TM 5-810-15
(4) Foam suppression is simple and efficient.
is very time consuming and costly.
Foaming chemicals have to be purchased. It is ideal
(2) The collected dust from the dust
where low moisture is necessary. Foam type
collector must be returned to the material flow
systems typically add less than percent moisture
which allows reentrainment of the dust at the next
as compared to up to 4 percent with standard water
pick-up point location.
spray systems. One foam unit is needed for each
(3) Table 5-1 shows a comparison of dry
central application location. No electricity is
dust collection versus wet dust suppression
required. Water and compressed air are required.
systems.
c. Dry dust collection systems. Dry dust collec-
tion systems utilize dry type bag filters which are
5-20.
Conveyor safety and safety devices.
designed to remove dust-laden air from unloading
a. General. Conveying system safety begins with
areas and transfer points throughout the coal
good design which, as far as is practical, tries to
handling system, as well as to provide ventilation
protect the operator from dangerous or hazardous
for bins, storage silos or bunkers. The main advan-
areas associated with conveyors. Safety should be
tage of this type of system is that it can be operated
considered in all phases of conveyor design, manu-
in both warm and cold climates.
facture, installation, operation and maintenance
(1) A dry dust collection system requires a
procedures. Conveyor operators must be properly
large amount of space for equipment and duct-
trained and made aware of possible recognizable
work, which makes it more expensive to install
equipment hazards, safety procedures and devices,
than a wet type dust suppression system. Operating
before they become involved in an accident. Con-
and maintenance costs are compounded as the size
veyor safety is covered in ANSI B20.1. In addition,
of the system increases. Changes or alterations
the following safety devices will be included for all
required after startup are virtually impossible
conveyors:
without completely modifying the entire system.
Filter bag replacement for the dust collector units
Table 5-1. Comparison of Dry Dust Collection Versus Wet Dust Suppression Systems.
Dry dust collection
Wet dust suppression
Foam suppression
When recommended
Enclosed hoppers, bins, silos,
Open coal storage piles
Stock piles
transfer/crusher houses.
Open or enclosed track hopper
Crushers
Silo, bunker or bin venting
buildings.
Op en or enclosed conveyor.
Enclosed track hopper
Transfer points
buildings
Enclosed transfer points
Note: Where an item is listed under both dry dust collection and wet suppression, an LCCA should be conducted to determine which
system should be used.
Disadvantages
More expensive.
Chemical additive be
Foaming chemicals must be
High operating and
purchased.
purchased
maintenance costs.
Questionable cold-weather
Changes or alteration to
operation.
system are costly.
Moisture is added to coal.
Time consuming filter bag
Requires a water supply.
replacement.
Requires freeze protection
Large amount of space
supply.
required.
Collected dust must be
returned to the material
flow.
Advantages
Can be operated in warm and Less expensive.
Same advantages as wet dust
cold climates.
Does not require costly or
suppression.
Does not add moisture to coal.
elaborate enclosures.
Can be used for bin or silo
Small space required for
venting,
installation.
Changes to system easily made.
5-13
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