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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 user’s 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 user’s 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 user’s 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.

Conclusion

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 cleaner’s physical and chemical properties, material compatibility test results, and other performance requirements are often available from the cleaner’s 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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ASTM D 6361 was developed by Committee D26 on Halogenated Organic Solvents and Fire Extinguishing Agents.

M. Kevin McGill is the president of Prospective Technology, Inc., an engineering consulting firm specializing in pollution prevention, industrial equipment optimization and corrosion engineering. He is subcommittee chair for the Cold Cleaning subcommittee of ASTM Committee D26 on Halogenated Organic Solvents and Fire Extinguishing Agents.