Chapter 15 Oxyfuel Gas Cutting 427 Copyright Goodheart-Willcox Co., Inc. 15.5.7 Gouging with the Cutting Torch Gouging is a process that removes metal from the sur- face of a part to a desired depth. Proper gouging cuts a U-shaped groove into the surface of the base metal. Gouging can be done with the oxyfuel gas process or one of several arc cutting processes. Gouging can be used to open up a defect (crack) in a part and provide a well-shaped U-groove in prepa- ration for a weld repair. It can also be used to cut out areas of a completed weld that are judged to be defec- tive, preparing the weld for rewelding. Oxyfuel gas gouging differs from oxyfuel gas cutting. For gouging, a lower oxygen cutting pressure and a special larger-diameter cutting tip orifi ce are used. The resulting lower-pressure oxygen jet allows the welder to move more slowly along the gouge line with- out cutting through the base metal. See Figure 15-33. The less forceful oxygen stream oxidizes the surface metal only and penetrates more slowly. This enables the welder to gouge or groove the base metal with greater accuracy. In a gouging tip, there are fi ve or six preheat ori- fi ces to provide an even distribution of the preheat fl ames. Some gouging tips have a small bump on the underside of the tip. This small bump helps the welder to achieve a more even depth of gouge by keeping the tip at a uniform distance above the metal surface. An automatic cutting machine with a gouging tip is capa- ble of creating a gouge with a very accurate depth and width. If the gouging cut is not started properly, the torch can cut too deeply or actually cut through the entire thickness of the base metal. The speed at which the torch is moved along the gouging line is important. Moving the torch too quickly creates a groove that is too shallow and narrow. Moving the torch too slowly creates a gouge that is too deep and wide. 15.6 Automatic Cutting Welding and cutting automation can be broken down into two basic categories: fully automatic and semiau- tomatic. The operation of automatic cutting equip- ment is controlled by a controller or computer. A cut- ting process that is fully automated does not require any manual adjustment of the equipment controls during cutting. Automated welding and cutting also requires only occasional or no observation of the weld or cut. The welder’s involvement is limited to acti- vating the machine to initiate the welding or cutting cycle. The controller or computer is programmed with the path and speed of the torch, torches, or cutting equipment. Solenoid valves start and stop the fl ow of gases. Electric motors, actuated by the controller or computer, precisely control the movement of the torch or torches. Because of these features, automatic cut- ting equipment produces identical parts every time. Feedback controls monitor the automatic cutting process and make necessary corrections. Feedback control may include vision devices that are used to keep the preheating fl ames at a specifi ed height above the base metal at all times. Manual cutting, defi ned as cutting with a torch that is manipulated by hand, is still the best process for many assemblies. However, implementing semiau- tomatic systems can increase quality, productivity, and profi tability. In semiautomatic cutting, the torch is held and moved by a mechanical device and manually adjusted by the welder in response to visual observations of the cut being made. The welder’s intervention consists of adjusting equipment controls as needed while the cut- ting operation proceeds. An example of a semiautomatic cutting operation is mounting an oxyfuel cutting torch on a motorized car- riage. The carriage moves at a constant speed along a track, usually to cut a straight line cut. See Figure 15-34. An OFC torch on a motorized carriage can be used to cut fl at plate and can also travel around large pipes. The oxygen and acetylene tanks, hoses, and regulators that support the automatic and semiautomatic OFC outfi t are turned on in the same manner as is done for man- ual cutting. Goodheart-Willcox Publisher Figure 15-33. A typical oxygen gouging operation. A low-velocity cutting jet is used to maintain better control of the gouge width and depth.