Aerospace customer previously used nPB (n-propyl bromide) for cleaning various metallic based investment castings (steel, stainless steel, titanium, aluminum, etc.), machined aluminum extrusions and formed aluminum sheet metal parts.
Due to recent and continuing regulations of n-propyl bromide and in 2012 the ACGIH (American Conference of Governmental Industrial Hygienists) confirmed nPB as an “Animal Carcinogen with Unknown Relevance to Humans” lead to Corporate mandates for elimination of nPB and other chlorinated solvents in their facilities. Based on this finding, in 2013 the U.S. Department of Defense released Chemical & Material Emerging Risk Alert 1-Bromopropane (1-BP) # 01-13 which addressed the concerns of National Toxicology Program (NTP) and Environmental Protection Agency (EPA) and the call for reductions of use with Department of Defense related applications.
Video of Aqueous System Process Steps
The cleaning process required the following contaminants to be removed from the parts:
- Master Chemical TRIM E206 cutting fluid
- Cenex premium anti-wear hydraulic oil INDOL ISO32
- Sunnen MB-30-55 hone oil
- Magnetic particle inspection (MPI) Magnaflux Magnaglo Carrier II Oil
- Magnaflux Magnaglo 14A Fluorescent Magnetic Powder
- ChemStation MnDak 5155
The process is required to adhere to cleanliness and cleaning chemical solutions requirements in BAC5763: Emulsion Cleaning and Aqueous Degreasing. Parts cleaning solution Chemetall Ardrox 6333A was tested on the various parts and passed the BAC 5763 specification cleanliness requirements.
Pictures of Automated Aqueous Cleaning System
Aqueous Part Cleaning System vs. Vapor Degreasing with nPB Process Steps
As can be seen in the above video, the system operates on a continuous flow of baskets from load, wash, rinse 1, rinse 2, conveyorized dryer and unload conveyor. A vapor degreaser works similar to the video below processing a basket in a singular flow (vs. continuous flow with above aqueous system).
Environmental Benefit of Aqueous vs. nPb Solvent Based System Processes
An aqueous-based cleaning system of cleaning and rinse tanks will evaporate water from the tanks over time which can be safely exhausted either within the manufacturing facility, or to outside air. The cleaning chemistry solution is designed to have minimal evaporative losses from the system; therefore, as long as evaporative water losses are replenished into the system, the concentration of cleaning chemistry remains fairly stable. Titration is performed regularly to check the concentration of the solution. Since this application is removing not only water based coolants, but also true, petroleum based oils, the cleaning chemistry is designed to separate the oils from the solution and allow them to float to the surface of the wash tank. The oil coalescer system sparges the oils off the surface of the wash tank into coalescing media that further separates the true oils from solution and can be disposed of in nearly pure oil form. This collected waste stream can be disposed via normal oil disposal procedures and typically not treated as hazardous waste. Over a long period of time, the wash tank solution will become loaded with other contaminants (other than filtered particulate and coalescer removed true oils) and will need to be replaced with a fresh tank of diluted aqueous chemistry. The previous wash solution can typically be processed through in-plant waste water treatment systems for disposal.
This system was designed to be a closed loop, zero discharge system meaning there would not be a continuous flow waste stream from the system and regular waste water from the rinse tanks is recycled and reused within the system via a closed loop, regenerative de-ionized water system. This system eliminates the rinse water consumption and waste from the system. This is a huge cost savings in both water supply and disposal.
Solvent Vapor Degreaser
A solvent-based vapor degreaser by design is able to re-distill and recycle the solvent used in cleaning, but at a certain point the solvent can no longer efficiently run with the oils and soils saturating the solution. When this occurs, a “boil down” procedure is ran on the system to boil out of the boil sump residual solvent still separated from the oils. The remaining solution is a blend of saturated solvent, oils, and other contaminants. This waste stream will need to be hauled off site for proper disposal. Sometimes this waste stream will also need to be treated as a hazardous waste upon disposal and the generating manufacturing facility will need to get a permit for hazardous waste generation.
Employee Safety Benefits
Regulatory bodies continue to tighten requirements on nPb for good reason: employee safety and environmental atmosphere ozone depletion. Over the years, recommended employee exposure limits have been reduced significantly based on testing and findings. The new, extremely low exposure levels are proof that nPb will eventually be phased out for use in the U.S. and abroad.
Aqueous-based cleaning chemistries are diluted to typically 5-25% concentration in water and there are no exposure limits set because no harmful vapor is emitted from the chemistry on evaporation.
Since 1992, Best Technology has offered the latest part cleaning and metal processing equipment integrating the latest chemical processing technology to reduce environmental impact and ensure employee safety while delivering clean parts for years to come.