|A hydraulic rescue tool blade is intentionally broken with extreme force in a press to test its limits. (Champion Rescue Tools Photo)|
Broken hydraulic rescue tool blades continue to be the number one cause of catastrophic tool failures in the field. With those failures comes an increase in firefighter and patient injuries and near misses. Since rescue tool blades are known to come apart under so much pressure that pieces can be propelled at upwards of 2,700 feet per second, it is remarkable that we haven’t seen more injuries.
So what do we, as firefighters, need to know to accomplish our jobs successfully and safely while using these metal-cutting monsters? First and foremost, we need to understand that not all rescue tool blades are manufactured in the same way, or out of the same material.
Rescue tool manufacturers make their own blades, and there is no industry standard by which they are made. Nor is there a National Fire Protection Association or other fire service standard governing them. The NFPA does have its 1936 Standard for Powered Rescue Tools. This standard lists, among other things, categories that rate rescue tools according to their ability to cut given materials. NFPA 1936 does not, however, deal with what materials should be used to make the blades or how blades are manufactured or how they should be maintained or when they should be replaced.
If you are not familiar with the NFPA 1936 standard, I would encourage you to take a look at it to round out your understanding of NFPA’s involvement (or lack thereof) with powered rescue tools. It will also help to make you a more informed consumer if you happen to sit on a department’s tool committee.
Current rescue tool blades are typically forged, cast, or cut from solid plate and laminated. The most common type of tool blades is forged. Forged blades are made of steel or alloy that is superheated (not liquefied) and then formed/pressed into the shape of the blade. For a simple reference, forging is the same process by which horseshoes are made and formed by blacksmiths (also known as farriers). The metal for horseshoes is heated to cherry red and then hammered and bent into shape to fit the horse.
Cast blades are made (simply stated) using processes by which the metal is heated into a liquid and then poured into molds. The gross variables in making forged and cast rescue tool blades are primarily found in the percentages of ingredients added to the steel used to help give it its strength; the purity of the added ingredients; and the quality control of the forging or casting process. If one or more of the aforementioned variables deviates, the resultant blade could be compromised. Forged and cast blades are then milled into their final shape and heat treated accordingly.
The other type of process used to make rescue tool blades today is laminating. I know of only one rescue tool manufacturer in the United States that uses this process, Champion. Laminated blades start with certified tool steel, which is then milled from its original plate or bar state into the structures that will make up the tool blade. These structures are then laminated together using a specialized welding process. Champion said it makes laminated blades to incorporate a patented safety tether into its blade design, something that would not be possible with a forging or a casting process.
All rescue tool blades are heat treated in various forms and fashions to give them their strength and cutting edges. The harder that a rescue tool blade, or a portion of it, becomes, the easier it is to use for cutting. However, the harder the blade becomes, the more brittle and prone to breakage it becomes.
A balance must be struck between hard and brittle in rescue tool blades, as we want the blades to be hard enough to cut or fracture the metal we’re working on, but we don’t want the blade to be so brittle that it breaks or chips. The need for this balance receives its biggest challenge from the ultrahigh-strength steel (Boron) used in today’s vehicles. This metal is so hard that it actually needs to be fractured as opposed to cut. This means that today’s tool blades need to be hard enough to cut and fracture ultrahigh-strength steel and not be so brittle that the blade fractures while trying to make the cut.
Metal has what is known as a “modulus of elasticity,” meaning it has elastic properties. This is relative to our discussion of rescue tool blades because we have learned that tool blades have a certain amount of “flex” calculated into them (due to their modulus of elasticity). We often think of the flex in tool blades when we see or hear about blades that skewed, or separated. What may come as a surprise is that blades can also flex toward each other, causing them to bind, and actually wear against themselves while cutting, potentially causing catastrophic breakage. So, to add to the mix, the modulus of elasticity of the metal in tool blades must also be considered during the manufacturing and heat-treating processes.
Many, if not all, rescue tool manufacturers put their blades through rigorous testing, wherein (in a controlled environment) they exert forces on the blades that are usually greater than those that can be exerted by the tool itself. The intent is to break the blade. The results of these tests give manufacturers information about when, where, and how these blades will fail, so as to help them (hopefully) improve on their design and/or on one of the many manufacturing processes that goes into building cutter blades.
Another common variable and difference among rescue tool blades is how they are bolted together. Most blades on the market today require regular preventative maintenance after each use to make sure that the blade bolt assemblies (the point where the blades are bolted together) are adequately greased and retightened. With the extreme forces being generated through the blades by today’s hydraulic rescue tools, a constant vigil must be kept on these bolt assemblies to make sure they remain safe for use.
Champion uses a patented flat, hardened, steel bearing insert as part of its blade bolt assembly. The company claims it eliminates the need for regular tightening and greasing of the blade bolt assembly.
As we come full circle, we must remember that until recently (the last three to five years), hydraulic rescue tools and their respective blades were only required to make cuts that in most instances required less than 150,000 pounds of cutting force to accomplish. In just those few short years, these same tools and blades that we use are being challenged with cuts that now require 300,000 pounds of cutting force (and more) to complete.
If tools and blades being sold in 2010 are failing on metals found in new vehicles, how could we possibly expect older tools to keep up with the current demands for blade and tool strength?
Editor’s Note: Carl Haddon is the director of Five Star Fire Training LLC, which is sponsored in part by Volvo North America. He serves as assistant chief and fire commissioner for the North Fork Fire Department in Idaho and is a career veteran of more than 25 years in the fire and EMS services in southern California. He has also served since the 1980s as a fire/safety director for numerous racing organizations, including Penske Motorsports, NASCAR, USAC and Mickey Thompson Racing. He is a certified Level 2 fire instructor, an ISFSI member and teaches 5 Star Auto Extrication and NFPA 610 classes across the country.