C. M. Consulting
P.O. Box 407
Odell, Oregon 97044
CD Road Equipment S & S
313 Cowie Crescent
Swift Current, SK S9H 4W1
C. M. CONSULTING
A Division of Cliff Mansfield Incorporated
HOW TO MAKE THE RIGHT CHOICES
WHEN BUYING AN ASPHALT PLANT
So, after years of buying hot mix from the local supplier
you've decided to purchase an asphalt plant and start producing it for yourself,
and perhaps sell it commercially. Congratulations, you've made an important
decision, one that, with planning and a modicum of luck, should make you
money over the coming years.
Now you are going to be called on to make a lot more
important decisions like AC plant type, style, size, brand and budget. Once
you've made those choices, more issues crop up, such as AC tank size, storage
silo size, number of cold feed bins, type of pollution controls and on and
on and on... For someone new to asphalt plants these are baffling issues.
In the following dissertation I am going to try to demystify the process
through which all these choices are made. Along the way I will attempt to
explain the various types and styles of AC plants and to help you with those
Assuming you have a place to put a plant and a good
rock source, the first couple of choices you will have to make are type and
style. Do you want a batch plant or a drum plant? Should it be portable or
stationary? To make these choices you need some idea about the strengths
and weaknesses of each type and style. In what follows I will try to define
these issues in common-sense terms.
TYPES OF ASPHALT PLANTS
A batch plant makes mix in batches. The feeders feed aggregate to a rotary dryer
where the moisture is removed. It is then transported to a set of screens where
it is divided into several component sizes (3/4"-1/2", 1/2"-1/4", 1/4"-1/8" and
1/8"-0" for example) and stored in 'hot-bins'. These aggregates are then
correctly proportioned into a weigh bin by the plant's blending computer. From
here it is introduced into a pugmill and 'dry-mixed' for a specified amount of
time. The oil is introduced at the proper time and the combination is then
'wet-mixed' for the required time. At the end of this cycle the pug gate opens
and the finished hot-mix is either discharged directly into a waiting truck or
it is dropped into a moveable chute, which leads to a slat conveyor and then a
Batch plants range in size from a 250# baby
Madsen (the smallest I know of) up through 18,000# monsters. I've heard of a
20,000# behemoth but have not seen one. They are generally rated at 1 batch per
minute, so a 4,000# plant would yield 120 tons per hour, while an 18,000# unit
would yield 540 tons per hour.
Strengths: A batch plant's strength lies
in its ability to make salable hot mix out of almost any reasonable stockpile of
aggregate. As one old timer put it: "You can feed 'er meteors and coprolites and
I'll make spec mix, sonny!" He was one wise man. Another strength inherent to a
batch plant is its ability to switch mix specifications mid-truck if needed.
Essentially, if you supply the plant with 3/4"-0" aggregate you can make any mix
that uses materials contained within those parameters. Depending on what screens
you have installed in the plant, you can make 3/8"-0" mix for one truck, then
switch to 3/4"-0" mix for the next and still be able to blend a nice 1/2"-0" mix
for the third. In some operating situations this is a very valuable ability.
Weaknesses: A batch plant utilizes
numerous steps to produce hot-mix. It is those very steps that make it so
valuable to someone in the position described under strengths. And those same
steps are its weakness to an operator who is making the same mix all the long
day. What it boils down to is the fact that a batch plant spends about 30% of
its time waiting on bins to weigh up, the pug to empty and similar activities.
To an operator who does not have to make a lot of daily mix changes and is
concerned with high production, perhaps a batch plant is not the right choice.
