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Compressed Gas Safety

Compressed Gases are used through out the laboratory for industrial and research use. Compressed Gas Association (CGA) Pamphlet P-1 is cited 29CFRPart1910.101(b) (OSHA) as requirements for the safe operation and use of compressed gases. New York State Fire Code also provides requirements for the safe storage and use of compressed gases. Compressed gases inherently pose pressure safety hazards as well as potential hazards from chemical exposure, oxygen deficiency hazards (ODH) if oxygen concentration can fall below 19.5% by volume. Cryogenic fluid system may also be considered compressed gases.

The following information is provided to help in the use of compressed gases:

Tracking and Labeling

Compress Gases are chemicals and are tracked by BNL's Chemical Management System (CMS).

Inert gases (including compressed air) and commonly used gases such as oxygen and propane are typically track by a static/revolving inventory system that identifies the gas, the location stored and the maximum allowed quantity authorized to be stored in that location. Most other hazardous gases are individually tracked by a bar coding system that can allow inventories to be recorded and assessed against regulatory requirements (such as the NYS Building Code). The CMS team attaches the bar code to the cylinder and to a holder that can be attached to the cylinder as shown below. The holder is used to contain bar code information and forms to transfer the chemical (to another user or different location) or to delete the chemical (when emptied). Transfer and deletion can also be performed on-line through the CMS Web Transactions and Forms site.

Either way, a Cylinder Status tag needs to be attached to the cylinder that identifies if the cylinder is full (no contents have been withdrawn), in use (contents have been withdrawn and/or cylinder has been attached to either a distribution system or regulator), or empty (to be returned/disposed).

cylinder tag for non-static inventory

Example of Cylinder Tag for Non-Static Inventory

cylinder tag for static inventory

Example of Cylinder Tag for Static Inventory

Compressed Gas Valve Connections

The Compressed Gas Association (CGA) has established standard valve outlet connections for gas cylinders. Standardized connections make a gas-tight seal and minimize the possibility of connecting a gas to a system not designed to handle that gas. The CGA connections listed in the table below are from CGA Pamphlet V-1 "Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections." They are for the more commonly used gases and do not include connections specified for gas mixtures. Vendors should be contacted for information on CGA connections for other gases and mixtures

There are several configurations of sizes, male/female orientations, left/right threads and mating surfaces. Regulators should be purchased for the gas to be used and will come with the proper CGA fitting to attach to the cylinder. These fittings should not be removed and changed from regulators. Do not use adapters. The mating surfaces of the majority of fittings are made to be leak tight without the use of aids such as Teflon tape. If leak tight connections cannot be made, then the outlet or attachment surfaces are damaged and should be removed from service.

Standard Compressed Gas Association (CGA) Valves and Connections

Gas CGA No. Gas CGA No. Gas CGA No.
Acetylene 510 Fluorine 679 Nitrogen 580
Air 590 Germane 350 Nitrogen Dioxide 660
Allene 510 Halocarbon-12
660 Nitrogen Trioxide 660
Ammonia, Anhydrous 240, 660 Halocarbon-13
660 Nitrosyl Chloride 660
Argon 580 Halocarbon-14
320 Nitrous Oxide 326
Arsine 350 Halocarbon-22
660 Oxygen 540
1,3-Butadiene 510 Helium 580 Phosgene 660
Butane 510 Hydrogen 350 Phosphine 350
Butenes 510 Hydrogen Bromide 330 Phosphorus Pentafluoride 330
Carbon Dioxide 320 Hydrogen Chloride 330 Propane 510
Carbon Monoxide 350 Hydrogen Fluoride 660 Propylene 510
Carbonyl Fluoride 660 Hydrogen Selenide 350, 660 Silane 350
Carbonyl Sulfide 330 Hydrogen Sulfide 330 Silicon Tetrafluoride 330
Chlorine 660 Iso-Butane 510 Sulfur Dioxide 660
Cyanogen 660 Iso-Butylene 510 Sulfur Hexafluoride 590
Cyclopropane 510 Krypton 580 Sulfur Tetrafluoride 330
Deuterium 350 Methane 350 Sulfur Dioxide 660
Dimethylamine 240 Methyl Chloride 660 Sulfur Hexafluoride 590
Dimethyl Ether 510 Methyl Mercaptan 330 Sulfur Tetrafluoride 330
Ethane 350 Monoethylamine 240 Trimethylamine 240
Ethyl Acetylene 510 Monomethylamine 240 Vinyl Bromide 510
Ethyl Chloride 510 Natural Gas 350 Vinyl Chloride 510
Ethylene 350 Neon 580 Xenon 580
Ethylene Oxide 510 Nitric Oxide 660

Compressed Gas Cylinder Sizes

Compressed Gas cylinders are provided in standard sizes. The following is a listing of sizes with associated volumes and weight (in pounds of water):

Compressed Gas Safety Guidance

Compressed gases are classified into general safety categories such as: inert, flammable, oxidizer, corrosive, pyrophoric, toxic and highly toxic. Guidance and best practices relating to the storage and use of these gases can at BNL is provided in Working Safely with Compressed Gas Systems.

