Gas bottles, also known as gas cylinders, are vessels used to store compressed gases. They come in various shapes, sizes and colours depending on the type of gas they contain.
Introduction to Gas Cylinders
Gas cylinders are built to withstand high pressures, usually several times the pressure of the gas inside them. They have thick walls and are usually made of steel, aluminium or composite materials. The colour coding allows for easy identification of the cylinder’s contents.
There are a few key parts of a gas cylinder:
- Cylinder body – the main cylindrical part that holds the compressed gas.
- Shoulder – the curved part between the cylinder body and the narrower neck.
- Neck – the narrower top part to which the valve is attached.
- Valve – the mechanism used to control gas flow in and out of the cylinder.
- Collar – a protective ring around the neck.
Gas cylinders have to meet very strict safety regulations. They are built to safely contain the high pressure gas inside. Proper handling, storage and transport of cylinders is critical.
Colour Coding of Gas Cylinders
Most countries follow some system of colour coding gas cylinders. This allows for quick visual identification of the cylinder’s contents.
While some minor regional variations exist, the most common colour codes are:
| Gas | Colour |
|---|---|
| Oxygen | Green |
| Nitrogen | Black |
| Hydrogen | Red |
| Helium | Brown |
| Acetylene | Maroon |
| Propane | Red |
| Chlorine | Yellow |
| Sulfur dioxide | Yellow |
In addition to colour coding, gas cylinders are clearly labelled with the name and details of the contained gas. But the colour provides an instant visual cue.
Why Colour Code Gas Cylinders?
There are a few key reasons for colour coding gas cylinders:
- Safety – Colour coding allows quick identification of cylinder contents. This is crucial in case of leaks, fires or other emergencies.
- Prevent mixups – Distinct colours help avoid dangerous mixups or mistaken use of gases.
- Quick visual checks – Workers can easily glance to verify they have the right gas cylinder.
- Convenience – Colour codes speed up the process of finding, moving and connecting gas cylinders.
Proper colour coding is a vital safety practice for compressed gas cylinders. It complements the detailed labelling and helps prevent use of incorrect gases.
Regional Variations in Colour Codes
While international standards exist, there are some minor regional variations in colour codes:
- In the UK, carbon dioxide is grey but black in the US.
- Argon is dark green in the US but light green in Australia.
- Hydrogen is red in most places but orange in Brazil.
- Sulfur dioxide is yellow in the US but light green in the UK.
However, for common industrial gases like oxygen, nitrogen, and acetylene, the colour codes are consistent worldwide. But it’s important to always check local regulations when working with gas cylinders in a new region.
Colour Codes for Small Cylinders
Small disposable cylinders may rely more on labels rather than colour. But full-size refillable cylinders almost always follow standard colour codes. The table below shows common colour schemes for small cylinders:
| Gas | Colour |
|---|---|
| Oxygen | Green |
| Acetylene | Maroon |
| Propane | Red |
| Butane | Blue |
| Carbon dioxide | Grey |
| Nitrous oxide | Blue |
For single-use disposable cylinders, label information is much more important than colour. But when possible, manufacturers follow the standard colour codes.
Unique Colour Codes for Dangerous Gases
Some highly hazardous gases have unique colour codings. This immediately alerts workers to take extra precautions.
For example, fluorine has unusual double-wall cylinders with aluminium bodies over wound glass fibre. They are painted black and have 4 painted yellow bands.
Similarly, deadly gases like arsine and phosphine have their own distinctive markings and colours:
| Gas | Colour |
|---|---|
| Fluorine | Black with yellow bands |
| Arsine | Black with yellow bands |
| Phosphine | Black with yellow bands |
These unique schemes immediately signal the user to take precautions. They help avoid accidental mishandling of extremely dangerous gases.
Requirements for Colour Coding
To comply with safety standards, the colour coding of gas cylinders should meet certain requirements:
- Full body of cylinder should be painted appropriately.
- Use durable weather-resistant industrial paints.
- Repaint during retesting if colour has faded or chipped.
- Do not rely solely on neck rings or shoulder colour codes.
- Gases with similar properties can’t have the same colour code.
- Colours must have enough contrast – light green vs dark green.
Compliance ensures colour coding remains effective for quick visual identification of cylinder contents from a safe distance.
When Colour Coding Can Fail
While colour coding gas cylinders is standard practice, it can fail in some cases:
- Old corroded cylinders where original paint has worn off.
- Cylinders painted by users after purchase.
- Usage of non-standard or non-compliant colour schemes.
- Faded colours that are hard to distinguish.
- Relying on just shoulder or neck ring colours rather than full body.
Always inspect and positively identify cylinders based on labels, not just colour. And ensure regulatory compliance with colour coding.
Other Colour Coding Standards
Beyond just gas cylinders, colour coding is used in many other industrial situations:
- Piping: Red for fire protection lines, green for drinking water, blue for cooling water.
- Electrical wiring: Red, black and blue for live, neutral and ground wires.
- Hoses: Red for fuel and gasoline, green for oxygen supply.
- Tags: Red for dangerous or defect equipment, green for safety checked.
Consistent colour coding for pipes, wiring, hoses, machines, etc. helps workers identify them at a glance.
Conclusion
In summary, colour coding of gas cylinders is a crucial safety practice. It enables quick visual identification of the cylinder’s contents. While some regional variations exist, most hazardous gases have globally consistent colour codes. Compliance with standards ensures colour codes remain clear and effective. Colour can never fully replace detailed labels – but it is an indispensable first level identification system for compressed gas cylinders in everyday industrial use.
