly the most significant issue related to gearbox failures. Be sure to check your oil. There are three reasons to check your oil. The first is to check the oil level and ensure it is not low.
Second, debris can mix with the oil, causing failure. Third, humidity can increase the water content in your oil. If excessive water is present in the oil, the oil thins out and causes rusting of gears.
In the belt drive, we need to check the belt tension and pulley alignment. We need to inspect V-belts for signs of cracking. If a belt is damaged or looks worn, replace it right away.
During overhauling the cooling tower, we need to:
Inspect drift eliminators and ensure they are free from mud or debris,
Clean eliminators by spraying pressurized water,
Clean fill media and basin,
Inspect spray nozzles, and
Lubricate bearings and gears
Cooling Tower Overhauls Part 2
We have been discussing the cooling tower in the last module. Let’s get our hands dirtier by taking an in-depth look at cooling tower overhauls. Skip to quiz!
Cooling Tower Overhauls
Have you noticed Canada's Abraham Lake during the winter? Lake water turns into ice bubbles. If our cooling tower is not drained before the shutdown, it will freeze. We need to drain it during overhauling if it is not operating during the winter months.
If there are deposits on the basin floor, we need to clean them during the overhaul. To check the basin floor, open the access doors of a cooling tower. Next, remove deposit buildup using a vacuum pump.
Recall that a float valve consists of a ball that detects elevation changes in the liquid. The float movement upwards and downwards for opening or closing a valve. These valves are similar to the ones we find in toilet tanks.
We need to check whether the float valve is functioning properly. If it does not function, the water level in the cooling tower cannot be maintained.
We need to check the strainer of a cooling tower feed pump. This is because corrosion byproducts break loose and clog feed pump strainers. We need to clean the clogged strainer using a pressurized water hose.
For fan motors, perform a bump test of the motor. The purpose of the bump test is to make sure the shaft rotates correctly and fan blades have proper clearance in the casing. In this test, the unit starts, and the rotor accelerates from zero speed.
Cooling tower basin heaters prevent cold water basin freeze-up during winter weather. Basin heater elements are located in the corners of the tower module.
Check our basin heater system before each cold season to ensure it’s operating correctly.
Recall that a contractor is a switch that controls the electrical power to a circuit. The contactor opens when the temperature reaches the set temperature.
The opening of a contactor will turn off the heater of a cooling tower. So to test the heater, we should manually alter the temperature set point and check if the contactor opens.
As the contactor opens, the circuit breaks, and the heater turns OFF. So to test the heater, we should manually alter the temperature set point and check if the contactor opens.
Next, we need to check the control panel of all the electricals. If dirt or debris gets collected on the panel and contact terminals, it will result in poor electrical connections. We need to clean a dirty control panel during overhauling.
When cleaning a VFD control panel, the best tool to use is a vacuum. This will allow all the dirt and debris to be removed from the panel and its parts, ensuring good electrical connections.
During overhauling a cooling tower, we need to:
Inspect and clean tower basin,
Check fan motor,
Inspect float valve,
Test basin heater, and
Clean VFD control panel.
Question #1: The drift eliminators trap greenhouse gases?
False
True
Scroll down for the answer...
Answer: False
Drift eliminators trap large water droplets from escaping.
Question #2: Arrange the following options in sequence that we follow for cleaning drift eliminator?
Remove drift eliminator from cooling tower.
Insert the eliminators back into place in the cooling tower.
Place drift eliminator gently on an elevated platform or the ground.
Wash eliminators by spraying pressurized water until debris is removed.
Scroll down for the answer...
Answer: Remove drift eliminator from cooling tower.
Place drift eliminator gently on an elevated platform or the ground.
Wash eliminators by spraying pressurized water until debris is removed.
Insert the eliminators back into place in the cooling tower.
We need to remove drift eliminator from cooling tower, Place them gently on an elevated platform or the ground, Next, wash eliminators by spraying pressurized water until debris is removed, Insert the eliminators back into place in the cooling tower.
Question #3: What is the correct water distribution pattern of a spray nozzle?
Scroll down for the answer...
Answer: Uniform flow pattern
We should get a uniform water flow pattern out of a nozzle.
Question #4: Why do we need to check the oil in the gearbox during overhauls? (select all that apply)
To ensure no debris is present in the oil
Low oil levels create vibration
Low oil level can reduce gear ratio
Oil level increases cooling tower fan speed
Scroll down for the answer...
Answer: To ensure no debris is present in the oil
Low oil levels create vibration
We need to check the oil to ensure no debris mixes with the oil, causing gear failure.
Question #5: We should remove deposit buildup like heavy metal flakes on cooling tower basin using?
Feed pump
Vane pump
Tower vacuum pump
Sump pump
Scroll down for the answer...
Answer: Tower vacuum pump
If heavy metal deposits are on the basin floor, we need to clean them using a vacuum pump.
Question #6: How would you check cooling tower electric basin heater is functional during overhauling?
Checking for oil leaks on the heater
Altering heater tripping temperature and checking contactor opens
Measuring time required for melting ice
Checking the color of the heater coil
Scroll down for the answer...
Answer: Altering heater tripping temperature and checking contactor opens
To test the heater, we should manually alter the temperature set point and check if the contactor opens.
Question #7: How do we clean the control panels of the chiller?
Using water
Using compressed air
Using vacuum
Using propylene glycol
Scroll down for the answer...
Answer: Using vacuum
When cleaning a VFD control panel, the best tool to use is a vacuum. This will allow all the dirt and debris to be removed from the panel and its parts, ensuring good electrical connections.