Elevator Compressed Gas Cylinder CautionAir Products is an industry leader in the use of compressed gases and provide "Safetygrams" on various related topics.

"Elevator Compressed Gas Cylinder Caution" image at right is provided as an example when a compressed gas is moved in an elevator.

Storage and Nesting

Compressed gases must be stored, specifically from the hazard of having the cylinder valve protective cap sheared off. The amount of stored energy can cause the cylinder to become a projectile and as demonstrated on the Discovery Channel™ show MythBuster's, can cause the cylinder to go through a concrete wall. When not in use, the cylinder valve protective cap should be installed (some older cylinders do not have caps, it is recommended that these be returned to the supplier). Some gas suppliers provide cylinder valve protection caps that can be used while a pressure regulator is attached.

cylinder valve protection cap

Cylinder Valve Protection Cap

regulator installed valve protection cap

Regulator Installed Valve Protection Cap

Insects can build nests inside caps, specially when stored outside. An approved method of control this problem is to install a pourous cover (such as a nylon "footee" (used in shoe stores) over the cap. The cap should only be installed hand tight. However, caps may become stuck on the cylinder. This issue is typical on cylinders stored outside. Only tools that do not enter the cap can be used to help remove the cap (such as a spanner wrench). The use of teflon tape is allowed on the cylinder threads to mitigate this problem.

NEVER use lubricants on the treads. They can contaminate the cylinder valve.

foot bootee cap cover

Foot Bootee Cap Cover

cap wrench

Cap Wrench

teflon tape installation

Teflon Tape Installation

Nesting depends on a three-point contact system such that all cylinders must be in contract at three points either with a secure wall or with another cylinder. The following are examples of properly nesting compressed gas cylinders and storage in racks:

Storage rack

Storage rack

nested wall support

Nested wall support (this diagram shows the minimum number of cylinders necessary)

nested upsupported

Nested upsupported (this diagram shows the minimum number of cylinders necessary)

Note: A chain is required when in the storage rack to provide the third point of support and is recommended when nested.

Proper Securing of Cylinders

Compressed gas cylinders need to be properly secured when being stored or in use. Cylinder racks typically provide the required three (3) point of contact when being stored. When in use, cylinders need to be secured. Appropriate means of securing include manufactured clamps that are installed on vertical surfaces such as walls or benchtops. If no vertical surfaces are available, then floor stands should be used.

Bench Top Clamps

Bench Top Clamps

Floor Stand Example

Floor Stand Example

Floor Stand Example

Floor Stand Example

Transport carts do not provide as safe of a securing method as clamps and stands unless specifically designed (see "Misuse of Gas Transport Cart" Lessons Learned). However, if the use is temporary in nature, then cylinders can be used on cylinder carts* provided the following:

  • The carts are stable four (4) wheeled, non-collapsible carts;
    • rear wheels should have a wheel-base equal or greater than the front wheels;
    • the cylinder is secure at or above the center of gravity (c.g.) or mid-point of the cylinder on the cart;
  • Unless in use and attended, the regulator must be removed and the cylinder valve protective cap must be installed;
    • Cylinders without valve protected caps can not be stored on cylinder carts.
  • The cart should be secured (such as locking or choking the wheels) if possible and be provision provided to protect the cylinder from accidental contact;
  • Cylinder location do not disrupt egress path ways;
  • Cylinder are not stored in work space areas of electrical panels.

* See the OSHA Standard Interpretation on allowed provisions for the use and stowage of Oxygen/Acetylene (Oxyacetylene) systems on carts.

Unacceptable for Storage

  • Securing Strap Broken
  • Narrow Back Wheels
  • Frame Bent

bad cart

bad cart

Improper Stowage

  • No Cylinder Valve Protective Cap
  • Securing strap below cylinder c.g.

bad cart

Acceptable Storage

  • Cylinder Valve Protection Cap Installed
  • Chain fasten above cylinder c.g.
  • Rear Wheelbase as wide or wider than front wheels
  • Located out of traffic area (first photo)

acceptable storage

acceptable storage

acceptable storage

acceptable storage

Oxygen Deficiency Hazard Analysis

Hazard Evaluation Tools provides tools for determining oxygen concentrations and ODH classifications using either cryogens or compressed gas that can be recorded in a data base maintained by Safety Engineering. Also a tool for Carbon Dioxide is available that will give potential CO2 exposure levels.

OSHA Standard Interpretations

Storage of Flammable gases with flammable materials is not allowed. This includes storing small gas cylinders, such as propane bottles in flammable cabinets. OSHA provided a Standard Interpretation on April 19, 1999 reinforcing this requirement.

Oxygen/Acetylene (Oxyacetylene) systems used for welding and torch work. OSHA provided a Standard Interpretation on May 8, 2005 on their use and storage.

