11/1/1996
Reducing VOCs In The Shop
By Don Lick
Well, here we are again, talking about how
to reduce VOCs (volatile organic compounds) in your shop. It's
surprising, in light of today's regulatory environment, to see
how many businesses still don't even think or care about the subject...but
it's an important part of our business lives.
In some states it seems that VOCs are like
a red flag held in front of a charging bull. In other states they
don't seem to care too much about the problem as long as the polluting
companies are providing an income for their economy.
But the day is coming when the "gurus"
who started the whole thing in California, i.e., Rule 66 which
was promulgated in the 1960s, will finally have their way across
the nation. Companies today must do business while the public
is peppered with news stories about water pollution and how it
is going to kill off the fish and maybe even us, ground pollution
from things such as leaking gasoline tanks buried underground,
and even plastics that don't naturally degrade.
So where does that leave the rebuilder? How
do we approach the problem of first accepting that we do have
to reduce the VOCs emitted to the atmosphere, then determine where
they are coming from in our individual plants? Let's take a look
at some of the sources and possible solutions.
Identifying the source
First, if you are a remanufacturer or builder
of new products, let's examine what kind of VOC and/or waste is
being generated during production. Are you using a cutting oil...a
cooling solution in the process? What is the percentage of oil
and/or solvent, and how much of the mix is just plain tap water?
You should realize that a mixture of seven
parts water to three parts oil (lubricant) would have a weight
of 1.8 lbs. of VOCs per gallon of material used (based on 6 lbs.
per gallon for the lube). How many gallons per hour do you generate?
Per day? Per week? Per year? And more importantly, how do you
get rid of it? Using our example, a machine using just one gallon
per hour, eight hours per day will generate 2,000 lbs. per year!
How many machines do you have that are producing that quantity
of VOCs annually?
There are people who think that since they
do not exhaust any of the air around a machining process, that
they are not releasing any VOCs. But let's ask where the air in
the plant came from, and where it is going? The answer is from
and into the atmosphere, of course. You can't segregate it.Okay,
so how do we reduce VOCs from this particular source? Well, first
let's take a look at our Material Safety Data Sheets (MSDS). Do
you have one for every fluid you are using? Do you have them on
file as you are required by law? Now let's contact the supplier,
and ask them to give you a hand in reducing the VOCs in the product
you are buying, or to perhaps change products to something with
a lower VOC content.
One thought that comes to mind would be the
installation of an oven-type machine that feeds the VOC mixture
into the work chamber at temperatures of 800°F to 900°F,
vaporizing the fluids, whether water or solvents. The exhaust
air from the machine raises the temperature to approximately 1,800°F,
thereby burning any remaining particulate and emitting a clean
airstream from the stack. If there are sludges or other materials
that cause the first part of the process to produce smoke, even
that is incinerated in the exhaust stack (remember, smoke is really
just a lot of tiny solid particles).
One of the most obvious sources of VOCs is
a painting operation. In the past, commonly used coatings, whether
air-dry or baking, produced as much as 6 lbs. per gallon. Today,
in states that have limits that are rigorously enforced, many
coatings have been reduced to less than 3 lbs. per gallon. In
the case of water-based paints, some are even lower. By and large,
these reductions have been accomplished by raising the percentage
of solids (what is left after evaporation of the solvent or water)
to somewhere in the 60-70% range.
In addition to reducing the amount of VOCs
allowed, most ruling agencies also impose a restriction on the
type of spray apparatus that can be used. In general, the only
approved application equipment that can be used is either electrostatic
or HVLP (High Volume, Low Pressure). Both are almost universally
considered to have a transfer efficiency of 65% or better. Electrostatic
uses the laws of nature that dictate negative and positive will
attract each other.
The coating is charged to negative DC as it
leaves the spray gun, and anything that is grounded is, therefore,
positive. In some cases, this allows completely coating a part
by spraying it from only one side, since the overspray that would
ordinarily miss the back side of the piece is induced to bend
it's path and deposit on the back side of the grounded part.
HVLP technology is a fairly recent development.
In simple terms, the HVLP spray gun takes in compressed air (for
atomization) at 50 psi and, releasing it in large volume, automatically
reduces the 50 psi to something in the area of 5 psi. The result
is a drastic reduction in the forward velocity of paint particles
coming out of the gun, thereby reducing the amount of overspray
that would otherwise not hit the part at all.
While the HVLP gun does not have the negative/positive
attributes of electrostatic applications, it does have the advantage
of costing about 10% or less of the electrostatic equipment. And
it does reduce the total VOCs by reducing the amount of material
sprayed, because the lower forward velocity allows more of the
sprayed material to be deposited on the part.
While we are on the subject of spraying, let's
also touch on another rule that has recently been imposed by many
environmental control agencies - gun cleaning. In the past, when
cleaning the spray gun, the operator would replace the paint in
the pressure tank, pump or siphon cup with a compatible solvent.
Pointing the gun at the exhaust filters or water-wash curtain
in the booth, he would simply spray until clean solvent was observed.
Not any longer.
In most areas where pollution control is actively
enforced, you must now use something we will generically call
a "gun cleaning station." The marketplace is full of
them, and they all do the same basic thing, i.e., contain the
cleaning solvents in a closed or partially closed container, greatly
restricting their release to the atmosphere.
Many of these manufacturers may tell you that
their equipment design does much more than the above. But, remember,
the only requirement of a gun cleaning station is to contain the
solvents and prevent their release to the atmosphere to the greatest
extent possible.
We can carry the gun cleaning idea to another
step - reclaiming the solvents in a small distilling machine in
your shop. Spent solvents are expensive to haul away, and most
of them can be redistilled in commercially available machines
that do not require anything more than plugging in to the proper
electric voltage. These machines typically are sold in a size
that will distill five gallons of solvent at a time. While this
probably points more to the reduction of hazardous waste hauling
than it does to VOC reduction, it is all part-and-parcel of the
pressures being applied to our industry to clean up its act.
