Interpreting a Fillet Weld Symbol on a Skid Frame
A fabricator receives a drawing for a skid frame. One detail shows a fillet weld symbol with the arrow pointing to a vertical member, the triangle on the side of the reference line away from the arrow, a 6 mm size to the left of the triangle, a length of 150 with a dash and a second number of 75, and a tail containing 'WPS-14.' The welder reads it as a continuous 6 mm fillet on the arrow side and begins laying a full-length bead. The inspector stops the work. The joint is a T-joint with 10 mm plate, and the drawing note says 'all dimensions in millimeters.'
1. Explain what the symbol actually requires and where the weld belongs.
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The triangle sits on the side of the reference line opposite the arrow, so the weld is on the other side, not the arrow side. The 6 mm to the left of the triangle is the leg size. The numbers after the length indicate intermittent welding: a 150 mm length of weld followed by a 75 mm space, repeated. The tail reference WPS-14 points to the welding procedure specification that governs the joint. So the requirement is a 6 mm intermittent fillet on the far side, in 150 mm segments with 75 mm gaps, not a continuous arrow-side bead. The welder's interpretation was wrong on both placement and length, which is why the inspector stopped the work before more material was consumed.
2. The welder asks whether the intermittent weld is acceptable on a skid that will see vibration. How would you respond using the drawing and code context?
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The drawing governs unless there is a documented conflict with the applicable code or a service requirement. Intermittent fillets are permitted in many structural codes for statically loaded members but are often restricted or prohibited where fatigue, impact, or corrosive service applies. The correct action is not for the welder to decide on the floor: raise a request for information to the designer, citing the vibration service and asking whether continuous welds are required. If the designer confirms intermittent is acceptable, follow WPS-14 exactly, including segment length and spacing, and document the confirmation. If continuous is required, issue a revised drawing and update the WPS. Either way, the decision must be traceable, not verbal.