CAUTION: It is vital to consult a certified technician before performing any sort of equipment tests.
The proper and responsible use of oxy-fuel equipment is essential for shop safety, and it is always a good idea to read and follow all manufacturer instructions on all equipment before use. Accidents can occur when equipment is improperly maintained or used, but luckily, most safe practices are based around common sense.
The safe operation of oxy-fuel equipment does require a clear understanding of oxy-fuel torch apparatus, as well as the fundamentals of combustion. Remember, the improper use of an oxy-fuel cutting torch can cause serious injury or death. These torches are probably the most dangerous piece of welding equipment out there, and the oxyacetylene process produces a flame over 3000 degrees C.
Triangle of Combustion
Combustion requires fuel, oxygen, and heat, and as an operator, you need to control them. Oxy-fuel processes produce sparks and flames, which is why a clean workspace is essential. This process also produces small amounts of infrared rays, so be sure to wear the appropriate personal protective equipment, or PPE, such as a full-face shield with safety glasses with the correct shade lenses underneath.
If you work in street clothes, wear tightly woven natural fibers. Wool, for example, is naturally flame retardant, as is denim. Wearing a welding jacket is ideal, and some intense applications require leather chaps and spats for further added protection. Long sleeves and pant legs (such as jeans) should be worn while oxy-fuel cutting. Short sleeves and shorts could lead to burns. Also, collars and upturned sleeves on button-up shirts and cuffed pant legs should be avoided since they provide the perfect environment to catch and collect falling slag and sparks.
Cylinders are not color-coded to indicate the specific gas contained within. Suppliers can paint their cylinders any color they choose. Always read the labels to be certain what gas you are about to use, and if there is no label, do not use it. All cylinders will have a United Nations ID number on their labels. Some common numbers are UN 1072 for oxygen, UN 1001 for acetylene, UN 1978 for propane, and UN 1077 for propylene.
Acetylene is most widely used, and other gases are commonly referred to as “alternate fuels.” These include propane, propylene, butane, natural, and methane gases.
Store your acetylene cylinders in an upright position and avoid using acetylene above 15lbs of pressure – they contain a porous mass that has been saturated with liquid acetone. The acetylene gas is then pumped into the cylinder, which is in turn absorbed into the acetone and released upon use. More than 15lbs of pressure and acetylene often tends to disassociate and cause a chemical reaction and spontaneous combustion.
Acetylene withdraw rate is critical – for safe use, never withdraw more than 1/7th of the cylinder’s volume per hour.
Cylinders are outfitted with gas-specific regulators since gases have different volumes and pressure requirements. Inspect regulator valves, seats, and threads to properly ensure they are free from oil and debris. Any contaminated parts must be cleaned and inspected by qualified service personnel. This is particularly important for oxygen valves; oil or grease combined with oxygen is flammable – or even explosive.
Remember, stand aside from the regulator when slowly opening the cylinder valve. It is highly unlikely that the regulator will fail, but if it does, it will most likely force the gas in the direction of the regulator bonnet. Open oxygen valves all the way, but for acetylene valves a ¾ turn is ideal. Alternate gas valves can be opened all the way.
When not in use, ensure all pressure is released and gauge needles are at zero and do not leave adjusting screws/T handles turned in. Pressure will change, and so will your settings and could cause damage to the regulator.
There are three grades of hoses: R- and RM-grade hoses, for acetylene, and T-grade hoses can be used for any type of fuel gas, and are the only grade permissible for use with alternate fuel gases.
Acetylene hoses are typically red, with a groove across one nut. This indicates it is a left-hand thread. Oxygen hoses are typically green and will not have a groove, meaning it is a right-hand thread. Check hoses for cracks and contaminants. It’s always a good idea to purge hoses before use. Simply adjust the regulator knob to about 5 PSI and let the gas flow for several seconds. This time may vary depending on the length of the hose. Once purged, close the torch adjusting knob or regulator adjusting screw and repeat for other hoses.
Torches can come in two pieces: the handle and its various attachments. However, single piece, or straight cutting, torches are relatively common as well.
Before adding any attachments, inspect the torch seating area as well as the thread assembly.
Always be sure to inspect your attachments before use; check the cone and that both O-rings are still present and undamaged. For cutting attachments, also check the seating end of the tip – any dents or scratches could cause a leak. Inspect cutting and heating tips to ensure holes are clear. The seating of cutting tips should be examined for scratches and dents also, and before use, make sure the lever for the cutting oxygen moves freely.
Once your attachments and tips have been connected, check your entire system for leaks. Completely back out the regulator adjuster and slowly open the torch gas valve on the cylinder until the high-pressure gauge stabilizes. Shut the torch valve off. Watch the gauge for any drop in pressure. If no leak is evident, open the cylinder valve again and adjust the regulator to deliver 20 PSI.
Repeat the process with the fuel gas, but make sure the fuel gas regulator only delivers 10 PSI. Afterward, close the valves on both cylinders. Turn the adjusting screw a ½ turn counterclockwise. Watch both gauges for a couple of minutes, and if the readings do not change, your system is not leaking.
Open the torch valves again. If the gauge needles move, that means there is a possible leak. Stop right away and do not use any leaking equipment. Check your connections, and if a leak cannot be found you should have the equipment inspected by a qualified technician.
You can also use an approved leak test solution by completely saturating all metal-to-metal connections with leak test fluid and watching for bubbles.
Purging Your Torch
Your torch should be purged to remove the chances of gases prematurely mixing. This could result in a flashback, or worse.
Completely open the oxygen valve on your torch handle, and open the preheat oxygen valve with a cutting attachment. Hold the cutting lever open for 5 seconds, then shut the oxygen valves and repeat for the fuel gas side.
For best quality cuts, ensure you are using the correct size tip. Refer to the tip charts that came with your tips for the ideal gas pressure. Flow rates might vary from brand to brand and tip size.
The longer your hose, the more pressure drop you will experience at the torch. Increase the PSI at the regulator to compensate. Adding additional gauges to the handle will help you monitor your pressure.
Support your cutting hand with your free hand, and keep an eye on your torch height. This reduces damage and/or injuries.
Shut down the oxygen first and the fuel gas last. This is another leak check. If you hear a pop or a snap, that means you have a leaking oxygen valve, but a small flame at the tip would mean it is a fuel gas leak.
To completely shut down, close both cylinder valves, and then release the pressure inside the system by opening the oxygen valve on your torch until the pressure slowly eases. Repeat on the fuel gas side. Next, ease the tension on the regulator. Turn the screws counterclockwise until they move unhindered. Check that both regulators show a zero pressure reading.
Always completely shut down your systems when you finish cutting, even if just for a short break, and never leave the oxy-fuel systems pressurized and unattended. A leaking hose or torch could cause gas to pool and create a life-threatening hazard.
Safety in the shop is everyone’s responsibility. By paying attention to your equipment and surroundings, you minimize the chances of an accident while using any oxy-fuel cutting apparatus. You also help make the shop a safe work environment for you and all those who work along with or around you.