Print Friendly

Multistage Fabricated Centrifugal Blowers

Spencer multistage fabricated blowers cover an extensive line of styles and models used for a wide range of air/gas services in industrial, commercial, institutional and municipal applications. The three basic designs are standard overhung SOH (impellers mounted on extended motor shaft), four-bearing overhung 4BOH (impellers mounted on shaft coupled to motor shaft) and four-bearing outboard 4BOB (impellers mounted on shaft supported at both ends by self-aligning ball bearings, coupled to motor shaft).

SOH and 4BOH machined are noted for the trademarked “sugar scoop” profile of their housings. These are among Spencer’s oldest products, so the sugar scoop profile is your visual assurance of genuine Spencer quality that has endured for more than a century.

These blowers are manufactured of heavy gauge, cold-rolled sheet steel with a tensile strength of 50,000 psi, welded and reinforced, creating an extremely rugged construction. The inlet, outlet and housing are built as an integral structure for greater strength. The fabricated construction allows easy substitution of other metals to counter very high temperatures, chemical or corrosive conditions. We routinely use Hastelloy®, monel, various stainless steels, aluminum, Cor-Ten® steel and many others that provide specialized abilities.

The rotating impeller assembly within the blower housing has ample clearance, 1/8″ or more, for simple, low-maintenance operation. The entire rotor assembly is dynamically balanced to ensure mechanical operation below 1.5 mils total amplitude on the bearing housing at design speed. With housing diameters from 14″ to 88″, these blowers can handle volume to 25,000 ICFM, pressure to 20 PSIG and vacuum to 15″ Hg.

For more information on our Multistage Fabricated Centrifugal Blowers, visit our Product Literature section

Standard Designs




The three standard designs of Spencer multistage fabricated blowers are standard overhung, four-bearing overhung and four-bearing outboard. The simple SOH design has impellers mounted directly on an extended motor shaft; the 4BOH design offers higher pressure and vacuum performance using impellers mounted on a steel shaft; the 4BOB design handles the highest pressures and volumes with ball bearings at both ends of the rotor assembly.