Converting from Acetylene to Alternative Fuels
The Acetylene Shortage
Acetylene has been the cutting fuel of choice for oxy-welding, brazing, and cutting because it reaches the highest possible temperature, provides clean, efficient cuts, and offers versatility. While most welders would prefer to continue using acetylene for their oxy-fuel welding, there will be a shortage on acetylene for the foreseeable future due to an explosion at the main acetylene manufacturing plant in Louisville, KY.
While welders regularly debate in online forums the merits of acetylene verses the numerous alternatives available, the current shortage makes switching to alternatives a necessity for many welders who want to continue meeting their objectives. Without weighing in on the debate over which fuel is best for oxy-fuel cutting, this guide will provide information about some alternatives to acetylene in order to help welders find the best options for their projects.
Is It Worth Switching from Acetylene?
While many acetylene welders have had to consider switching for the first time due to the current fuel shortage, there are welders who have already switched from acetylene to propylene, propane, and the more recent HGX propane for cutting (technically “oxy-cutting)” and brazing. While some welders use acetylene for welding applications and can use MAPP as an alternative to acetylene, this guide will focus on using finding acetylene substitutes for cutting and brazing operations.
As with most welding decisions, fuel gas selection depends on the material's thickness and length of cut. Therefore, switching from acetylene to one of these alternatives will sometimes be easier depending on the nature of the project. However, with a few modifications, most welders can stay on task with one of the acetylene alternatives.
When considering a fuel gas switch, welders will need to figure out which gas can help them achieve the desired temperature for cutting Acetylene was long the favorite because it burned hotter than any other gas. However, many welders have been able to adjust their setups and techniques for alternative fuels and have been quite happy with the results. A cutting operation that uses a propane-based fuel alternative will also enjoy significant savings.
Below we’ll outline what you need to know about the alternative fuels, compare their benefits and drawbacks, and how to make the switch from acetylene.
Acetylene Alternatives for Welding and Cutting
Propane for Oxy-cutting
Propane and other propane-based fuels are frequently used as substitutes for acetylene. In fact, many cutting operations have switched over to propane in order to save on fuel costs. While propane doesn’t burn hot enough for welding, its outer cone offers a high number of BTUs. The flame for acetylene concentrates the heat inside the cone, which means that welders used to acetylene will need to adapt their technique in order to achieve the appropriate cutting temperature.
Welders who switch to propane may need to wait a little longer in order to heat the metal, but if they use the outer edge of the heat cone, they’ll find that preheating won’t take much longer than acetylene. Though acetylene tends to pre-heat faster, there are some important changes welders need to make in order to switch over to propane.
While many welders correctly note that it’s possible to switch over to propane by only changing a torch tip (see below on changing torch tips), such a limited changeover will make the propane far less effective. Propane requires a different torch (injector style) because propane is a much heavier than other fuels and flows properly through a low-pressure injector torch.
Changing to the correct torch and torch tip enables propane to reach a higher temperature than what's possible with only a new tip. In addition, an injector torch allows welders to make cuts that some claim to be cleaner and faster than acetylene. Propane also offers more versatility for bending and heating.
Much like propane, propylene is often misunderstood as ineffective as a fuel for cutting since it requires an injector torch in order to achieve optimal heat flow and cuts and concentrates the heat on the outer edges of the heat cone. Propylene requires different tips from acetylene, but they rarely need cleaning. The propylene tips provide eight holes for effective pre-heating. In other words, effectively using propylene rests entirely on having the correct torch and tip set up.
Welding Tips and Tricks recommends propylene as a great alternative, and offers the following comparison of propylene with acetylene:Advantages of Propylene:
- More stable and safer than acetylene
- No 15 psi limit on working pressures
- No soot
- More BTU's of heat for heating large parts and thick metal
- Cuts metal quickly and with a very long tip to work distance
- Acetylene prices are rising much faster than propylene
- Better heat transfer properties than acetylene
- No withdrawal rate limitations
- Can’t gas weld with it...too much pressure and too much flow rate
- Requires different tips and T grade hose
- Slight learning curve on lighting and setting the torch
While propylene has some minor drawbacks and requires an investment in some new tools, no one can deny that a cylinder of propylene will outlast acetylene at about 3 to 1, making it a cost-effective alternative for cutting. Therefore, any new equipment costs can be made up with significant fuel savings.
