Cooling Tower Maintenance Guide

FRP Cooling Tower Maintenance

Cooling tower Maintenance in your industry is as important as maintaining any other machinery or component. To keep all other machinery in your industry you need to take care of your cooling towers that help you control temperature and save cost all the while keeping your machine’s efficiency the top priority

We have divided Cooling Tower maintenance into 3 broad categories on the basis of time and they are:

  • Monthly basis
  • Quarterly basis
  • Half-Yearly basis

Not every activity is required to be done on a monthly basis so we have bifurcated it for your ease of understanding. 

What Cooling tower maintenance  activities do you need to perform monthly?

  1. Check the transparency of sump water
  1. Check for water leakage
  1. Check the water pressure
  1. Check the motor amperage reading
  1. Check the line voltage

What Cooling tower maintenance activities do you need to perform quarterly?

  1. Check if the water flow is obstructed at the orifices/splash caps. Get them cleaned/treated if necessary.

  2. .Check the motor and fan assembly, inspect for any loose bolts. If any loose bolts are found, tighten them to the optimum or specified torque.

  3. Get in touch with your water treatment partner and check if there is any biological growth in the cooling towers if found then get a suitable treatment done to eliminate it.

  4. Check for scaling, if found get it treated or install a non-chemical water treatment device like the Delta Device that will continuously prevent scaling efficiently without incurring any power expenses or external expenses.

What Cooling tower maintenance activities do you need to perform half-yearly?

  1. Complete cleaning of cold water sump: The cold water sump should be thoroughly cleaned to remove any contaminants that might have accumulated over the period of time.

Major points to remember for cooling tower maintenance activity:

  • Before any maintenance is performed on the cooling tower, make sure that all power to cooling tower components is disconnected and locked out.
  •  A water treatment program to stop biological contamination and the creation of conditions conducive to the development of legionella bacteria is strongly urged with any cooling tower system. Also, a water bleed-off and full-flow filter system are recommended to control dissolved solids and turbidity in the system.
  • If a chemical treatment system is being used, check operation water treatment in the cooling tower system, operation of automatic chemical treatment unit, and operation of both the bleed-off and bleed-back lines on a regular basis.
  • Water conditions should be checked periodically. The water should be clean as possible since dirty water can cause excessive pump seal wear.
  • All fasteners should be checked for tightness and re-tightened where applicable with care taken not to overtorque the fasteners. This is a natural function of the FRP settling after installation and transportation.
  •  Fan motor bearings should be checked for noise and lubrication. Use only good quality lithium base or lithium complex grease with a base oil that has a viscosity of 100 -140 oC St @ 40 oC, consistency NLGIg grade 2 o r 3 and continuous temperature range of -30 oC to 130 oC. 
  •  All external pipe hangers in the cooling tower should be checked regularly for the proper tension and that they are still securely tied down.
  • Splash Caps in the cooling tower should be checked periodically to ensure that the spray remains at original full shape and that the flow rate through each holes is approximately the same.
  • discharge should both be checked periodically to make sure there are no obstructions or blockages. Blockages create regions of high air velocity and this results in inefficient cooling tower performance.

Safety: One of the most important parameters to consider before starting:

At Delta Cooling Towers safety is always the priority.

There are a few maintenance safety “reminders” that may be helpful to review before engaging in maintenance on your cooling tower.

Before working on the cooling tower, the internals should be disinfected at a level of residual chlorine of between 5 and 15 mg/l for 5 hours while the water is circulated. Before servicing or adjusting switch off and isolate the fan set and tower electrically. You must lock-out/ensure that

the power cannot be restored while an adjustment or service is in progress. All the parts must be at rest or standstill before opening the unit for service.

The circulating water in a cooling tower may be harmful, and therefore under no circumstances should any maintenance be carried out while the liquid is circulating in the tower. Among the potential hazards typically presented by cooling tower water:

• Burns – It is possible for the circulating water to be hot and cause burns, especially in an industrial application.

• Chemical Exposure – Depending on the specific water treatment program employed at your site, many chemicals used to control biological growth and scaling in the tower can damage human tissue and these may enter the body through the skin, through abrasions, or as droplets into the nose or mouth or eyes.

Biological Contaminants – It is also possible for bacterial or other microorganisms to be present in your circulating water, presenting a health hazard.

There are a few basic rules that should be followed to prevent possible damage to  your Cooling Tower during winter or freezing-temperature operation:

  • Never operate towers fans when the exit water temperature is below 45 deg.F. At this temperature, it would be possible to generate ice within the tower. It is a good operating practice to limit the tower operation to water conditions above 40 deg.F.
  • It is necessary for 65% of the design water flow to be maintained over the cooling tower to prevent the water loading from becoming so light that ice may start forming in the fill media.
  • If the circulating water cannot be secured and when continuous operation in winter is expected, a winter bypass should be installed before operating the cooling tower in freezing conditions. The bypass should allow a portion of the entering hot water to go directly to the water basin. 
  • This will give the necessary control to maintain desired temperatures in the basin. Be certain to maintain ample water on the fill media to prevent the formation of ice.
  • The fans are the primary means of water temperature control. The fans will cycle “on” or “off”, based upon the exit water temperatures. When a VFD is used with your tower fan motors, the fans will not cycle, but change speed in response to changes for exit water temperature.

