Aside from when passing through a hospital, or pausing to watch a welder or other metal fabricator at work, most people don’t pay very much attention to how many compressed gas bottles there are all around us.
Food trucks and RV’ers use propane bottles for cooking, balloons are inflated from helium bottles at circuses, scuba divers need oxygen bottles whenever they head offshore, and carbon dioxide bottles are routine supplies in aquaculture. Even the fire extinguishers in homes and workplaces are pressurized gas bottles.
Regardless of their capacity, contents, or how widespread their usage is, gas bottles all share one common attribute. They’re highly pressurized vessels that contain unimaginable amounts of potential energy, and failing to make sure that they’re properly restrained at all times during transport, storage, or use, can have catastrophic consequences.
Let’s take a moment to get to know a bit more about gas bottles, and to consider just how important it is to have the correct restraining equipment at all times for both their safe handling and operation.
Secured For Safety
It’s impossible to overstate just how sturdily constructed even the most mundane gas bottles are. With the ordinary service pressure for most ultra-high purity and industrial-grade bottles ranging between 500psi and 2,000psi, they’re manufactured to maintain their integrity through decades of pressuring, and even over-pressuring with diligent handling. It’s for this reason though, that correctly sized and mounted gas bottle restraints are so crucial for ensuring that that integrity isn’t compromised by bottles tipping or falling over, even if they’re only partially full or assumed to be completely empty.
Restraints are designed to firmly secure bottles and cylinders to walls and other immovable mounting surfaces, and can be used to restrain bottles individually, or in groups of up to 4. Australian Standard AS4332 ultimately prescribes the processes and standards for the safe handling and storage of bottled gases, so it’s critically important that users always check the data stamped into the bottle’s shoulder to determine that the gas bottle holder or restrain that they’re using is sufficient for their size and weight of the bottle they need to secure.
As a minimum, however, firm, anti-friction restrains are going to be a central component of that safe handling process; and it underlines just how serious a risk is posed by bottles that are either improperly secured, or not secured at all.
The Right Position
There’s no shortage of concerns about the restrictions on where a gas cylinder restraint system should be physically located, including:
- Not in areas where ambient temperatures are above 52°C;
- Not near potential sources of ignition or static electricity;
- Not where access to doors or hallways would be obstructed;
- Not where exposure to corrosive substances is possible; and,
- Not where full bottles can become commingled with empty ones.It’s the actual positioning of the restraints themselves though that’s probably the single most important aspect of ensuring bottles are properly secured.
Gas bottles need to be upright at all times; and other than for brief periods during carriage, gas bottles should never be left or utilized in a horizontal position. From the possibility of pressurized gases becoming separated and decomposing, to the potential for a delayed adverse reaction once the bottle returns to being vertical, there are a variety of explanations for not allowing bottles to remain horizontal. The primary reasons, though, are the most obvious ones:
To Protect Relief Valves from Impact
Keeping bottles upright prevents safety relief valves from incurring any kind of blow that could damage them, or cause them to be sheared away from the bottle. The uncontrolled release of compressed gas due to a ruptured relief valve will instantly turn a damaged cylinder into a lethal, thrust-propelled projectile.
To Ensure Protective Caps Stay in Place
Maintaining an orientation that allows a bottle’s protective cap to stay in place for as long as possible reduces the chance of an accident compromising a relief valve’s integrity. A failed or inoperative relief valve can result in a cylinder failing almost immediately.
To Ensure Separation Between Gas Classes
Rather than relying wholly on the colour-coding of bottles to distinguish their contents, storing bottles upright allows users to physically segregate gases that pose a hazard of toxicity or asphyxiation, and to separate gases like fuels and oxidizers that should never be stored together. Separation also minimizes the likelihood of gases being inadvertently mixed up.
In short, the type of gas bottle bracket or holder used needs to keep the bottle stably situated on its base and on the ground at all times; and any deviation from that approach dramatically increases the likelihood of a serious accident occurring.
Suffice it to say, prudence is absolutely critical when handling any type of gas bottle. Excluding specialized compressed gas bottles like cryogenic and hydrogen fuel containers, there are, in fact, more than 30 different types of low, high and ultra-high pressure rated bottles. Their capacities notwithstanding, however, the distinctions between them are very straightforward.
These are typically large diameter, lightweight, thin-walled bottles that are seam-welded, and have foot-ring bases. They can withstand service pressures up to 500psi and are typically used for storing LPG, propane and refrigerants.
These are typically tall, narrow, thick-walled bottles made of welded, or seamless tube aluminium or steel alloy. They can withstand normal service pressures between 2,000psi – 4,000psi, and are used for all kinds of gases, including nitrogen, carbon dioxide, and ordinary welding gases.
Ultra-high Pressure Bottles
These bottles are similar in appearance to high-pressure ones, but are constructed from thicker materials, as well as composites. Because of the thicker material, they’re significantly heavier than other high-pressure bottles, and can withstand service pressures in ranges from 6,000psi, to an extraordinary 10,000psi.
No bottle should ever not be restrained; and ideally, gas bottle holders should always be positioned at points 1/3 and 2/3 of the height of every bottle. And this is especially true with heavier bottles whose contents are likely to be under exponentially higher pressure, and whose sudden release could have unimaginable consequences. Invariably though, it takes knowing the bottle basics crucial to understanding how to prevent that kind of occurrence from happening.
The Final Word
At the end of the day, it’s important to understand that because of the nature of their contents and the purposes they serve, gas bottles require handling and oversight processes that exceed almost any other kind of commercially available equipment.
The risks from gas bottles accidentally depressurizing, becoming over-pressurized due to inappropriate storage, and ultimately rupturing are simply too great not to employ gas bottle restraints as the first measure of bottle safety.
If you work with pressurized gas bottles, make sure that you also have the right equipment to keep them restrained. it’s a small investment with a huge return on safety.