1. Scope and Purpose
This guide describes the mandatory procedures for the preventive and corrective maintenance of industrial cooling towers, focusing on the inspection and cleaning of filling media, treatment of circulating water, balancing of fan motor sets and cleaning of the collection basin. Strict application of these guidelines aims to optimize thermal efficiency, reduce energy consumption, prevent premature component failures and extend equipment life. Maintenance must be carried out according to the schedule established by the manufacturer (OEM) and adapted to the specific operating conditions of the installation, generally at semi-annual or annual intervals.
2. Safety Precautions
ATTENTION: Maintenance operations in cooling towers involve significant risks of accidents due to moving parts, electrical energy, chemicals and wet surfaces. Strict adherence to the following precautions is mandatory.
- Locking and Tagging (LOTO): Before any intervention, ensure that the electrical system of the fan motor, water pumps and any other auxiliary equipment are completely de-energized, locked and tagged in accordance with the NR-10 standard. Check the absence of voltage with a suitable voltmeter.
- Confined Space: The cooling tower basin and other internal areas can be considered confined spaces. Follow the NR-33 confined space entry procedures. Require work permit, atmospheric monitoring and rescue team on standby.
- Chemicals: Wear nitrile gloves, safety glasses, and chemical-resistant aprons when handling biocides, corrosion inhibitors, or other water treatment agents. Consult the FISPQ (Chemical Product Safety Information Sheet) for each product.
- Moving Parts: Never operate the fan or pumps with the protective guards removed. Fan blades pose a severe shear hazard.
- Risk of Falling: Use paratrooper-style safety harnesses with double lanyards and secure anchor points when working at high heights or in areas with a risk of falling. ABNT NBR 16489.
- Slippery Surfaces: The inner and outer surfaces of the tower may be wet or covered in silt and algae. Wear safety shoes with non-slip soles.
- Biological Contamination: The water from the tower may contain bacteria (e.g. Legionella spp.). Avoid inhaling aerosols. Wear a PFF2 (N95) mask and protective glasses. Wash your hands and shower after work.
- Waste Disposal: Dispose of the water in the basin and the sludge removed in accordance with local environmental regulations, following NBR 10004.
3. Tools and Materials Required
| Tool/Material | Specification | Quantity |
|---|
| LOTO Kit | Padlocks, tags, locking devices | 1 set |
| Digital Multimeter | CAT III 600V, with continuity test | 1 |
| Vibration Analyzer | Accuracy ±5%, range 10 Hz to 10 kHz | 1 |
| Dynamic Field Balancer | For industrial fans | 1 |
| Torque Wrench | 50-500 Nm, with metric sockets | 1 |
| Combination Keys | 8mm to 32mm | 1 set |
| Universal Pliers | Isolated 1000V | 1 |
| Ultrasonic Thickness Gauge | For checking corrosion in metal structures | 1 |
| Digital Thermometer | -20°C to 200°C, with immersion probe | 1 |
| pH and Conductivity meter | Accuracy 0.1 pH, 1 µS/cm | 1 |
| Water Chemical Test Kit | For chlorine, hardness, alkalinity, iron | 1 |
| High Pressure Hydrojetting Machine | 150-200 bar, fan and rotating nozzle | 1 |
| Nylon/Steel Brushes | Various sizes for cleaning | 1 set |
| Plastic Scrapers | For scale removal | 1 set |
| Industrial Liquid Vacuum Cleaner | Minimum capacity 50 liters | 1 |
| Complete PPE | Helmet, safety glasses, nitrile/PVC gloves, hearing protection, PFF2 mask, safety shoes, seat belt. | 1 per technician |
| Water Hoses | Ø 1", with quick couplings | 20m |
| Waste Containers | Buckets, reinforced garbage bags | Various |
| Bearing Grease | Type NLGI 2 complex lithium | 1 cartridge |
| Reducer Oil (if applicable) | As per OEM specification | 1 liter |
| Drinking Water | For final cleaning | As needed |
| Photo Camera/Smartphone | For condition record | 1 |
4. Pre-Maintenance Inspection Checklist
| Item | Verification | Acceptance/Rejection Criteria | Observations |
|---|
| 1. Basin Water Level | Visual | Within OEM operating range. | If low, check leaks/replacement. If high, check drain/float valve. |
| 2. Fan Operation | Hearing/Vibration | No abnormal noises or excessive vibrations (see standard ISO 10816). | Record unusual sounds or tremors. |
| 3. Condition of Fan Blades | Visual (external) | No cracks, erosion, excessive accumulation of dirt. | Accessible via inspection hatch. |
