Page 107 - Root Cause Failure Analysis

98 Root Cause Failure Analysis

exhaust air from a space. Figure 8-1 illustrates a belt-driven propeller fan appropriate
for medium-duty applications.

This type of fan has a limited ability to boost pressure. Its use should be limited to
applications where the total resistance to flow is less than 1 in. of water. In addition, it
should not be used in corrosive environments or where explosive gases are present.

Axial

Axial fans are essentially propeller fans enclosed within a cylindrical housing or
shroud. They can be mounted inside ductwork or a vessel housing to inject or exhaust
air or gas.

These fans have an internal motor mounted on spokes or struts to centralize the unit
within the housing. Electrical connections and grease fittings are mounted externally
on the housing. Arrow indicators on the housing show the direction of air flow and

Figure 8-1 Belt-driven propeller fan for medium duty applications (Higgins and Mobley
1995).