Explosive facts about cleaning oxygen systems

Liquid or gaseous oxygen system components are often soiled during manufacturing and must be cleaned and dried prior inspection, assembly, and packaging.

The slightest contamination or residue left on the systems’ moving parts may cause friction, which could produce enough heat that when combined with access to a fuel source (residue) could combust, auto-ignite, and possibly explode inside oxygen-rich systems.

Cleaning and inspecting hoses, tubes, pipes, regulators, and meters is crucial for the medical oxygen system to perform safely and to comply with standards.

Oxygen system contaminants fall into three categories: Organic hydrocarbon-based greases and oils; Inorganic pollutants such as nitrates, phosphates, water-based cutting oils, and other acids and solvents; and particulates including lint, dust, or welding dross.

Multiple cleaning methods

Depending on the contaminants encountered, there are different ways to clean medical oxygen system components.

• Mechanical cleaning uses wire brushing, sandblasting, or grinding to remove scale, paint, coatings, or welding dross

• Aqueous cleaning, with or without detergents and spray agitation, uses very hot water or steam to remove water-soluble contaminants; detergent must be rinsed off and parts dried before further processing Alkaline or caustic cleaning using caustic salt dissolved in water removes grease, wax, and hydrocarbon oils; the caustic solution is applied using swabbing, spraying, or immersion, but the cleaning solution must be rinsed well to prevent parts damage

• Vapor degreasing is lesser known but highly effective; a simple thermo-mechanical process boils and condenses a specially engineered low-boiling, non-flammable cleaning fluid to remove contaminants; cleans, rinses, and dries parts in one machine making the cleaning process simple, repeatable, and easy to validate

Better cleaning alternative

Vapor degreasing uses a closed-loop system containing two chambers: the boil sump and the rinse sump. The boil sump contains a low-boiling, non-flammable cleaning fluid. Parts are immersed and cleaned inside the heated fluid. Once cleaned, the parts mechanically transfer to the rinse sump for a final rinse and dry in more pure, uncontaminated fluid, or inside the fluid vapors themselves.

The right vapor degreasing fluid

Excellent materials compatibility: Modern vapor degreasing fluids are ideal for use on a variety of materials. They have a low boiling point and heat of vaporization which translates to greater safety for sensitive or delicate oxygen system parts such as gaskets, seals, and parts made from mixed materials.

Thorough cleaning: Advanced vapor degreasing fluids have low surface tensions and are less viscous than water, allowing the fluid to easily flow through small, complex parts for thorough cleaning and enables the fluid to flow back out from inside the components, preventing contaminants from getting trapped.

Sustainable cleaning: Vapor degreasing fluids traditionally used in production facilities include n-propyl Bromide (nPB), Trichloroethylene (TCE), and Perchloroethylene (Perc). Many manufacturers are searching for alternative fluids that clean as effectively but without worker safety or air quality concerns of the traditional solvents. There are several options available that offer better worker exposure levels and feature low global warming potential (GWP) and zero ozone depleting potential (ODP) characteristics.

No residue, no rinsing: Solvent-based cleaning fluids don’t require an extra rinsing step, and since the cleaning fluids are water-free, they remove the potential for rust.

Hostile to pyrogens: Water, and some of the detergents used with it, are a natural breeding ground for bacteria and mold.  A minuscule amount of moisture left in hard-to-reach areas can encourage their growth and for this reason many medical oxygen system fabricators are turning to vapor degreasing and solvent-based cleaning fluids to minimize the bioburden risk.

Improved workplace safety: Many modern vapor degreasing fluids are nonflammable for improved safety in the workplace by virtue of their azeotropic properties which ensure they are thermally stable and safe to use.

Vapor degreasing benefits

Easy to validate, use: Aqueous cleaning requires engineers to monitor and test to ensure the mixture of water, detergents, and other additives are consistent throughout the cleaning process. When modern cleaning fluids are used, there isn’t a need for complicated process monitoring and controls at every stage in the cleaning process. Due to the fluid(s) ability to maintain purity levels, production managers get peace of mind that there’s no variation in the cleaning fluid chemistry while reducing process costs.

Cleans any size components: Vapor degreaser fluids provide excellent cleaning results on parts of any size and almost any geometry. One vapor degreasing machine is adaptable to clean valves, control devices, and assemblies in a range of sizes and quantities. If the part (or finished assembly) fits into the vapor degreaser, it can be effectively cleaned. Most parts are cleaned without the need for special fixturing (other than a basket to hold the parts).

Ask for help

Cleaning medical oxygen systems made to transport and store pure liquid or gaseous oxygen requires the greatest care and attention to safety. Any particulate or residue contamination could cause a catastrophic explosion within the system. Small and complex tubing, gages, pumps, filters, and valves can all entrap contaminants, making cleaning them a challenge. Contamination varies widely: from simple particulate to difficult grease, wax, and oil residue. Vapor degreasing using modern, nonflammable fluids is an excellent method to clean these soils and reduce the potential for fire or explosion when exposed to oxygen-rich environments.

For those looking for help in selecting the best nonflammable, fast-drying, and residue-free cleaning fluids, seek the help of a fluid manufacturer with expertise in both vapor degreasing and medical oxygen system cleaning. They can help determine which will work best on specific soils and substrates.

About the Author: Elizabeth Norwood is a senior chemist at MicroCare LLC.

MicroCare LLC: https://www.microcare.com