DRUM PLANTS: What is a drum mix asphalt plant? Essentially,
a drum mix plant is a continuous mix facility that takes the hot-mix manufacturing
process to its basics. In the feeders it proportions the aggregates into
the correct blend to meet job requirements. This material is then conveyed
to the dryer/mixer where the first two thirds of the unit is dedicated to
moisture removal. In the last third of the unit the correct percentage of
asphalt is injected and the resultant material is thoroughly mixed. At this
point it is discharged into a slat conveyor for transport to a storage silo
where it is distributed to the waiting trucks. Drum plants range from 8
ton per hour toys to 800 ton per hour giants. The most common plants are
between 150 & 400 tons per hour.
Strengths: The fact that a drum plant reduces the
hot mix process to its essentials is its big strength. By eliminating most
of the steps taken by a batch plant to produce mix a drum plant is able to
do its job more economically. They will also operate at a higher rate of
production for a given drum size, since the mixing process is continuous.
Weaknesses: By the nature of their design, drum plants
are limited to producing one mix design at a time. If you introduce properly
gradated 1/2"-0" aggregate into the unit you are going to get the same thing
out of it. For a contractor who is required to supply several different mix-designs
in the same production run a drum plant may not be the best choice. This
problem can be overcome through the use of multiple silos and a sharp operator,
but multiple silos are not as practical if you must be portable.
IN SUMMARY: Basically, a batch
plant is the best choice for an operation where the plant will be called upon to
make various blend mixes in the same operational 'run', or if the plant will be
doing a lot of starting and stopping in the course of the day. A drum plant is
the correct plant for a company not concerned with switching back and forth to
various mixes and foresees the luxury of long production runs. Another
consideration is the fact that batch plants utilize many more moving parts than
drum plants, therefore they are more expensive per ton to operate and year-end
maintenance costs are higher.
STYLES OF ASPHALT PLANTS
There are two styles of asphalt plants, portable and
stationary. It's fairly easy to choose between the two, once you know the
answers to a couple of questions: Do you need to move your plant? If so,
how often will it be moved? One incontrovertible rule is that portable plants
cost substantially more than their stationary brethren. If you only need
to move your plant once every few years then it is possible that the cost
of moving the plant is considerably less than the cost of portability on
the original order. I recommend that companies in this category consider
buying a skid-mounted plant with flexible wiring, like SO cord, equipped
with quick disconnects. Companies that plan to move their plants several
times a year must purchase a portable facility. When looking at these units
it is strongly recommended that a self-erect silo/drag combination be considered.
In the Northwest a crane to set the silo and drag conveyor can easily cost
in excess of $5,000.00 per move. It doesn't take a rocket scientist to see
that if you move your plant four times a year, you can pay for the difference
in cost for a self-erect in about two years.
SIZE OF ASPHALT PLANTS
How much production do you need? This is a difficult
question to answer. One of the fundamental mistakes that I see is a company
trying to size their plant to their highest production days. I recommend
that a plant be sized to the average for a company's busiest month.
New companies, without a track record for mix production,
must analyze their market and decide from there. If you feel that you can
sell 3,000 tons per day, 10% of the time and 1,000 tons per day the rest
of the production season, I suggest that a 200-ton per hour plant is more
appropriate than a more expensive 400tph unit. Thinking along the same lines,
it's difficult to justify the million dollar cost of a new 350tph plant if
you plan on making 40,000 tons a year, regardless of how fast you can make
it. To summarize, plant sizing is a function of market demand. Try not to
size the plant so small that in a year or so you will be looking to upgrade
to a bigger facility. But then again, don't go so big that the thing is idle
for long periods of time. In general, a plant is most efficient when it is
running at about 80% of its rated capacity, and the things last longer when
they are not stopped and restarted constantly. Another thought: A smaller
AC plant with lots of storage capacity can often turn out as much mix on
a given paving day, because it might not have to stop while waiting for trucks,
while the larger plant fills its silo in a hurry and then must wait for the
silo level to go down. This dead time takes away from productivity and adds
to the cost per ton of mix.
NEW VS. USED ASPHALT PLANTS
Do you need a new machine or will a used one do? Both have distinct advantages over the other.
