#Industry News
Breathe out and relax
Elizabeth Norwood, senior chemist at precision cleaning solutions specialists, MicroCare, explains how we can all breathe much easier with effective oxygen system parts cleaning.
Oxygen supply and distribution systems play a critical role in supporting aircrew and passengers during high altitude flights. Oxygen systems must function as intended and without exception whether used for normal operations or in an emergency situation.
The manufacture process of the various parts and components contained in these systems leaves surface contaminants that need to be eliminated prior to assembly of the finished product. It is critical to performance and safety of the systems that the parts be perfectly clean.
The contamination risk
Common Oxygen system components contaminants include, but are not limited to, dust, metal chips, greases, oils and acids. When not properly removed, production particulate can affect the operation of system components including sensors, valves and controls, and pipes, hoses, tubes, regulators and meters.
Any soils left behind during production can also be a combustibility risk. Particulate can produce friction in moving parts which can create both a heat and a fuel source. Materials used within an oxygen system become easier to ignite because their flammable ranges start to expand and their auto ignition temperatures begin to drop. In an oxygen-rich environment, any residual particulate can spontaneously auto-ignite and cause an explosion. It is therefore critical that every single component within the system is perfectly cleaned and dried before inspection, assembly and packaging.
How to clean?
As you would expect, there are strict guidelines to be followed when manufacturing components for any gaseous or liquid oxygen system to ensure it passes rigorous quality standards. ASTM G93 - 03(2011), the ‘Standard Practice for Cleaning Methods and Cleanliness Levels for Material and Equipment Used in Oxygen-Enriched Environments’ is just one of the international specifications that must be followed. The Standard details the need to precision clean surfaces and areas that come in contact with pure O2 or those operating with pressurised O2. Additionally, it also covers the selection of cleaning apparatus and equipment as well as the recommended cleaning materials or fluids to be used on parts intended for service in oxygen-enriched environments.
There are several recommended cleaning methods for cleaning oxygen system parts. Some of the most popular methods include vapor degreasing, aqueous, acid, alkaline and mechanical cleaning.
With so many cleaning methods it can be challenging to find a solution that works best. In addition to thorough, precision cleaning, there are other factors to consider when cleaning components. The increased governmental and environmental regulatory scrutiny has increased the importance to choose a method that not only critically cleans but also addresses regulatory, safety and environmental sustainability issues.
Of the various cleaning methods there is one that clearly stands out. Vapor degreasing offers best cleaning performance while complying to emerging regulatory, safety and sustainability criteria.
A vapor degreaser is a closed-loop system that contains two chambers: the boil sump and the rinse sump. In the boil sump, the cleaning fluid is heated and the parts are immersed and cleaned in the fluid. Once cleaned, the parts are mechanically transferred to the rinse sump for a final rinse in a pure, uncontaminated fluid. The parts come out clean, dry, spot-free and immediately ready for the next step in the manufacturing process or for packaging.
A vapor degreaser offers a simple process that is extremely effective at removing contaminants. The low viscosity of modern cleaning fluids used within a vapor degreaser, combined with their volatility, allow them to clean very effectively. Additionally, because the cleaning fluids have low boiling point, they evaporate quickly helping to ensure the cleaning fluid and contaminants don’t get trapped inside end holes, blind holes or other tiny part cervices. No residue is left behind which significantly reduces any flammability risk.
Modern vapor degreasing fluids have a low boiling point and heat of vaporisation. This translates to greater safety for sensitive oxygen system parts, especially delicate gaskets and seals. Most vapor degreasing fluids also are very heavy and dense, usually 20-40% heavier than water, which aids in dislodging particulate from the components.
Vapor degreasing benefits
Vapor degreasing is an extremely effective method to precision clean all parts of an aerospace oxygen system, but there are several other benefits too:
Regulatory Compliance - The cleaning fluids used with a vapor degreaser meet evolving quality and regulatory standards like ASTM G93 - 03(2011). Importantly they meet stringent process validation specifications which are essential when manufacturing oxygen systems and parts produced within a cleanroom environment.
Additionally, the latest advances in cleaning fluid technology have led to modern vapor degreasing fluids being an environmentally sound option to comply with strict local and national air quality regulations and operator safety requirements.
As regulations and guidelines change, many of the older cleaning fluids that have been used for years are now becoming obsolete. Modern cleaning fluids are unlike older legacy solvents including n-propyl bromide (nPB), perchloroethylene (PERC) and trichloroethylene (TCE) that are under air quality scrutiny. The newer vapor degreasing fluids are not considered a Hazardous Air Pollutant (HAP).
Modern vapor degreasing chemistries maintain highest levels of performance and worker safety. Formulations are created with low-VOC (volatile organic compound) and low GWP (global warming potential) chemistries for improved environmental properties (ozone-friendly) while maintaining compliance with various directives including United States EPA regulations and European F-Gas and REACH legislation.
Validation - Validation is extremely important when producing parts for any oxygen system. Validation helps ensure that parts consistently meet established quality standards, including those found in cleanroom settings. To meet validation criteria, the chosen cleaning process must be consistent, compatible with established procedures and easily documented. Vapor degreaser cleaning is a well-engineered process that is simple, consistent and repeatable, making it easy to qualify and validate for aerospace oxygen system part manufacturers.
More controlled production environment - Vapor degreasing also helps maintain facility temperature and humidity since the vapor degreasing machines generate minimal heat, and no moisture, fumes or dust. Unlike other cleaning methods including aqueous cleaning, vapor degreasers do not require special blowers and fans or any particular climate controls to maintain air quality or ambient temperature and humidity.
Breathe more easily
When it comes to aerospace oxygen systems, the cleaning of parts post-manufacture must meet many strict standards and regulations. If parts are not consistently cleaned, there is a risk of fire through auto ignition or the possibility of affecting the purity of the oxygen system.
Vapor degreasing using modern cleaning fluids addresses the challenges that parts fabricators face when producing parts for use in aerospace oxygen systems. Through this efficient and validated method, companies can breathe easy that their devices are working consistently and reliably in the air.
www.microcare.com
