COMPRESSED GAS CYLINDER SAFETY 1 INTRODUCTION

Compressed gas cylinders are frequently used in laboratories and workshops. These cylinders contain gases that vary in chemical properties from inert and harmless to toxic and explosive. In addition, gases under high pressures also present significant mechanical hazards.

2 SCOPE

This guide outlines the safe use of compressed gas cylinders including:

identification,

inspections,

transportation,

storage,

installation,

use, and

disposal

This note does not cover the protection of personnel against inhalation hazards associated with the accidental dispersion of gases.

3 DEFINITIONS

Compressed Gas - A gas, other than in solution, that is in a packaging under charged pressure and is entirely gaseous at a temperature of 20°C (293K).

Cylinder - Cylinder used in the gases, as a pressurized vessel, must be

designed and tested (and re-tested on a frequent basis) to acceptable standard.

Nature of Gas - The gas shall be defined as per classification under GHS

system.

Standard Cylinder Status Tag - All compressed gas cylinder shall bear the status of the cylinder as - full, in use, or empty.

Types of Hazards:

Physical Damage: Cylinders are very hazardous when exposed to damage

from falling over, tipping, heat, electric circuits, motion, vibration, or anything that can cause a weakness or crack in the cylinder wall or shell. Such damage can cause the cylinder to rupture and explode sending sharp metal pieces, like shrapnel, blasting through the area.

Tipping and Falling: The most common hazard associated with cylinders occurs when cylinders tip or fall over; the consequences often may be very severe. Since cylinders are heavy and awkward to handle, they require special care and equipment in handling and securing so they do not fall or tip over and cause injury.

Valve Leakage: Cylinder valves can leak, causing their contents to

discharge. To minimize hazards from leaks, use proper ventilation and storage. The content of the cylinder is thus important with various consequences ranging from asphyxiation, acute poisoning and fire/explosion.

Fire: All compressed gas will expand when heated. Cylinders will explode

and release its content with great force when released wither via the relief valve, if any, or when the cylinder rupture. This will cause a fire - ball.

4 RESPONSIBILITIES

4.1 Department or Division Heads are responsible for ensuring the purchase of gases needed by the department/division and these are stored safely.

4.2 Principal Investigators and laboratory managers are responsible all

compressed gases are used safely. No toxic gases are to be released into the environment. Specifically, PI and managers should ensure users are trained in the use and handling of cylinders and their content.

4.3 Purchasers are responsible to ensure the selected supplier is reliable in that:

cylinders are (hydrostatic) test regularly;

correct labels are attached with the gases requested (or request a Certificate of Analysis);

standard cylinder status tag to each cylinder at the time of delivery to the user;

cylinders properly transported and secured. (This is to ensure that accidents with cylinders on NTU roads do not cause damage to NTU property and its community.); and

the gas outlet of the cylinder is adequately protected from grease and dirt which will otherwise cause poor seal with the connectors (regulators or manifold). (Use of masking tape as sealant is discouraged.)

5 PRACTICES/PROCEDURES

5.1 General

Identification - Compressed gas cylinders shall be legibly marked, with either the chemical or trade name of the gas. This is for the purpose of identifying gas content. Cylinders shall be marked with stencil, stamp, or securely attached label. Whenever practical, the marking shall be on the shoulder of the cylinder. Markings, labels, decals, tags, or stencil marks used for the identification of contents shall not be defaced. No marks or numbers stamped into a cylinder shall be changed or obliterated. (Note: DO NOT reply on the colour coding of gas cylinders as identification of gases.)

Repairs and Alterations - Cylinders, valves, or safety-relief devices shall not be repaired or altered except by the cylinder owners only.

Connections - Compressed gas cylinders shall be equipped with a connection suitable for the gas. All manifold connections MUST be designed, tested and certified by a competent person, preferably by the compressed gas supplier.

