What Are Cylinders & Fittings?
Compressed gasses are stored in heavy-walled metal cylinders constructed, manufactured and tested for use with compressed gases. Cylinders are made in a wide range of shapes and sizes. They vary from small lecture bottles, mostly used for demonstration purposes, to large cylinders over 3 meters in length. Transport cylinders must comply with CSA standard CAN / CSA-B339 “Cylinders, Spheres and Tubes for the Transportation of Dangerous Goods.”
This principle refers to specifications for the manufacture, inspection, testing, labelling, requalification, reheating treatment, repair and reconstruction of cylinders, spheres and tubes (containers) for the transport of hazardous goods. It also contains the criteria for the certification of new designs and the specifications for registration.
Cylinders that meet this same criteria are often referred to as ‘TC approved’ cylinders. Cylinders are permanently labelled, usually on the shoulder or on the top of the collar.
Usually, cylinders must be retested or checked every five or ten years. The date of each test shall be marked on the cylinder.
Cylinder Valves & Connections
The compressed gas cylinders must only be connected to the regulators and the gas equipment in the cylinder. Because attaching the wrong equipment can be hazardous, a range of different standard cylinder valve outlets is available for different gas groups. For example, these standard connections prevent the connection of a valve to a flammable gas from fitting the connections to an incompatible gas, such as an oxidising gas.
Many compressed gas cylinders have valve caps or some other means of protecting the valve from damage throughout handling and transport. A dust cap may also be placed over the valve outlet itself to help keep it clean.
What Are Cylinder Safety Devices?
Most cylinders have one or more safety relief devices. These devices may prevent the cylinder from breaking if the internal pressure exceeds the design limits. Pressure may become dangerously high if the cylinder is exposed to fire or high temperatures, along with high storage temperatures.
There are three types of safety relief devices. Each reduces excessive gas pressure in a different manner:
Safety-or Pressure-Relief Valves: these are usually part of the cylinder. Normally, they are kept closed by the spring. The forces holding the valves closed is determined by the amount of gas in the cylinder. The valves open when the pressure in the cylinder exceeds the safe operating limit. Gas is released until the pressure of the cylinder falls back to the safety limit. The valve then closes and keeps the remaining gas in the cylinder.
Rupture disks (also known as frangible or bursting disks): these disks are usually made of metal. They burst or rupture under a certain pressure, releasing the gas in the cylinder. The bursting pressure is built such that the disk ruptures before the test pressure of the cylinder are reached. These devices can not be re-enclosed, so the contents of the cylinder are released.
Fusible plugs (also known as a fuse or melt plugs): temperature, not pressure, activates fusible plugs. These safety devices are used where the heat could trigger an explosive chemical reaction. The pressure relief valve or the rupture disk acts too slowly and too late to prevent the cylinder from breaking when an explosive reaction has already begun. The fuse plug releases the gas before a hazardous reaction can begin. Fusible plugs are made of metals which melt at lower temperatures. E.G. acetylene cylinders have a fusible plug which melts at a temperature of about 100 ° C ( 212 ° F). This temperature is below the temperature at which hazardous polymerisation may occur.
Not all compressed gas cylinders are equipped with safety devices. Some gasses are so toxic that their release through the safety device would be hazardous. The cylinders for these gasses are designed to withstand higher pressures than the normal cylinders. If these “toxic gas” cylinders are involved in a fire, the area needs to be evacuated.
Why is Proper Ventilation Important?
Well-designed and well-maintained ventilation systems eliminate gasses from the workplace and minimise their hazards.
The amount and quality of ventilation required depends on the nature of work, the quality and quantity of materials used, and the size and configuration of the work area.
Assess the different ways in which the workplace stores, manages, uses and disposes of compressed gases. An evaluation can be made if current ventilation controls and other hazard management measures are sufficient. Some workplaces may require a complete system of hoods and ducts to provide appropriate ventilation. Others can involve a single, well-positioned exhaust fan. Facilities for hazardous materials like chlorine may require extra ventilation or continuous monitoring with suitable emergency alarms. No special ventilation system may be required for other workplaces using small amounts of inert gases.
You must ensure that ventilation systems are designed and built in such a way that they do not result in an unintentional hazard. Ensure that the hoods, ducts, air cleaners and ventilators are made of gas-compatible materials. Systems may require explosion-proof and corrosion-proof equipment. For some compressed gases, completely separate ventilation systems may be needed to keep them away from exhausting incompatible substances systems.
How Do I Store Compressed Gas Cylinders?
Store compressed gas cylinders in adherence to occupational health and safety regulations and fire and building codes applicable to your workplace. These laws may specify the types of storage areas permitted and the construction of such storage areas. They may also specify the types and quantities of different gasses that can be stored in safe storage areaS.
What Should You Do When You Receive Cylinders?
Inspect all incoming cylinders before storage to ensure that they are undamaged and labelled correctly. Do not accept a faulty cylinder delivery. Be sure they don’t give off smells, fumes that are visible or they are making hissing noises. Check when the cylinder was last tested and ensure it’s within the required time period which is usually between 5 and 10 years, but some containers may be as short as three years or as long as 12 years).
