Oxygen cleaning services can be defined as specialized cleaning for components, equipment, piping, and systems used in the production, storage, distribution and use of gaseous oxygen (GOX) and liquid oxygen (LOX). LOX is the liquid form of elemental oxygen (O2). Examples of industries that use LOX systems include Aerospace, Military and Defense ( NASA), and the Compressed Gas industry.
Oxygen cleaning services are necessary for both safety and product purity considerations. Oxygen cleaning reduces contaminants that can lead to a fire or potential explosion. It also reduces the chance of autoignition at a temperature much lower than expected by material selection. Combustion in systems that contain enriched oxygen requires only fuel and an ignition source because the gaseous or liquid oxygen is the oxidizer.
Types of Contaminants Removed in Oxygen Cleaning
The primary goal of Precision Cleaning for oxygen service is the removal of any material, chemical, residue, contaminant, or particulate matter that could promote combustion or impact product purity.
Contaminants can be classified into three categories:
- Organic Compounds
- Volatile organic compounds (VOC)
- Grease and oils (Hydrocarbon based)
- Inorganic Compounds
- Water-based detergents and cutting oils
- Mineral acids and solvents
- Weld slag and metal grindings or filings from fabrication
- Particles, lint, and fibers
Oxygen equipment and systems, including all components and parts, must be appropriately cleaned to remove harmful contamination prior to the introduction of oxygen. An example of this is hydrocarbon-based residue. These are often made up of small amounts of oils and greases, which are commonly used in manufacturing environments and end up on the surfaces of newly-produced hardware.
When a hydrocarbon-based residue comes into contact with an enriched oxygen atmosphere or a strong oxidizer, the temperature at which it will ignite and burn is lowered – sometimes low enough that it will catch fire at or below room temperature. If a fire ignites, the presence of many oxygen molecules in the immediate area causes it to burn hotter and faster than usual, so much so that it may even cause an explosion.
The other contaminant of concern is particulate matter. These can travel in a stream of moving gas within a pipe or tube. In an oxygen-enriched atmosphere, especially one under high pressure, things that normally are not considered flammable may catch fire and burn. The only requirement is a spark. If particles are travelling with the gas stream and they strike the wall of the pipe or tube with enough velocity, a small hot spot may develop.
Moreover, if the particle is metallic, a spark might even occur. In either case, contaminants in the pipe, or even the wall of the pipe itself, may catch fire. This can result in a pipe rupture, releasing high-pressure gas and thereby endangering everything in the area. High-pressure gas ruptures are essentially explosions and it is not uncommon for shrapnel to be propelled for some distance.
For oxygen-enriched environments constructed using certain alloys (i.e. Stainless Steel) , require not only combustible organic and particulate contamination removal but also an optimal passive surface which provides corrosion resistance. A passive layer surface will inhibit oxidation and corrosive reactions, thus minimizing particulate contamination.