Gas & Cylinders

• Absolute Pressure: Based on a zero-pressure reference point, the perfect vacuum. Measured from this point, standard atmospheric pressure at sea level is 14.7 pounds per square inch (psi) or 101.325 kilo Pascals (kPa). This is usually expressed as psia where the ‘a’ indicates an absolute measurement or kPa. 
• Asphyxiant Gas: Any non-toxic gas which displaces atmospheric oxygen below limits required to support life. These gases are usually colorless, odorless and tasteless and include nitrogen, argon and helium. 
• Compressed Gas: A compressed gas is any gas which when enclosed in a container gives: 
  •  An absolute pressure reading greater than 276 kPa (40 psi) at 21°C (70°F) or 
  • An absolute pressure greater than 717 kPa (104 psi) at 54°C (129.2°F) or
  • Any flammable liquid having a vapor pressure greater than 276 kPa (40 psi) at 38°C (100.4°F). 
• Compressed Gas Cylinder: A compressed gas cylinder is any metal cylinder of the type approved by the Govt for storage and transportation of gases under pressure, including liquefied gases. 
• Corrosive Gas: A gas that is in contact with living tissue causes destruction of the tissue by chemical action. 
• Cryogenic Liquid: A liquid with a normal boiling point below -150°C (-238°F). 
• Cryogenic Liquid Cylinder: Pressurized container designed and fabricated to hold cryogenic fluids. There are three common types of liquid cylinders: 
  • Gas dispensing. 
  • Liquid dispensing.
  • Gas and liquid dispensing. 
• Cylinder Valve: A mechanical device attached to a compressed gas cylinder that permits flow into or out of the cylinder, when the device is in the open position and prevents flow when in the closed position. 
• Dewar: Dewar is an open-mouthed, non-pressurized, vacuum-jacketed container used to hold cryogenic fluids. 
• Flammable Gas: A material that is a gas at 68° F (20°C) or less at 14.7 pounds per square inch atmosphere (psia)
  (101 kPa) of pressure [a material that has a boiling point of 68°F (20°C) or less at 14.7 psia (101 kPa)] which: 
  • Is ignitable at 14.7 psia (101 kPa) when in a mixture of 13% or less by volume with air; or 
  • Has a flammable range at 14.7 psia (101 kPa) with air of at least 12%, regardless of the lower limit. 

        The limits specified shall be determined at 14.7 psi (101 kPa) of pressure and a temperature of 68°F (20°C).

• Gauge Pressure: The pressure above or below atmospheric pressure. Therefore, absolute pressure minus local atmospheric pressure equals gauge pressure and is usually abbreviated as psig or kPa. 
• Handling: Moving, connecting or disconnecting a compressed or liquefied gas container under normal conditions of use. 
• Highly Toxic Gas / Toxic Gas: A material which produces a lethal dose concentration that falls within any of the following categories: 
  • A chemical that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.
  • A chemical that has a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between two and three kilograms each. 
  • A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume, or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each. 
    
    
• High Pressure Gas: A gas in a container that has a pressure of 3448 kPa (500 psig) or higher at 21.1°C (70°F). 
• Inert Gas: A gas which is chemically inactive. 
• Liquefied Gas: A fluid within a pressurized container, other than in solution, which exists both as a liquid and gas at 20°C (68°F). Examples include propane, butane, ammonia, carbon dioxide, and sulfur dioxide. 
• Manifold: A gas distribution system which transfers product through multiple outlets/inlets to or from compressed gas containers. 
• Nonflammable Gas: A gas which, within the packaging, exerts an absolute pressure of 280 kPa (40psi) or greater at 20°C (68°F) but is not a flammable gas as defined previously. 
• Oxidizing Gas: A gas that can support and accelerate combustion of other materials. 
• Pressure Regulator: A mechanical device used to safely control the discharge pressure of a compressed gas from a container. 
• Pressure Relief Device: A pressure and/or temperature activated device used to prevent the pressure from rising above a predetermined maximum and thereby prevent rupture of a pressurized container. 
• Pyrophoric Gas: A gas that will spontaneously ignite in air at or below 54.4°C (130°F). Examples include silane and phosphine. 
• SCF: One “Standard Cubic Foot” of gas at 21°C (70°F) and 101.325 kPa (14.696 psia). 
• Storage: Holding of gas, in its packaging, either on a temporary basis or for an extended period in such a manner as to not constitute usage of the gas. 