The automotive rebuilding industry is slowly
turning away from the old tried and true methods of painting,
and looking instead to the electrostatic powder paint application
methods. Additionally, the industry is more and more realizing
the benefits of automatic application methods from both quality
and cost standpoints. Our company recently completed a system
for Motor Car Parts & Accessories (MPA), Torrance, CA, that
coats and bakes 1,400 parts per hour with a coating that is far
superior to most wet coatings in general use today, while doing
it with only two people.
So, why powder? Steve Kratz, vice president
of Motor Car Parts & Accessories answers, "Powder coating
allows MPA to produce better quality parts more efficiently and
ensures long-term compliance with current and future pollution
control regulations.
"The most important goal, is the reduction
of VOCs to a point where they are almost non-existent. The pollution
"guardians" won't give it a zero, but will generally
accept powder coating at something under 4%. In addition, if you
are of an operational size that can't justify anything but hand-held
painting, you can make anyone in your shop a professional powder
coater in a matter of minutes. No more need for the ultimate skill
of a seasoned spray painter! And your existing spray booth can
possibly be revamped to make it legal and logical to spray powder.
When it comes to cleaning the spray equipment in a powder application,
there is no requirement for any sort of cleaning station. There
is no solvent to evaporate to atmosphere. There is no water.
Core cleaning concerns
Another area that may prove of interest to
the rebuilder is the removal of oil and dirt residue from the
incoming parts. Among other processes, the vibratory cleaner with
a water/solvent/detergent mixture is popular, but it does create
some pollution problems, not the least of which is the disposal
of the waste. One solution would be the addition of the continuous-feed
incinerator mentioned earlier. Another would be the installation
of a centrifugal cleaning unit on the vibratory machine.
This process utilizes the same principles
found in dust collection with a cyclone. Centrifugal force pushes
the particulate in the bath to the outside of the container. This
also tends to keep the "cake" fairly dry, so that the
accumulated sludge can be transported as hazardous waste in a
drum that would probably represent a great number of drums without
its use.
While it is probably not too obvious, the
reduction in VOCs results from the reduced number of times the
bath in the vibratory cleaning machine needs to be replaced. This
may or may not be considerable, but it is worth looking at.
A second method of cleaning incoming parts
is with what is called a "burn-off" oven. This system
is not too far removed from the sludge incineration machine we
discussed earlier. But this machine takes a basket of parts (number
and weight depends on machine size), raises the temperature to
the point at which the contaminates start to char or burn, and
holds them at the assigned temperature until all have been burned
away.
Oven cleaning creates a generous amount of
smoke, which upsets the environmental people, so the oven should
also have it's own afterburner. The stack temperature is raised
to at least 1400°F with a retention time that meets the minimums
of the various regulatory agencies, and the stack gases are virtually
clean and clear of any VOCs.
The only thing left in the oven at the end
of the cycle is a fine white ash, which is technically hazardous
waste. However, depending on the volume of parts cleaned, the
quantity of this ash may be so small that many, many cycles (perhaps
hundreds) are required to accumulate enough ash to have a drum
full.
Many engine rebuilders already employ a burn-off
oven. There are several good manufacturers of this type of product,
and most of them have local or regional representation with personnel
that are quite expert in this field. Likewise, if you are a remanufacturer
of electric motors, the burn-off oven probably provides one of
the least expensive methods for removing varnish insulation from
component parts.
A typical burn for most small parts, for example,
will use approximately $7 worth of gas and a few pennies worth
of electricity. With this process, as with most, subsequent abrasive
blasting is probably in order to achieve a new-looking part. Rebuilders
should closely examine the costs of cleaning and the disposal
of waste in order to determine which processes make the most sense.
Cost considerations
Reduction of VOCs, as you probably already
know, is not necessarily an inexpensive project. For example,
here is an estimate of the cost of the various machines we have
discussed:
| CONTINUOUS SLUDGE INCINERATION: |
$45,000 |
| HVLP SPRAY GUN:
| $385 |
ELECTROSTATIC PAINT OUTFIT
(HAND OR AUTOMATIC):
|
$4,000 |
CENTRIFUGAL SLUDGE
REMOVAL:
| $5,000 |
ELECTROSTATIC POWDER SPRAY GUN
(HAND OR AUTOMATIC):
|
$5,000 |
| PAINT BURN-OFF OVEN:
| $20,000 |
The prices shown here are obviously going to change depending
on the needs of your particular operation and the specific model
of equipment purchased. A burn-off oven, for example, can range
from several thousand dollars to $30,000 to $40,000 depending
on size and type.
The electrostatic powder price is for the gun only. To this must
be added the cost of the oven and, if employed, the conveyor.
Should you wish to reclaim the powder oversprayed for reuse, then
add money for the special spray booth. Depending on numbers and
size of parts required, a powder paint system can range from $50,000
to $250,000 or more.
Your best plan of attack may be to call a reputable firm and ask
them to make an evaluation of what you can do to reduce VOCs emissions
from your plant. Most companies will accommodate you without charge,
or with a very minimal charge, to cover their expenses. Some will
even provide you with suggested new paint-finishing machine layouts
at no charge. The added benefit to you may very well be the discovery
of a change in manufacturing processes that can save you money
and increase the profitability of your operation.
Don Lick is president and CEO of Omega Industrial Sales Co.,
Santa Ana, CA. His primary responsibilities are as a designer
of finishing systems and as a consultant for such companies as
Boeing Military Airplane Co., Dow Chemical, Black & Decker
and others. He is past chairman of AFP/SME in Los Angeles.