Safe Practices of handling compressed gas cylinders

“Train employees and workers who are required to handle and use compressed gases and ensure that compressed gases are handled in accordance with safe working practices.” – R.R. Nair

1. Introduction

A compressed gas is a material which is a gas at normal room temperature and pressure, but is packaged as a pressurized gas, pressurized liquid or refrigerated liquid and is contained usually in a cylinder. The compressed gases may be toxic, flammable or explosive.

The compressed gas cylinders can present a variety of hazards due to their pressure and/or contents. It must be stored and handled very carefully. Regardless of whether a compressed gas is packaged in an aerosol can, a pressurized cylinder or a refrigerated container, it must be stored and handled very carefully. Puncturing or damaging the container or allowing the container to become hot may result in an explosion.

This article will focus on the type of compressed gases, its hazards, testing and inspection of cylinders, safe practices of handling the cylinders, etc.

2. Compressed Gas – Definition

As per the Gas Cylinder Rules 2004 of India, “compressed gas” means any permanent gas, liquefiable gas or gas dissolved in liquid under pressure or gas mixture which in a closed gas cylinder, exercises a pressure either exceeding 2.5 Kgf/cm2 abs. (1.5 Kgf /cm2 gauge) at 15 deg C or a pressure exceeding 3 Kgf/cm2 abs. (2 Kgf/cm2 gauge) at +50 deg C or both.

It may be stated here that, the pressure of most compressed gases will not exceed 2000 to 2640 psig (138 to 182 bar), though some do go up to 6000 psig (414 bar).

3. Type of compressed gases

The three main types of compressed gases that are stored in gas cylinders, which are as follows:

1. Liquefied Gas: The liquefied gases are gases that become liquids at room temperature when compressed at high pressure in a cylinder. e.g., Carbon Dioxide, Chlorine, LPG, Ammonia (See Label at Fig 1).

   

2. Non-liquefied Gas: The non-liquefied gases are gases that remains gases at room temperature even at high pressure. e.g. Oxygen, Methane, Hydrogen (See Label at Fig 2).

3. Dissolved Gas: The dissolved gases are gases that are dissolved in a volatile solvent in order to stabilize them. e.g. Acetylene (See Label at Fig 3).

   

4. Nature of Hazards

As per the nature of hazards, compressed gases are classified into four types which are as follows:

1. Flammable or combustible: Gases are flammable, if their flashpoints (temperature above which there is not sufficient vapours given off to ignite) are lower than room temperature (See Fig 4). In these situations there is an ever present danger of fire or explosion.

2. Corrosive: Gases that causes visible destruction or permanent changes in the skin tissue at the site of contact (See Fig 5).

   

3. Poisonous: Exposure to poison gases and vapours can go unnoticed for long periods of time (See Fig 6).

4. Inert: An inert gas is non-reactive gas and is usually a member of noble gas family. It is a non-flammable gas (See Fig 7).

   

5. Main Hazards

The main hazards associated with gas cylinders are:

1. Asphyxiation caused by gas leaks.
2. Contact with the released gas or fluid (such as chlorine).
3. Fire resulting from the escape of flammable gases or fluids.
4. Impact from the blast of a gas cylinder explosion or rapid release of compressed gas.
5. Impact from parts of gas cylinders that fail, or any flying debris.
6. Impact from falling cylinders.
7. Manual handling injuries.

6. Main Causes of Accidents

The main causes of accidents relating to gas cylinders are:

1. Inadequate training and supervision for handling the cylinders.
2. Poor installation or maintenance of cylinders.
3. Faulty equipment and/or design, e.g. badly fitting valves or regulators.
4. Poor handling or storage of cylinders.
5. Inadequately ventilated working conditions.

7. Testing and Inspection of Cylinders

Manufacture, possession and use of any gas when contained in cylinders in a compressed or liquefied state is regulated under the Gas Cylinders Rules, 2004, of the Government of India as amended from time to time.

Gas cylinders which are in use are subject to wear and tear during handling. Thus with the passage of time, they may become unsafe for further use. In order that their safety might be ascertained, gas cylinders which have been in use are periodically inspected and tested at regular intervals.

The periodical inspection comprises visual examination, measurement of the wall thickness, internal cleaning, weighing and hydrostatic testing. Such periodical inspection is carried out in accordance with the instructions of the Chief Controller of Explosives of the Government of India. However, the cylinder is subjected to external visual examination as per IS 5845:1984, whenever it comes for refilling.

8. Relevant Standards

Bureau of Indian Standards has issued a number of standards relating to the design, transportation and handling of compressed gases. The specifications of colour codes for industrial gas cylinders are dealt in IS 4379:1981. The specifications for LPG are given in IS 4576:1999. The test methods of LPG are dealt in IS 1448:2007. The flameproof electrical fittings to be used in the filling area is as per specification of IS 2148:2004. The methods for Hydrostatic Stretch testing are dealt in IS 5844:1970. Periodical inspection interval for gas cylinders in use are dealt in IS 8868:1998.

9. Safe Practices

Observe the following practices while handling the compressed gas cylinders:

1. Contents of the gas cylinder should be clearly identified.
2. Read the MSDS and labels for all of the materials you work with.
3. Color coding is not a reliable means of identification. Cylinder colors vary from supplier to supplier.
4. Do not deface or remove any markings, tags or stencil marks used for identification of contents attached by the gas vendor.
5. Gas cylinders should always be used in a vertical position, unless specifically designed to be used otherwise.
6. Never roll, drag, or drop cylinders or permit them to strike each other.
7. Close all valves when cylinders are not in use.
8. Use cylinder trolley when handling gas cylinders.
9. Transport cylinders with valve caps. Do not lift cylinders by the cap.
10. The vehicles / containers used for transporting the compressed gases must use respective Haz- chem Code, TREMcards & MSDS regardless of colour code used for cylinders (See Fig 8 & Fig 9).
11. Gas cylinders should not be stored for excessive periods of time. Only purchase sufficient quantities of gas to cover short-term needs.
12. Store gas cylinders in cool, dry, well-ventilated areas, away from incompatible materials and ignition sources.