Do’s 

• Always keep cylinder in an upright position.
• Gas Cylinder should be kept within well-ventilated area.
• Filled cylinder should be separated from empty cylinders.
• Gas Cylinder should be kept in the order in which they are received.
• Gas Cylinder should secure with a chain or appropriate belt above the midpoint, but below the cylinder’s neck. Laboratory cylinders less than 18 inches tall may be secured by approved stands or wall brackets.
• Gas Cylinder should be kept with cap on, when not in use.
• All Gases with the same hazard class are stored in the same area. Inert gases are compatible with all other gases and may be stored together.
• Gas Cylinder storage area/room should be at least 20 feet away from all flammables, combustible or incompatible substances. Storage areas that have a noncombustible wall at least 5 feet in height and with a fire resistance rating of at least 30 minutes may be used to segregate gases of different hazard classes in close proximity to each other. 

Don’ts

• Do not keep cylinder in exits or egress routes.
• Never keep cylinder in damp areas i.e., near salt, corrosive chemicals, fumes, heat; or exposed to the weather without a roof housing.
• Gas Cylinder should not store more than one year without use.

• Never drag or physically carry cylinders (lecture cylinders may be carried).
• Never pick up by the cap (i.e., not by crane).
• Never paint a cylinder.
• Never do horseplay with cylinders.
• Never leave cylinders in areas where they will be subject to damage from falling objects, corrosion or public tampering.
• Never subject cylinders to artificially created low temperatures without approval from the supplier. 

Lifting and moving requirements

• Wear PPEs i.e., safety helmets, hard-toed safety shoes.
• Do not use steel wire ropes, chains and slings to suspend cylinders, unless the cylinder was designed for that use.
• Do not use magnets to lift cylinders.
• Use only suitable cradles or platforms to hold a cylinder when lifting.
• Use a hand-truck designed for the transport of cylinders.
• Secure cylinder caps during transport.
• Vehicle Transport
  • Only transport cylinders or cryogenic liquid containers in university vehicles.
    Proper cylinder hand-truck.
  • Cylinders or cryogenic liquid containers must only be transported in a truck bed and properly secured.
  • Do not transport cylinders of cryogenic liquid containers in the passenger compartment of any vehicle.
• Elevator Transport
  • Do not accompany a compressed gas cylinder containing highly toxic gas on an elevator.
  • Place the cylinder in the elevator and press the destination floor.
  • Attach a sign to the cylinder, telling others not to use the elevator during the cylinder’s trip.
  • Another person should be stationed at the destination of the elevator entry. 

To safely use valves and regulators 

• Ensure the regulator pressure control valve is closed before attaching it to cylinders.
• Do not stand in-line with the regulator and valve outlet when attaching the regulator to the cylinder. 
• Close valves on gas cylinders when a system is not in use. 
• Remove all pressure from regulators not currently used (by opening equipment valves downstream after the regulators are closed). 
• Do not install shut-off valves between pressure relief devices and equipment.
• Use pressure relief valves in downstream lines to prevent high pressure buildup in the event that a regulator valve does not seat properly, and a
  tank valve is left on. 
• Vent relief valves to a fume hood or ventilated gas cabinet, when using flammable or toxic gases. 
  