Call compressed gasses by the name on the supplier label. This reduces confusion, promotes the recognition of the hazards involved and the precautions to be taken, and may prevent the accidental use of the wrong gas. If oxygen is called “air,” anyone who needs air to operate a device will use oxygen with potentially bad consequences. Leave the valve cap secured in place until the cylinder is used. Evaluate the cylinder valve by looking through the ports of the valve cap. Do not accept dirty, rusty or otherwise defective valves and fixtures.
How Do I Transport or Move Cylinders?
Only transport cylinders that have valve caps or valve protection. Pulling cylinders along by their valve caps, rolling them on their sides, dragging or sliding them can cause damage. Rolling cylinders on the bottom edge may be acceptable for short distances; however, lifting cylinders with magnets, chains or wire rope slings is the safest option along with transporting cylinders on hand carts that have been specially designed or trolleys or other devices designed for this purpose. All transport devices should have some way to secure the cylinders to stop them from falling off.
What Should You Know About Compressed Gas Storage Areas?
Always store compressed gas cylinders separately, away from handling and preparation areas and incompatible materials. Separate storage can minimise personal injury and damage in the event of fires, spills or leaks. Many compressed gasses can undergo dangerous reactions when they come into contact with incompatible materials (liquids, gasses or solids) so they can be stored separately. For example, store oxidising gasses at least 6 meters (20 feet) away from fuel gasses or other fuel materials, or separate them with an authorised firewall.
Indoor storage areas should have walls, floors and fittings made of appropriate material. For example, use non-combustible building materials in gas oxidising storage areas and corrosion-resistant materials in corrosive gas storage areas. Make sure the floors are level and protect the cylinders against moisture. Avoid overcrowding in storage areas or storage of cylinders in out-of-way locations.
Always chain or securely hold cylinders upright to a wall, rack or other solid structure wherever they are stored, handled or used. It is best to secure each cylinder individually. The stacking of groups of cylinders together provides some security, but if this is done incorrectly, the entire group or individual cylinders may fall.
Always store compressed gas cylinders in areas which are:
- Well-ventilated, dry.
- Fire-resistant and supplied with appropriate fire-fighting equipment, including sprinklers, as appropriate.
- Away from electrical circuits and sources of fire, such as sparks, flame or hot surfaces.
- Must be accessible at all times, and away from elevators, stairs or main roadways where cylinders can be dangerous obstacles.
- Labelled with appropriate warning signs.
- Keep full cylinders segregated from empty cylinders.
What should you know about compressed gas storage temperatures?
- Store compressed gas cylinders in dry, cool locations, out of direct sunlight and away from steam pipes, boilers and other heat sources.
- Follow the recommendations of the gas supplier for temperature storage and use. Avoid exposing cylinders to temperatures above 52 ° C (125 ° F) in order to avoid unnecessary pressure build-up. Do not subject them to temperatures below-29 ° C (-20 ° F) unless they are designed to do so. Cylinders that are frozen to the surface can be released with hot water (less than 52 ° C). Never apply direct heat to your cylinder.
General Precautions For Compressed Gas Storage At All Times:
- Allow only trained, authorised people to enter storage areas.
- Keep the number of compressed gasses in storage as small as possible.
- Regularly inspect storage areas for any inadequacies, such as damaged or leaking cylinders and poor housekeeping.
- Fix all deficiencies ASAP
What Should You Know About Using & Discharging Compressed Gas Cylinders?
General Precautions
- When moving cylinders, securely fasten them to an appropriate cylinder conveyor.
- Secure the cylinder in place at the site with a chain or another appropriate method.
- Remove the valve cap once the cylinder has been safely installed and then check the cylinder valve and the fixtures.
- Remove dirt and rust. Any grit, dirt, oil, or dirty water can cause gas leaks if they enter the cylinder valve or the gas connection.
- Do not open a damaged valve. Please contact your gas supplier for advice if you need to open damaged valves.
There are four standard types of cylinder valve outlets that prevent the exchange of gas handling equipment between incompatible gases. Use only the proper equipment to discharge a particular gas from its cylinder. Never use homemade adapters or force connections between the outlet of the cylinder valve and the gas handling equipment.
- Whether the compressed gas is a liquefied, non-liquefied or dissolved gas, the gas supplier can provide the best advice on the most appropriate gas discharge equipment and the safest way to use it for a specific purpose.
- Do not lubricate cylinder valves, control threads or fittings or apply sealing compounds and tape.
- Use only the lubricants and sealants recommended by the supplier of gas.
- Cylinders that are stored in cold areas may have frozen valves. You should only use only warm water to defrost the valve or bring the cylinder to a warm area and allow it to defrost at room temperature.
- Only use the correct keys or handwheels to open the valves.
- Do not use longer keys or manipulated keys to increase your power.
- If it is badly worn, do not attempt to open the valve even with the correct key.