    

13. Gas cylinders should be stored away from sources of ignition, other flammable materials or oxygen cylinders.
14. Cylinders (full or empty) shall be secured by chains, straps, or other sturdy tiedowns during storage and transport (See Fig 10 & 11).

    

15. Full cylinders shall be separated from empty cylinders within the storage area.
16. Flammable gases shall be separated from nonflammable gases.
17. Cylinders shall not be stored at temperatures above 125 oF (52ºC) or in direct sunlight, or outside of the temperature range specified by the manufacturer.
18. Cylinders shall be protected against tampering and damage.
19. Cylinders shall not be refilled except by authorized suppliers.
20. Open flames and smoking shall not be permitted in areas where oxygen is used or stored.
21. “No Smoking” & “No Open Flames” signs shall be conspicuously posted in these areas.

10. Safe Use of Regulators

A regulator is a device that receives gas at a high pressure and reduces it to a much lower working pressure (See Fig 12). Regulators are gas specific. However, many a times adequate care is not taken to maintain and handle the regulators. Thus the following precautions may be taken while handling the regulators:

1. Be sure to use the proper regulator for the gas tank in the cylinder.
2. Always check the regulator before attaching it to a cylinder.
3. If the connections do not fit together readily, discard the wrong regulator.
4. Before a regulator is removed from a cylinder, close the cylinder valve and release all pressure from the regulator.
5. Regulators shall be removed from the cylinder during transport.

11. Use of personal protective equipment

1. Wear appropriate personal protective equipment such as safety shoes, safety glasses, aprons, gas masks for all work involving in compressed gas cylinders.
2. Poisonous and irritating gases, such as Chlorine should be handled only by well-informed operators with appropriate safety equipment.
3. Fire extinguishers and heat protecting gloves should be used with gas welding equipment.
   Flame arrestors should be used in acetylene lines, where acetylene is used with compressed air.

12. Conclusion

Personnel who handle compressed gases should be familiar with potential hazards before using the gas. In addition to the chemical hazards of compressed gases, hazards accompanying high pressure or low temperature may also be present due to the physical state of the gas, i.e., liquefied or non-liquefied. All compressed gases must be labelled packaged and transported in accordance with local and national requirements and industrial standards.

The vehicle /container used for transporting the compressed gases must use respective Hazchem code, TREMcards and MSDS, regardless of colour codes used for the cylinders. Prepare safe operating procedures to complete any given job.

The supervisor or responsible person shall designate and train employees and workers who are required to handle and use compressed gases and ensure that compressed gases are handled in accordance with safe working practices. It is the supervisor’s responsibility that employees and workers using compressed gases understand the proper procedures. Address potential emergencies and corresponding measures necessary to safely avoid such emergencies. Consider scenarios that could result in gas leaks or other emergencies in order to be fully prepared to react appropriately.

References

1. Canadian Centre for Occupational Health and Safety – Compressed Gases Hazards, 2011.
2. Canadian Centre for Occupational Health and Safety – How do I work safely with compressed Gases, 2008.
3. India, The Gas Cylinder Rules, 2004, Universal Law publishing. Delhi.
4. IS 1448:2007 – Methods of Test for Petroleum and its Products
5. IS 2148:2004 – Flameproof enclosure of Electrical apparatus.
6. IS 4379:1981 – Identification of Contents of Industrial Gas Cylinders.
7. IS 4576:1999 – Liquefied Petroleum Gas – Specifications.
8. IS 5844:1970 – Recommendations for Hydrostatic Stretch Testing of Compressed Gas Cylinders.
   IS 5845:1984 – Code of Practice for Visual Inspection of Low Pressure Welded Steel Gas Cylinder in use.
9. IS 8868:1988 – Periodical Inspection Interval for Gas Cylinders In Use.
10. Nair, R.R. – Glossary of Technical Terms used in the Material Safety Data Sheets. Safety and Health Information Bureau, Navi Mumbai, 1989, 56 pages.
11. Nair, R.R. – Hazards of Anhydrous Ammonia. Safety and Health Information Bureau, Navi Mumbai, 1989, 40 pages.
12. Nair, R.R. – Hazards of Carbon Disulphide. Safety and Health Information Bureau, Navi Mumbai, 1989, 36 pages.
13. Nair, R.R. – Safe Handling of Compressed Gases. Industrial Safety Review, P 38, March 2012.
14. Nair, R.R. and Chakravarti, S. – Safe Handling of Hazardous Chemicals (AICTE-CEP Publication Code No. 1016), AICTE, Bangalore, 2001.
15. United Nations Committee of Experts on Transport of Dangerous Goods – Recommendations on the Transfer of Dangerous Goods, 9th Ed. New York, United Nations, 1995,
16. University of California – Environmental Health and Safety – Compressed Gases Safety Programme, 2004.
17. University of Illinois at Urbana – Champaign – Compressed Gas Cylinder Fact Sheet 2011.

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About Author: Mr. R. R. Nair has more than 50 years’ experience in Occupational Safety, Health & Fire Protection. He is author of 15 books and about 70 articles in various topics on Safety, Health & Environment. He has carried out more than 60 safety / fire safety audits in various industries, occupancies including high rise buildings.

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