Q. Design Air Coolers for plant layout?

As air coolers (sometimes called aerial coolers, or fin-fans) have extensive heat transfer surfaces, they are more vulnerable to failure under fire conditions than shell and tube exchangers, so should be located well away from fired equipment. They should not be located over any of the following:

• Pumps or compressors handling flammable materials.

• Drums or heat exchangers containing flammable materials (unless they are part of the same process unit).

• Drums or heat exchangers containing flammable materials above 316 °C (600 °F) or above its auto-ignition temperature (whichever is lower).

• Over or within 3 m (10 ft.) horizontally of major pipe racks (except when a better location is not possible) as this introduces maintenance difficulties as well as a higher fire involvement. If they are located over / near pipe racks, the following requirements must be met:

- There should be at least 2.5m (8 ft.) clearance between the lowest part of the air cooler and the top of the pipe rack.

- Flanges, valves and manifolds not associated with the air cooler should not be located directly below the air cooler or within 3 m (10 ft.) horizontally in any direction.

- Minimum horizontal spacing requirements from both the air cooler and the pipe rack to adjacent equipment must be met.

- Crane access must be provided for removal and replacement of motors, fans and tube banks.

- Structural supports for the air cooler and pipe rack must have passive fire protection installed.

Air cooler units should be located at a suitable elevation to ensure maximum air flow. Piping should be top inlet and bottom outlet. No equipment should be installed immediately under air cooled heat exchangers or other equipment that is part of the heat exchanger system. No equipment should impede the exhaust air stream above the exchanger.