A Conduct electricity B Focus the plasma arc C Spin the compressed air D Control the temperature
28 What is the recommended torch standoff of an extended tip in inches
A 1 B frac12 C frac14 D 18
29 The tip size of the torch is directly proportional to what PAC characteristic
A Voltage B Amperage C Speed rating D Material composition
30 What is the recommended pierce starting position of the PAC torch in relation to
the workpiece
A Perpendicular to the workpiece B Parallel to the workpiece C Slightly angled away from you D Slightly angled toward you
31 What is the PAC current selection based on
A Ambient temperature B Type of electrode C Thickness of the workpiece D PAC manufacturer
32 The PAC should be inspected at the beginning of what
A Project B Workday C Workweek D Month
33 The condition of torch consumables is directly related to what torch
characteristic
A Cutting speed B Production efficiency C Output amperage D Duty cycle
34 What does a kerf refer to on the workpiece
A Molten material left on the bottom of the workpiece B Amount of material removed by the cutting process C Direction of travel of the gas swirl D Bevel angle on the edge of the cut
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35 What are drag lines on the surface of the cut
A Ripples along the surface of the cut B Scratches left by the torch tip C Gouges left by the grounding strap D Measurement marks
36 What causes top edge rounding on a cut edge
A Torch is too close to the workpiece B Torch is too far away from the workpiece C The arc is hotter at the top of the cut D The arc is cooler at the top of the cut
37 How often should an electrode be replaced
A Once a day B Once every ten hours of operation C After significant wearing appears D After every job
38 Which gas is considered to produce the least dross
A Compressed air B Hydrogen C Argon D Nitrogen
39 What is the effect of oxidation on a workpiece
A Increases melting temperature B Causes the metal to warp C Increases welding quality D Causes a crystalline deposit
40 How do you determine the maximum cutting speed of a PAC torch
A Arc current nozzle diameter and metal thickness B Arc current electrode material and type of metal C Gas pressure nozzle diameter and metal thickness D Gas pressure electrode material and type of metal
41 Why is very little workpiece preparation necessary after plasma cutting
A Preciseness of the arc B The lack of chemical reactions C The low temperature used D Potential harm to material
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42 What causes a bevel angle on one side of a workpiece
A Amperage and angle of the torch B Direction of swirl of the plasma gas C Size and standoff of the torch D Standoff and amperage of the torch
43 How do you correct a negative bevel angle
A Decrease the torch speed B Increase the torch speed C Decrease the torch angle D Increase the torch angle
44 What occurs to the workpiece when the cutting speed is too slow
A Kerf gets sharper edge B Less dross is formed C Kerf gets wider D Oxidation increases
45 What has the greatest effect on the appearance of drag lines
A Amperage and angle of the torch B Height and speed of the torch C Speed and amperage of the torch D Standoff and amperage of the torch
46 What ANSI standards should be followed when selecting the proper filter glass
shade numbers
A Z491 B Z591 C Z691 D Z791
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Trade Terms Introduced in this Chapter Dross The oxidized material that melts during cutting and adheres
to the workpiece
Hafnium A grey metallic element that resembles zirconium chemically and is found in zirconium minerals used in filaments for its ready emission of electrons
Kerf The groove or cut made by the cutting torch
Ionized A gas is acted upon by the intense heat of plasma causing a net electric charge by adding or removing one or more electrons
Oxidation The deposit that forms on the surface of a metal as it oxidizes This deposit increases the melting temperature of the metal causing uneven flow of welding material and therefore a bad weld
Plenum The state or space in which a gas usually air is contained at a pressure greater than atmospheric pressure
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Additional Resources and References This chapter is intended to present thorough resources for task training The following reference works are suggested for further study This is optional material for continued education rather than for task training Basic Plasma Theory Hypertherm New Hampshire 2000 Colt Jim The Evolution of Plasma Cutting Hypertherm New Hampshire 2004 Plasma Cutting and Gouging Miller Electric Manufacturing Company 2009 Plasma Cutting Guide Miller Electric Manufacturing Company 2009 Safety Quick-Guide for Arc Welding and Cutting the Safe Way Miller Electric Manufacturing Company 2007 Welding and Allied Processes S9086-CH-STM-010CH-074R4 Commander Naval Sea Systems Command Washington DC 1999 Welding Theory and Application TM 9-237 Department of the Army Technical Manual Headquarters Department of the Army Washington DC 1976
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