• Place a person on fi re watch. Sparks and hot metal can go through cracks into other areas or fall onto other fl oors of a building. • Do not heat, cut, or weld on tanks or other containers until appropriate safety steps have been taken. Containers may have been used to store explosive or chemically toxic materials. Specifi c steps for cleaning must be followed to ensure that explosions do not occur. The local fi re or industrial safety department can advise you on how to clean a container properly prior to welding. • Wear earplugs in any workplace where there are very loud noises. Ear plugs also keep sparks out of your ears when welding out of position. • Wear safety glasses when chipping. Wear fl ash goggles under the welding helmet for protection from refl ected rays. • Use engine-driven welders only in an open, well-ventilated area. Vent exhaust fumes outside. Striking an Arc An electrode holder is generally held with one hand. It can be gripped like a hammer or screwdriver. The electrode lead may be draped over the lower arm to make the electrode holder feel lighter. See Figure 12-1. In order to strike an arc, the electrode must fi rst touch the base metal. The electrode should only remain in contact with the base metal momentarily. This causes electricity to start fl owing. The electrode is then pulled a short distance away from the base metal. Current continues to fl ow across this gap, creating an arc. Most electrodes have a relatively thin covering of fl ux. When an arc is struck using a thinly covered electrode, the arc can be seen. An open arc is an arc that can be seen. Two methods are used to strike an arc. In the fi rst method, the welder scratches the electrode on the metal and then withdraws it. The second method is to use a straight up-and-down or pecking motion. See Figure 12-2. After the arc is struck and stabilized, it is brought down to the correct arc length. The arc length is the distance between the electrode and the base metal. This distance should be approximately equal to the diameter of the electrode. If the arc is not struck correctly or if the arc length is not maintained properly, the electrode may become welded to the base metal. To release the electrode, proceed as follows: 1. Keep your welding helmet down and release the electrode from the electrode holder. 2. Lift your helmet. 3. Place the electrode holder on an insulated hook. 4. Grasp the electrode near the base metal. Bend the electrode back and forth until it breaks free. Arc Blow When electric current travels through a wire or an electrode, a magnetic fi eld is created around the wire or electrode. The magnetic fi eld changes direction as the current changes direction. See Figure 12-3. The arc is defl ected from its normal path by these magnetic forces. This defl ection is called arc blow and can present a challenge during arc welding. When alternating current (AC) is used, the magnetic fi eld is continually canceled as the current changes direction. Therefore, arc blow is not a problem when AC is used. However, when direct current (DC) is used, the current fl ows in one direction and a strong magnetic fi eld may develop. A magnetic fi eld travels best through a conductive Goodheart-Willcox Publisher Figure 12-1. The electrode holder can be held like a hammer. Draping the electrode lead over the forearm makes the holder feel lighter. Chapter 12 SMAW: Flat Welding Position 169 Copyright Goodheart-Willcox Co., Inc.