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§ 17

Load's centre of gravity in container

Is the load's centre of gravity close enough to the centre of the container?

Answer: When a container is packed with heavy loads, the load must be distributed so the centre of gravity lies close to the container's centre. Otherwise the container hangs skew in the spreader, a truck or a chassis can be overloaded at one end, and the load can shift. CTU Code says the centre of gravity as a rule should lie within ±5 % of the container's length from centre. The rule of thumb is 60/50: at least 60 % of the weight should stand in the middle half of the container. The calculator finds the centre of gravity for up to three loads with the moment method.

Formula

Tyngdepunkt fra frontvæggen = (vægt 1 × afstand 1 + vægt 2 × afstand 2 + vægt 3 × afstand 3) ÷ samlet vægt

Afvigelse = tyngdepunkt − halvdelen af containerens længde

CTU Code: deviation should not exceed 5% of length, i.e. approx. 0.30 m in a 20-foot and approx. 0.60 m in a 40-foot container

Eksempel: (6.000 × 1,2 + 8.000 × 3,2 + 4.000 × 5,0) ÷ 18.000 = 2,93 m. Midten er 2,95 m, så afvigelsen er 0,02 m

Symbols and units in the formula
SymbolMeaningUnit
laengde_mContainer's internal lengthm
w1Batch 1: weightkg
x1Batch 1: centre of gravity measured from front wallm
w2Batch 2: weightkg
x2Batch 2: centre of gravity measured from front wallm
w3Batch 3: weightkg
x3Batch 3: centre of gravity measured from front wallm
=Centre of gravity deviation from the middle% af længden
=Centre of gravity measured from the front wallm
=Deviation from centre (+ toward the door, − toward the front)m
=Largest permissible tolerance (5%)m
=Load's total weightkg

Validity and source

Source
CTU Code (IMO/ILO/UNECE 2014) + ISO 3874: centre of gravity within ±5% of length

Does not apply when

  • Distance is measured from the front wall (the end without doors) to the centre of each section. A section is a uniform block of goods, e.g. a row of pallets. Set the weight to 0 for a section you do not use. The container's maximum gross weight and CSC plate still apply. For special goods, CTU Code can accept up to 10%, but only by agreement with the person who will lift the container.

Worked example

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

Substituted

  • Container's internal length5.90 m
  • Batch 1: weight6,000 kg
  • Batch 1: centre of gravity measured from front wall1.20 m
  • Batch 2: weight8,000 kg
  • Batch 2: centre of gravity measured from front wall3.20 m
  • Batch 3: weight4,000 kg
  • Batch 3: centre of gravity measured from front wall5 m

Giver

  • Centre of gravity deviation from the middle0.3 % af længden
  • Centre of gravity measured from the front wall2.93 m
  • Deviation from centre (+ toward the door, − toward the front)-0.02 m
  • Largest permissible tolerance (5%)0.30 m
  • Load's total weight18,000 kg

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Sådan bruger du den

Du bruger den, når du stuffer en container med tunge partier, fx maskiner, stålemner eller sække, og vil sikre, at tyngdepunktet ligger tæt på midten. Ligger det skævt, hænger containeren skævt i spreaderen, og en ende kan blive for tung for chassis eller truck.

Step by step

  1. Del lasten op i partier, fx tre blokke af paller.
  2. Vej hvert parti, og mål afstanden fra frontvæggen til partiets midte.
  3. Gang vægt × afstand for hvert parti, læg sammen, og del med den samlede vægt.
  4. Træk halvdelen af containerens længde fra. Det er afvigelsen.
  5. Afvigelsen må højst være 5 % af længden.

Typical errors

  • At måle fra døren. Afstanden måles fra frontvæggen.
  • At måle til partiets forkant i stedet for dets midte.
  • At stuffe det tunge gods først og helt fremme, fordi det er nemmest.
  • At glemme at tungt gods også skal stå på tværs i midten.

Examples from everyday life

20 fods container med tre partier

En 20 fods container har 6.000 kg ved fronten (1,2 m), 8.000 kg i midten (3,2 m) og 4.000 kg ved døren (5,0 m).

Container's internal length
20 feet (approx. 5.90 m interior)
Batch 1: weight
6,000 kg
Batch 1: centre of gravity measured from front wall
1.2 m
Batch 2: weight
8,000 kg
Batch 2: centre of gravity measured from front wall
3.2 m
Batch 3: weight
4,000 kg
Batch 3: centre of gravity measured from front wall
5 m

It means: Tyngdepunktet er 2.93 m fra fronten. Afvigelsen er -0.02 m, altså 0.3 % af længden. Det er inden for grænsen på 0.3 m.

40 fods container stuffet forfra

En 40 fods container er stuffet med 9.000 kg maskindele helt fremme (1,5 m), 7.000 kg ved 4,0 m og 2.000 kg ved døren (10 m). Resten er tom.

Container's internal length
40 feet (approx. 12.03 m interior)
Batch 1: weight
9,000 kg
Batch 1: centre of gravity measured from front wall
1.5 m
Batch 2: weight
7,000 kg
Batch 2: centre of gravity measured from front wall
4 m
Batch 3: weight
2,000 kg
Batch 3: centre of gravity measured from front wall
10 m

It means: Tyngdepunktet er 3.42 m fra fronten, altså -2.6 m fra midten. Afvigelsen er 21.6 % af længden, mens grænsen er 5 %, altså 0.6 m. Containeren skal stuffes om.

Samme gods flyttet mod midten

Du flytter maskindelene til 4,5 m og det mellemste parti til 7,5 m.

Container's internal length
40 feet (approx. 12.03 m interior)
Batch 1: weight
9,000 kg
Batch 1: centre of gravity measured from front wall
4.5 m
Batch 2: weight
7,000 kg
Batch 2: centre of gravity measured from front wall
7.5 m
Batch 3: weight
2,000 kg
Batch 3: centre of gravity measured from front wall
10 m

It means: Nu er tyngdepunktet 6.28 m fra fronten, og afvigelsen er 2.2 % af længden. Det er inden for grænsen.

Rule of thumb

60/50-reglen: mindst 60 % af vægten skal stå i containerens midterste halvdel.

How to check the answer

Tyngdepunktet ligger altid mellem det forreste og det bageste parti. Ligger det udenfor, er der tastet forkert.