What is oxygen enrichment and how is it defined?Read More
Gaseous oxygen (GOX) is packaged, transported, and used in compressed gas cylinders by many industries throughout the world. This portable, versatile packaging of oxygen is used for breathing gas (medical, aircraft, scuba diving, etc.), combustion (cutting, welding, etc.), and other applications like laboratory-scale experimentation in the power, metal refining and chemical processing industries.
All compressed gas cylinders should be used with caution due to their high-pressure contents, which can quickly turn a cylinder into a rocket if dropped, shearing off the isolation valve (Google “Myth Busters Air Cylinder Rocket”). For more information about general pressure-related hazards of compressed gas cylinders, there are many useful resources available from trade associations like the Compressed Gas Association (CGA) and regulatory agencies like OSHA. GOX cylinders present a unique hazard, however: the risk of fire. They require special handling and operating practices that differ from any other compressed gas.
GOX cylinders are typically fitted with a stand-alone cylinder valve or a valve integrated pressure regulator (VIPR). Stand-alone cylinder valves are designed to be connected to a stand-alone regulator or a manifold and require special handling (as outlined below). VIPRs require less special handling because the cylinder valve and regulator are combined in one device but users must follow manufacturer instructions and particularly avoid contaminating the ports of the VIPR, especially the fill port.
Regardless of application, all oxygen cylinder users should know best practices associated with safe use. At WHA we believe in educating people with the “why” behind the “what,” so users can better understand (and remember) how to safely handle and operate compressed oxygen in cylinders and associated systems.
In this article, our engineers have outlined several best practices that are taught in every WHA oxygen safety course.
Oxygen hazards can seem mysterious, and proper handling methods are not always intuitive. The best way to remember oxygen safety practices is to recall the “fire triangle” illustration that many of us learned about in science class. The fire triangle has three sides which, at the most basic level, remind us there are three factors that all must be present for a fire to occur: oxidizer, fuel, and ignition.
In a compressed oxygen cylinder, pure oxygen gas is the oxidizer, not the fuel – it is not a flammable gas and will not ignite or burn by itself. Instead, oxygen works to make materials (fuels) more flammable and easier to ignite. It is one of three primary elements required for a fire to occur.
Oxygen makes up almost 21% of our atmosphere, which is not necessarily a high concentration, but sufficient to enable many materials to ignite and burn in the presence of an energy or heat source. Of course, there are also many materials will not easily burn under normal atmospheric conditions.
However, as oxygen pressures and concentrations increase, nearly all materials will ignite and burn more easily than they do in air! Even the stainless steel components of a regulator can ignite and burn with the ample oxidizer provided within a compressed oxygen cylinder.
The basic philosophy behind oxygen safety, therefore, is to reduce risk by limiting potential ignition and/or fuel sources in the given oxygen environment. Common oxygen hazards include:
Finally, the safe use of oxygen also includes concepts such as reducing fire consequence by minimizing personnel exposure (i.e. standing to the side of a valve while opening) and limiting the kindling chain of potential fuels that could propagate a small ignition into a large fire.
Always assess your equipment before using an oxygen cylinder. Only use oxygen cylinders:
Inspecting and “clearing” or purging the cylinder valve is a critical first step when using any oxygen cylinder to avoid ingesting potential contaminants from the cylinder valve into your regulator or downstream system.
In the United States, most compressed oxygen cylinders utilize a special connection called a CGA-540 fitting.
System start-up is one of the most critical steps in using an oxygen cylinder due to the risk of compression heating ignition, which can occur if high-pressure oxygen rapidly pressurizes in compatible downstream components. Chances are that you’ll never experience an oxygen fire, but these good practices reduce the risk.
It’s important to note that oxygen cylinder valves have different construction and application from oxygen regulators. Cylinder valves are designed only for “isolation” purposes. As such, they should be operated either completely open or closed. Never partially-open an oxygen valve and leave it to “throttle” or control flow. Although it’s extremely rare, this improper operation can lead to ignition of the plastic valve seat.
Compressed gas cylinders, including oxygen cylinders, should never be emptied completely. Eliminating a positive pressure inside a cylinder can allow contaminants to enter the cylinder and endanger future users. Most suppliers recommend keeping pressures above 25-100 psig at all times.
It bears reminding that ALL users of oxygen cylinders should have a basic understanding of oxygen fire hazards and be trained in their proper use.
For end-users, WHA’s engineers have developed Level 2: O2 Practice, a training course that focuses on oxygen system operations and maintenance, including safe use of oxygen cylinders. This course is conveniently available for clients on-site, via live webinar, or as an interactive e-training module. Best practices are also reinforced in every comprehensive upper-level WHA oxygen safety course.
Do your personnel need safety training for oxygen cylinders and associated systems? Contact us to schedule a free 15-minute consultation with one of our experienced instructors.Contact Us
What is oxygen enrichment and how is it defined?Read More