CWS (Other exams) flashcards
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- Shade number selection
- Welding helmet lens shade depends on process and current: roughly shade 10-13 for SMAW/GMAW above 160 A, lighter shades for low-current work. Too light risks arc eye.
- Hot work permit
- Written authorization for welding or cutting outside a designated area; requires fire watch, combustible clearance (about 35 ft), and fire watch continuing 30 minutes after work ends.
- Discontinuity vs. defect
- A discontinuity is any interruption in the weld (porosity, slag); it becomes a defect only when it exceeds the acceptance criteria of the governing code.
- Acetylene cylinder pressure limit
- Acetylene cylinders are never used or stored above 15 psig because acetylene is unstable and can decompose violently at higher pressure; regulators are never interchanged with oxygen.
- Cold cracking cause
- Hydrogen-assisted cold cracking occurs hours after welding; controlled by preheat, low-hydrogen electrodes, clean joint surfaces, and post-weld heat treatment.
- Visual inspection limits
- VT finds surface discontinuities before, during, and after welding but cannot detect subsurface flaws; UT, RT, MT, or PT are needed for internal defects.
- Open-circuit voltage hazard
- OCV is present at the electrode holder before the arc starts; damaged insulation, wet gloves, or a wet work area can cause fatal shock even when not welding.
- Fume control hierarchy
- Source capture at the arc is preferred over general dilution ventilation; confined-space welding requires forced air and continuous atmospheric monitoring.
- Governing code selection
- The contract specifies the code: AWS D1.1 for structural steel, ASME Section IX for procedure and performance qualification. The code's acceptance criteria govern, not preference.
- Work lead placement
- The work (ground) lead attaches as close as practical to the weld; using structural steel or piping as a return path requires engineering approval to avoid damage and shock.
- Heat input formula
- Heat input in kJ/in = (voltage × current × 60) / (travel speed in in/min × 1000). Higher heat input widens the heat-affected zone and changes properties.
- Duty cycle meaning
- A 60% duty cycle at 300 A means 6 minutes of arc in any 10-minute period; exceeding it causes thermal shutdown or reduced output.
- Operator factor
- Operator factor (arc time) is the fraction of paid time the arc is actually on; manual SMAW typically runs roughly 20-40%, mechanized processes much higher.
- Cost per foot formula
- Cost per foot = labor (rate × hours per foot) + electrode cost + gas or flux cost + allocated overhead. Labor usually dominates manual welding cost.
- Deposition efficiency
- Deposition efficiency is deposited metal weight divided by electrode consumed weight; SMAW runs roughly 60-70% because of stub loss and spatter.
- Groove angle cost effect
- Reducing bevel angle from 60° to 45° cuts groove cross-section and fill-metal volume, lowering arc time, consumable use, and distortion.
- Rework cost components
- Rework cost includes labor, consumables, NDT, and schedule impact; a small repair rate on high volume can exceed savings from a cheaper process.
- Cost per deposited pound
- Purchasing compares consumables by cost per deposited pound, not cost per package; a cheaper box can cost more per pound of deposit.
- Arc time improvement
- Labor cost per foot = (labor rate × arc time per foot) / operator factor; raising operator factor lowers labor cost without changing the process.
- Efficiency loss categories
- Track spatter cleanup, rework, fit-up gaps, electrode stub loss, and changeover time as separate cost categories to find the biggest loss.
- Weld fill volume driver
- Groove weld cross-section determines fill volume and pass count; joint design, bevel angle, and root gap are the main controllable cost drivers.
- Qualification vs. certification
- Qualification is demonstrated ability proven by test; certification is written confirmation by a certifying body. A welder can be qualified without being certified.
- WPS and PQR relationship
- A WPS is the written procedure; the PQR is the record of the test that qualified it. Welder qualification then tests the welder to that WPS.
- Essential variables
- Essential variables (process, filler classification, thickness range, position, preheat) cannot change without requalification or a new WPS.
- Position-specific qualification
- A welder's qualification is position- and process-specific; a welder qualified only in flat position cannot be assigned vertical-up production work.
- Low-hydrogen electrode storage
- Low-hydrogen electrodes are held in heated holding ovens after opening; exposure limits are set by the code, and wet electrodes are never used.
- Corrective action loop
- Identify the nonconformance, contain it, find root cause with 5-Why or fishbone, implement the fix, verify effectiveness, and update the procedure.
- Records as objective evidence
- Inspection reports, welder qualification records, and NDT results are objective evidence; missing records are treated as a nonconformance regardless of weld quality.
- Delegation by qualification
- Assign work by qualification and position, not seniority; assigning an unqualified welder creates a nonconformance and liability even if the weld passes.
- Crew performance metrics
- Measure arc time, repair rate, and first-pass yield per welder; coach on the specific metric rather than giving general feedback.
- Written shift handover
- Pass on WPS changes, open nonconformances, and pending inspections in writing; verbal handover loses traceability and causes missed inspections.
- Qualification expiry tracking
- Track qualification dates and expiry; a lapsed qualification is a nonconformance even when the welder's skill and weld quality are unchanged.