CWS (Other exams) cheat sheet

Arc flash (UV/visible light) burns skin and eyes: welding helmets use shade 10-13 for SMAW/GMAW above 160 A; shade 8-9 for light work below 60 A.

Ozone and nitrogen oxides form in GMAW and plasma arcs; ventilation must keep fume below the applicable exposure limit - natural dilution is not acceptable indoors.

Shielding gas cylinders: acetylene is never stored above 15 psig and never on its side; oxygen and fuel-gas regulators are never interchanged or oil-lubricated.

Hot work permit requires: fire watch, 35 ft (11 m) clearance of combustibles, or guards; fire watch continues 30 minutes after work ends.

Weld discontinuity vs. defect: a discontinuity is any interruption in the weld; it becomes a defect only when it exceeds the acceptance criteria of the governing code.

Common weld discontinuities: porosity, slag inclusion, lack of fusion, lack of penetration, undercut, overlap, spatter, and cracking (hot, cold, lamellar).

Acceptance rules come from the contract code - AWS D1.1 for structural steel, ASME Section IX for procedure/performance qualification; the code governs, not preference.

Visual inspection is performed before, during, and after welding; VT finds surface discontinuities, but subsurface flaws require UT, RT, MT, or PT.

Hydrogen cracking (cold cracking) is controlled by preheat, low-hydrogen electrodes, and post-weld heat treatment; it can appear hours after welding.

Deposition rate (lb/hr) = (electrode feed rate in in/min × electrode cross-section in² × density lb/in³ × 60) / 1, or use manufacturer deposition tables for the process.

Travel speed and heat input: heat input (kJ/in) = (voltage × current × 60) / (travel speed in/min × 1000); higher heat input widens the HAZ.

Duty cycle: 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.

Arc time (operator factor) is the fraction of paid time the arc is on; typical manual SMAW factors run roughly 20-40%, mechanized processes much higher.

Cost per foot = (labor rate × hours per foot) + (electrode cost per foot) + (gas/flux cost per foot) + overhead allocation; labor usually dominates manual welding.

Welding cost reduction levers: joint design (fewer passes, smaller groove), fixture and position, process change (FCAW/GMAW vs. SMAW), and arc-time improvement.

Weld size and volume: groove weld cross-section drives fill volume; a bevel change from 60° to 45° reduces fill metal and arc time proportionally.

Efficiency loss sources: spatter cleanup, rework, fit-up gaps, electrode stub loss, and changeover time - track them as separate cost categories.

Qualification vs. certification: qualification is demonstrated ability (test); certification is written confirmation by a certifying body - a welder can be qualified without being certified.

WPS → PQR → welder qualification chain: the WPS is supported by a procedure qualification record; welders are then qualified to that WPS.

Essential variables (e.g., process, filler classification, thickness range, position, preheat) cannot be changed without requalification or a new WPS.

A welder's qualification is position- and process-specific; a change in position or process outside the qualified range voids the qualification.

Supervisor responsibilities: verify WPS availability at the point of use, confirm welder qualification records are current, and control consumable storage (low-hydrogen electrodes in holding ovens).

Corrective action loop: identify nonconformance, contain it, find root cause (5-Why, fishbone), implement fix, verify effectiveness, and update the WPS/procedure.

Documentation discipline: inspection reports, welder qualification records, and NDT results are objective evidence; missing records are treated as nonconformance.

Crew performance: measure arc time, repair rate, and first-pass yield per welder; coach on the specific metric rather than general feedback.

Fume extraction: source capture at the arc is preferred over general dilution ventilation; confined-space welding requires continuous monitoring and forced air.

Electric shock prevention: never weld with damaged electrode holder insulation or wet gloves; open-circuit voltage (OCV) is present before the arc starts.

Grounding: the work lead must be attached as close as practical to the weld; never use structural steel or piping as the return path without engineering approval.

PPE baseline: flame-resistant clothing, leather gloves and sleeves, safety glasses under the helmet, hearing protection in high-noise processes (plasma, air-carbon arc).

NDT methods and what they detect: PT/MT find surface and near-surface flaws; UT finds internal planar flaws; RT finds volumetric and internal flaws but is poor on planar defects aligned with the beam.

Weld quality metrics: repair rate, first-pass yield, and NDT rejection rate - track per welder and per joint type to find systemic problems.

Labor cost per foot = (labor rate $/hr × arc time per foot) / operator factor; improving operator factor cuts labor cost without changing the process.

Electrode consumption: deposited metal = electrode weight × deposition efficiency (SMAW roughly 60-70% due to stub and spatter loss).

Bulk gas and consumable purchasing: compare cost per deposited pound, not cost per unit package - a cheaper box can cost more per pound of deposit.

Rework cost = labor + consumable + NDT + schedule impact; a 1% repair rate on a high-volume job can exceed the savings from a lower-cost process.

Delegation rule: assign by qualification and position, not by seniority; a welder qualified only in flat position cannot be assigned vertical-up work.

Shift handover: pass on WPS changes, open nonconformances, and pending inspections in writing - verbal handover loses traceability.

Training records: track qualification dates and expiry; a lapsed qualification is a nonconformance even if the welder's skill is unchanged.

Performance review: use objective data (repair rate, arc time, safety observations) rather than impressions to reduce bias.