Safety, Productivity, and Cost Control
Safety and money share the same variables
Under OSHA 1910.252, hot work needs a permit where required, a fire watch where combustibles are exposed within 35 ft, and the fire watch must continue for 30 minutes after welding stops. Ventilation must control fume; confined spaces need atmospheric testing and an attendant. Cylinders are stored upright, secured, and separated from fuel gas; cables and electrode holders must be insulated and intact.
Productivity metrics
Know the difference between machine duty cycle and operator factor. Duty cycle limits the power source; operator factor (arc time ÷ clock time) measures how much of the paid hour the arc is actually on. Deposition rate drives arc time; fit-up, position, and repositioning drive operator factor. Rework and repair rates are direct cost multipliers.
Traps
- Using 50 ft instead of 35 ft for the fire watch distance, or omitting the 30-minute post-watch.
- Assuming maximum current always raises productivity; it can raise spatter, burn-through, distortion, and rework.
- Comparing two processes on deposition rate alone, ignoring deposition efficiency and cleanup.
Worked example
A weld needs 0.6 lb of deposit per foot. Electrode costs $2.00/lb and deposition efficiency is 65%, so purchased filler is 0.6 / 0.65 = 0.92 lb/ft, or about $1.85/ft. At 3 lb/hr, arc time is 0.2 hr/ft; at a 40% operator factor that is 0.5 clock hr/ft, or $30.00/ft at $60/hr. Total ≈ $31.85/ft before overhead and rework.