Freeze Protection :

When towers are installed in a cold climate and operated year round, it is recommended that basin heaters be utilized. If specified and furnished for your installation, these sump immersion heaters have been supplied with a self-contained control system. This system provides for the heaters to come into service based on the set point established for each site. This feature

Should be checked each year for serviceability before winter operating temperatures are experienced, as well as during winter operation. The heater was sized to protect your basin down to 0ºF ambient conditions with no wind chill Factor.

Winter Storage :

When cooling towers are not in service for any extended period of time, the water should be drained. The drain valve should be left open to prevent rain or snow from collecting in the basin. The motors should be run periodically during the storage period. Please refer to them or to manufacturer’s recommendations.

When the cooling tower needs to be shut down for short periods such as overnight or on weekends, and it is not going to be drained, a basin heater is recommended. These heaters are preprogrammed to turn on when the basin water drops to below a minimum set point, and should remain on until the temperature reaches the preprogrammed “off” value.

Seasonal Shutdown:

The following services should be performed whenever the Cooling Tower it to be shut down for a prolonged period :

• Drain the cold water sump and all piping.

• Clean and flush the hot water and cold water basins with the sump strainers in place. Leave the cold water sump drain open so rain etc. will drain from the tower.

• Clean the sump strainers and reinstall.

• Cover the hot water sump (if any) to keep out dirt and debris.

• Lubricate the fan shaft bearings and motor base adjusting screw.

• Close the shutoff valve in the make-up water line and drain all exposed makeup water piping.

When the system has to be shut down for an extended period of time, it is recommended that the entire system (cooling tower, system piping, heat exchangers, etc.) be drained.

During shutdown, clean the tower and make any necessary repairs. Moisture will condensate inside of the motor if the motor stops running for long term. Even during the seasonal shutdown period, it’s suggested to run the motor at least 3 hours per month (this is known as “exercising”), this dries up the windings and relubricates the bearings.

Two-Speed Fan Drives (When Applicable) :

 If two speed fan drives are employed, it is important to allow a time delay of 15 to 20 seconds after turning off the high speed and before energizing the low speed. Undue strain is placed on the mechanical equipment unless the fan is at

or below the low speed RPM before energizing the low speed winding. The time delay switch should be so arranged that it is impossible to go from high to low speed without first going through a stop.

Going from low speed to high speed poses no problems. One and one-half to two minutes time delay should be allowed before energizing the motor when changing the fan rotation.

Cold Water Sump : 

The cold water sump should be inspected regularly. Any trash or debris which may have accumulated in the sump or on the strainers should be removed. Each month, the entire cold water sump should be drained, cleaned, and flushed with fresh water to remove the silt and sediment which normally collects in the sump during operation.

If not removed periodically, this sediment can become corrosive and cause deterioration of the protective finish. When flushing the sump, the strainers should be left in place to prevent the sediment from reentering the system. After the sump has been flushed the strainers should be removed, cleaned, and replaced before refilling the sump with fresh water.

Make-Up Valve :

A float operated water make-up is furnished as standard equipment on all units. The float controlling the valve is mounted on a threaded rod, held in place by wing nuts to facilitate adjustment of the operating water level. Ensure the adjustment as per the season.

Because the winter load is frequently less than the summer load, the winter evaporation rate is also frequently less than the summer evaporation rate. In such cases, the water level in the cold water sump will increase unless the float is readjusted.

Corrosion Protection :

The Delta Cooling Tower is constructed entirely of corrosion-resistant material. The casing, fill, etc. is made of an inert synthetic material that requires no protection against rot, decay, rust, or biological attack. The balance of the construction is hot-dip galvanized steel.

Cause of Deterioration : 

An unacceptable rise in the temperature of the re-cooled water may be due to a number of causes. Before investigation of the Cooling Tower itself, it is necessary to check that:

• System has deteriorated from a known and accepted standard, i.e. commissioning of test data, and that design parameters of thermal loading and design W. R. have not been exceeded.

• No alterations to the cooling system, which could have invalidated design data.

• Any noise or vibration above that initially accepted, is identified and rectified before any attempt is made to investigate thermal characteristics.

Regularly maintaining a cooling tower can save you from many unexpected expenses and hassle. This guide will help you keep a track of the maintenance activities and keep your activities running smoothly, coolly and efficiently.

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