Level 1 Textbook highlights Flashcards
Extension lives should be separated by a distance of what?
1.6 mm
What are centrelines used to indicate?
The centre of holes and cylinders
What are the two types of leader lines?
An arrowhead and a black dot instead of the arrowhead
What do phantom lines show?
Alternate positions of moving oarts
What effect do we want to avoid by using a fillet weld?
Notch effect
What are conventional dimensions used for?
Welded fabrication of tanks, hoppers, bases and frames when tolerance is not rigid.
What are running dimensions primarily used for?
Structural fabrication of columns, beams and trusses.
How is the thickness of steel sheet specified?
Gauge number or millimetres
What does HSS stand for?
Hollow structural sections
What does UNC and UNF stand for?
United National Coarse and United National Fine
What does ‘Class of thread fit’ mean?
The degree of tolerance allowed in the fit of the threaded fastener
Unless otherwise specified in the specification, what type of thread is it?
A right-handed thread
What is another name for shop drawings and what other drawing are they developed from?
Fabrication drawings developed from engineering drawings
What does AISI stand for?
American Iron and Steel Institute
What does ANSI stand for?
American National Standards Institute
What does BP stand for?
Base plate
What does ELL stand for?
Elbow
What does F&D stand for?
Flanged & Dished
What does P&ID stand for?
Piping and Instrumentation Drawings
A spool is a collection of what?
Pipes, associated components and fittings that form a required assembly or sub-assembly to be fabricated and shipped.
What is the takeoff formula?
Takeoff = (centre to centre length) - (total length of fittings) - (total length of gaps)
What is the faying surface?
The mating surface of a workpiece in contact with or near another workpiece to which it is to be joined
The flange on a T-joint must project at least what?
Twice the fillet weld size to permit the weld bead to be deposited.
As per CSA Standard W59, the minimum overlap of parts in a lap joint shall be what?
5x the thickness of the thinner part joined and not less than 25 mm, while the gap between the mating surfaces should not exceed 2 mm.
What is the formula for theoretical throat?
TT = leg x 0.707
When joining two different thicknesses of material with a butt joint, what must the end of the thicker section be tapered at?
No more than 1:2.5
In an edge weld, what is fused?
The full thickness of the member
What is the strength of a fillet weld governed by?
The effective throat thickness
What is the effective throat thickness?
The shortest distance from the root of a weld to its face, less any convexity.
Where are intermittent fillet welds mostly used?
Mostly on lap and t-joints, sometimes square joints
What is a joint with backing?
Used when there is no access for welding from the other side
When is a back weld used?
It’s used on the other side of the joint after a single groove weld is made
When are melt through welds used?
When complete joint penetration and root reinforcement is required in welds made from one side.
When is backgouging performed?
When welding is required from both sides, it may be necessary to remove base and weld metal from the second side to ensure that complete joint penetration is achieved.
What position are stringer beads normally used for?
Horizontal and overhead positions
What is referred to as a GF assembly?
A single bevel groove weld with a specified root opening and backing
For thicker plates, why are unequal double groove preparations made?
Minimize the tendency of distortion
Having prequalified joint status allows the regulatory authority to approve what?
The procedure without the requirement of mechanical testing
What is a flare groove weld?
A joint that is the result of one or both parts of the joint consisting of a 90• bend or convex surface in section that is produced.
What is the cheapest and quickest method of preparing straight edges on a plate up to 3/4’’ thick?
Shearing
Saws are versatile and effective tools for what?
Cutting. Shaping and bevelling material.
Bevelling by grinding is usually limited to a bevel depth of what?
3-5 mm
What grit size will basically polish the surface?
100-150
What grit size is for rapid stock removal and rough grinding?
24-40
Oxy-fuel cutting is what type of reaction?
Chemical
What colour is the acetylene vs oxygen hose?
Acetylene red, oxygen green
For a neutral flame, what ratio of oxygen to acetylene is needed?