Inspections - Compressed gas cylinders shall be inspected by the user prior to and during use to determine that cylinders are in a safe condition for use. Inspect for corrosion, valve damage or leaks, evidence of tampering, etc. Never use a flame to detect flammable gas leaks.

Periodic Testing - Most compressed gas cylinders are required to be retested periodically (5 years/10 years). These dates are marked on the cylinder shoulder (see Appendix A).

All cylinders shall be equipped with means of connecting a valve protection cap, or with a collar or recess to protect the valve.

Cylinders shall not be used for any other purpose other than for storing and dispensing gases.

Cylinders shall not be refilled by anyone other than the owner of the cylinders.

5.2 Cylinder Use

5.2.1 Moving and Handling

Caps shall be kept on at all times except when cylinders are physically connected to a regulator, manifold, or distribution apparatus.

Cylinders can also be protected by a collar. (See Left)

Cylinders shall not be lifted by the cap or collar.

Cylinders shall not be dropped or permitted to strike against each other or other surfaces violently.

Cylinders shall not be lifted with a lifting magnet. Slings, ropes, or chains should not be used unless provisions have been made on the cylinder by the manufacturer for appropriate

lifting attachments, such as lugs. A crane may be used only when a safe cradle or platform is provided to hold the cylinders.

Cylinders shall be transported by suitable hand trucks (preferable on a stable three or four wheeled trolley (inert right), or rolled on the bottom edge (see below) for short distances only. (Note: Two wheel trolley will likely cause manual handling problems.)

Rolling compressed gas cylinders on the bottom edge for short distances is acceptable, for example, moving the cylinder from a cart to it's final resting place (generally not more than 2 metres). (Note: The cylinder is heavy and it may be necessary to have two persons to assist in the manipulation of cylinders.)

Cylinders shall not be rolled over any electrical cables.

Cylinders cannot be rolled when conditions are unsafe, such as when surfaces are wet or a slope.

No cylinders shall be dropped from a raised platform.

Before returning cylinders to the supplier, the valve shall be closed and the protective cap reattached.

No cylinders shall be rolled horizontally on the ground.

Cylinders should not be transported horizontally on a push cart.

Cylinders shall not be transported in any passenger lifts with any occupants.

5.2.2 Storing Cylinders

Compressed and liquefied gases in portable cylinders shall be stored in accordance with guidelines given by SCDF (for flammable gases) and good practice.

Total quantities stored shall not be more than the quantity specified by the licence issued by SCDF.

Each cylinder should preferably be individually restrained firmly against a surface of adequate strength, a sufficiently large object, a hard bearing wall or a fabricated anchored

stand suitably designed for the purpose. (See Appendix 2 for examples.)

Where gases of different types are stored at the same location, cylinders should be grouped by types of gases, and the groups arranged to take into account the types of gas contained, e.g., flammable gases shall not be stored next to oxidizing gases.

Cylinder storage areas shall be posted prominently with the types of gases to be stored. Where possible, signs should be in line with the GHS hazards pictogram.

Whenever oxygen and a fuel gas such as acetylene or hydrogen are to be stored, they shall be separated by a suitable distance or by a non-combustible barrier at least 1.5m high having a fire-resistance rating of one hour.

Cylinders shall not be stored near highly flammable or combustible substances, shall not be exposed to sparks or flames, and shall not be located where they could become part of an electrical circuit.

Charged and empty cylinders should be stored separately. Old stock should be stored in an accessible area so as to be removed first. Empty cylinders shall have their valves closed and the cylinder status tag displayed. (Note: It may be permissible for individual laboratories to devise system to denote cylinder status so long as the method is communicated.)

The gas cylinder storage area shall be dry, cool, well ventilated, and, where practical, fire resistant.

Cylinders should not be stored in the open exposed to direct sun and rain.

Do not store near elevators, stairs or gangways, or in locations where cylinders will likely be knocked over or damaged by passing or falling objects. Do not store cylinders in unventilated enclosures unless protected by gas detectors.

