8.0 Gas Cylinder Set Up and Usage

Safety Warning

  • Always have the regulator valves pointed away from you when opening or closing valves.
  • Never install cylinder adapters on a regulator.
  • Do not attempt to repair cylinders or cylinder valves or force open cylinder valves.  Contact the compressed gas supplier for advice.

Cylinder Valves, Regulators, or Other Fittings

Set up the gas cylinder so that its valve is easily accessible at all times. For cylinders equipped with a stem valve, the valve spindle key should remain on the stem when the cylinder is in service.

Valves and Regulators

Prior to use, the threads on cylinder valves, regulators, and other fittings should be inspected to ensure compatibility. To prevent the mixing of incompatible gases, the Compressed Gas Association (CGA) has devised standard cylinder-valve outlet connections. Since outlet threads used vary in diameter and placement, the use of CGA-standard combinations of valves and fittings is recommended. Correct CGA regulator numbers for the commonly used laboratory gases are listed below.

table - Common Laboratory Gass and CGA Regulator Number

Refrigerated liquefied gas tanks/cylinders usually have a number of valves on the top of the cylinder. All valves should be clearly marked as to their function. These cylinders can vent the gas or vapor when a preset internal cylinder/tank pressure is reached, therefore, it is very important that they are stored or placed in service where there is adequate ventilation.

Valves on refrigerator liquefied gas cylinders

Safety Precaution

  • Only gas cylinder specific special wrenches or keys provided by the cylinder supplier should be used to open or close cylinder valves. Please contact Steve Stange at 384-4045 for assistance.
  • Do not use a wrench to open or close a hand wheel-type cylinder valve. Never use pliers!
  • Never use a Monkey wrench to loosen the gas cylinder cap.

Testing for Leaks

Leak test all connections to a cylinder because any gas, regardless of its health hazard, may cause asphyxiation by displacing oxygen. Piping systems should also be inspected for leaks on a regular basis. Leak detection procedures should be implemented prior to using any compressed gas system.

Opening and Closing Cylinders

  1. Open the cylinders slowly, with the valve pointing away from you and others, and open it all the way.
  2. Do not use excess pressure if you cannot open it by hand.  It is strongly advised to contact the gas cylinder supplier for a replacement gas cylinder.
  3. Close the cylinder valves when not in use, and then bleed pressure from the regulator.
  4. Avoid leaving the valve open when the cylinder is not in use, even when empty.
  5. Leave at least 25 psi in spent cylinders to prevent suck-back contamination.
  6. Air and moisture may diffuse through an open valve causing contamination and corrosion within the cylinder.
  7. Store the cylinders with caps in place.

Things to Avoid

  1. Do not attempt to use a cylinder without a regulator or some other pressure-reducing device in place.
  2. Never strike an electric arc on a gas cylinder and keep it clear of sparks, flames and electrical circuits. Arc burns can make the metal brittle and weaken the cylinder.
  3. Never tamper with cylinders in any way. Do not repaint them, change markings or identification, or interfere with valve threads or safety devices.
  4. Apart from the fact that it is illegal, it can be dangerous for non-specialists to refill cylinders or to change their contents.  Explosions, cylinder contamination, or corrosion can result.
  5. Plastic fittings or tubing should not be used for any portion of a high-pressure system.
  6. Do not use Teflon tape on cylinder connections or tube-fitting connections because it could interfere with the fittings and cause leaks or clogging.
  7. Copper fittings or tubing, including bronze or brass ones containing more than 65% copper, should not be used on acetylene tanks – explosion may result. Acetylene also forms explosive compounds in contact with silver and mercury or their alloys.
  8. Ammonia attacks brass and can react with mercury to form an explosive compound. Do not use mercury pressure gauges in ammonia systems!
  9. Do not hang clothes or equipment over a compressed gas cylinder. Clothing can become saturated with a hazardous gas. If the gas is oxygen, clothing can catch fire and burn easily.
  10. Never interchange regulators and hose lines specifically for one kind of gas for another. Explosions can occur if flammable gases or organic materials come in contact with oxidizers (oxygen) under pressure.
  11. Never tamper with or attempt to alter cylinders, valves, or any safety relief device. Return cylinders to the supplier for all repairs.