  
• Pressurize regulators slowly and ensure that valve outlets and regulators are pointed away from all personnel when cylinder valves are opened. 
• Leave the wrench in place on the cylinder valve, when needed, to open the main valve. Use adequately sized wrenches (12 inches long) to minimize ergonomic hazard when turning tight tank valves. Cylinders with “stuck” valves should be returned to suppliers to have valves repaired. 
• Fully open valves during cylinder use. A fully open valve improves the internal seal and helps prevent packing leaks. 
• Use a cylinder cap hook to loosen tight cylinder caps. Never apply excessive force to pry off caps. Return a cylinder to the supplier to remove “stuck” caps.

• Never apply excessive force when trying to open valves. Don’t use cheaters (wrench extensions). 
• Never allow hot work i.e., flames or concentrated heat sources to come in contact with a gas cylinder. 
• Never allow a gas cylinder to become part of an electrical circuit/hazard to ensure electrical safety. 
• Never partially open a cylinder valve to remove dust or debris from the cylinder inlet. 
• Never use cylinder gas as a compressed air source. 
• Never use adapters or exchange fittings between tanks and regulators. 
• Never use Teflon tape on Compressed Gas fittings (straight thread) where the seal is made by metal-to-metal contact. Use of Teflon tape causes the threads to spread and weaken, increasing the likelihood of leaks. Small pieces of tape can also become lodged in the valve mechanism resulting in possible valve failure. 
• Never attempt to open a corroded valve; it may be impossible to reseal, or it may break and release the cylinder’s contents.

• Where compressed gas cylinders are connected to a manifold, the manifold and its related equipment, such as regulators must be of proper design for the product(s) they are to contain at the appropriate temperatures, pressures and flows. 
• Use only approved valves, regulators, manifolds, piping, and other associated equipment in any system that requires compressed gas. 
  • Ensure pressure gauges on regulators are correct for the pressure of the gas cylinder used. 
  • Gas threads, configurations and valve outlets are different for each class of gases to prevent mixing of incompatible gases. Lecture bottles are an exception. 
• Lecture bottles use universal threads and valves, some of which are interchangeable. Label all associated equipment with the gas name, to prevent unintentional mixing of incompatible materials.  
• Contact Safety/EHS Officer for any questions or queries regarding cylinder.

• Keep piping, regulators and other apparatuses gas tight to prevent gas leaks. 
• Confirm the connection seal by using compatible leak test solutions (e.g., soap and water) or leak test instruments. 
• Release pressure from systems before connections are tightened or loosened and before any repairs. 
• Fluorescent light can be used to check for grease or oil in regulators and valves. 
• Valve and Regulator Maintenance
  • Refer histories or previous near miss / accident of valve and regulator maintenance before use. 
  • Valves and regulators should undergo periodic maintenance and repair as necessary. 
  • Perform a visual inspection before each use to detect any damage, cracks, corrosion, or other defects. 
  • Valves that pass visual inspection are still subject to failure. It is critical that toxic or poisonous gases are used in ventilated enclosures and have local exhaust ventilation in place for downstream pressure relief valves. 
  • Long term maintenance or replacement periods vary with the types of gases used, the length of use, and conditions of use. Consult the cylinder, regulator or gas supplier for recommended valve and regulator maintenance schedules. 
  • Valves and regulators should only be repaired by qualified individuals. Consult valve and regulator manufacturers, gas supply companies, or valve and regulator specialty shops for any repair needs.

• Use only the vendor label for positive identification of contents of the cylinder. Be aware that color coding may be inconsistent from vendor to vendor. 
• Mixed gases must be clearly labeled with the contents of the cylinder. 
• Empty cylinders must be labeled with the word “empty”. 
• Know the contents of each cylinder you are using. Preferred labeling includes the identity of the material, statement of hazard and the associated signal word. 
• Only the gas supplier is allowed to mix gases in a cylinder. 
• Do not use cylinders for any other purpose than holding the contents as received. 
• Leaking, defective, fire burned, or corroded containers must not be shipped without the prior approval of the supplier.