NEW: The advantages of a new plant are obvious: It's
new, so there is no guesswork as to its condition. It comes with full factory
support. This is very important in such issues as DEQ air quality compliance
and plant troubleshooting, should any problems develop. Additionally, most
factories will assist you in the set-up and start-up of their plant. This
is a real plus for companies new to the world of AC plants.
USED: Used plants offer advantages too. Most notably,
they can be considerably less expensive. The trick is to find a used plant
that hasn't been abused to death, and one that is offered direct from the
owner or his primary broker. This is important since a plant may be listed
through numerous brokers who work together and if you don't pick the primary
listing agent you may have to pay finder's fees to several and not even realize
it. In general, try to find out as much information as possible about a
particular plant if it catches your eye. Don't be afraid to ask questions.
Most brokers are willing to help you. If they aren't, find another plant.
Once you decide on a particular piece of equipment, have it appraised. Get
an impartial opinion of the plant. Several companies, including mine, offer
this service. It is money well spent and quite possibly could save you from
major repair bills in the future.
BRAND OF ASPHALT PLANT
Are there any substantial differences between the brands?
This will not sit well with the big guns of the industry, but essentially,
an asphalt plant is an asphalt plant. Manufacturers like to extol the virtues
of their particular features, and some have valid points, but in the long
run they are all very similar and when configured the same, any two brands
will do the same job: Produce hot mix. I have a favorite, but it is not the
purpose of this article to hype anyone's product. Look closely at the specification
sheets on each plant you are considering. Compare them to the competition
and remember: The cheapest is not always the least expensive.
COSTS OF ASPHALT PLANTS
How money much should you expect to spend? New plants
run a wide gamut of pricing. A very popular small manufacturer offers a
30tph portable plant for under $150,000.00 complete. That same manufacturer
offers a 325tph counter-flow double drum with RAP capability for around $1,350,000.00.
Other manufacturers offer similar pricing and prices soar when the larger
sizes are considered. 500tph plants, with counter-flow technology and RAP
capability, set-up to run in sunny California can exceed $4,000,000.00.
The best advice is to do your homework, then shop for pricing. If you can't
foresee a need for a certain option, don't buy it! Keep your plant as simple
and basic as you can. This will aid you in the troubleshooting and repairs
in the future. The used AC plant market is usually very good. There are
more plants for sale than there are buyers. This is good for the contractor
looking to buy a used plant, but it also makes the choice of a plant more
confusing because most brokers will bury a prospective customer in information.
The list of available plants can quickly overwhelm the average guy and render
any possibility of making an informed decision virtually impossible without
a large investment in time and airfare traveling across the country inspecting
plant after plant. I suggest you find a broker you trust and have him do
the legwork and find you a piece of equipment that fits your needs.
USED PLANT PRICES
Pricing varies greatly from season to season.
What is presented here is a sampling of what is available at the start of the
1997 paving season. These prices are presented in a low/high format and are not
intended as an offering of any type. These are simply a result of the author's
research into the subject.
Eagle-200 20tph, $ 75,000.00
Boeing BCE-50, 250,000.00
Barber-Greene DM-50, 160,000.00
AEDCO DM526, 380,000.00
Boeing BCE-200, 280,000.00
300 and up:
Barber-Greene DC-70, 375,000.00
CMI PVM-10X, 990,000.00
As you can see from these prices, there is a wide spread,
even among similar equipment. For this reason it is imperative that you
inspect and analyze in minute detail any piece of equipment that you are
interested in. When in doubt, seek the help of an industry specialist.
