TM 5-815-1/AFR 19-6
d. Dust hopper design. A properly designed dust
recommended for ash containing unburned
hopper should be air tight and large enough to prevent
combustibles or char for the same reason.
the dust level from reaching the cyclone dust outlets.
Selection of materials
Dust hoppers are usually conical or pyramidal in shape
and are designed to prevent dust buildup against the
a. Conditions. Cyclones can
be constructed of a
walls. All designs should include a means of
variety of types of metals. The type of materials
continuous removal of dust from the hopper to a
specified is dependent upon the erosion characteristics
storage bin, with an adequate alarm system to indicate
of the dust, the corrosion characteristics of the gases,
a malfunction. Bin level alarms are frequently used for
and the operating temperature of the cyclone.
this purpose. On negative pressure systems, hoppers
Generally, cyclones are constructed of mild steel or
and removal system must be air tight. If hot unburned
cast iron. (See para 7-5 for additional information on
combustibles or char are present in the collected
materials selection for pollution control systems).
particulate, introduction of fresh air can cause a hopper
b. Erosion. Erosion is the single most important
fire. Pneumatic ash transport systems are not
criterion in specifying the materials for cyclone con-