| 4. Casing/Structure Integrity | Visual | No corrosion, visible structural damage, loose screws. | Focus on solder areas and joints. |
| 5. Purge System Operation | Visual | Adequate drainage for solids control. | Check for clogging or improper operation of the valve. |
| 6. Condition of the Drop Eliminator | Visual | No excessive scale/algae buildup, no damage. | Excessive drag losses indicate failure. |
| 7. Spraying the Distributor Nozzles | Visual | Uniform spray pattern over the entire filling. | Check for clogged or damaged nozzles. |
| 8. Condition of Water Pumps | Hearing/Vibration/Leakage | No abnormal noises, vibrations (ISO 10816), leaks in gaskets/seals. | Check discharge pressure and amperage. |
| 9. Electrical Connections | Visual | No signs of overheating, intact insulation, tight connections. | Pay special attention to the engine and panel terminals. |
| 10. Access and Security Guards | Visual | All guards and hatches in place and secure. | Handrails, steps and platforms in good condition. |
5. Step by Step Maintenance Procedure
5.1. Deactivation and Security
- De-energize the Equipment: Perform the complete LOTO procedure for the cooling tower, including motor fan, water circulation pumps, chemical dosing pumps and water replacement systems. Don't just rely on emergency stop buttons.
- Drain the Basin: Open the basin drain valve to completely empty the water system. If the system has a surge tank or clarifier, empty those as well.
- Ventilate the Space: If it is necessary to enter the basin, open all access hatches and use a portable exhaust fan to ventilate the space for at least 15 minutes before entering. Perform gas monitoring.
5.2. Inspection and Cleaning of Filling Media (Filling)
- Access: Remove the upper drip eliminators (if necessary and designed for such) to have visual access to the filling.
- Visual Inspection: Examine filling for:
- Scaling: Build-up of mineral deposits (calcium carbonate, silica). Fouling severely reduces the thermal exchange area.
- Sludge/Algae Formation: Accumulated organic material.
- Physical Damage: Breakages, deformations or collapse of the filling plates.
- Clogging: Obstruction by debris or sediment.
- Mechanical Cleaning: Using a water jetter (150 bar, fan nozzle), carefully wash the filling plates from top to bottom. For more severe encrustations, it may be necessary to remove some sections of the filling and clean with plastic brushes and scrapers. Avoid direct and concentrated high-pressure jets that can damage the filling.
- Chemical Cleaning (if necessary): For persistent mineral encrustations, use specific acidic solutions (e.g. sulfamic acid diluted at 5-10%) after consulting the OEM and chemical supplier. Strictly follow the safety instructions for handling acids. Rinse thoroughly after application.
- Repair/Replacement: Replace filling sections that show significant damage or irreversible clogging.
5.3. Water Treatment and Basin Cleaning
- Sludge and Debris Removal: With the basin drained, use an industrial liquid vacuum cleaner to remove all accumulated silt, sediment, leaves and other debris. Brush the walls and bottom of the basin.
- Cleaning the Basin: Wash the basin with a water jet (150 bar). For resistant stains and deposits, use brushes and appropriate industrial detergents. Rinse completely.
- Basin Inspection: Check the integrity of the basin for cracks, leaks or corrosion. Apply appropriate repairs or sealants.
- Y Filter and Screens Inspection: Clean the Y filters in the pump suction lines and check the protective screens for obstructions or damage.
- Water Replenishment: After cleaning, close the drain valve and restore the water in the basin to the operational level. Monitor the level and adjust the float valve.
- Initial Chemical Treatment: Add water treatment chemicals as per your treatment specialist's program. This generally includes:
- Biocide: For control of microorganisms (algae, bacteria, fungi).
- Corrosion Inhibitor: To protect the system's metal surfaces.
- Dispersant: To prevent the formation of deposits.
Consult the concentrations recommended by the supplier. - Water Quality Analysis: Perform a complete analysis of the basin water (pH, conductivity, hardness, alkalinity, chlorine/biocide level, iron, suspended solids) using the test kit. Parameters must be within the ranges established by the treatment program. Adjust chemical dosage and purge rate as needed.
