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Net load per load diagram

How much can the load weigh when the hook and tackle are deducted?

Answer: The figure in the loading diagram is not what the load may weigh. The hook block, straps, shackles, lifting lug and deductions the diagram itself mentions (e.g. a mounted jib) also hang on the crane and count. The calculator subtracts your own deductions from the figure you read in the loading diagram for your reach and setup and shows the maximum load weight and how much of the diagram the lift uses.

Formula

Samlet last = byrde + krogblok + anhugningsgrej + andre fradrag

Byrden må højst veje = tilladt last i lastdiagrammet − krogblok − grej − andre fradrag

Udnyttelse = samlet last ÷ tilladt last × 100

Example: 2,600 kg in diagram − 120 kg hook − 40 kg gear ⇒ load must weigh 2,440 kg. A load of 2,300 kg gives 2,460 kg in crane and uses 95%.

Symbols and units in the formula
SymbolMeaningUnit
kapacitet_kgPermitted load in load diagram at deployment and setupkg
krog_kgHook block or hook (from marking)kg
grej_kgSlinging gear: straps, shackles, yokekg
andet_kgOther deductions that the load diagram requires (e.g. mounted jib)kg
byrde_kgLoad weightkg
=Utilisation of load diagram%
=The load must weigh at mostkg
=Total load in cranekg
=Luft til lastdiagrammet (negativ = overlast)kg

Validity and source

Source
Kranens lastdiagram · Liebherr «Influence of wind» (løftelast = last + krog og grej)

Does not apply when

  • Indicative. Permitted load is read from the crane's own load diagram for the current set-up (outreach, boom length, support legs, counterweight). Read the diagram's own text about what should be subtracted. With Liebherr for example, the hook block is part of the load. The crane's load moment limiter is not a substitute for the calculation.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Permitted load in load diagram at deployment and setup2,600 kg
  • Hook block or hook (from marking)120 kg
  • Slinging gear: straps, shackles, yoke40 kg
  • Other deductions that the load diagram requires (e.g. mounted jib)0 kg
  • Load weight2,300 kg

Giver

  • Utilisation of load diagram95 %
  • The load must weigh at most2,440 kg
  • Total load in crane2,460 kg
  • Luft til lastdiagrammet (negativ = overlast)140 kg

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Sådan bruger du den

På kurset lærer du at læse lastdiagrammet. Men tallet dér er ikke det, byrden må veje: krogblok, grej og evt. jib skal trækkes fra. Beregneren viser hvad byrden højst må veje, og hvor meget af diagrammet løftet bruger.

Step by step

  1. Aflæs tilladt last ved udlæg og opstilling.
  2. Find krogblokkens vægt.
  3. Læg stropper, sjakler, åg eller vakuumløfter sammen.
  4. Tilføj fradrag fra diagrammet.
  5. Sammenlign med byrden.

Typical errors

  • At sammenligne byrden direkte med diagrammet.
  • At glemme tungt grej som vakuumløftere og åg.
  • At aflæse ved forkert udlæg.

Examples from everyday life

Stålbjælke med mobilkran

Lastdiagrammet giver 2.600 kg ved udlægget. Krogen vejer 120 kg og stropperne 40 kg. Bjælken vejer 2.300 kg.

Permitted load in load diagram at deployment and setup
2,600 kg
Hook block or hook (from marking)
120 kg
Slinging gear: straps, shackles, yoke
40 kg
Other deductions that the load diagram requires (e.g. mounted jib)
0 kg
Load weight
2,300 kg

It means: Byrden må højst veje 2,440 kg. Samlet er der 2,460 kg i kranen, det er 95 %, og luften er 140 kg.

Glasrude med vakuumløfter på minikran

En minikran kan tage 1.500 kg ved udlægget. Krogen vejer 15 kg, og vakuumløfteren 220 kg. Ruden vejer 1.200 kg.

Permitted load in load diagram at deployment and setup
1,500 kg
Hook block or hook (from marking)
15 kg
Slinging gear: straps, shackles, yoke
220 kg
Other deductions that the load diagram requires (e.g. mounted jib)
0 kg
Load weight
1,200 kg

It means: Ruden må højst veje 1,265 kg. Med 1,435 kg i kranen er udnyttelsen 96 %, og der er kun 65 kg luft. Vakuumløfteren alene æder en stor del.

Rule of thumb

Krog og grej er sjældent under 5 % af diagrammets tal, og med vakuumløfter eller åg kan det være over 15 %.

How to check the answer

Byrdens grænse + krog + grej + fradrag = diagrammets tal.