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58 Cards in this Set
- Front
- Back
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carbon buildup from the CAC-A process left in the bottom of a groove that will be welded can cause |
a brittle weld |
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a CAC-A carbon electrode that has graphite and arc stabilizers in it can be used with |
DCEP, DCEN, and AC |
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a large travel angle of the electrode produces what kind of groove? |
wide |
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a welding power source used for CAC-A should have a minimum open circuit voltage of |
60V |
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an AC electrode with an AC welding power source produces a superior cut on wHich metal |
copper |
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an insolated standoff is used to ______ |
maintain constant tip-to-work distance |
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becore connecting two DC welding power sources in parallel, you should make sure of what? |
manufacturers representative has been consulted. |
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CAC-A on carbon, low alloy and stainless steels commonly uses? |
DCEP with a DC electrode |
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consumable PAC torch components can be interchanged between different equiptment manufacturers torches. TRUE/FALSE |
false |
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cutting nozzles are normally made of which material |
copper |
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for which CAC-A application are uncoated DC carbon elecrodes still being used |
salvage work |
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how should the air jets on a CAC-A electrode holder be positioned? |
between the electrode and the work piece |
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if the air pressure is too low to blow the molten metal from the cut, you should____ |
decrease travel speed |
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if you need a groove 10 mm (3/8 in.) wide, wich electrode size should you use |
6.4 mm (1/4 in.) |
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in which welding position should the carbon electrode be pointing almost parallel to the electrode holder |
overhead |
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it is important that there is enough air pressure and volume to |
blow away molten base metal. |
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pac torches that use compressed air as the plasma and cooling gas are commonly used to cut ____ |
low carbon steel |
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regardless of design every PAC torch uses a |
plasma gas |
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the carbon electrodes used in CAC-A are actually made with _______ |
Graphite |
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the ceramic heat shield on a PAC torch must not be subjected to ________ |
rough handling |
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the choice of plasma gas is decided by the______ |
type of metal being cut |
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The compressed gas or air for CAC-A is most often supplied by? |
an air compressor
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the cooling gas in an air cooled torch blows |
between the heat shield and the cutting tip |
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the current requirements for CAC-A are generally _________ for smaw
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higher than
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the purpose of the pilot arc is to
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initiate the main arc
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the usual PAC power source is either an inverter or ______
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a high voltage transformer-rectifier
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what is one method to increase the depth of the groove being cut?
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decrease travel speed
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what is the advantage of inverter type power sources for PAC
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small and light weight
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What is the air pressure required for medium to heavy duty CAC-A?
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550 to 700 kPa (80 to 100 psi)
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what is the main differance between a CAC-A electrode holder and a smaw electrode holder?
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The air jet orifices
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what is the purpose of the copper coating on some CAC-A electrodes
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reduces their rate of burning
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what is the recommended current settings for a 6.4 mm (1/4 in.) DC carbon electrode
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200 to 400 A
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what is the recommended electrode stickout when you use CAC-A?
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100mm to 150mm (4 to 6 in.)
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What size welding cable is reccomended for CAC-A applications?
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4/0
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when too much molten metal sticks to the edges of a cut what is the usual cause?
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the air pressure is too low
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when using CAC-A you should
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start the air flow then strike the arc
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which factor is the most important in determining the with of the groove?
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electrode diameter
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which gas is often used as a secondary gas for cutting stainless steel?
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carbon dioxide
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which gas must never be used as a compressed gas in CAC-A
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Oxygen
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which is NOT a type of carbon electrode used in CAC-A
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AC bare electrodes
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why is it sometimes necessary to cconnect DC welding power sources in parralel?
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To increase current capacity.
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why should the carbon electrode not touch the workpiece when you use CAC-A
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carbon is deposited in the groove
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wich plasma gas produces the best results on stainless steel
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nitrogen
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which polarity is used for PAC
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DCEN
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wich type of groove preperation are flat electrodes designed for
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wide, shallow grooves
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wich type of plasma gas is commonly used to cut carbon steel
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compressed air
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You are connecting DC welding power sources in paralell, how would you connect them?
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positive to positive and negative to negative to increase
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your carbon electrode burns away very quickly and starts to glow red after gouging for only a few centimeters, the correct action is to _______
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reduce the amperage setting
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which factor or factors must you consider when preparing to make a plasma cut |
thickness and type of metal |
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when you cut thicker metal, you might have to __________
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increase the current setting
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the best cuts on thin material are produced with ___________ |
a low standoff distance |
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one cause of double arcing is _________ |
a blocked tip orifice |
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a damaged heat shield can cause __________ |
the tip to overheat |
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the parts of a PAC torch that must be periodically inspected and replaced are called __________ |
consumeables |
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"double arcing" describes what happens when a small arc appears between the electrode and the ______ |
cutting nozzle |
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double arcing is harmful because it ____________ |
damages the cutting nozzle |
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which operating variable has the most effect on cut quality? |
travel speed |
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insufficient gas pressure can cause what problem? |
double arcing |