Cylinders shall not be exposed to continuous dampness, partially submerged in water and shall not be stored near salt or other corrosive chemicals or gases. Corrosion may damage the cylinders and may cause the valve-protective caps to stick.

Cylinders shall not be stored on two wheeled carts, except for the purpose of repairs in the case of building works.

Any cylinders not being used for a period longer than 6 months should be reviewed for storage and encouraged to be returned to the gas supplier.

5.2.3 Installation

Compressed gas cylinders should be handled only by personnel who have been trained (or has the competency) on compressed gas safety.

The user is responsible for the cylinder and for its installation shall check the identity of the gas before use. The cylinder shall be returned to the supplier, unused, if:

o the cylinder content is not identified; o hydrostatic test date is past due; o the cylinder is in any way damaged; or o the gas shown on the decal (shoulder) differs from the

stenciled gas on the body of the cylinder.

Cylinders shall be secured properly.

Valve-protective caps shall be kept in place until the cylinder is connected to a regulator or manifold.

Suitable pressure regulating devices must be used in all cases where gas is admitted to systems designed for pressure less than cylinder pressure. Only regulators approved by the manufacturer for the gas being used and is in good condition 1 shall be installed.

Before connecting a cylinder to a regulator, the valve protection cap should be removed. When fixing on the regulator or the connectors of the manifold, the threading of the regulator should snugly fit into the socket. The locking nut shall be tighten adequately (but not over tightened with the use of tools). Stand to the side of the outlet, never in front of it when opening the stem valve.

Avoid crack of compressed gas cylinders particularly a flammable or oxygen cylinder near sparks, flame, or other sources of ignition.

1 A) The two gauges indicating cylinder and delivery pressures are functional and pressures clearly seen at

eye level B) the threads of connectors are not dented and is clean C) the connectors and regulators is not

corroded. D) there is a valve handle on the regulator

5.2.4 Withdrawing Cylinder Content

Cylinder valves should be opened slowly. Never direct high-pressure gas streams toward the body as embolisms can result from gas forced under the skin or entering a wounded area.

Do not use wrenches or tools to open a cylinder valve except those provided or approved by the gas manufacturer. Never „hammer‟ the valve wheel in attempting to close the valve.

Do not attempt to open valves or caps that are hard to open or frozen because of corrosion. Return these cylinders to the vendor as soon as possible. NEVER USE ANY LUBRICANT especially on oxygen cylinders.

Never use compressed gas, unless protected by suitable check valves, where the cylinder or its contents is apt to be contaminated by the feedback of process material.

Valves should be kept tight to prevent leakage. Where hoses or metal coils are used, they should be maintained in good condition. Use soapy solution or „snoopy‟ to check for leaks. A flame shall not be used for leak detection.

Before a cylinder is removed from service, determine that the cylinder valve is closed securely and all pressure is released from the connected system. When removing regulator or connector, make sure all gases have been purged; open slowly.

Connections to piping, regulators and other equipment shall be checked by competent persons.

At the end of the experiment, ensure the cylinder main stem valve is closed.

5.2.5 Securing Cylinders

Cylinders shall be secured to fixed structures or to movable carts in the case of gas, welding, or cutting apparatus.

Cylinders shall be secured by the body, at two-thirds the height of the cylinder from the base, and not by the valve.

Cylinders can be secured by one of the following methods, depending on size and use:

o Safety chain provided with a positive locking device such

as a nylon strap with a locking buckle or self-locking hook to prevent accidental release of cylinder.

o Nylon strap and buckle assembly with attachment fixture.

This item is specially designed to restrain portable gas cylinders.

o A cradle with indentations designed to accommodate gas

cylinders in a horizontal position. (Not for liquefied gases and acetylene.)

o An upright storage box or

cage with individual cells designed to hold several cylinders at one time (see insert).

5.2.6 Tagging Procedure

At the time of delivery, a Standard Cylinder Status Tag should be placed on all cylinders by the supplier.

