COMPRESSED GAS CYLINDER
SAFETY
Many industrial and
laboratory operations require the use of compressed gases for a variety of
different operations.
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Compressed
gases present a unique hazard. Depending on the particular gas, there is a
potential for simultaneous exposure to both mechanical and chemical hazards.
Gases may be:
- Flammable or combustible
- Explosive
- Corrosive
- Poisonous
- Inert
- or a combination of hazards
Careful procedures are necessary
for handling the various compressed gases, the cylinders containing the
compressed gases, regulators or valves used to control gas glow, and the piping
used to confine gases during flow.
Identification
The contents of any compressed gas cylinder must be clearly identified. Such identification should be stenciled or stamped on the cylinder or a label. Commercially available three-part tag systems may also be used for identification and inventory.
No compressed gas cylinder should
be accepted for use that does not legibly identify its contents by name. If the
labeling on a cylinder becomes unclear or an attached tag is defaced to the
point the contents cannot be identified, the cylinder should be marked
"contents unknown" and returned directly to the manufacturer.
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Always read the label!! |
Never rely on the color of the cylinder for identification. Color coding is not reliable because cylinder
colors may vary with the supplier. Additionally, labels on caps have little
value because caps are interchangeable.
All gas
lines leading from a compressed gas supply should be clearly labeled to
identify the gas, the laboratory or area served, and the relevant emergency
telephone numbers.
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The labels should be color coded to
distinguish hazardous gases (such as flammable, toxic, or corrosive substances)
(e.g., a yellow background and black letters).
Signs should be conspicuously
posted in areas where flammable compressed gases are stored, identifying the
substances and appropriate precautions (e.g., HYDROGEN - FLAMMABLE GAS - NO
SMOKING - NO OPEN FLAMES).
Handling & Use
Gas cylinders must be
secured at all times to prevent tipping.
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Cylinders may be attached to a bench top, individually to the wall,
placed in a holding cage, or have a non-tip base attached. Chains or sturdy
straps may be used to secure them.
If a leaking cylinder is discovered, move it to a safe place (if it is
safe to do so) and inform the Environmental Health & Safety Department.
You should also call the vendor as soon as possible.
Under no circumstances
should any attempt be made to repair
a cylinder or valve.
should any attempt be made to repair
a cylinder or valve.
Standard cylinder-valve outlet connections have been devised by the
Compressed Gas Association (CGA) to prevent mixing of incompatible gases. The
outlet threads used vary in diameter; some are internal, some are external;
some are right-handed, some are left-handed. In general, right-handed threads
are used for non-fuel and water-pumped gases, while left-handed threads are
used for fuel and oil-pump gases.
To minimize undesirable connections, only CGA standard combinations of
valves and fittings should be used in compressed gas installations; the
assembly of miscellaneous parts should be avoided. The threads on cylinder
valves, regulators and other fittings should be examined to ensure they
correspond and are undamaged.
Cylinders should be placed with the valve
accessible at all times. The main cylinder valve should be closed as soon as it
is no longer necessary that it be open (i.e., it should never be left open when
the equipment is unattended or not operating). This is necessary not only for
safety when the cylinder is under pressure, but also to prevent the corrosion
and contamination resulting from diffusion of air and moisture into the
cylinder after it has been emptied.
Cylinders are equipped with either a hand wheel or stem valve. For cylinders equipped with a stem valve, the valve spindle key should remain on the stem while the cylinder is in service. Only wrenches or tools provided by the cylinder supplier should be used to open or close a valve. At no time should pliers be used to open a cylinder valve. Some valves may require washers; this should be checked before the regulator is fitted.
Cylinder valves should be opened
slowly. Oxygen cylinder valves should be opened all the way. Open up the oxygen
cylinder valve stem just a crack. Once the needle on the high pressure
gauge has stopped, open up the valve all the way. This back-seats the
valve. Oxygen cylinders must have the valve opened up all the way
because of the high pressure in the cylinder. There is a back-seating
valve on the oxygen cylinder. This prevents the high-pressure gas from
leaking out through the threaded stem.
When opening the valve on a cylinder containing an irritating or toxic
gas, the user should position the cylinder with the valve pointing away from
them and warn those working nearby.
Cylinders containing flammable gases such as
hydrogen or acetylene must not be stored in close proximity to open
flames, areas where electrical sparks are generated, or where other sources of
ignition may be present.
Cylinders containing acetylene shall never be stored on their
side.
An open flame shall never be used to detect leaks of flammable gases.
Hydrogen flame is invisible, so "feel" for heat. One common practice
is to use a natural bristle broom to "sweep" the air in front of you.
All cylinders containing flammable gases should be stored in a well-ventilated
area.