HGX-3 is a new product on the market that can be added to propane in order to increase its performance, creating a mixture, referred to commonly as HGX propane, that cuts metal at temperatures comparable to acetylene. One gallon of HGX-3 can be added 1,000 gallons of propane.
HGX-3 increases the flame temperature of propane gas by 15% over, reaching flame temperatures of 5400°F and uses less oxygen than acetylene. This makes HGX propane a viable alternative for welders used to the heat output and speed achieved with acetylene for flame cutting, brazing, and even some welding procedures such as aluminum welding and cast iron welding. Much like other alternative fuels, HGX propane reduces slag and makes for a smoother, cleaner cut, but it also requires specific components such as compatible tips and hoses.
One of the biggest advantages alternative fuel gases such as HGX propane have over acetylene is its supply and storage. Acetylene must be supplied in individual cylinders with a maximum capacity of approximately 400 cubic feet per cylinder, while the alternative fuel gases can be supplied in either cylinders, bulk stations, and even from a pipeline.
While HGX remains a relatively new product, there is information available online with technical information about how it works and fuel comparisons. Baker's supplies HGX at several of their locations.
MAPP for Welding
MAPP gas is one of the leading substitutes for acetylene in Oxy-welding. While other gases such as propane, propylene, and HGX Propane are more widely used for cutting and brazing, MAPP can be used in place of acetylene, even though MAPP doesn’t burn quite as hot and can be expensive for large-scale operations.
Since the current acetylene shortage resulted from an explosion at a manufacturing plant, it goes without saying that safety is a major concern when choosing a cutting gas. One welder noted that the gas delivery driver is more than happy to switch from acetylene to propane.
Acetylene generated from calcium carbide—the majority of it is generated this way—can contain toxic impurities. In addition, using acetylene in a pressurized state makes it highly unstable. These reasons alone make switching to an alternative fuel preferable.
In addition, flashbacks and backfires, common headaches and hazards for welders using acetylene, are far less common for welders using propane-based alternatives. Leading welding industry publications such as The Fabricator are quick to point out the hazards of welding with acetylene. See the following articles: Safety: the Burning Issue in Oxy-fuel Torch Use and The Basics of Oxy-Fuel Use.
Propane is the most stable cutting fuel, and when HGX is added to propane, it remains stable while cutting at temperatures comparable to acetylene. In other words, HGX propane offers the safety and low cost of propane with the same cutting temperatures as acetylene.
Every business needs to weigh the cost of their materials against their performance. While HGX, propane, and propylene require some torch modifications and a slightly different position for welding, they are generally able to provide cost-effective and efficient solutions for welders impacted by the acetylene shortage.
How to Make the Switch from Acetylene
While welders switching from acetylene to a propane-based fuel may be able to cut with a new tip, they are sacrificing the quality of their cuts, losing valuable time, and creating safety hazards. While a new tip is a given, a new torch will make effective cuts. I addition, running an R-Grade hose with an alternative fuel such as propane will deteriorate the hose over time and could lead to an explosion.
Here are the equipment changes you need to make in order to convert from acetylene:
Cylinder: Alternative Fuels are stored in different cylinders than acetylene including different sizes, wall construction, and valves.
Hose: There are many welders who assert that Grade "R" and "RM" hose are acceptable for acetylene, and they are technically correct as far as performance goes. However, “R” and “RM” hoses will deteriorate when used for alternative fuels. A Grade "T" hose will not deteriorate with alternative fuels.
Cutting & Heating Tips: Cutting and heating tips are designed for use with the related gases in order to allow for the proper level of gas flow and therefore sufficient temperatures for cutting. Learn more about the right cutting tips at The Fabricator.
Regulators: While some say that a regulator change is only necessary for those doing a lot of heating which requires a higher PSI, keep in mind that alternative fuel gas regulators have different pressure ranges and are marked specifically for the type of gas they service. These regulators will deliver the alternative fuel at higher pressures than acetylene which will facilitate the heating process. Once again, the old regulator may work, but using the wrong equipment with a new gas will sacrifice some of its performance.