A compressed gas cylinder is a portable pressure vessel for storing a high volume of gases above atmospheric pressure. A typical compressed gas cylinder can be at a pressure of around 2500 PSI however it may be lower or even higher depending upon its design and safety factors. Compressed gas cylinders are typically used to supply gases for metal cutting, welding, instrumentation, medical purposes, breathing air, chemical processing, etc.
Types of compressed gas cylinders
Although there are different sizes and shapes of compressed gas cylinders available, however, they are categorized depending on the state of gas stored in the cylinders. There are three major groups of compressed gas cylinders:
1. Liquefied Gas Cylinders
Liquefied gases can become liquids at normal temperatures when they are inside cylinders under pressure. Carbon dioxide, chlorine, propane, and nitrous oxide are some examples of liquefied gases.
2. Non-Liquefied Gas Cylinders
Non-liquefied gases are permanent gases that do not become liquid when compressed at normal temperatures, even at very high pressures. Common examples of these gases are compressed air, oxygen, nitrogen, helium, and argon.
3. Dissolved Gas Cylinders
These cylinders are packed with an inert, porous filler saturated with a solvent that stabilizes the volatile gas. An acetylene cylinder is a common example. Acetylene is chemically unstable, and its cylinders are packed with an inert, porous filler saturated with acetone. When acetylene gas is added to the cylinder, the gas makes a solution with acetone which becomes stable and safe to store.
What makes them dangerous?
There are a wide range of safety hazards associated with compressed gas cylinders specific to their contents and use; however, the following are the most common hazards which are associated with all types;
1. Pressure Hazard
All types of compressed gas cylinders are dangerous because of the high pressure stored inside. The main risks associated with high pressure are cylinder explosions and becoming airborne due to the sudden release of high-pressure gas. The use of nonstandard/untested cylinders is the main cause of cylinder explosions and unprotected valves & fittings are the main causes of cylinders becoming airborne.
2. Fire & Explosion Hazard
Flammable gases inside compressed gas cylinders, such as acetylene, hydrogen, ethylene, etc., are extremely dangerous and may cause burn injuries, serious fire, or explosion in case of slight negligence. Most of these flammable compressed gases are heavier than air, and any leakage in a poorly ventilated area will cause the gas to accumulate, leading to fire or explosion. Also use of substandard and poor-quality fittings/accessories with compressed gas cylinders is one of the leading causes of flash fires and burn injuries.
3. Health Hazard
Some compressed gases like ammonia, sulfur dioxide, and chlorine are toxic in nature and can cause various health problems. Although the use of such gases in compressed gas cylinders is limited, however, proper personal protective equipment must be used whenever handling and use of these types of compressed gases.
4. Asphyxiation Hazard
Compressed gas cylinders containing inert gases such as nitrogen, argon, and helium pose serious asphyxiation hazards. Although these gases are not toxic and do not burn or explode, they can cause death by displacing enough air to reduce oxygen levels. Extreme care must be taken while handling or using such compressed gas cylinders indoors or in poorly ventilated areas.
5. Indirect Hazards
- In addition to the above-mentioned safety hazards, there can be other indirect hazards associated with compressed gas cylinders which can lead to accidents. Here are some of the indirect dangers;
- Improper handling of compressed gas cylinders can result in personal injuries like cuts, bruises, sprains, strains, and broken bones.
- Tripping accidents can occur due to the horizontal placement of compressed gas cylinders on the ground.
- Unsecure cylinders may fall on anyone and, as a result, can cause severe injury or even death.
- Improper transportation of compressed gas cylinders can cause serious road accidents.
- Cold burns can occur due to the sudden release of gases, causing an extremely cooling effect.
- Certain gases stored in compressed gas cylinders seriously damage the environment when released.
What Should be the Safety Precautions?
- Always clearly identify the contents of all compressed gas cylinders.
- Never rely on the color of the cylinder for identification as they may vary with the supplier.
- Avoid mishandling compressed gas cylinders.
- The cylinders must be secured/chained at all times to prevent tipping.
- Always segregate cylinders as per hazard classes while in storage.
- Oxidizers (oxygen) must be separated from flammable gases.
- Oxygen cylinders must be stored at a minimum of 20 feet from flammable gas cylinders or the storage area be separated, at a minimum, by a firewall five (5) feet high with a fire rating of 30 minutes.
- Never store acetylene cylinders on their sides.
- Never drag, slide or roll a cylinder.
- Always use a cylinder cart or basket and have the protective cap covering the valve when transporting the cylinder.
- Only properly trained personnel should handle compressed gas cylinders.
- Never heat a cylinder to raise the pressure of the gas.
- Never try to repair the cylinders.
- Never use a flame to detect a gas leak. Use soapy water.
- Never use copper fittings on acetylene cylinders as this may result in an explosion.
- Handle empty cylinders as carefully as full ones; residual pressure can be dangerous.
- Never use compressed gas to dust off clothing, this could cause injury to the eyes or body and create a fire hazard.
- Always use proper personal protective equipment while handling and use of compressed gas cylinders.
- In case of cylinder leakage, remove it to an isolated area, away from possible ignition sources.
- Allow it to remain isolated until the gas has discharged, making certain that appropriate warnings have been posted.