1.0 - 1.0
For a carburizing (excessive acetylene) flame, what oxygen vs acetylene ratio is needed?
0.9 oxygen - 1.0 acetylene
For an oxidizing flame, what oxygen vs acetylene ratio is needed?
1.5 oxygen - 1.0 acetylene
For an edge prep where the top edge is melted and rounded, the face is irregular with deep gouges, and bottom edge very rough and regular: where was the fault?
Cutting speed too low
For an edge prep where the top is fairly sharp with slight beading, draglines have pronounced backward rake and considerable undercutting just below top edge: what was the fault?
Cutting speed too fast
For an edge prep, when the top edge is badly melted and rounded over with the face otherwise square: where was the fault?
Preheat flames too high above the work
For an edge prep, where there is a noticeable taper from top to bottom of cut and considerable undercutting below the top edge: where was the fault?
Cutting oxygen pressure too high
For an edge prep, the top edge is slightly rounded, heavy beads along top edge, face is smooth and square, bottom edge sharp and could actually be considered a fairly good cut: where was the fault?
Preheat flames too close to the work
For an edge prep, where the top edge is rounded over, heavy beads along entire length of top edge with a considerable taper from top to bottom cut: where was the fault?
Preheat flames too long
What may be problematic during OFC of light-gauge sheet metals?
Distortion, considerable buckling and warping
Carbon arc gouging is performed using CC power sources provided what?
They have a high open-circuit voltage of at least
60 V
CAC-A is thought of as a cutting process, but it is frequently used to what?
Remove weld defects when repairing or modifying existing weldments
What type of electrode is a good general purpose solution to removing metal and maintaining a consistent tip size?
Pointed electrode
What type of electrodes are designed to be joined together so the stub can be consumed to reduce waste?
Jointed electrode
What type of electrode is mainly used to make wide, rectangular and shallow grooves?
Flat
What electrode produces both a shallow and broad groove?
Half round
What process is mainly used to cut metals that are difficult or impossible to cut using the oxy-fuel process?
Plasma arc cutting (PAC)
For PAC, the gas is ionized by what current?
High voltage direct current
What is capable of conducting an electric current due to the ionized particles and behaves like a metal conductor?
Plasma
Plasma is an ionized gas this is created by super heating a gas so that…..
It’s molecules are separated into ionized atoms
Which transferred arc mode does the current go through the piece?
Transferred arc mode
What is the surface condition produced in the plasma arc process?
Rough bevelled side
The PAC process uses what kind of power?
DC/CC
PAC power sources are usually designed with a very high open circuit voltage of usually what?
120-400 V
What shielding gas is best for cutting carbon steels?
Oxygen
What shielding gas is best for aluminum and stainless alloys?
Nitrogen
What shielding gas is the universal second choice because of its convenience and economy?
Air
PAC has a fast cutting speed of up to what?
7620 mm (300’’) per minute
With PAC, the HAZ in aluminum plate will be deeper than those in a stainless-steel of the same thickness, because of what?
Higher thermal conductivity in aluminum
Surface hardening in the HAZ of a plasma cut is minimal while using what as the plasma gas?
Oxygen
What is the acronym for laser?
Light amplification by stimulated emission of radiation
A laser is monochromatic. What does monochromatic mean it has?
One wavelength
What is a gas laser?
An electric current is discharged through a gas medium to produce coherent light
The gas laser was the first laser to operate on the principal of what?
Converting electrical energy to a laser light output
What temp does the material have to be in water jet cutting?
COLD
The effective throat size will always be what on the what symbol?
In brackets
A plug weld is made with what type of hole?
Circular
A slot weld is made with what type of hole?
Elongated
The difference between a backing, spacer and consumable insert symbol:
Backing is a rectangle, a spacer is a box on the reference line, a consumable insert is a square
What 3 weld symbols are depicted by a rectangular? And what’s the difference?
Plug, slot and backing.
