Cooling Tower Fan Stacks Maintenance Guide

The fan stack—also called the cowl or cylinder—guides hot, moist air away from the fill and prevents it from being drawn back into the tower. A clean, round, dimensionally-accurate stack is therefore essential for rated airflow, low fan power and minimum noise. Begin every intervention with lock-out/tag-out; de-energise the motor, close the make-up and allow hot surfaces to cool.

I.Cooling Tower Fan Stacks Inspection

Walk the perimeter every month, looking for chalking, frayed glass fibres, cracked gel-coat, missing hardware or ovalisation. Pay special attention to the bottom flange where cyclic loads are highest; a hairline crack here will propagate into the laminate within weeks. Measure the inside diameter at 90° intervals; any diameter difference > 6 mm indicates that the stack has "sagged" and will rub the blade tips at high speed.

II.Cooling Tower Fan Stacks Cleaning

Algae, lime and sulfate deposits roughen the surface and create local turbulence. Rinse with low-pressure (≤ 4 bar) water, then spray a 5 % citric or glycolic solution on mineral scale. Allow 15 min contact, brush with a soft nylon broom and rinse again. Never use hypochlorite on polyester resin; micro-cracking will appear within months. Remove ice in winter with tempered water; striking the laminate will cause star cracks.

III.Cooling Tower Fan Stacks Surface repair

Grind small cracks into a 60° V-groove until the white laminate disappears, blow off dust and fill with silica-thickened epoxy. For through-wall damage, cut back to sound glass 50 mm beyond the crack, feather the edge, and hand-lay three layers of 450 g m⁻⊃2; chopped-strand mat plus a surface veil. Roll each layer to remove air, cure at > 15 °C and finish with UV-stable polyurethane top-coat.

IV.Cooling Tower Fan Stacks Geometry & clearances

Re-check the fan-to-stack clearance after any repair. The gap should equal 0.3 % of fan diameter (minimum 10 mm). Adjust the gear-box or motor base with stainless shims; a 3 mm change at the foot usually moves the blade tip 1 mm. Re-torque hold-down bolts to 75 % of yield and apply a dab of silicone to prevent edge-lift corrosion.

V.Cooling Tower Fan Stacks Hardware & vibration

Replace missing drain holes (6 mm Ø at the low point) so condensate cannot freeze and split the wall. Inspect vibration-cut-out switches; a stack that is out-of-round by only 5 mm can double the blade-pass frequency and trigger false trips. Grease the extended lube lines every 1 000 h (induced-draft) or 2 000 h (forced-draft) with polyurea grease until fresh grease purges from the seal.

VI.Cooling Tower Fan Stacks Corrosion protection

Fiberglass stacks: re-apply UV-resistant gel-coat when colour changes from original green/blue to pale yellow. Galvanised steel stacks: wire-brush white rust, prime with zinc-rich epoxy and two coats of aliphatic polyurethane (total 120 µm). In coastal zones add a fluorosilicone finish for salt-spray resistance.

VII.Cooling Tower Fan Stacks Record & schedule

Log diameter readings, crack locations, repair materials and blade clearances. Review data annually; a gradually increasing ovalisation usually means the support ring is corroding or anchor bolts are loosening. With systematic cleaning, prompt patching and correct clearances the stack will last 15–20 years and keep fan power within 3 % of design.