When the cylinder is placed in use, the bottom of the tag with the word "Full" should be removed.

When the cylinder is no longer required, the "IN USE" section of the tag should be removed. All cylinders shall be treated as though residual gas remains.

5.2.7 Removal

When cylinders are empty or are no longer needed, remove from the installation. Never leave cylinder stored over a long period of time (6 months unused).

5.2.8 Cylinder Defects and Disposal

If a cylinder leak cannot be stopped by tightening a valve gland or packing nut, close the valve; and if possible, detach the cylinder from the installation. Remove the leaking cylinder from the building and allow it to empty safely in the open. Cool cylinder if necessary (unless the gas reacts with water).

When cylinders, valves, contents, etc., are in such a condition that the only safe or practical solution is disposal, arrange for replacement.

6 SPECIAL GASES

6.1 Toxic Gases

Persons handling and using toxic gases shall have procedures for handling, storage and approved emergency response.

Toxic gases shall be used only with the approval of the PI. Additional review and approval may be necessary especially chlorine gas cylinders are exposed to steam or hot water.

6.2 Other Gases

6.2.1 Acetylene

Acetylene shall be used only with a pressure-regulating valve and gauge with pressures not exceeding 15 PSIG ( or 100kPag)

An acetylene valve shall not be turned more than one and one-half turns on the spindle.

If a wrench is required to open an acetylene valve, it shall be left on the cylinder-valve stem during use.

Acetylene cylinders shall be stored and used only in an upright position.

Flashback arrestors shall be used on acetylene cylinders.

6.2.2 Liquid Oxygen, Nitrogen, and Argon

Cylinders containing these gases must be transported, stored, and used in an upright position to permit venting of the vapor to maintain safe internal pressure.

6.2.3 Oxygen

Oxygen cylinders shall not be stored within 7 metres of flammable gases or highly combustible materials, particularly oil or grease. (Note: Oil and grease in the presence of oxygen may ignite violently). Alternatively, oxygen may be separated from flammable and combustible materials by a fire rated wall at least five feet high.

Oil, grease, or other combustible material shall not come into contact with valves, regulators, gauges, or any fittings used with oxygen.

Such cylinders should never be handled with oily hands or gloves.

Oxygen shall never be used as a substitute for compressed air.

Never point oxygen hose at anyone, including yourself and must never be used as an “air-gun”.

Appendix A: Markings on cylinders - what they mean (From Airgas)

Markings Specialty gas cylinders are stamped with markings designed to indicate ownership, specifications, pressure ratings, and other important data. Some suppliers also utilizes a bar code label for product identification and tracking. 1. Cylinder Specification:

DOT - Department of Transportation governs the use of cylinders in USA. This is one of the acceptable standards used in Singapore. The requirements specify the type of material of construction (e.g., 3AA) and service or working pressure in pounds per square inch (e.g., 2,265 psig).

2. Cylinder Serial Number 3. Date of Manufacture:

This date (month-year) also indicates the original hydrostatic test. 4. Neck Ring Identification:

The cylinder neck ring displays the name of the original owner of the cylinder. 5. Retest Markings:

The format for a retest marking is: Month - Facility - Year - Plus Rating - Star Stamp. The + symbol (Plus Rating) indicates that the cylinder qualifies for 10% overfill.

The H symbol (Star Stamp) indicates that the cylinder meets the requirements for 10-year retest, instead of a 5-year retest.

6. Bar Code Label:

The bar code label provides a unique cylinder identifier and is used by computer systems to track cylinders throughout the fill process. As an optional service, we have the capability of tracking cylinders to and from customers.

7. Cylinder Manufacturer’s Inspection Marking 8. Cylinder Tare (Empty) Weight:

This value may be preceded by the letters TW.

Restraints may be on a gypsum wall it is secured well via suitable expanded clips. These anchors MUST be checked every three months to ensure they are still suitable for use.