The backing symbol will be accompanied by a groove weld symbol opposite the reference line
What does RSW stand for? And what’s does this symbol look like?
Résistance spot welding, a circle straddling the reference line
What does coalescence mean?
The joining or merging of elements to form one mass or whole
What is a seam weld?
Continuous weld produced between overlapping members with a coalescence initiating and occurring at faying surfaces
What does a seam welding symbol look like?
A circle straddling the reference line with two horizontal lines through it
What does a stud weld symbol look like?
A circle with an ‘X’ in it
What does TB stand for?
Torch brazing
When there is a weld size and effective throat size depicted on the weld symbol, in comparison to each other, what will they always be?
The size will always be more and the effective throat will always be low
The percentage of NDT required will be where in relation to the NDT symbol?
Right of the symbol
What does AWS stand for?
American Welding Society
How does the AWS group categorize welding processes?
PRIMARILY, on the mode of energy transfer, SECONDARY, on the influence of capillary action in effecting distribution of filler metal in the joint (as in brazing or soldering)
Soldering is done at what temp?
Below 450•C
Brazing is done at what temp?
Over 450•
What does SSW stand for?
Solid state welding
What temp is SSW done at?
Below melting point (no melting occurs)
Which welding processes are by far the most commonly used processes in welding?
Arc welding
What is the ionized gas region between the electrodes called?
Plasma
What 4 processes use a consumable electrode?
SMAW
GMAW
FCAW
SAW
Name 3 processes that produce an autogenous weld:
GTAW
Electron Beam
Laser welding
What type of current do SMAW and GTAW use?
CC
What is the arc efficiency of SAW?
90-95%
What is the arc efficiency of SMAW, GMAW and FCAW?
65-85%
What is the arc efficiency of GTAW?
20-45%
Where does the first voltage drop occur?
Over the electrode extension (the length of electrode between point of electrical contact with the contact tip and its melting point)
The magnitude of the voltage drop depends on what 3 things?
Electrode extension, wire diameter, and current
The 2ND voltage drop is due to a small thin gaseous region next to the what?
CATHODE DROP ZONE*
The 4TH voltage drop is in the region called the what?
ANODE DROP ZONE*
Arc blow is more likely to be present during welding of what type of materials?
Magnetic materials
Rectifier changes what to what?
AC to DC
In North America, AC is supplied at how many cycles per second?
60 cycles/sec
(60 Hz)
DCEP can sometimes be called what?
Reverse polarity
DCEN can sometimes be called what?
Straight polarity
Describe resistance heating:
When an electric current flows through a conductor, a certain amount of heat is generated due to the current having to overcome the electrical resistance of the conductor
Resistance heating allows what to melt?
The electrode
When the dew point is low, what does that mean for the gas?
Dry (no humidity)
The lower the dew point, the drier the gas
Define cold crack:
Defects that form as a result of the contamination of the weld metal microstructure by hydrogen
What 4 things must be critical for hydrogen-induced cold cracking to occur?
- Susceptible microstructure (based on chemistry and cooling rates)
- Stress
- Critical level of hydrogen
- Temp typically below 150•C
GTAW is often used for:
Welding thin materials and difficult metals (corrosion resistant alloys, aluminum, titanium and magnesium)
Orbital welding generally uses what type of current?
Pulsed DC
GTAW typically isn’t used to weld materials thicker than what?
10 mm
GTAW power sources operate at wide current and voltage ranges. What are they?
Amperage up to 350 A
Voltage ranges from 10 to 35 V
Which control initiates the arc?
Arc Force
The current is higher is the DCEN half cycle than the DCEP half cycle because why? What is the resulting imbalance called?
The electrons are not emitted as effectively, causing the current to be lower. The resulting imbalance is called inherent rectification.
What is a main advantage of pulsed DC?
Able to control current better in all positions
What are the two types of GTAW torches?
Air cooled and water cooled
Air cooled torches typically have a current carrying capacity of what?
Less than 200 A