5.4. Balancing and Inspection of the Fan Assembly
- Preliminary Visual Inspection: Before restarting, visually inspect:
- Fan Blade: Check for cracks, obvious unbalance (accumulation of material), damage to the edges. Clean any dirt accumulated on the blades.
- Gearbox/Pulleys and Belts: Check the oil level in the reducer (if applicable) and the condition of the belts and pulleys. Check belt alignment and tension.
- Motor and Reducer Bearings: Check for signs of overheating or grease/oil leaks.
- Fixing: Make sure that all the motor, reducer and fan fixing screws are tight.
- Lubrication: Lubricate motor and reducer bearings per OEM specifications and grease type (NLGI 2, complex lithium type, generally). Do not exceed the recommended amount of grease to avoid overheating.
- Torque Check: Check and retighten the fastening screws of the fan motor assembly and the support structure. See torque table below. Loose screws are a common cause of vibration.
| Bolt (Class) | Diameter (mm) | Torque (Nm) | Observations |
|---|
| Carbon Steel (8.8) | M10 | 48-52 | With medium chemical lock |
| Carbon Steel (8.8) | M12 | 82-88 | With medium chemical lock |
| Carbon Steel (8.8) | M16 | 200-220 | With medium chemical lock |
| Paddle Screw (Specific) | M10 | 35-40 | Check OEM manual |
- Dynamic Field Balancing:
- Vibration Measurement: With the system energized and operating (after restarting the pumps and fan), use the vibration analyzer to measure the vibration levels of the fan assembly in the three axes (horizontal, vertical, axial) at the support points of the motor and reducer bearings. The levels must be within the ISO 10816-3 standard (for industrial machines).
- Balancing Procedure: If vibration readings exceed limits, use a dynamic field balancer to identify and correct unbalanced fan blades. Add or remove counterweights as instructed by the balancing equipment. Unbalance can cause structural damage and premature bearing failure.
- Post-Balancing Check: Remeasure vibration levels to confirm reduction to acceptable limits.
- Alignment Check: Check the alignment between the motor and the reducer (if there is a coupling transmission) using a laser aligner. Misalignment must be less than 0.05 mm for flexible couplings. Excessive misalignment causes vibration and premature bearing wear.
5.5. External Cleaning and Finishing
- External Frame Cleaning: Remove dirt, dust, and debris from the external surfaces of the tower.
- Coating Inspection: Check the tower's protective coating for damage or areas of corrosion. Perform repairs or paint touch-ups as needed.
- Valve and Piping Check: Inspect all valves and piping for leaks or signs of corrosion.
- Reinstall Guards and Access: Make sure all security guards, hatches and access panels are correctly installed and securely closed.
- Documentation: Record all activities performed, vibration readings, water analysis results, parts replaced and any anomalies found in the equipment maintenance history.
6. Post-Maintenance Verification Checklist
| Test | Expected Result | Actual Result | Pass/Fail |
|---|
| 1. Basin Water Level | Stable in operating range | | |
| 2. Fan Operation | Silent, without abnormal vibrations (ISO 10816-3) | | |
| 3. Spray Pattern | Uniform, no dry areas in the filling | | |
| 4. Water Analysis (pH, Conductivity, Chlorine) | Within the ranges recommended by the program | | |
| 5. Leaks | No visible leaks in pipes or basin | | |
| 6. Bearing Temperatures | Within the manufacturer's limits (e.g. < 70°C) | | |
| 7. Security Guards | All in place and safe | | |
| 8. Motor Current Consumption | Within nominal range | | |
7. Troubleshooting Guide
| Symptom | Probable Cause | Corrective Action |
|---|
| Excessive Fan Vibration | Unbalance of the blades; Damaged/dirty blades; Worn motor/reducer bearings; Loose fixing screws; Misalignment of the assembly. | Perform dynamic balancing; Clean/Replace blades; Replace bearings; Retighten screws (see torque table); Realign assembly with laser. |