There are numerous other factors past price and size
that you will need to consider when choosing a plant. Some of these things
AC Tank Size: How far away from your proposed plant site is the nearest
oil supplier? How long does it take to lap a truck from your plant to the
refinery and back? These are questions that need to be answered before you
can decide on oil storage capacity. In general, a 300tph plant will use about
17.4 tons of oil per hour at a mix design percentage of 5.8%. A 30,000-gallon
tank holds roughly 116.7 tons of oil at 7.78ppg (approximate weight of PGA-58-22
@ 300degrees). Since we cannot pull all of the oil out of the tank because
they are set-up so that the heaters stay immersed in oil (electric models)
let's assume we can use 114 tons of liquid. At 17.4 tons per hour we can
run approximately 6.5 hours on the oil we have. To stay even with our rate
of consumption we will need to get a 35ton load of oil every 2 hours. If
this is not possible, we need to increase our oil storage capacity. In general
I advise using as much storage as you can afford. This means you are not
as much at the mercy of your oil supplier and his truckies.
Hot Mix Storage:
Larger silos generally mean less truck turn-around time in the yard, which
equates to more money on the bottom line. A large capacity silo can also
help a smaller plant perform with the big boys as far as mix shipped per
hour, since when the trucks are gone the plant can run longer, refilling
the silo. If you start the plant early enough in the morning to have the
silo full when the first truckloads, it will help the plant stay ahead of
the trucking for several hours. In general, buy as much storage as you can
afford. I tell contractors that it's easy to put 50 tons in a 200-ton silo;
it's tough to put 60 tons in a 50-ton silo.
Cold Feeds: Does your state
use mixes that require the aggregates to be broken down into more than one
or two stockpiles, such as 3/4"-1/2", 1/2"-1/4", 1/4"-10 and 10-0"? If so
you will need to make sure your new plant accommodates all the materials
you will need to be using. If you have to blend sand into your mixes you
could find that you need 5 feed bins.
Wet Wash vs. Baghouse: It's no great secret
that an asphalt plant cost considerably more when equipped with a baghouse as
opposed to a wet-scrubber. But what may not be so well known is the fact that
within a few short years the Federal DEQ regulations may obviate the use of wet
scrubbers through default by making their use so expensive that the small
operator can't afford to comply with all the requirements. As an example: Here
in the Northwest, Washington State has enacted a new law that takes effect
October 4th and is going to require all wet-scrubber operators to line all ponds with an impermeable membrane (Concrete, polyurethane
or something similar). They will also have to perform water testing on a weekly basis (possibly
more often) of any discharged liquid. In the near future I foresee a wave of states following
in Washington's footsteps. With these regulations taking effect on the state
level, can the Feds be far behind? If you can afford it, buy a plant with
a baghouse, or at least price a baghouse to fit the plant you are considering.
If the Feds mandate baghouses in the near future, the cost of these units
will skyrocket. Current portable units, sized for a 200tph plant, sell for
around $140,000.00 new and $70,000.00 or more used. It costs additional money
to retrofit a baghouse to a plant. So, it is quite possible that, in light
of imminent near future actions by our government, there is really no choice:
You must buy a baghouse or operate at an economic disadvantage to those operators
Buying an asphalt plant is a big step, and the best
advice I can think of is to be thorough. Research your market and know your
potential customers. Ask yourself the tough questions: What will it take
to get the business away from those who will be your competitors? What do
you have to offer them that the other guy doesn't? If you plan to buy a
plant to service your own paving operation then ask yourself how a plant
will aid in that operation. Will it give you access to mixes you can't get
elsewhere? Do you have enough yearly volume to support the payments on such
a large investment?
Once you have a thorough understanding of these issues
you are ready to proceed with the purchase of a plant if it is warranted.
Be just as thorough in your investigations of potential pieces of equipment.
Ask questions and seek advice from anyone knowledgeable in the subject. Money
spent on plant appraisals and consulting help could turn out to be the best
investment you make. One last bit of advice: Start on the Air Quality Permit
process the minute you decide to get a plant. This process, under adverse
conditions, can drag on for months and under some situations actually kill
the entire project. Know your prospects for getting all the needed permits
For additional information on this subject
or help with any problems encountered
contact Cliff Mansfield,
7:30am to 9:00pm Pacific Standard Time.
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