Maintenance & Reliability · SOP
Cooling Tower Fill Media Inspection And Scale Removal
Chemical descaling and mechanical cleaning procedure for PVC film-type cooling tower fill. Removes calcium carbonate, silica, and biofilm deposits that degrade heat transfer efficiency and increase fan energy consumption.
Estimated Time
180 min
Difficulty
Intermediate
Regulation
CSA Z432 / WorkSafeBC
Version
1.0
Purpose
Cooling tower fill media is the primary heat transfer surface in evaporative cooling systems. Scale deposits — primarily calcium carbonate, silica, and biological fouling — progressively block air passages, reduce heat rejection capacity by up to 40%, increase fan power draw, and create breeding grounds for Legionella. This SOP defines a repeatable inspection and chemical descaling procedure to restore fill performance without damaging the PVC film structure, extending media service life and maintaining approach temperature within design limits.
Scope
This procedure applies to all crossflow and counterflow induced-draft cooling towers equipped with PVC film-type fill media, typically found in HVAC chiller systems, industrial process cooling loops, and refrigeration condenser circuits. It covers visual inspection, scale identification, dry debris removal, chemical descaling via biodegradable acid, high-pressure rinse, neutralisation, and post-cleaning documentation. This SOP does not cover splash bar fill replacement, structural repair, or drift eliminator replacement — those are separate PM tasks.
Safety Precautions
- Lockout/tagout (LOTO) all cooling tower fan and pump electrical disconnects — verify zero energy with a qualified electrician. Tag out at the MCC bucket as well as the local disconnect. No exceptions.
- Full PPE: chemical-resistant gloves (nitrile or neoprene), splash-proof goggles, face shield, rubber apron, and steel-toe boots. Respirator (N95 or half-face with organic vapour cartridges) is required when misting descaling solution.
- Read the SDS for the descaling chemical before handling. Citric acid is generally safe at 5–10%, but phosphoric acid requires additional neutralisation steps. Keep pH test strips and soda ash neutraliser on deck before starting.
- Confined space entry protocols apply if tower access requires entering a basin or plenum. Do not climb onto fill media directly — it cannot support body weight. Use a ladder or extension platform for tall towers.
- Keep all electrical panels dry. Use only GFCI-protected power tools and extension cords rated for wet conditions. No power washer wand within 3 metres of any open electrical enclosure.
Required Tools & Materials
- Biodegradable descaler (citric acid or phosphoric acid, 5–10% concentration)
- pH test strips or digital pH meter (range 0–14, ±0.2 accuracy)
- Lockout/tagout kit with multiple padlocks and hasps
- Low-pressure water supply (garden hose with spray nozzle, max 100 psi)
- High-pressure washer (1,500–2,500 psi) with fan spray tip (15°–25°)
- Safety data sheets (SDS) for all chemicals used
- Stiff nylon brushes (non-metallic), plastic scrapers
- Pump sprayer (8–15 L capacity) for chemical application
- Containment sump cover or drain filtration bag (captures debris and neutralised runoff)
- Camera or borescope for pre- and post-inspection documentation
- Soda ash (sodium carbonate) for pH neutralisation if needed
- Containment buckets, rags, and disposal bags for chemical waste
Procedure: Step-by-Step
1
Lockout/Tagout and System Isolation — Complete electrical and mechanical lockout/tagout per plant LOTO procedure. Isolate cooling tower fan and pump at the MCC and local disconnect. Verify zero energy with a qualified electrician. Apply tags: "DANGER — DO NOT OPERATE — MAINTENANCE IN PROGRESS." Close tower isolation valve if present.
2
Visual Inspection and Photo Documentation — Remove access panels and inspect fill media bundles with a bright LED work light. Identify scale type: white/chalky (calcium carbonate), grey/hard (silica), or green/brown slime (biofilm). Document percentage of blocked air passages. Photograph affected areas in at least three locations (top, middle, bottom). Check for mechanical damage (cracked, collapsed, or distorted fill sheets). Record findings on PM log.
3
Dry Debris Removal and Pre-Rinse — Using a vacuum (wet/dry shop vac) or low-pressure compressed air, remove loose debris (leaves, dust, insects, bird droppings) from the top surface and air inlets of the fill. Then, with a low-pressure hose (garden hose, max 100 psi), rinse fill media from top to bottom to dislodge loose silt and lightly attached scale. Direct all runoff to the drain — do not let it pool in the basin.
4
Chemical Descaler Preparation and Application — In a clean 15 L pump sprayer, prepare descaling solution per manufacturer instructions. Typical mix: 5–10% citric acid by volume in water at 20–40°C. Do not exceed 10% concentration — higher concentrations can attack PVC. Spray all fill surfaces from top to bottom until saturated. Work in 1.5 m wide sections. Maintain a pH below 3.5 — test with strips periodically. Allow a dwell time of 20–30 minutes. Re-apply if solution drips off before dwell time.
5
Agitation and Mechanical Loosening — While fill is still wet with descaler, use stiff nylon brushes to gently agitate stubborn scale deposits. Work in vertical strokes, following the fill flute direction. For heavy, multi-layered scale, extend dwell time to 45 minutes and re-apply solution as needed. Do not use metal brushes, scrapers, or wire wheels — they will permanently damage the film surface. Rinse brush frequently to avoid re-depositing scale.
6
High-Pressure Rinse and Neutralisation — Rinse fill thoroughly from top to bottom using a high-pressure washer (1,500–2,500 psi) with a 15°–25° fan nozzle held 12–18 inches from the surface. Use overlapping passes, moving left to right. Continuously test runoff pH with strips. Continue rinsing until runoff pH is between 6.5 and 8.5. If pH is below 6.5, apply a soda ash solution (0.5 kg per 10 L water) via sprayer and rinse again. Confirm neutral pH before proceeding.
7
Post-Cleaning Inspection and Documentation — Allow fill to drain for 15 minutes. Re-inspect with bright lighting and a camera. Confirm: all visible scale removed, no chemical residue, no brush abrasion marks, and no mechanical damage. Photograph the same locations as step 2. Record percentage of fill now clear. If scale remains >20% coverage, repeat steps 4–6. Sign and date the PM log with observations.
8
System Restart and Operational Check — Remove LOTO tags and padlocks. Re-install access panels securely. Open tower isolation valve. Restart cooling tower pump, confirm water flow across fill is even — no dry channels. Restart fan. Listen for vibration or rubbing. Check amperage draw on fan motor — should be within 5% of nameplate FLA. Monitor for 15 minutes. Verify basin water level returns to normal operating level.
9
Disposal and Housekeeping — Collect all chemical containers, used PPE, pH test strips, and filtration bags. Dispose of descaling solution and rinse water per local environmental regulations — never send acidic runoff to storm drains. Neutralise all chemical waste to pH 7.0 before disposal. Clean and store tools. Complete the PM log sign-off: date, technician name, total time, and any variance notes. File the completed log in the equipment maintenance file.