| Low Cooling Efficiency | Dirty/encrusted/damaged filling; Clogged/damaged distribution nozzles; Low water flow; High thermal load; Basin water with a high concentration of solids. | Clean/Replace filling; Clean/Replace nozzles; Check pump and valves; Optimize process; Adjust purging and chemical treatment. |
| High Water Consumption (drag) | Damaged/dirty drip eliminators; Basin water level too high; Excessive fan speed; Non-uniform water distribution. | Clean/Replace eliminators; Adjust float level; Reduce fan speed; Clean dispensing nozzles. |
| Sludge/Algae Formation | Inadequate dosage of biocide; High organic load in water; Insufficient purging; Excessive direct sunlight. | Adjust biocide dosage and purge; Investigate source of contamination; Evaluate shading or cover. |
| Corrosion in the Structure | Inadequate anti-corrosive water treatment; Water pH out of range; Failure of the protective coating; Excessive oxygenation. | Adjust chemical treatment program; Repair coating; Check corrosion inhibitors. |
| Abnormal Noises | Worn bearings; Problem gearbox; Fan blades scraping; Build-up of debris in the fan. | Replace bearings; Reducer maintenance; Check clearances; Clean fan. |
8. Recommended Maintenance Schedule
| Task | Frequency | Estimated Duration | Skill Level |
|---|
| Daily Visual Inspection | Daily | 15-30 min | Operator |
| Water Analysis (Basic Parameters) | Weekly | 30 min | Junior Technician |
| Cleaning Sieves and Filters | Monthly | 1-2 hours | Junior Technician |
| Detailed Inspection and Nozzle Cleaning | Quarterly | 2-4 hours | Full Technician |
| Inspection/Cleaning of Fillers and Eliminators | Semiannually | 4-8 hours | Full Technician |
| Deep Basin Cleaning | Semiannually/Annually | 6-12 hours | Full Technician |
| Dynamic Fan Balancing | Annually/As needed | 8-16 hours | Senior Technician |
| Bearing Inspection and General Lubrication | Annually | 4-8 hours | Full Technician |
| Complete Vibration Analysis | Annually | 4-6 hours | Reliability Eng. |
Water Chemistry (Complete Analysis) | Annually | 1-2 hours | Chemical Specialist |
9. Spare Parts Reference
| Part Description | Typical Specification | UNITEC category |
|---|
| Filling Medium (Filling) | PVC/Polypropylene, honeycomb type, high efficiency | Tower Components |
| Drop Eliminators | PVC/Polypropylene, chevrons design | Tower Components |
| Spray Nozzles | ABS plastic, full/hollow cone type, orifice Ø | Tower Components |
| Fan Blades | Fiberglass/aluminum, specific diameter and profile | Fan Components |
| Bearings for Motor/Reducer | SKF/FAG/NSK, shield 2RS/ZZ, C3 clearance | Bearings and Transmissions |
| V or Timing Belts | Gates/Optibelt, specific profile and length | Bearings and Transmissions |
| Elastic Couplings | Falk/Lovejoy, jaw/gear type | Couplings |
| Electric Motor | WEG/Siemens, IP55, 4 or 6 poles, Power (kW) | Motors and Drives |
| Speed Reducer | SEW/Nord, reduction ratio, housing type | Motors and Drives |
| Float Valve | Brass/Inox, connection Ø, working pressure | Valves and Controls |
| Level Gauges | Ultrasonic/Float type, measuring range | Instrumentation |
| Vibration Sensors | Piezoelectric, mV/g sensitivity | Instrumentation |
| Filter Elements | Media for Y filters, specific mesh | Industrial Filtration |
| Mechanical Seals for Pump | Silicon/carbon carbide, shaft diameter | Pump Components |
| Pump Gaskets | Graphite/PTFE, gauge and material | Pump Components |
To purchase these and other high-quality replacement parts, consult our complete e-catalog at: https://www.unitecd.com/e-catalog/
10. References
- ABNT NBR 10004: Solid Waste - Classification.
- ABNT NBR 16489: Personal Protective Equipment against falls from heights — Selection, use, conservation and inspection.
- NR-10: Safety in Electrical Installations and Services.
- NR-12: Workplace Safety in Machines and Equipment.
- NR-33: Safety and Health at Work in Confined Spaces.
- ISO 10816-3: Mechanical vibration — Evaluation of machine vibration by measurements on non-rotating parts — Part 3: Industrial machines with nominal power above 15 kW and nominal speeds between 120 r/min and 15 000 r/min when measured in situ.
- Cooling Tower Original Manufacturer (OEM) Operation and Maintenance Manual.
- CTI (Cooling Technology Institute) Good Practice Manuals.
