Plasma/torch cutting

Stainless steel sheet stock is used to form custom products such as tees, elbows, and reducers. The sheets are cut with a band saw or plasma torch into smaller pieces and custom formed into final product shapes using various forming and bending equipments. 

Figure 10 A cut away representation of the three concentric tube design of an argon inductively coupled plasma torch. The pneumatically generated sample aerosol is entrained up through the central quartz tube and enters the hole of the toroidally shaped plasma.

In the dismantling of the metallic structures and components of the plant, conventional as well as newly developed cutting techniques are applied besides mechanical techniques, others such as plasma torch and laser cutting techniques are available. By using appropriate installations, uncontrolled dissemination of radioactive particles during this work can be reliably precluded. The subsequent treatment of the dismantled parts depends both on the level and on the state of the radionuclides associated with them. 

Steel can be cut with great accuracy using an oxyacetylene torch (see Figure 24.25). However, not all metals cut as readily as steel. Cast iron, stainless steel, manganese steels, and nonferrous materials cannot be cut and shaped satisfactorily with the oxyacetylene process because of their reluctance to oxidize. In these cases, plasma arc cutting is recommended. 

Plasma arc cutting operates on the principle of passing an electric arc through a quantity of gas through a restricted outlet. The electric arc heats the gas as it travels through the arc. This turns the gas into a plasma that is extremely hot. It is the heat in the plasma that heats the metal. A typical power source for plasma arc cutting is about the size of a small transformer welder and comes equipped with a special torch, as shown in Figure 24.29. 

Figure 12 shows, for each trial configuration, the variations in the tool wear coefficient, according to the thickness being cut. Wear in the hacksaw blade and the plasma torch nozzle are too small to be shown. 

The plasma torch is the most rapid tool from 500 to 600 mm of cut per minute in 10 mm thick steel, while the hacksaw is the slowest about 10 mm of cut per minute in 10 mm steel. The power requirement of the hacksaw is less than one tenth that of the plasma torch. 

Figure 30.17 Tape adhesion test results at various water boiling times for primer on methane-plasma treated ETA-3183 with six cross-cuts made before and after immersion into boiling water 2 3 torches, 2.0 A arc current, 1000 seem argon, 10 seem methane, 270mtorr pressure, and 1.9 s plasma exposure time.

Figure 7.29 Axial (end-on) ICP torch position showing how the shear gas cuts off the cool plasma tail plume. Light emitted from the plasma passes through the ceramic interface into the spectrometer on the right side of the diagram (not shown). [From Boss and Fredeen, courtesy of PerkinElmer Inc. (www.perkinelmer.com).]...

Hazards The plasma-cutting arc produces hot metal and sparks, especially during the initial piercing of the metal. It also heats the work piece and the cutting torch. 

---