Compressed Gas Oxidizing Agent FlammableExplosive
The compressed gas industry use colour codes as a quick reference guide to the cylinders contents. This should not be used as a definitive indicator of the contents only as a guide. The only way to accurately identify the contents of a cylinder is the label.
Oxygen Description BOC oxygen is typically supplied with a purity of 99.5% or better. Colourless and odourless. Does not burn but supports and accelerates combustion. Hazards However most lubricants are not compatible; oil and grease can ignite spontaneously burning with explosive violence and should not be used with oxygen. Oxygen must never be used with Polytetraflouroethylene (PTFE) tape, as it will cause combustion. Uses Widely used with a fuel gas for cutting, welding, brazing and soldering. The use of oxygen gives higher flame temperatures than if air is used. Copper, brass and high quality stainless steel are the most commonly used metals and are compatible with oxygen
Propane Description propane is heavier than air. Leakage will collect in low-lying areas such as drains or ducts. most propane is stenched to give a fish-like odour. supplied as a liquid in cylinders available for vapour or liquid withdrawal from cylinders. non-toxic (can cause dizziness at high concentrations). highly combustible, having explosive limits in air between 2.2% to 9.5% by volume Hazards propane has some solvent properties and therefore hoses should be of the correct material as shown and the correct colour, orange. only use purpose-manufactured equipment with propane and always use correct lighting up procedures. you will require a separate regulator, flashback arrestors, hoses, nozzles and torches when using propane. Uses used in oxy-propane soldering and brazing
Acetylene Description the hottest and most efficient of all the fuel gases, providing high levels of productivity lighter than air and will not accumulate at low levels low ignition energy non-toxic (may cause dizziness in high concentrations) acetylene is stored in specially-designed cylinders to prevent decomposition. It can form explosive acetylide compounds with some metals, most notably copper, silver and mercury. Hoses used with acetylene are coloured red and are designed to resist acetone. For this reason other fuel gas hoses must not be used. Hazards care must be taken when using acetylene as it is an asphyxiant. acetylene is highly reactive. It is dissolved in acetone and contained within a porous mass inside the cylinder
Carbon Dioxide Description A colourless and odourless gas that can cause the nose to sting in high concentrations. Toxic in high concentrations. An asphyxiant (does not support life). Slightly corrosive in the presence of moisture. Heavier than air, carbon dioxide will collect in ducts, drains and low-lying areas. At elevated temperatures, carbon dioxide reacts with many substances. Cylinders of both liquid and gaseous carbon dioxide are available. Dip tubes are used in liquid withdrawal carbon dioxide cylinders to extract the liquid from the cylinder. The tube runs down the centre of the pressurised cylinder and draws the liquid up through the valve. To identify these cylinders, a white stripe is painted down the length of the cylinder. Benefits Higher density than air provides good blanketing properties. Applications and Uses Balancing pH levels in swimming pools Compressed liquid carbon dioxide can also be used in small pipe-freezing applications
Hydrogen Description Odourless, colourless and tasteless Will ignite easily so cylinders must not be snifted Burns with an invisible flame Produces a flame of approximately 2834°C when used with oxygen Benefits Has the highest thermal conductivity of all gases. Is supplied at higher pressures than other fuel gases. Burns with a clean carbon-free and soot-free flame. Applications and Uses Can be used as an alternative power source when used with a fuel cell to generate electricity. In the glass industry, used to form the rim on glasses
Fuel Gasses Fuel gasses are burned to generate heat, different gasses have different characteristics; you should familiarize yourself with the fuel gas that you are using. Make sure the equipment that you are using is suitable for the gas that you are using.
Nozzle Gas nozzles come in a variety of sizes depending on the application. All of the nozzles burn at the same temperature but the bigger the nozzle the greater the volume of heat that can be delivered. Too small a nozzle will not get the work up to soldering temperature. Too big a nozzle will heat the work up too quickly and risk over heating or burning the pipe & fitting.
