Main Material of Motor in Cooling Tower

Cooling-tower fan motors are built with special materials because they operate in a wet, high-humidity, corrosive, and high-vibration environment. Below are the materials used in each part of a cooling-tower motor and why they are chosen.

✅ Material of Motor in Cooling Tower

Marley, BAC, Evapco, and OEM cooling-tower-duty motors generally use the following:

  1. Motor Frame / Housing

Common materials

Material	Why Used	Notes
Cast iron	Strong, rigid, good vibration resistance	Most common for cooling-tower-duty motors
Aluminum	Light, corrosion-resistant	Used on smaller motors (5–20 hp)
Stainless steel (rare)	High corrosion resistance	Used in severe corrosive or coastal environments

Most large cooling-tower motors (20–200 hp) use cast iron frames because they hold alignment better with gear drives.

2. Coatings (Critical in cooling towers)

Motor housings are usually coated with:

* Epoxy coating (2-part industrial epoxy)

* Polyurethane topcoat

* Zinc-rich primer beneath epoxy

* Marine-grade enamel for coastal or chemical plant towers

Many motors are rated Cooling-Tower Duty and come with factory corrosion-resistant coatings.

3. Shaft Material

Cooling tower motors normally use:

* Stainless steel shafts (303, 304, 316)

* Carbon steel with anti-corrosion plating (less common)

Stainless shafts prevent rust transfer into the coupling or gearbox input shaft.

  4. Bearings

Bearings typically use:

* Stainless steel bearing housings or

* High-grade steel bearings with:

* Double seals

* Water-resistant grease

* Premium insulation and moisture protection

Some motors have inboard/outboard bearings oversized to handle fan/gearbox loads.

5. Terminal Box / Conduit Box

Materials:

* Cast iron (most common)

* Aluminum

* Stainless steel (for corrosive applications)

Terminal box is coated like the frame because this part gets the most splash.

6. Internal Components

Insulation:

* Class F or H insulation

* Moisture-resistant varnish (dip and bake)

* Some have tropicalized windings to resist humidity

Rotor & Stator Core:

* High-grade silicon steel laminations

* Epoxy-coated to resist corrosion

7. Cooling Method / Enclosure

Common motor enclosure materials:

Enclosure	What It Means	Materials
TEFC (Totally Enclosed Fan Cooled)	Fan blows air outside	Cast iron or aluminum
TENV (Totally Enclosed Non-Ventilated)	No external fan	Stainless/Aluminum on small units
TEAO / TEWD (Cooling Tower Duty / Waterproof Duty)	Designed specifically for wet, humid airflow	Heavy epoxy-coated cast iron

Cooling-tower-duty motors often have:

* No external cooling fan (uses tower airflow instead)

* High-seal endbells

* Special moisture barriers

8. Hardware & Fasteners

To prevent corrosion:

* 304 or 316 stainless steel bolts

* Stainless washers

* Anti-seize on all stainless fasteners

Carbon-steel hardware is avoided (rusts instantly in tower mist).

⭐ Summary — Most Common Material Set

A typical Marley or BAC cooling-tower motor is made of:

* Cast iron frame (epoxy coated)

* Stainless steel shaft

* Double-sealed bearings

* Epoxy-coated rotor and stator

* Stainless or coated terminal box hardware

* TEFC or TEAO enclosure

This combination resists moisture, corrosion, vibration, and continuous duty loads.