|Clean and Green
by M. Kevin McGill
Market response to environmental guidelines has led to a plethora
of new, greener industrial cleaners. A new ASTM standard, based
on practical guidelines used by the American military, helps engineers
and production managers decide which cleaner will do the job right.
Since the early 1990s when the environmental movement began to
replace industrial cleaners and degreasers containing ozone-depleting
compounds (ODCs) with more environmentally friendly products,
users have been confounded by their options. There are literally
hundreds of cleaners on the market that tout their cleaning capabilities
and safety for the worker and the environment. There are publications
sponsored by the U.S. Environmental Protection Agency and other
organizations listing environmentally preferable or environmentally
safe cleaners. But neither the cleaner manufactures nor the proponents
of these lists provide the user with any guidance as to how to
select an appropriate cleaner for their cleaning needs.
Trial and Error Does Not Work
Because no real guidance existed on cleaner selection, users were
forced to resort to expensive trial-and error-methods to select
cleaners. Although the cleaners selected may have been safer for
the environment and did not destroy the ozone layer, many of these
environmentally safe cleaners failed to provide the cleaning effectiveness
needed for a particular cleaning job. In addition, some of these
cleaners were not compatible with the materials being cleaned.
In some military applications this resulted in extensive damage
to very expensive parts. The trial and error method for selecting
cleaners does not work.
This method was so unsuccessful because the selection of cleaners
must be application-specific. A cleaner that works fine for one
cleaning job will not necessarily work for all cleaning jobs.
For the most part, chlorinated solvents used in vapor degreasers
were used as universal cleaners. But aqueous, semi-aqueous, and
non-ODC solvents cannot be used without regard for the specifics
of the cleaning task.
ASTM D 6361
ASTM D 6361, Standard Guide for Selecting General Cleaning Agents
and Processes, is based largely on a protocol established by the
U.S. Army Acquisition Pollution Prevention Support Office. It
is the first consensus standard to assist design engineers, manufacturing/
industrial engineers and production managers in selecting the
best-fit cleaning agents and processes. The standard guides the
engineers and managers through the cleaning material selection
process, calling for engineers to customize their selection based
on the requirements of the cleaning task at hand.
Guide Principles in Practice
The Corpus Christi Army Depot (CCAD) has used the process depicted
in the guide for several years to select the proper cleaning agents
and processes for specific cleaning tasks. In one instance, in
their engine cleaning shop, shop personnel were cleaning baked-on
carbon deposits from aircraft turbine engine components using
a hand-wipe solvent. The depot wanted to reduce the volume of
the hazardous solvent they were using as well as decrease the
number of hours spent cleaning the parts. In wanting to find a
product that did not contain any hazardous air pollutants, they
limited their search for a cleaner to those that contained no
such chemicals. Some of the parts to be cleaned had small holes
and the depot determined that the appropriate process technology
would be an immersion bath, utilizing ultrasonic agitation. CCAD
therefore acquired a four-stage ultrasonic cleaning unit, and
began searching for a cleaner that would remove the carbon deposits.
CCAD found an aqueous cleaner that had been specifically designed
to remove carbon deposits from various materials, and could be
used in an ultrasonic system. They acquired the necessary test
results from material compatibility testing on the parts they
intended to clean in their ultrasonic unit, and began using the
cleaner. After optimizing the process parameters (time, temperature,
etc.) the results achieved have been tremendous. The parts are
cleaner using the automated machine than when they were being
cleaned by hand. Further, automating the cleaning process reduced
the time spent cleaning by one and a half to two hours per part.
Other Army activities have been utilizing the principles of ASTM
D 6361 since the publication of the Army protocol in 1997 with
much success. For instance the Tank-Automotive and Armaments Command,
acquisition pollution prevention integrated process team, requires
the use of the Army protocol (and now the ASTM guide) prior to
approving any cleaning material substitution activity.
Five Steps to Selecting a Cleaner
The guide offers a five-step approach for selecting general cleaning
agents and processes for use in manufacturing, overhaul, and maintenance
in industrial operations. For each step, the user of the guide
provides specific information on some aspect of their cleaning
operation. The guide then provides information on what characteristics
the cleaner should be evaluated against in order to support the
specific cleaning operation. In this way, the guide allows the
industrial engineer to customize the selection of the cleaning
product based on specific items such as the material of the part
being cleaned, the subsequent process for the part, and environmental,
cost, and health and safety concerns.
1. Determine Facility Requirements
The initial step for the engineer using this guide is to determine
the requirements of the facility that may impact the selection
of the cleaner and process. These factors will certainly include
environmental, safety, and health concerns. For example, the South
Coast Air Quality Management District in southern California strictly
regulates the volatile organic compounds (VOCs) of solvent cleaners
and degreasers used for industrial cleaning. If the facility is
in this area, the user should not even consider the further evaluation
of any cleaner that contains more than 50 gallons per litre of
VOC. There may also be other physical or chemical properties of
cleaner that would render them unsuitable for use in a given facility.