Torch Body Most manufactures make proprietary nozzles that only fit there own product, you will need to know the manufacturer and model number when ordering replacement nozzles. Some torches have a built in igniter powered via a peizo electric unit. The torch should be visually inspected prior to use making sure there are no signs of damage, the nozzle and hose are securely attached and the controls function correctly.
Hose Propane hose should be orange, this is the standard colour for propane. Propane hose must not be used for acetylene. The hose should conform British Standard BS5120 or the new European Standard EN559. The hose is usually fitted to the regulator and torch by the manufacturer; the hose can be bought in lengths and fitted by the end user. When fitting a hose you must use the correct fittings / clips and it must be test for both mechanical strength and gas soundness.
Regulator The regulator as the name suggests regulates the amount of gas that passes from the cylinder to the torch. The regulators are designed specifically for the gas so you must only use the specified regulator for each type of gas. Some regulators are fixed giving you a constant line pressure, others are adjustable allowing you to vary the amount / flow of gas. Except for a very small number of specialist applications fuel regulators have a left hand threat so they can not be fitted incorrectly.
Torch On/Off Valve The on / off valve not only turns the gas on & off but also controls the gas flow through the torch, this makes the flame bigger or smaller. Make sure the valve works with a smooth operation and that it can be turned off quickly if there is a need. If the knob is damaged or missing do not try to operate the equipment.
Cylinder Isolation Valve The cylinder isolation valve allows the gas out of the cylinder into the regulator. There are two main types of isolation valve; wheel operated and key operated. The wheel operated valve pictured above left is opened and closed by hand. The key operated isolation valve requires a special ‘key’ to open and close the valve. Make sure you familiarize yourself with the operation of the valve before you use the equipment, in case you need to turn the equipment off in a hurry.
Left-handed Nut Fuel gasses have a left hand thread, this is a safety feature and stops them being connected to the wrong part of the heating or cutting equipment. The left handed thread is denoted by the ‘notch’ machined in the nut. The bottom picture shows the ‘bullnose’ this is the part of the regulator that creates the gas tight seal. The bullnose should be protected from damage as small scratches can lead to gas leaks.
Hose Crimp Clip When fitting hoses the correct clip must be used. The clip pictured above left is often referred to as a ‘jubilee clip’ these should not be used on gas hoses as the clip can be over tightened and cut in to the hose. The clip pictured below left is the type of clip that should be used be used. These are called double eared hose clips and are fitted with a special crimping tool.
Use of Blowtorch As with any task planning is an important part of the safe operation. Look at where you are about to work and situate your gas cylinder in an appropriate place; close enough to be able to access if needed but far enough away that it will not be heated be the torch. It should also be out of you way so it does not constitute a trip hazard.
Purging The hose should be purged of air prior to lighting. Purging is the process of opening the control knob on the torch for a few seconds to push any air out of the hose. This dramatically reduces the risk of flashback.
Lighting When lighting the blowtorch you should use a spark igniter as lighters can explode if the torch is passed over them. The gas is turned on and then ignited, the flame is adjusted to the required setting. Once the work is complete the gas is turned off and the flame extinguished. Take care where you place the torch down as the nozzle will be very hot for some time.
Leaks If you can smell gas even when the torch is off check the tightness of the regulator, if it is lose tighten the nut by ¼ of a turn. If the hose is damaged it should be replaced. If there are flames coming out where the nozzle is attached to the body of the torch check to see if the nozzle is fitted correctly.
Planning Always plan for unexpected eventualities, have a plan of what you are going to do if there is a fire, a gas leak, etc. Have fire fighting equipment available and accessible.
Risks When using a blowtorch you can become very focused on the task in hand and become oblivious to your surroundings, as a result you can accidently set fire to the surrounding area; to minimize this risk make sure all flammable material is removed from the area you are working in. Remember heat can travel through heat resistant mats and scorch any surface behind.