Cutting Torch Operations

By Thomas F. Kenney

A while back I was speaking with one of the big names in fire and rescue about rescue tools, and he said that the use of cutting torches is a lost art in the fire service. I don’t think it is lost as much as it has been pushed aside by new technology in tools, changes in operating procedures, and an overall decrease in training. Never underestimate the simplicity and dependability of oxygen-acetylene cutting in forcible entry and rescue situations involving ferrous metal. Like all of the other tools we carry, it is only as good as the firefighters operating it. The basic principles of operating the torch really haven’t changed in the past 100 years. However, the torch has been made safer, more portable, and more efficient.

The American Welding Society defines the cutting torch process as oxygen and fuel cutting. The fuels available vary and include acetylene, propane, and gasoline. This article focuses on understanding the oxygen-acetylene cutting torch and the role it can play in technical rescue, fireground forcible entry, and rapid intervention.

Success with cutting torches requires knowing the process, appreciating the components, following the safety issues, and practicing hand-to-eye coordination as well as torch height-to-speed coordination. Keep in mind that the oxygen fuel cutting process is originally for production and fabrication. The fire service chooses the tool to take things apart, and usually with an urgency not required in industry. This has resulted in some cutting information and calculations having importance in industry but not in fire and rescue operations. Our goal when using the torch is to safely, quickly, and completely cut steel. We are not going to be putting it back together. Total consumption, kerf widths, and cut edge conditions are not priorities in most of our situations. Safe, quick, and efficient cuts are.

TORCH COMPONENTS

Tips are the working end of the torch. They are designed with a series of outer holes to create the preheat flame comprised of acetylene and oxygen and a center hole for the delivery of the oxygen jet used to oxidize or blow away the molten steel-two distinct actions from two locations within one tip. The thickness of the steel to be cut determines the torch’s tip size. The tip size used in the torch determines the pressures at which the regulators are set. This information is found on the tip chart the torch manufacturer provides.

In addition to tip sizes and pressures, the chart provides information on the volume of gases used. The acetylene cylinder size in relation to the volume consumed by a given tip is an issue. The industry rule for drawing acetylene requires that no more than one-seventh of the cylinder be used per hour for continuous cutting. To determine how much acetylene we are using, we refer to the manufacturer’s tip chart. It is shown in cubic feet per hour. Multiply that by 7, and you know if your cylinder will feed that tip. Each manufacturer has engineered values on the tip chart to operate the tip in the most efficient and safest manner. The pressures listed on a tip chart not only provide the most efficient flame for cutting that size steel but also are engineered to cool the torch.

There is no firehouse formula for setting regulator pressures. The regulator is a precision instrument that allows gas to be taken from a cylinder in a safe and controlled manner. Regulators are specific to the gas they are designed for and have a thread compatible with that very gas. Oxygen regulator threads are all the same, whereas acetylene cylinders have four available threads.

You must use the right regulator with the right cylinder. Fire companies use various sizes of acetylene cylinders, but we are often restricted in the cylinder size by the storage space we have on the apparatus (photo 1). This also restricts the torch tip size. The cylinder size dictates available volume; the tip determines consumption. Keeping the one-seventh rule for acetylene in mind, you could simplify things by saying “Small cylinders, small tips; big cylinders, big tips.”

(1) Photos by author.

There are no rules on consumption of oxygen; most often, oxygen cylinders are paired with acetylene cylinders of like sizes. Two types of torches are commonly used: a gas welding torch with a cutting attachment and straight cutting torches. The gas welding torch allows different attachments such as a welding tip or a heating tip to be connected.

The handle is often referred to as a mixer. It has two wheel valves at the incoming end: One valve controls oxygen, and the other controls fuel (photo 2). When the cutting attachment is added, it has a valve on it to control preheat oxygen and has the lever for cutting. A straight cutting torch just has two wheel valves at the incoming end and a lever for cutting.

PREPARING FOR USE

Whichever torch you are using, the lighting procedure is the same, as are the skills required. The six-step method of fuel, spark, fuel, oxygen, oxygen, oxygen is a simple format to follow to light and set a cutting torch flame.

Once the torch is lit and the flame is set, you are ready to cut, so wear your safety equipment before lighting. The equipment varies for the cutting task you are undertaking. The minimum safety ensemble for a firefighter would be turnout gear, eye protection, and leather gloves (to protect against radiant heat and slag). The gloves are not for picking up molten metal, and clearly synthetic rescue gloves are not suited to this task.

Molten slag will go through turnout gear as well, so consider the position the torch operator will be working in. Out of position cutting, such as lying down, may put the torch operator under a rain of molten slag, one speck of which can end a career if it ends up in your eye or your eardrum. You can add ear plugs, a hood, and a respirator to protect the operator.

