COOLING TOWER MATERIALS

Overview

Material selection is critical for cooling tower longevity, performance, and cost. The choice depends on corrosiveness of water/air, temperature, structural requirements, budget, and maintenance philosophy. Here’s a breakdown by component:

1. STRUCTURAL CASING & SUPPORTS

Fiber Reinforced Plastic (FRP)

• Composition: Glass fibers + polyester/vinyl ester resin.
• Advantages:
  • Excellent corrosion resistance (ideal for coastal, chemical plants).
  • Lightweight, easy installation.
  • Low maintenance (no painting).
  • Smooth surface resists scaling.
• Disadvantages:
  • UV degradation requires UV-stabilized resin.
  • Temperature limited (~65°C continuous).
  • Lower structural strength than steel/concrete for very large towers.
• Typical Use: Packaged towers, industrial casings, basins, fan stacks.

Galvanized Steel (Galv Steel)

• Composition: Carbon steel coated with zinc layer (hot-dip galvanized).
• Advantages:
  • Strong, durable, cost-effective.
  • Good corrosion resistance in mild environments.
• Disadvantages:
  • Zinc coating can degrade in aggressive water (low pH, high chlorides) or coastal salt air.
  • Requires maintenance painting after coating failure.
• Typical Use: Structural framework, casing for HVAC towers.

Stainless Steel (SS)

• Grades: 304 (general), 316 (high chloride environments), 2205 duplex.
• Advantages:
  • Superior corrosion resistance.
  • High strength, temperature tolerance.
  • Long life with minimal maintenance.
• Disadvantages:
  • High initial cost.
  • Can still suffer from pitting/crevice corrosion in specific conditions.
• Typical Use: Critical components in harsh environments, food/pharma, marine applications.

Concrete

• Types: Reinforced concrete, pre-cast panels.

• Advantages:
  • Extremely durable and strong.
  • Fireproof, UV resistant.
  • Low lifetime cost for large towers.
• Disadvantages:
  • High capital cost and long construction time.
  • Can crack; susceptible to acidic water corrosion over decades.
• Typical Use: Large natural draft hyperbolic towers, field-erected industrial towers.

Wood (Traditionally Treated)

• Types: Redwood, Douglas Fir, treated pine.
• Advantages:
  • Natural corrosion resistance (redwood).
  • Good thermal insulation.
  • Repairable.
• Disadvantages:
  • Decays over time (fungi, rot).
  • Requires chemical treatment.
  • Environmental sourcing concerns.
  • Less common in new builds.
• Typical Use: Older industrial towers, some Cross Flow fills.

2. FILL / PACKING MATERIALS

PVC (Polyvinyl Chloride)

• Form: Thin sheets formed into corrugated film fill or splash bars.
• Advantages:
  • Lightweight, excellent corrosion resistance.
  • High thermal efficiency (film fill).
  • Low cost.
• Disadvantages:
  • Temperature limited (~50-60°C).
  • Can deform under load or at high temperature.
  • Susceptible to fouling (biofilm adhesion).
• Typical Use: Most common fill material for film and splash fill in industrial/HVAC towers.

Polypropylene (PP)

• Advantages:
  • Higher temperature tolerance than PVC (~70-80°C).
  • Good chemical resistance.
  • Often used in more aggressive thermal/chemical environments.
• Disadvantages:
  • More expensive than PVC.
  • Softer material, can be less rigid.
• Typical Use: Hot water applications, certain chemical processes.

Wood (Splash Fill)

• Advantages:
  • Handles dirty water well (less prone to clogging).
  • Good structural strength.
• Disadvantages:
  • Degrades over time (rot, biological attack).
  • Heavier, less efficient than film fill.
• Typical Use: Older towers, or in applications with high suspended solids.

Ceramic / Clay

• Advantages:
  • Excellent high-temperature resistance.
  • Inert, excellent fire resistance.
• Disadvantages:
  • Very heavy, fragile.
  • High cost.
• Typical Use: Special high-temperature industrial applications (e.g., metallurgy).

3. COLD WATER BASIN MATERIALS

Monolithic FRP

• Advantages:
  • Seamless, leak-proof.
  • Excellent corrosion resistance.
  • Lightweight.

• Typical Use: Standard in modern packaged FRP towers.

Concrete (Poured-in-Place or Precast)

• Advantages:
  • Permanent, durable.
  • Can be coated with epoxy for chemical resistance.
• Disadvantages:
  • Can crack and leak.
• Typical Use: Large field-erected towers.

Coated Steel

• Coatings: Epoxy, coal-tar epoxy, polyurethane.
• Advantages:
  • Strong, cost-effective.
• Disadvantages:
  • Coating failure leads to rapid corrosion.
  • Requires diligent maintenance.

Polyethylene (PE) Liners

• Advantages:
  • Low cost, corrosion-resistant barrier.
  • Used as a liner in concrete or steel basins.
• Disadvantages:
  • Can tear/puncture.
• Typical Use: Retrofit or repair of existing basins.

4. DRIFT ELIMINATORS

PVC

• Most common. Corrugated sheet assemblies. Efficient, low cost.

FRP

• Used in corrosive environments or for structural strength.

Wood

• In older towers.

5. NOZZLES & DISTRIBUTION SYSTEM

ABS (Acrylonitrile Butadiene Styrene)

• Common for nozzles. Tough, chemical resistant.

PVC / PP Piping

• For distribution piping.

Brass / Stainless Steel Nozzles

• Used for high temperature/pressure or where abrasion is a concern.

6. FANS & MECHANICAL COMPONENTS

• Fan Blades:
  • Aluminum: Lightweight, general use.
  • FRP: Corrosion resistant, balanced.
  • Stainless Steel: For harsh environments.
• Shafts: Stainless steel or carbon steel with protective coating.
• Bearings: Sealed, lubricated for wet environment.
• Drive Assemblies: Steel with galvanized or painted protection.

MATERIAL SELECTION MATRIX BY ENVIRONMENT

Environment / Condition	Recommended Materials	Avoid / Use With Caution
Coastal / High Salt Air	FRP, 316 Stainless Steel, Special Coatings	Galvanized Steel, Mild Steel
Chemical Plant / Aggressive Water	FRP, PVC/PP Fill, 316SS/duplex SS	Galvanized Steel, Carbon Steel
High Temperature Water (>60°C)	PP Fill, Stainless Steel, Concrete	PVC, Standard FRP resins
Dirty Water / High Solids	Splash Fill (PVC or Wood), Easy-clean design	Fine-cell film fill (clogs easily)
Fire Risk Area	Concrete, Ceramic, Special Fire-retardant FRP	Standard Plastics, Wood
Cost-Sensitive, Mild Environment	Galvanized Steel, PVC fill	Stainless Steel, FRP

TRENDS & BEST PRACTICES

1. FRP Dominance: FRP has become the standard for casings and basins in packaged towers due to its all-around durability and low lifecycle cost.
2. PVC for Fill: PVC film fill dominates for efficiency, but PP is growing for hotter applications.
3. Hybrid Construction: Common to use galvanized steel structure with FRP casing panels or PVC fill for cost optimization.
4. Coatings & Linings: Epoxy and polyurethane coatings extend life of concrete and steel basins significantly.
5. Material Degradation Awareness:
   1. UV on FRP → Use UV-inhibited resin.
   1. Chlorides on stainless → Use 316 or duplex.
   1. Low pH water on galvanized steel → Accelerated coating loss.