Compressed Gas Regulators

To safely use compressed gases, pressure reducing regulators are used. The two (2) primary types are single stage and dual (2) stage regulators. Both are safe as long as they are used per the manufacture's recommendation. Single stage regulators use one reducing assembly. They can be used where high flows are needed however the output pressure is subject to changes in cylinder (input) pressure. 2-Stage regulators provide stable output pressures for a large range of input pressure. For more detail information see Fisher-Rosemount Technical Monograph 27, the " Fundamentals of Gas Pressure Regulation." To avoid catastrophic failure of regulators, pressure relief devices are installed. The chart gives VICTOR regulator models (typically used at the laboratory) along with there respective output pressure ranges and relief valve part numbers and relief settings. Note: Regulators internal pressure relief devices are designed to protect the regulator body from the source pressure and therefore represents the maximum pressure that the regulator can put out in any failure condition.

VICTOR Regulators

Model Pressure Range (psi) Relief Valve Part Number Relief Setting
VTS 450A 2-15 0600-0016 300 psi
VTS 450B 2-40 0600-0016 300 psi
VTS 450D 5-125 0600-0018 400 psi
VTS 450E 10-200 0600-0023 500 psi
VTS 452A 2-15 0600-0070 300 psi
VTS 452B 2-40 0600-0070 300 psi
VTS 452D 5-125 0600-0071 400 psi
VTS 452E 10-200 0600-0067 500 psi
VTS 452MD 5-125 0600-0071 400 psi
VTS 452ME 10-200 0600-0067 500 psi
VTS 453B 2-40 0600-0016 300 psi
VTS 453D 5-125 0600-0018 400 psi
VTS 453E 10-200 0600-0023 500 psi
VTS 460A 2-15 N/A N/A
VTS 461B 2-40 N/A N/A
VTS 461D 5-125 N/A N/A

Tubing and Hoses for Compressed Gases

Typically compressed gas uses tubing or hoses to supply the system. Pressure rating and material compatibility is essential for their safe use. The following information is provided for reference in the choice of tubing/hoses:

If the tubing/hose is purchased with connectors, the user should ensure that it is marked with its pressure rating. If the end fittings are installed by the user they might require the use of pressure rated clamps. Note that typical worm-type clamps (i.e. automobile radiator clamps) do not have a pressure rating (a typical automobile cooling system is only pressurized to 16 psig). The type of clamps used should not cause damage to the tube/hose and must prevent the connection from loosening. If clamps are used on barbed fittings, they must be placed at the proper location on the fitting. If the tube/hose does not have a manufacturer's pressure rating (stamped or printed), then a proof test (at 110% of operating pressure) needs to be performed and documented.

Ear Clamp Type 1

Ear Clamp Type

Ear Clamp Type 2

Ear Clamp Type

T-Bolt Clamp Type

T-Bolt Clamp Type

Band Clamp Type

Band Clamp Type

Pipe Doping

It is important that if sealant are used on threaded connections (a.k.a. doping), that the material is compatible with the fluid (gas/liquid) used. Note, Sealant need to be used on all National Pipe Taper (NPT) threads and fitting. The most common forms of Pipe Dope are Pipe thread compounds and Polytetrafluoroethylene (PTFE) tape (commonly referred to as Teflon tape).

Pipe Tread Compounds

When selecting the pipe thread compounds, check the fine print very carefully to insure the product is listed as approved for the application you intend to use it for as some of these products have a very limited range of applications. White compounds are typically not compatible with flammable gases or oxygen. Specific applications include:

  • Potable water
  • Non-potable Water
  • Natural Gas
  • Propane
  • Fuel oils (#1 through heavy bunker oils)
  • Gasoline
  • High & Low pressure air
  • Low pressure steam
  • High pressure steam
  • Refrigerants
  • Electrical conduits

As the PTFE tape industry evolved into more products, they adopted a standardized color code (Always read the packaging to ensure compatibility).

  • WHITE -Single density: should only be used on NPT threads up to 3/8 inch.
  • YELLOW - Double Density: yellow double density is often labeled as "Gas type" (flammable gas)
  • RED - Triple Density: (Note-the container is red but the tape itself appears as a pale pink color). Presently required on all joints ½" diameter or greater.
  • GREEN - Oil Free PTFE tape: Required for use on all lines conveying oxygen (I.E. –medical oxygen or welding oxygen lines).
  • COPPER COLOR: contains granules of copper and is to be used as a thread lubricant but is not approved as a thread sealant. (Generally it is used as a thread lubricant on bolts or pipe threads for mechanical applications where no physical seal is required.)

PTFE tape is only approved as a thread seal when applied correctly. To apply you begin at the end of the pipe and wrap the tape under tension in the direction of the thread turns. Each successive layer should overlap the previous layer by ½ to 2/3 and continue wrapping until the entire threaded portion of the pipe is covered. (Minimum of 3 full turns).