BTEB Welding Exam common mistakes
BTEB Welding Exam · Understand the traps and how to avoid them.
Treating the electrode size and current as fixed for every joint, so the candidate welds a thin sheet with the same 3.2 mm electrode and 110 A used on 6 mm plate.
Candidates memorise one 'good' setting from a practice piece and never learn to relate current to electrode diameter and plate thickness, so they repeat the setting regardless of the job.
What to do instead
Before striking an arc, state the electrode diameter, plate thickness, and chosen current aloud, then check them against a current-range chart; practise setting current for three thicknesses in one session so the link between thickness and amperage becomes automatic.
Holding a long arc (visible gap between electrode tip and molten pool) because the candidate is afraid of sticking the electrode to the work.
Fear of arc sticking and lack of practice in maintaining a short arc lead to lifting the electrode, which causes spatter, poor penetration, and an unstable arc.
What to do instead
Practise striking and re-striking on scrap with the electrode dragged at a short arc length, counting seconds of stable arc; learn that a short arc reduces spatter and gives deeper penetration, and adjust current slightly upward if sticking persists.
Moving the electrode too fast along the joint, producing a narrow, high-crowned bead with undercut edges and no visible penetration.
Candidates rush to finish the bead and do not watch the molten pool, so travel speed is set by nervousness rather than by the pool size and joint preparation.
What to do instead
Weld short runs while watching the rear edge of the molten pool, keeping its width about twice the electrode diameter; compare bead width and toe wetting on scrap runs at slow, medium, and fast travel to build a feel for correct speed.
Failing to prepare the joint: not cleaning mill scale, rust, oil, or paint, and not setting the correct root gap and land before welding.
Candidates treat preparation as optional because they want to start welding quickly, and they do not connect contamination and wrong root gap to porosity, slag inclusion, and lack of fusion.
What to do instead
Adopt a fixed pre-weld checklist (grind to bright metal, degrease, set root gap with a feeler gauge or spacer, check alignment) and inspect the joint before striking the arc; practise one butt joint with and without preparation to see the defect difference.
Dragging the electrode without the correct angle or without a steady rest, so the bead wanders off the joint line and the slag runs ahead of the arc.
Candidates lack a body-support habit and do not understand electrode angle: too steep an angle gives a narrow, piled bead, too shallow an angle gives poor penetration and slag entrapment.
What to do instead
Brace the forearm or wrist on a rest, keep the electrode at about 70–80 degrees in the direction of travel, and practise straight-line beads on a marked line until the bead stays within the line; check angle in a mirror or with a partner.
Removing slag and inspecting only after the whole joint is finished, or chipping slag carelessly with the eyes close to the weld.
Candidates want to finish quickly and skip interpass cleaning, and they underestimate eye and face injury from flying slag.
What to do instead
Clean slag after every pass with a chipping hammer and wire brush, inspect each pass for porosity, slag lines, and cracks before the next pass, and always wear goggles or a face shield while chipping; make interpass cleaning a fixed step in the sequence.
Using the arc helmet or hand shield with a cracked filter lens, or lifting the shield to look at the arc 'just for a second'.
Candidates find the dark lens inconvenient for positioning and do not believe that brief exposure causes harm, so they peek at the arc or use damaged equipment.
What to do instead
Inspect the lens and shield before every session, replace cracked or pitted filters, set the shade to suit the current, and position the electrode by touch or with the shield down; treat any arc flash as a reportable incident and know the symptoms of arc eye.
Welding near solvent, paint, or degreaser residues, or in a confined space without ventilation, because the candidate only checks for visible fire hazards.
Candidates focus on sparks and fire and do not know that welding heat and ultraviolet light break down chlorinated solvents into toxic gases, and that shielding gases displace oxygen in confined spaces.
What to do instead
Remove or clean off solvents and coatings before welding, weld only in ventilated areas or with extraction, never weld on containers that held fuel or solvents without proper purging and testing, and treat confined-space welding as a permit job with a standby person.
Leaving the electrode holder on the workbench or on the workpiece with the machine still energised, and changing electrodes with bare hands.
Candidates underestimate the open-circuit voltage and treat the holder as harmless because the arc is not lit, and they forget that gloves are part of the circuit protection.
What to do instead
Switch off or isolate the machine when changing electrodes or leaving the station, hang the holder on an insulated hook, never place it on the work or the table, and wear dry leather gauntlets; check cable and holder insulation for damage before each session.
Answering theory questions about electrode classification, current type, and polarity from vague memory, mixing up electrode coding digits or AC/DC polarity effects.
Candidates spend practice time at the bench and leave theory revision to the last minute, so they cannot decode electrode designations or explain why DCEN gives deeper penetration than DCEP.
What to do instead
Build a one-page decoding table for electrode classification (position, coating type, current type) and a polarity comparison table, then test yourself by decoding five electrodes and predicting bead shape for each polarity before checking against the workshop chart.