How to Save Dollars on Dust Control
Times are tough and cost control is
the key to profitability. Air quality
standards are a fact of life and quarries have little choice but to spend money
on control measures that will keep them in compliance. But why spend more than you have to? .
What’s the difference between a
million dollar and a ten thousand dollar race horse? Does the former run one hundred times faster
than the latter? Of course not. The difference is the nose that gets across the
finish line first. In other words, it’s
the little things that count. If you
want to save money on dust control, do the little things that will add up to
Here ten money-saving tips to
control dust from roads, piles and crushing plants.
The slower a vehicle travels the
less dust it produces. On most roads,
vehicles that travel at 15 mph do not produce appreciable dust emissions. A
speed limit of 10 mph is even better. Is a 15 mph practical for haul routes? If trucks can get stone up to the primary
crusher fast enough at 15 mph, it makes sense.
If they can’t, calculate the minimum speed required to the maintain
production rate and set speed limits accordingly. I’ve seen haul trucks race to a primary
crusher at 40 mph in a cloud of dust only to sit there for 10 minutes waiting
to dump – that’s what you want to avoid.
No. 2 - Enforce Speed Limits
Posted speed limits won’t reduce
dust if they aren’t enforced. That can
be tough if truck drivers aren’t your employees. Speed bumps can help trucks to observe speed
limits but banging tailgates can cause a noise problem. Rumble strips are more likely to slow trucks
down without causing gates to bang. Posting
and rigorously enforcing speed limits is the best way to reduce dust emissions
and the frequency of treating unpaved roads.
Plant management has to set the example.
If you blast around the plant in your pick-up, don’t expect anyone else
to slow down.
Shorten traffic routes as much as
possible. Fewer vehicle-miles traveled
means less dust in the air and less road to water or chemically treat. Use flags or other markers to delineate
traffic areas and install concrete barricades to make sure trucks do not wander
off of designated routes. Keep paved roads clean by restricting access to them
from unpaved roads.
No. 4 – Improve Road Structure
Poor construction, bad drainage and
lack of maintenance all aggravate dust emissions and track-out. Inspect roads to make sure they have a proper
crown, a good mix of fines and aggregates and a well-compacted surface. When surface material has more than 30% silt,
dust control measures will work but will not be cost-effective. Put some chips or other coarse aggregate down
to reduce the amount of silt on the surface.
This will reduce the frequency of treatment and the amount of water or
chemical used per square yard.
No. 5 - Use Road Dust Suppressants
A wide variety of chemical additives
are used as road dust suppressants. Just
about every sticky, gooey or gummy chemical you can imagine has been used to
control road dust. They can reduce the
frequency of treatment to the point where they are less costly than routine
watering especially in dry, arid environments where water is hard to come by. Vendors may be willing to provide a free
trial to let you gauge effectiveness of chemicals and determine cost savings.
If you are currently using chemicals
to control road dust, try to use a waste product for this purpose. For example, waste brine produced from oil
and gas wells can be just as effective as more refined and expensive products. Pulp and paper plants, steel mills, oil refineries
and chemical plants may all be sources of waste or off-spec materials that can
be used on unpaved roads.
No. 6 – Replace Tankers with Sprinklers
Install a stationary sprinkler
system instead of using a mobile tanker for road dust control. It can cost in excess of $100,000 annually in
capital and operating costs to employ a mobile tanker to water roads in a large
quarry. Stationary sprinkler systems can
significantly reduce these costs depending on the distance that requires
watering. Simple computer controls can
be used to optimize the frequency and duration of treatment. Just make sure that the sprinklers are
protected from errant trucks and can be drained in cold weather.
No. 7 – Train Loader Operators in Control Measures
Loaders are the most active vehicles
in quarries. Train operators to take
personal responsibility for dust control.
That means not overfilling buckets and spilling stone as they load trucks. Avoiding sharp turns and rapid accelerations
also helps to keep dust down. Loading
out from the lee side of a pile on windy days can also make a big
difference. In most cases, dumping
quickly can help to reduce the amount of dust that gets into the air.
No. 8 - Choke feed crushers
Good operating practice can not only
reduce dust but also improve production.
Choke feeding crushers is one example.
Crushers, particularly horizontal or vertical shaft impactors produce
less airborne dust when they are operating at capacity because they are moving
less air. Some plants I’ve seen are a
Frankestein mix of mis-matched equipment slapped together with screens or belts
to small to keep up with their crushers.
Dust produced from impactors that are operating at less than 50% of
capacity is almost impossible to control.
No. 9 - Avoid Interruptions
Avoiding interruptions in process
flow also reduces emissions and keeps production rates up. Crushers that are “windmilling” an put ten
times the dust into the air as they do when they’re loaded. The most common reason for intermittent
operation is the lack of sufficient haulage to sustain primary plant
operation. Stone runs through the plant
in a burst of production followed by a burst of dust.
No. 10 – Enclose Dust Sources
Enclosing dust sources is one of the
most cost-effective ways to reduce emission levels and your reliance on more
expensive controls like wet suppression systems or baghouses. The EPA estimates that partial enclosure of a
dust source like a transfer point or hopper on three sides with a cover has a
control efficiency of 70%. Adding a
simple rubber dust curtain at discharge points also helps to contain
emissions. Make sure that belt skirting
is in good shape and there is enough idler support at load points to prevent
dust and spillage. Workers have their
greatest exposure to respirable dust when they have to shovel or bobcat
spillage caused by leaking skirts. Much
of this work can be accomplished using scrap steel, old belting and a little
Conclusion – Implement the least expensive control
A cost-effective dust control plan
designed to comply with air quality standards at the lowest possible cost
requires the use of good operating and engineering practices combined with a
proper wet suppression (or dry collection) system. Good operating practice means training operators
to take personal responsibility for minimizing dust. Training them to do so is barely a blip in
the budget and can have a big payoff.
Good engineering practices that emphasize the containment of dust
sources can often be implemented with in-house labor and material. Do the least expensive things first. You’ll find that the savings that result will
go a long way in reducing the costs of more expensive controls like wet
suppression and dry collection systems.