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UCLA Department of Chemistry and Biochemistry

Chemical Safety Office

Safety Notes

Newsletter #8

January 1999

COMPRESSED GAS CYLINDERS

Safe Cylinder Handling
Compressed gases are routinely used in chemistry laboratories. While most personnel are familiar with the rules of safe handling, there have been recent examples of improper handling and storage. The rules1 for the safe handling of compressed gases include the following:
  1. Handle cylinders of compressed gases as high energy sources and therefore as potential explosives.
  2. Restrain cylinders of all sizes, whether empty or full. Use chains with cylinder racks to prevent them from falling.
  3. When storing or moving cylinders, have the protective caps securely in place to protect the valve stems.
  4. When moving compressed gas cylinders, chain or strap them to properly designed, wheeled carts to ensure stability.
  5. Do not expose cylinders to temperatures higher than about 50C. Some rupture devices on cylinders will release at about 65 C. Some small cylinders, such as lecture bottles, are not fitted with rupture devices and may explode if exposed to high temperatures.
  6. Never use cylinders if their contents cannot be identified positively.
  7. Never lubricate, modify, force, or tamper with cylinder valves.
  8. Use toxic, flammable, or reactive gases in fume hoods only. Cylinders, connections, and hoses should be checked regularly for leaks. Do not allow leaks to go unrepaired
  9. Cylinders awaiting use should be stored outdoors, protected from the weather.
  10. Be aware that rapid release of a compressed gas will cause an unsecured gas hose to whip dangerously and also may build up a static charge that could ignite a combustible gas.
  11. Do not extinguish a flame involving a highly combustible gas until the source of gas has been shut off; otherwise, it can reignite causing an explosion.
  12. Close the main cylinder valves tightly when not in use.
  13. Promptly remove the regulators from empty cylinders and replace the protective caps at once. Label the cylinder to show that it is empty.
  14. Never bleed cylinders completely empty. Leave a slight pressure to keep contaminants out.
  15. Use the appropriate regulator on each gas cylinder. The threads on the regulators are designed to avoid improper use. Adaptors or homemade modifications can be dangerous; never use these devices.
  16. Do not put oil or grease on the high-pressure side of an oxygen, chlorine, or other oxidizing agent cylinder. A fire or explosion can result.
  17. Never direct high-pressure gases at a person.
  18. Always wear safety glasses when handling and using compressed gases.
  19. Observe the following special rules when working with acetylene:

    Always store acetylene cylinders upright. They are partially filled with liquid acetone, which can be discharged instead of or along with acetone.

    Ensure that the outlet of an acetylene cylinder is protected with a flash arrester.

    Never exceed the pressure limit indicated by the warning red band of an acetylene pressure gauge.

    Use the correct kind of tubing to transport the gaseous acetylene. Some tubing materials such as copper form explosive acetylides.

    Safety in Academic Chemistry Laboratories, American Chemical Society, Washington, D.C., 1995.

Handling Corrosive Gases
  1. Corrosive gases, such as hydrogen chloride, hydrogen sulfide, sulfur dioxide, should be stored for the shortest possible periods before use, preferably less than three months.
  2. Storage areas should be kept as dry as possible. A good supply of water should be available, since most corrosive gases can be absorbed in water.
  3. Corrosive gases should not be stored in areas containing instruments or other devices sensitive to corrosion. Minimum quantities should be stored.
  4. Corrosive gases should be used in a fume hood or gas cabinet.
  5. When corrosive gases are discharged into a liquid, a trap, or check valve should be used to prevent dangerous reverse flow.
  6. When corrosive gases are being used, the cylinder valve stem should be periodically opened and closed to prevent "freezing".
  7. Regulators and valves should be closed when the cylinder is not in use.
  8. Control devices should not be left on a cylinder, except when it is in frequent use.
  9. When cylinders are returned to storage, all regulators, control valves etc. should be removed from the valve outlet and flushed with dry nitrogen or air to keep them in good working order.

Bill Peck, Chemical Safety Officer, Young Hall 4204, (20)6-3661REMINDERS FROM THE RECEIVING DEPARTMENT
  1. Return the cylinder caps with the cylinders.
  2. Return the cylinder cart immediately after using. There are only a few carts available.
  3. Do not store cylinders for use on the cylinder cart. They are to be used for transporting cylinders, ONLY.
  4. Don't store or stockpile cylinders in laboratories if they won't be used within a short period of time.
  5. If cylinders are not being used, return them to Receiving. There is a demurrage charge for each cylinder. It can add up to hundreds of dollars. These charges can be much higher than the price of the gases used.
  6. >
  7. Be sure to sign the log sheet when taking and when returning cylinders.
  8. 7. Teflon tape should not be used on CGA gas cylinder fittings or on compression fittings. Teflon tape should be used on tapered pipe thread where the seal is formed in the thread area.

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Department of Chemistry & Biochemistry, UCLA
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