Many industrial facilities limit the flash point of the materials
used, and therefore products with a low flash point should be
eliminated from consideration.
2. Determine Part Materials
The second task for the engineer using this guide is to determine
the material or materials of the parts being cleaned. This is
critical because certain cleaners have adverse effects on certain
materials and this is to be avoided. When the material is determined,
the engineer will consult ASTM D 6361 to determine which material
compatibility tests the cleaners should be evaluated against.
For example, if the material of the component being cleaned is
aluminum, the guide lists five material compatibility tests including
total immersion corrosion (ASTM D 930 or F 483) and sandwich corrosion
(ASTM F 1110). Should a cleaner perform poorly in these tests
for aluminum, that cleaner should no longer be considered as a
cleaner for that aluminum part. Making sure that a cleaner is
compatible with the part being cleaned is essential in assuring
that the cleaning process will not degrade the part and lead to
expensive material replacements in the future.
If a part is a combination of two or more materials, then the
tests outlined in the guide for those two materials can be combined
to reflect the full series of tests that should be performed on
the cleaner prior to its use on the part. The guide provides material
compatibility tests for 20 of the more commonly used materials
in industrial or manufacturing applications.
3. Determine Cleaning Process
The third step in using this guide is to determine the processes
that are acceptable to be used for the specific cleaning application
at hand. The cleaning process is simply how the cleaner is to
be applied to the part. In determining the acceptable processes,
analysis of the shape of the part will be critical. For example,
if the user were trying to clean a part that has as part of its
geometry small or deep holes, using a high-pressure spray cleaning
process would be a poor choice. It is unlikely that the spray
would be able to reach into deep recesses, therefore not thoroughly
cleaning the part. An immersion bath, possibly with agitation,
would be a much better option. The guide asks the user to select
between three part shapes or characteristics, and then determines
which of 14 process types are appropriate for the application.
It is important to determine the process type because many cleaners
are formulated for use in specific processes.
4. Determine Reason for Cleaning
The fourth step in using the guide is to establish the performance
requirements for the cleaner to be used, since the user is cleaning
the part. Every cleaning task is application-specific. If the
user is cleaning a part just to make it look good or easier to
handle it will require a far less stringent level of cleanliness
than if the user intends to bond this same part to paint. The
guide asks the user to select the most appropriate reason for
cleaning the part from a list of seven choices. The guide then
provides the user with an appropriate inspection type and performance
requirement that the cleaner should be evaluated against to ensure
that the cleaner would provide the appropriate level of cleanliness.
For example, if the user intends to bond the part being cleaned
to another part using an adhesive, the guide indicates that a
good predictor of whether the cleaning process will work is the
floating roller peel resistance test (ASTM D 3167). However, if
the cleaning were being performed for cosmetic purposes only,
a white glove test would be sufficient.
5. Final Selection
The first four steps are designed to systematically eliminate
cleaning products that will not work for the users specific cleaning
applications. The order in which these first four steps are used
is not critical. When the evaluation process is complete it is
likely that a number of products will satisfy the users specific
cleaning requirements. The fifth and final step outlined in the
guide is to make the final selection. This final selection may
be based on the price of the candidate cleaners or other business
factors specific to the users facility. The user may also want
to re-evaluate the final list of acceptable cleaners based on
their physical and chemical properties of step one. In performing
this re-evaluation, one cleaner may have a higher flash point
or a lower level of VOCs than the rest, or may require less personal
protective equipment. The user can then choose this cleaner for
those reasons, specific to their facility.
The trial-and-error method of selecting replacement cleaners does
not work, wasting countless dollars on re-cleaning components,
and even more money on damaged components because of material
compatibility issues. Using the guidance presented in ASTM D 6361
allows the user to make a decision on which cleaning agent and
process to use, based on their specific cleaning application.
The guide is not intended to be a list or database of cleaners,
rather a guidance tool to assist the industrial and manufacturing
engineers to make sound technical judgements when selecting cleaners.
Further, this guide was not intended to generate greater expense
for the user. Information on a cleaners physical and chemical
properties, material compatibility test results, and other performance
requirements are often available from the cleaners manufacturer.
The guide is intended to be used to streamline the cleaning material
selection process and provide objective criteria for users to
compare one cleaning product with the next. By using the principles
of ASTM D 6361 the user can select an appropriate cleaner and
process with the confidence of knowing that the parts will be
clean enough for the next maintenance process and the cleaner
will not damage the materials of the parts being cleaned. //
Copyright 2000, ASTM
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