Dogging (DG) common mistakes
Dogging (DG) · Understand the traps and how to avoid them.
Treating the working load limit as a fixed number regardless of sling configuration, so the candidate quotes the single-leg capacity for a two-leg or four-leg sling without applying the sling angle and asymmetric-load factors.
The WLL printed on a tag or in a table is derived for a specific configuration; candidates memorise one figure and reuse it, missing that capacity falls as the angle from horizontal decreases and that multi-leg assemblies rarely share load equally.
What to do instead
Work every capacity problem from first principles: state the configuration, note the angle from horizontal, apply the appropriate multiplier, then apply an unequal-load allowance for multi-leg slings. Practise converting a rated single-leg WLL into a two-leg and four-leg result at 90, 60, 45 and 30 degrees until the pattern is automatic.
Reading a load chart or tag and ignoring the units, the radius basis, or the condition notes attached to the rating, such as a deduction for a reeved or choked configuration.
Charts and tags compress several assumptions into one number, and under exam time pressure candidates grab the headline figure and skip the footnotes that define how the rating was established.
What to do instead
Before using any rating, write down the units, the reference point for radius or angle, and any qualifying note. Build a habit of restating the rating in your own words on the scratch paper before calculating, so a mismatched unit or a missed deduction becomes visible.
Estimating sling tension by dividing the load by the number of legs only, without resolving the vertical and horizontal components at the actual included angle.
The simple division works only for vertical legs; candidates default to it because it feels intuitive and produces a plausible number, so the error goes undetected.
What to do instead
Always draw the triangle: vertical component equals the share of load carried by that leg, and tension equals that share divided by the sine of the angle from horizontal. Work through asymmetric two-leg and three-leg examples where the centre of gravity is offset, and check the answer against the sum of vertical components equalling the total load.
Assuming a load's centre of gravity sits at its geometric centre, then specifying equal-length legs or a single central lift point for an irregular or asymmetrically weighted item.
Textbook examples are symmetrical, so candidates carry the assumption into real-shaped loads such as a motor with a heavy drive end or a bundle with an offset mass.
What to do instead
Before selecting the rig, identify how the centre of gravity would be found in practice: by inspection of mass distribution, by a test lift, or by trial and adjustment. State explicitly that the lift point must be above the centre of gravity and that unequal legs or a spreader may be needed to keep the load level.
Describing a communication method vaguely, such as saying 'use hand signals', instead of naming the specific signal, who gives it, and what happens when the signal is lost or ambiguous.
Candidates know a method exists but have not rehearsed the operational rules around it, including the single designated signaller, the emergency stop signal, and the requirement to stop when a signal is not clearly understood.
What to do instead
Learn each signal by its described motion and practise describing it in words without a picture. Memorise the governing rules: one nominated signaller, anyone may give the emergency stop, and the operator must stop on any unclear or conflicting signal. Rehearse the lost-communication procedure as a short script.
Producing a lift plan that lists hazards but omits the control measures, the responsible person, and the verification step, so the plan reads as a hazard inventory rather than an actionable document.
Candidates conflate hazard identification with risk assessment and run out of time before writing controls, owners and review points.
What to do instead
Use a fixed structure for every plan answer: task step, hazard, consequence, existing control, additional control, person responsible, and how the control is verified before the lift. Practise writing one plan in that template so the structure carries into the exam.
Failing to classify a lift correctly, treating a lift near people, near power lines, or with a tandem or complex rig as routine when it meets the criteria for a higher category requiring a documented plan and competent person review.
The classification thresholds are easy to skim, and candidates judge difficulty by load weight alone rather than by consequence, complexity, or proximity to hazards.
What to do instead
Memorise the criteria that escalate a lift: proximity to personnel or infrastructure, non-standard rigging, multiple cranes, loads near capacity, and unfamiliar loads. For each practice scenario, state the category first and justify it, then write the plan at that level.
Inspecting lifting gear by looking only for obvious damage and missing the rejection criteria: missing or illegible tags, stretched or distorted hooks, broken wires in a rope, cuts or abrasion in webbing, and corrosion or cracking at fittings.
Visual inspection under exam conditions becomes a general glance; candidates have not learned the specific defect thresholds that make an item unfit for service.
What to do instead
Learn the rejection criteria item by item for each gear type and practise a systematic sweep: tag, body, fittings, and any wear points. State that gear without identification or with any defect meeting rejection criteria is removed from service and quarantined, not returned to the rack.
Controlling the load only at the start of the lift, then letting it swing or rotate during travel without a tag line or controlled descent, and omitting the exclusion zone under the load.
Candidates focus on the rigging calculation and treat the movement phase as automatic, forgetting that load control is a continuous activity with named controls.
What to do instead
Describe the movement as a sequence with a control at each stage: pre-tension and check, clear the exclusion zone, controlled hoist, tag line or guide for rotation, controlled lowering, and a check that the load is stable before releasing the rig. Name who holds the tag line and who authorises movement.
Answering safety and legislative questions from general impression rather than from the specific duty, so the candidate names a general obligation but not who holds the duty, what it requires, and how it is discharged.
Legislation is studied as background reading rather than as a set of duties with named holders, and candidates confuse the roles of the person conducting the business, the competent person, and the dogger.
What to do instead
Build a duty table: duty holder, the obligation, the practical evidence that it has been met. Revise by writing the table from memory, then test yourself by describing a workplace scenario and naming which duty applies and what record or action demonstrates compliance.