Components and hardware that are used in oxygen environments may require specialized oxygen cleaning services performed in a designated cleanroom. Cleanrooms are special facilities designed to maintain extremely low levels of airborne particulates, such as dust, airborne organisms, or vaporized particles. The primary contaminants of concern that must be removed for oxygen service environments are hydrocarbon-based residues and particles. If contamination is not removed, contaminants may hinder a component’s operation and increase ignition hazards.
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Contaminants can be classified into three categories, per ASTM G93.
- Volatile organic compounds (VOC)
- Grease and oils (Hydrocarbon based)
- Water-based detergents and cutting oils
- Mineral acids and solvents
- Metal grindings or filings from fabrication
- Particles, lint, and fibers
What is the difference between Oxygen Cleaning and Precision Cleaning?
Both require that a surface be cleaned, but precision cleaning requires some sort of measurement or analysis of the surface cleanliness to quantify and/or validate the level of cleanliness achieved.
When even small amounts of hydrocarbon-based residue are present in an enriched oxygen atmosphere, the combustion temperature is lowered. Thus, the possibility of an explosive reaction resulting in a fire must be eliminated because the hydrocarbon-based contaminants both lower the temperature in which a fire can be started, and act as fuel for the propagation of the fire. The presence of an increased concentration of oxygen molecules in enriched oxygen systems means that the fire will burn hotter and faster. Hence, precision cleaning of residual contaminants must be performed for safety reasons in these types of systems.
Another harmful contaminant of concern is particles. Particles can travel in a stream of moving gas or liquid oxygen within the system or component. In oxygen-enriched atmospheres, and at high velocities, particles can strike or impact the surface and create sparks, especially if the particles are metallic. If a spark occurs, contaminants within any component or assembly within the system may catch fire. In summary, component parts to be used for enriched oxygen systems, or pure oxygen environments, must be free of residues and particles.
Table 1. Particulate cleanliness levels
|IEST-STD-CC1246E Level (Maximum Particle Count)|
|min (μm)||max (μm)||25||50||100||200||300||400||500||750||1000|
Note that particles are counted down to a size of five μm, which cannot be seen with the unaided eye. This entire process is termed a particle count.
Oxygen Cleaning in the Cleanroom
Oxygen cleaning services performed at an Astro Pak Cleanroom consist of two steps. The surfaces are cleaned using approved equipment, chemicals and processes. Secondly, cleanliness verification testing is performed to confirm that the components or hardware meet the requirements of the specification, procedure and its intended system environment.
In the cleanroom, a variety of cleaning processes may be utilized. Aqueous detergents, approved solvents, acids, ultrasonic cleaning, high-pressure spraying, hand detailing, vacuum environment, , and other methods are common. All cleaning agents, whether water-based detergents or solvents are selected for the effectiveness of the component being cleaned and according to industry and customer standards such as ASTM G127.
The cleaned components and hardware are handled by personnel in appropriate cleanroom gowning attire and gloves so that cleanliness is preserved, and that recontamination does not occur. Astro Pak has controlled AS9100 / ISO Certified Class 5, 6, and 7 cleanrooms available for oxygen cleaning services, including a Large Component Cleanroom
All customer hardware processed at our facilities is tested and certified by Astro Pak chemists in one of our verification laboratories. Testing includes verifying critical surfaces for residues using Gravimetric Non-Volatile Residue (NVR) verification, as well as black light and white light inspections. In addition, many components that have been cleaned for oxygen service are also tested to confirm the removal of microscopic particle contamination. Particles on critical surfaces are counted and sized using accepted standard Particle Count Analysis methods.
Table 2. Nonvolatile residue cleanliness levels
|Level (μg/cm2 or μg/0.1cm3)||Former Designation Level||Maximum allowable NVR limit mass / 0.1 m2 or mass / 0.1 L|
A / 100
A / 50
A / 20
A / 10
A / 5
A / 2
Coast to Coast Cleaning Facilities
Astro Pak is home to the largest and most advanced contract precision cleaning facilities in the United States. Our southern California facility houses AS9100 / ISO certified Class 5 & 6 (FED STD Class 100 & 1,000) cleanrooms and labs. The highlight of this facility is the 21,222 cubic ft Large Component cleanroom featuring a 26’W x 15’H high-speed roll up door, 18ft ceilings and a two-ton overhead bridge crane to accommodate hardware that is too large for most traditional cleanrooms.
Astro Pak’s new Florida facility resides just outside of the Kennedy Space Center. This signature feature of this 38,000 square foot facility is the 15’x15’ enclosed tower (70’ vertical) which enables the processing of stainless steal convoluted hoses up to 60’ in vertical orientation. Adjacent to the ISO 7 & 6 (FED STD Class 1,000 & 10,000) cleanrooms and labs is a shop area with a 2-ton bridge crane and expanded hydrostatic, hydraulic and pneumatic testing capabilities.
Trust the Experts
Astro Pak has over 60 years of experience in precision cleaning a variety of componentry including fittings, tubing, valves, hoses, 3D printed parts, large high-pressure GOX and LOX tanks, and vast array of equipment, assemblies and miscellaneous hardware . We house an extensive library of approved procedures and meet the requirements of hundreds of industry specifications including Boeing, Aerojet Rocketydyne, Northrop, ULA, NASA, the Air Force, Department of Defense, and many other private organizations.
Our Research & Development professionals can develop a customized oxygen cleaning process that meets nearly any requirement in an efficient and cost-effective manner.
Astro Pak commits to providing customers with the level of excellence they expect and deserve by:
- Advanced Chemistry & Process Technology
- Highly Trained Personnel delivering superior consulting services
- Rapid Response
- State of the Art Equipment and Locations Nationwide
- Superior Documentation (Meeting cGMP Requirements)
In addition, our Certification packages are QMS/cGMP compliant for your systems and equipment maintenance records. Let our experienced and credentialed team of chemists, engineers, and other professionals on staff EXCEED your expectations. Contact us today for more information.
Frequently Asked Questions
Oxygen Cleaning, also referred to as Oxygen Service Cleaning, is cleaning parts that will be used in an oxygen or oxidizer environment. To accomplish this, parts are not cleaned using oxygen; rather, the parts are degreased using solvents and/or alkaline detergents in an aqueous solution to remove the contaminants and residue that are not compatible with an oxygen system. This cleaning process is important to ensure that substances which are incompatible with oxygen or other oxidizers are removed from the part. Failure to do so may result in system failure, product failure, and/or combustion.
There is a wide range of cleanliness criteria for oxygen service depending on the use of the system. The less critical conditions include breathing air, non-oxygen gases; and the more critical conditions include liquid oxygen, high pressure gaseous oxygen, spacecraft systems, etc.
For each environment there is a set cleanliness criteria established. Usually the standard is noted in a cleaning specification, and the cleanliness verification target ranges from 47 mg/sq foot of non-volatile residue (NVR) for the least critical conditions, to 1 mg/sq foot of NVR and below for the more critical systems. Cleanliness criteria can be less than 1 mg/sq foot for oxygen systems, but typically 1 mg/sq foot of NVR represents the more common lower limit range of the requirement.
After a part has been cleaned and verified, it is important to package the part correctly in order to maintain the cleanliness level until use or assembly into the final hardware, equipment, or system. For high pressure and liquid systems, cleanliness criteria usually also includes particle count limits. The allowable particles are typically in the range of level 100 – 300 (measured in micrometers), as noted in such specifications as IEST 1246.