The type of operation, such as forcible entry vs. collapse rescue, can also dictate what to wear. Use appropriate safety gear! Also consider fire protection when using the torch’s open flame. In rescue situations involving cutting close to a patient, consider cooling the metal and preventing heat transfer as well as covering the patient to protect against slag.

CUTTING STEPS

With gloves on and goggles in position, ease on the wheel valve for acetylene (step 1) and strike a spark in front of the tip at the same time (step 2). The intent is to start with a small acetylene flame, so ease it on as you’re sparking it. Once lit, continue to slowly increase the acetylene and watch the black smoke produced start to disappear-but not to the point of the flame leaving the tip (step 3). Next, slowly introduce preheat oxygen with the oxygen wheel valve. You will see changes in the flame as it turns from yellow to blue. Continue to introduce preheat oxygen until the tip establishes clearly visible inner cones on the tip (step 4). Squeeze and hold the cutting lever (step 5). If you notice any changes in the shape or size of the flame, then while holding the cutting lever, add additional oxygen with the oxygen wheel valve (step 6) until you have a clean, distinguishable flame with all tips of the preheat flame the same size (photo 3). If you have set the regulator pressures according to the tip size and followed this six-step lighting process, then it is a tip height-to-speed hand-eye-coordination task.

Cutting torch tip position is everything. The height of the torch tip in relation to the work piece is critical. The tip needs to be ¼ to 3⁄8 inch off the piece-too far away, and the steel doesn’t get hot enough, which slows or prevents your cut altogether; too close, and the steel will get too hot and want to melt back in behind the cut.

The direction in which the torch tip is pointed dictates the directions in which the heat is going and the slag will be blown. Consider the four types of cutting positions most commonly used: edge, forehand, backhand, and piercing.

Edge. With edge cutting, the torch tip is pointed down onto the work piece, keeping the starting point on the edge. Once the edge is bright red, squeeze and hold the cutting lever to initiate cutting (photo 4). Maintain the height of the tip off the work and the speed of the torch movement across the work equally. A steady stream of slag should be coming off of the bottom of the piece being cut. If slag is bubbling up and out of the kerf, the cut is not all the way through. Since the speed of travel across a work piece depends on the metal getting up to melting temperature to be blown out of the way, you must hold the tip steady at the same height off the work piece during the cut. This will ensure a continuous temperature hot enough to melt the steel and allow it to be blown out of the way.

Forehand. A forehand cut starts off the same as an edge cut, but continue it by rotating the torch tip in the direction you want. Provided the tip size is adequate for the steel size, the cut can be faster; every British thermal unit is preheating the steel in the direction of the cut. Remember that the direction of the tip also dictates the direction in which the slag is blown. This may be a consideration in cuts made close to a victim.

Backhand. Backhand cutting also starts off as an edge cut; however, rotate the torch tip back toward the initial kerf. The results are a slow, choppy cut because of heat lost in the kerf. You can improve the cut with a side-to-side motion that widens the kerf. The only advantage to backhand cutting is that the slag will be directed away from the cut.

Piercing. Piercing is used to get an initial hole in the work piece. Once you have created the hole, you are back to edge cutting. The difference is on the initial pierce: There is no place for the molten slag to go, so an aggressive piercing will provide the torch user with a face full of slag. To avoid this problem, hold the torch on the spot until you reach the melting temperature and before you apply the cutting oxygen, tilt the torch tip away and ease the cutting oxygen on. Once the slag starts to fly away, rotate the torch tip to the straight up-and-down position while applying cutting oxygen full force; at that point, you are back on an edge cut.

Before the next cutting torch job, grab the torch off the rig, review safe operating practices, put on the safety gear, light it up, and practice your cutting techniques. Start with simple cuts on stock such as rebar, flat bar, chain, and expanded metal. Then move on to bigger continuous cuts such as box iron and I-beams. The results of your drill time will enhance your skills and allow you to recover that lost art.

Thomas F. Kenney is a 33-year veteran and a lieutenant with the Hyannis (MA) Fire Department. He is a rescue team manager and structural collapse instructor for DHS FEMA and Massachusetts USAR Task Force 1. As a partner with Heavy Rescue Incorporated, he teaches fire and rescue programs for Barnstable County Fire Academy, New Hampshire Fire Academy, and the FDIC.

Thomas F. Kenney will present “Fire and Rescue Cutting Torch Operations” on Thursday, April 10, 10:30 a.m.-12:15 p.m., at FDIC 2014 in Indianapolis.