Gas cylinders are a common sight in many industries and facilities. They contain pressurized gas that is used for various applications such as welding, cooking, medical purposes, etc. Proper identification of gas cylinders is crucial for safe handling, storage and use. Misidentification can lead to potentially dangerous situations. Here are some tips on how to properly identify gas cylinders.
Check the Cylinder Label
Gas cylinders have labels attached to them that provide key information for identification. These include:
- Gas name – This specifies the name of the gas contained such as oxygen, acetylene, carbon dioxide, etc.
- Chemical formula – The chemical formula for the gas is provided e.g. CO2 for carbon dioxide.
- Cylinder color – Cylinders are painted in specific colors for each gas type per industrial standards. This color coding helps in quick visual identification.
- Cylinder size – The water capacity of the cylinder in liters is listed.
- Warnings – Cylinder labels have hazard warnings that indicate flammability, toxicity, etc.
- Cylinder number – A unique serial number is stamped on the cylinder for inventory tracking.
- Company information – The name of the gas company providing the cylinder is listed.
Always read the cylinder label carefully to check this key data. Do not use any cylinder that has an unreadable label.
Look for Color Coding
Gas cylinders follow a standardized color coding scheme that helps identify the gas type instantly:
| Gas Type | Cylinder Color |
|---|---|
| Oxygen | Green |
| Nitrogen | Black |
| Hydrogen | Red |
| Helium | Brown |
| Acetylene | Maroon |
| Propane | Red |
| Carbon dioxide | Gray |
| Compressed air | Light green |
| Argon | Dark green |
Some cylinders may have additional color bands to indicate specialized information. For example, an oxygen cylinder may have a green body with white shoulder bands to indicate medical or ultra high-purity grade gas.
Identify by Shape
The shape and size of gas cylinders provides clues for identification. While cylinders come in many diameters and lengths, some distinct shapes are associated with specific gas types:
- Tall, thin cylinders – Typically used for gases like oxygen, acetylene, hydrogen, nitrogen, etc.
- Short, fat cylinders – Commonly used for liquefied petroleum gas (LPG) like propane, butane, propylene, etc.
- Small, rectangular cylinders – Often indicates compressed breathing air used with SCBA equipment.
- Large jumbo cylinders – Used for inert gases like nitrogen, argon, etc. that are consumed in large volumes.
- Small lecture bottles – Portable cylinders for gases like helium, hydrogen, etc. used in the lab.
Check for Additional Markings
Apart from the main gas identification labels, cylinders will have additional markings that provide supplementary information:
- Tare weight – Indicates the empty weight of the cylinder.
- Test date – The date of last hydrostatic testing.
- DOT number – Department of Transportation (DOT) designation for hazardous material.
- NFPA diamond – National Fire Protection Association (NFPA) hazard diamond showing flammability, health, instability risks.
- UN number – United Nations (UN) number for hazardous goods classification.
These markings should correlate with the primary gas identification labels for consistency.
Use Gas Detection Sensors
Electronic gas sensors can be used to reliably identify the contents of a gas cylinder. They detect the presence of specific gases and display the readings directly. Common types include:
- Combustible gas detectors – Detect flammable gases like hydrogen, acetylene, etc.
- Oxygen detectors – Measure oxygen concentration levels.
- Carbon dioxide detectors – Measure CO2 concentration.
- Multi-gas detectors – Measure multiple gases in a sample including O2, CO2, CO, H2S, etc.
Gas detection sensors are very useful for confirming cylinder contents, especially when the labels are unclear or contradicting.
Use a Cylinder Gauge/Regulator
Attaching a compatible pressure gauge or regulator to a gas cylinder is another way to verify the contained gas. Steps include:
- Select a gauge/regulator designated for the suspected gas type.
- Securely connect the gauge/regulator to the cylinder valve.
- Briefly open the cylinder valve to pressurize the gauge/regulator.
- Check the pressure reading on the gauge or gas flow from the regulator.
- The reading should match the expected pressure and flow parameters for that gas.
- For toxic/corrosive gases, an indirect method may be used with a standpipe manometer for safety.
Gauges and regulators calibrated for a specific gas will only work properly with the correct gas type.
Match the Cylinder Threads
Gas cylinders have unique valve threads that correspond to each gas type. The thread diameter, pitch, shape, and size are standardized for compatibility with matching regulators and connectors. Some common thread types include:
| Gas Type | Cylinder Thread Type |
|---|---|
| Oxygen | Right-hand, 25 mm Diameter, 1.814 mm Pitch |
| Acetylene | Left-hand, 25 mm Diameter, 1.814 mm Pitch |
| Nitrogen, compressed air | Right-hand, 22 mm Diameter, 1.814 mm Pitch |
| Hydrogen | Left-hand, 18 mm Diameter, 1.814 mm Pitch |
| Propane, butane | Left-hand, 21.8 mm Diameter, 1.814 mm Pitch |
Checking that the cylinder valve threads match the required gas type provides a good visual check.
Use a Multi-Gas Analyzer
A multi-gas analyzer can identify an unknown gas inside a cylinder. It extracts a small sample and analyzes the gas composition. Some techniques used include:
- Fourier-transform infrared spectroscopy (FTIR) – Detects infrared absorption patterns of different gases.
- Raman spectroscopy – Measures characteristic molecular vibrations of gases.
- Gas chromatography – Separates gas components which are then identified selectively.
- Electrochemical sensors – Detect specific gases based on unique chemical reactions.
- Photoionization detector – Analyzes gases using UV lamp ionization.
The gas profile is matched to a library of known gases to identify the cylinder contents. This provides the most reliable verification when other methods are inconclusive.
Check Compatibility with Equipment
The gas cylinder should only connect and work properly with equipment designated for that specific gas type. For example:
- An oxygen cylinder valve will only fit oxygen compatible regulators.
- Hydrogen gas will only ignite and burn in a hydrogen torch.
- Toxic gases will only be detectable on corresponding gas monitors.
- High pressure nitrogen will only register on nitrogen cylinder pressure gauges.
Trying the cylinder with incompatible equipment is a quick way to validate the contained gas when other indicators seem unclear.
Review Purchase Records
Cross-check the cylinder number, labels, color coding, etc. with your purchase records to verify that it matches the requested gas type. This will confirm whether the supplier did in fact send the correct gas cylinders.
You should have invoices, packing slips, purchase orders, etc. that mention the gas type, quantity, cylinder serial numbers supplied. Matching this paperwork audit trail will validate the gas delivery.
Return Questionable Cylinders
When in doubt, adopt a safety first approach. If a cylinder cannot be conclusively identified even after applying all the checks, quarantine it and return to the supplier for replacement. Mark it clearly as an unidentified or mislabeled cylinder. Don’t take risks when the contents are uncertain.
Conclusion
Identifying gas cylinders properly is vital for operational safety and regulatory compliance. Follow the standard labeling, color coding, markings and use gas detection tools for reliable verification. When in doubt, handle the cylinder as potentially hazardous until the contents can be confirmed definitively. Proper identification is a basic requirement before using any gas cylinder.