Evaporative Technology for Waste Stream
Reduction in Aqueous Parts Washers
By Hydro Blast, Inc.
Aqueous parts
washers are rapidly replacing solvent cleaning systems and steam cleaners for
out-of-frame cleaning of large parts and engines. The impetus for this arises
from employers concerns about a "hazard- sensitive" workplace,
environmental issues, and significant labor savings by reducing the time
needed to clean parts.
By using the right
aqueous parts washer, it is possible to significantly reduce hazardous waste
streams and not sacrifice cleaning performance. Some variables to consider
are the spray, action and temperature, the required cleaning time, the
detergent, the rinse, and wastewater disposal.
The Spray Action
Aqueous cabinet
parts washers use a high water volume spray to clean parts. Parts rotate on
turntable and are washed with jets of hot water from the top, bottom and both
sides. Hot water and detergent, usually heated to 140 to 180° Fahrenheit,
quickly raise the temperature of the parts to where dirt, grease, oils and
other contaminates are easily washed away. The hot parts quickly dry and are
ready for repair. The pressure in an aqueous parts washer is very low
compared to pressure washing.
Cleaning Time
Complete diesel
engines and large parts can be washed without removing most accessories
(blowers, fan, turbo, pumps etc.) in larger aqueous parts washers. Blocks
take approximately 15 to 30 minutes to thoroughly clean. After the block is
cleaned and drying, accessories are washed usually in 5 to 15 minutes,
depending on the level of contamination. In smaller aqueous parts washers,
small parts and accessories must be removed and cleaned separately in a parts
basket. They should not be cleaned with the block and head.
Due to the weight of
diesel engines and related components and large parts, the parts are usually
loaded into an aqueous parts washer using a crane. An overhead loading door
is standard on all Hydro-Blast cabinet style parts washers.
The Detergent
Because of the
variety of metals (cast iron and aluminum) in diesel engine, an
all-metal-safe detergent is recommended. A high pH soap will give better
results on heavy carbon or baked on oil and grease but will discolor and
attack soft metals. All detergents should contain an anti-foamer and a rust
inhibitor.
Rinse
A fresh water rinse
cycle is an option most cabinet parts washer manufacturers offer. The rinse
removes residuals left by the detergent. Usually a rinse cycle is not
necessary for this level of parts cleaning because re-machining or final hand
cleaning of cylinder bores or other critical areas may be required.
Another rinse option
is to use a 2-gpm/1000 PSI pressure washer to rinse the block or engine or
parts in the cabinet. This adds water to the washer and helps maintain a
constant water level.
Wastewater Disposal
· Washwater eventually becomes too contaminated to clean effectively. Most
companies refuse to discharge this waste to the sewer and risk the potential
fines. Recycling the water is an option. However at some point, this water
cannot be recycled further and must be disposed of properly. Evaporation is a
very cost-effective option when compared to having a commercial waste hauler
dispose of the wastewater three to five times a year.
· When wastewater is disposed of through evaporation, oil is removed from
the wastewater using an oil skimmer. It is channeled to an outside reciprocal
for recycling or burning in a waste oil heater. Then the wastewater disposal
system is started by using under floor heating. The wastewater boils until
evaporation is complete. This usually takes eight to twelve hours. The
heaters shut off automatically at the end of the evaporation cycle.
· The steam from evaporation is ducted outside the building with the aid of
a in-line draft inducer. This steam is no different from the steam that
escapes when you open the door at the end of a wash cycle. It is not
hazardous.
· After evaporation is complete, a small quantity of residual solids will
remain on the floor of the cabinet. This sludge is easily removed with a
wet/dry vacuum or scooped up with a dust pan. These residual solids must be
disposed of properly. A certified laboratory can do a Toxicity Characteristic
Leaching Procedure (TCLP) on the solids to determine its contents and
classify it as hazardous or non-hazardous waste. Traditionally the TCLP test
is a one time test and cost when cleaning like parts. Test costs vary from
$180 to $300 depending on the laboratory.
· Evaporation will reduce the weight and volume of a waste stream by as
much 95%. It will also reduce costs for on-site training, handling, storage
and disposal of hazardous wastes and the potential fines associated with
wastewater spills. Evaporation is an effective way to reduce EPA assessments
from a medium generator to a small waste generator.
· A typical diesel repair facility would usually find that the build up in
the bottom of a cabinet parts washer would require wastewater disposal
(evaporation) every three months. Evaporation is recommended when the level
of dirt at the bottom of the cabinet parts washer reaches a depth of about
one inch or the washer is not cleaning properly.
Hazardous Waste and Toxic Reduction Program
Several states have
a hazardous waste and toxic reduction program with specific guidelines that
meet or exceed U.S. Environmental Protection Agency requirements. As an
example Technical Information Memorandum, Number 86-3, published by the
Washington State Department of Ecology, contains information and guidance on
how generators may treat their own dangerous waste(s) on-site, without
dangerous waste treatment permits. The Department of Ecology is actively
promoting treatment by generator for several reasons. Treatment often is
preferred to the disposal of a waste because it may be more environmentally
desirable and economically feasible. You should contact your local
agency for guidelines.
A case example for
evaporation would be: Machine shops that generate large amounts of waste
water mixed with spent caustic solution that test hazardous for lead and
corrosively. By using an evaporator these shops can reduce the quantity of
their waste in an environmentally safe manner.
Summary
Aqueous parts
washers clean parts to acceptable levels of cleanliness using detergent and
hot water. Besides the cost and labor saving aqueous parts washers offer,
evaporation is another cost savings and added environmental advantage.
However, one of the best advantages of aqueous parts washers are they can
usually pay for themselves in less than one year in labor savings.