- Do not use handwheels with pipe wrenches or similar devices. Any such practice could easily damage the seat or spindle of the valve.
- Don’t use extreme force when opening cylinder valves — use no more than three-quarters of a turn, if possible.
- If a problem arises, the valve can be quickly closed. Leave the keys on the cylinders when the valves are open so that the valve can be quickly closed in an emergency. Many cylinder valves, such as oxygen valves, have double seats. Such valves should be completely opened. Otherwise, they could leak.
Do not use undue force when the cylinder valve is opened or closed. When you close it, just turn it around enough to stop the gas flow completely. Never try to force the valve shut.
Shut the cylinder valves when the cylinder is not in use. Do not stop the gas flow from the cylinder by simply closing off the regulator. Regulators can develop leakage from the seat, allowing pressure to build up in the equipment that is attached to the regulator. If the cylinder valves are left open, foreign matter may enter the cylinder if the cylinder pressure drops below the pressure in the attachment. First, close the cylinder valve and then close the regulator.
Liquefied Gases
Manual valves are commonly used in cylinders containing liquefied gases. Special fluid flow regulators are also available. If it is important to extract both liquid and gas from the container, address this with the gas supplier before ordering. Some liquefied gas cylinders have tubes that allow the liquid to be drained from the cylinder. Correct cylinders and special instructions can be given by the manufacturer.
Do not extract the gas quickly. The pressure in the cylinder could be lower than the required level. If this happens, or if quick removal of gas is needed, follow the advice of the gas supplier.
Non-Liquefied and Dissolved Gases
Use automatic pressure regulators to reduce the gas pressure from the high level in the cylinder to the safe level for a specific job.
There are two main types of automatic pressure regulators: single-stage and two-stage. In general, two-stage regulators provide more constant pressure under more accurate conditions than single-stage regulators. Manual flow controls are sometimes used for non-liquefied gases. Fine flow control can be achieved, but the operator must be there and present at all times. Controls for manual flow do not automatically adjust to pressure build-up in blocked systems.
What Are Important Guidelines For Safe Handling And Use?
Use the smallest feasible cylinder size for a particular job. Do not keep cylinders longer than recommended by the supplier. Compressed gas cylinders are like containers, designed to be as lightweight as possible and as safe and durable as possible. Don’t drop cylinders or allow them to hit or bang into each other. Rough handling, including the use of cylinders as hammers or rollers to move equipment, can cause serious damage.
- Use the smallest feasible cylinder size for a particular job. Do not keep cylinders longer than recommended by the supplier.
- Don’t hit a cylinder with an electric arc. Arc burns can cause the metal to become brittle and weaken the cylinder.
- Never interfere with cylinders in any way whatsoever. Do not paint, change markings or identification, or tamper with valve threads or safety devices.
Aside from the fact that it’s not legal, it can be unsafe for non-specialists to recharge cylinders or change their contents. Explosions, contamination of the cylinder or corrosion may result.
What Should You know About The Equipment Associated With Compressed Gases?
All equipment used with compressed gasses must be clean, designed properly, maintained and made of gas-compatible materials. E.G. Acetylene can form explosive compounds when in contact with copper, silver and mercury or alloys, this includes bronze or brass containing more than 65 percent copper. Ammonia affects brass and can lead to the forming of an explosive compound with mercury. Don’t use mercury pressure gages in ammonia systems.
In general, do not pressurise ordinary gas equipment. Use specially made gas safety equipment. When the cylinders are connected to a manifold or header, make sure that a specialist designs and installs the system properly. Use effective flashback arrestors for acetylene and other flammable gas systems.
Always follow the proper procedures for assembling and disassembling compressed gas equipment. Check that all of the connections are clean and do not leak. Test for leakage using the approved method of the gas suppliers, after installation and before starting to use the equipment. Never use old clips or twisted wire to connect the hoses. When the hose works loose and flails about, serious injury can result. Poor hose connections are common causes of accidents.
Acetylene can explode under pressure. Never use acetylene outside the cylinder at pressures above 103 kPa (15 psig) unless you take protective measures. If the acetylene cylinder is mistakenly left on its side, set it upright for at least an hour before use. Otherwise, when the valve is opened, it will emit a burst of solvent instead of gas.
Corrosive gasses may “freeze” the stem of the valve, making it difficult to open the valve. This results from the corroding of the metal valve by gas. Minimise “freezing” by rotating the stem of the valve at least once a day while the cylinder is in use. In addition, flush the regulator or manual control valve with dry nitrogen or dry air as soon as possible after each use.
Can You Use Compressed Gases In Confined Spaces?
You should always comply with the relevant health and safety legislation when working in confined spaces. When you are using compressed gas, including inert gases, in a confined space, be sure to check that all equipment connections are leak-proof. Remove cylinders or linked devices that are not in operation in confined spaces, even during brief breaks. Check the level of oxygen in the air (high and low). Check for any potential poisonous, corrosive or flammable gases, before entering enclosed spaces and during extended periods of work. Never work on your own.