Oxygen cylinders, full or empty, shall not be stored in the same
vicinity as flammable gases. The proper storage for oxygen cylinders requires
that a minimum of 20 feet be maintained between flammable gas cylinders and
oxygen cylinders or the storage areas be separated, at a minimum, by a fire
wall five feet high with a fire rating of 0.5 hours. Greasy and oily materials
shall never be stored around oxygen; nor should oil or grease be applied to
fittings.
Regulators are gas specific and not necessarily
interchangeable!
Always make sure that the regulator and valve
fittings are compatible.
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If there
is any question as to the suitability of a regulator for a particular gas,
check with Environmental Health & Safety Services or call your vendor for
advice. After the regulator is attached, the cylinder valve should be opened
just enough to indicate pressure on the regulator gauge (no more than one full
turn) and all the connections checked with a soap solution for leaks. Never
use oil or grease on the regulator of a cylinder valve.
The following rules should always be followed in regards to piping:
- Copper piping shall not be used for acetylene.
- Plastic piping shall not be used for any portion of a high-pressure system.
- Do not use cast iron pipe for chlorine.
- Do not conceal distribution lines where a high concentration of a leaking hazardous gas can build up and cause an accident.
- Distribution lines and their outlets should be clearly labeled as to the type of gas contained.
- Piping systems should be inspected for leaks on a regular basis.
- Special attention should be given to fittings as well as possible cracks that may have developed.
A cylinder should never be emptied to a pressure lower than 172 kPa (25
psi/in2) (the residual contents may become contaminated if the valve is left
open). When work involving a compressed gas is completed, the cylinder must be
turned off, and if possible, the lines bled.
When the cylinder
needs to be removed or is empty, all valves shall be closed, the system bled,
and the regulator removed. The valve cap shall be replaced, the cylinder clearly
marked as "empty," and returned to a storage area for pickup by
the supplier.
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Empty and
full cylinders should be stored in separate areas.
Where the possibility of flow reversal
exists, the cylinder discharge lines should be equipped with approved check
valves to prevent inadvertent contamination of cylinders connected to a closed
system. "Sucking back" is
particularly troublesome where gases are used as reactants in a closed
system. A cylinder in such a system
should be shut off and removed from the system when the pressure remaining in
the cylinder is at least 172 kPa (25 psi/in2).
If there is a possibility that the container has been contaminated, it
should be so labeled and returned to the supplier.
Liquid bulk cylinders may be used in laboratories
where a high volume of gas is needed. These 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 will also vent their contents when a preset
internal pressure is reached, therefore, they should be stored or placed in
service where there is adequate ventilation.
Always use safety glasses (preferably with
a face shield) when handling and using compressed gases, especially when
connecting and disconnecting compressed gas regulators and lines.
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All compressed
gas cylinders, including lecture-size cylinders, must be returned to the
supplier when empty or no longer in use.
Transportation of Cylinders
The cylinders that contain compressed gases are primarily shipping
containers and should not be subjected to rough handling or abuse. Such misuse
can seriously weaken the cylinder and render it unfit for further use or
transform it into a rocket having sufficient thrust to drive it through masonry
walls.
- To protect the valve during transportation, the cover cap should be screwed on hand tight and remain on until the cylinder is in place and ready for use.
- Cylinders should never be rolled or dragged.
- When moving large cylinders, they should be strapped to a properly designed wheeled cart to ensure stability.
- Only one cylinder should be handled (moved) at a time.
To complete the Compressed Gas
Cylinder Training Module, please take the Quiz.
Compressed
Gas Cylinder Quiz
- If the regulator to an oxygen cylinder is difficult to thread, you should:
- Oil the threads
- Return the cylinder or regulator to the supplier
- Use a crescent wrench to tighten it
- Use a regulator from a nitrogen cylinder
- If you find a compressed gas cylinder without a label, you should:
- Make your best guess as to what the gas is, based on cylinder color
- Attach a regulator and test the gas
- Mark the contents “unknown” and return immediately to the supplier
- Segregate in a storage closet until identification can be made safely
- It is safe to conduct minor repairs on the valves of cylinders containing “harmless” gases.
- True
- False
- Cylinders may safely be secured by:
- Duct tape
- Bracing the cylinder on two sides by non-movable objects such as a refrigerator and storage bench
- Chains
- All of the above
- When equipment is left unattended or not operating, cylinder valves should always be:
- Closed
- Left open
- Oxygen cylinder valves should be opened all the way
- True
- False
- Which type of cylinder should never be stored on its side?
- Acetylene
- Helium
- Self-Contained Breathing Apparatus
- Oxygen
- Cylinders containing flammable gases shall not be stored near:
- Areas where electrical sparks might be generated
- Bunsen burners
- Pilot lights
- All of the above
- It is acceptable to use plastic piping for parts of a high pressure system
- True
- False
10.
Cylinders should never be rolled or dragged
- True
- False
Quiz Answers
1.
B
2.
C
3.
B
4.
C
5.
A
6.
A
7.
A
8.
D
9.
B
10.
A
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