Who Are We_ Global Lifting Serv - Barry.pdf

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Safe Working Load
Safe Working Load

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What does it mean
What does it mean
It’s a safety factor
Given by a competent person
This information is gathered by using:
1. Knowledge of the equipment
2. The way it’s used and service conditions
3. Materials used in its construction
4. Past history

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Working Load Limit ( WLL )
Working Load Limit ( WLL )
The maximum load which an item of lifting equipment is
designed to:
1. Raise
2. Lower
3. Suspend
The WLL does not take account of the particular service
conditions which may affect the final rating of the equipment
WLL is given by the manufacturer

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Safety Factors
Safety Factors
Why
5:1 for wire ropes
25% for cranes
All lifting equipment has a safety factor

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Calculation Method for Slings
Calculation Method for Slings
BF = Breaking Force
R = Gross Mass ( Gross Weight )
G = Acceleration ( 9.81 )
N = Number of Sling Legs
V = Angle from Vertical
(30˚ = 0.866 45˚ = 0.707)
SF = Safety Factor ( Reference Load Chart )
BF min = x SF
___R x G___
N ( 3 ) x V
Safety Factor
Safety Factor
Chart
Chart

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A sample of rope is tested to destruction
This is called the Minimum Braking Load ( MBL )
The actual braking load should always be higher than the MBL.
If not the wire is discarded.
The safe working load of the wire is 5 x less than the MBL
16mm wire rope has a MBL of 15000 Kg so the safe working
load is 15000 divide by 5 = 3 Te
How the Safety Factor is Calculated
How the Safety Factor is Calculated

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Sling Assembly Calculations
Sling Assembly Calculations
4 leg sling assembly's have a safety factor of 6.5:1 to allow for
displacement of loads and allows for the different lifting angles
The Sling Fitted to Container or Skid unit should be rated at
30% higher than the Gross weight of the unit
So if a container weighs 10 tonne the sling fitted should be not
less than 13 tonne
Sling assembly's should be fitted with quad links. Three links for
a 4 leg sling. One large master link fitted with two small links, the
small links support no more than two wires each.
All ropes used in a sling assembly should have hard eyes fitted
to lower the radius angle on the rope

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Sling Angles
Sling Angles

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A lot of people are unaware of the reduced loading when using
single leg slings as assembly's
If 4 x 16mm ( 3 Tonne ) single leg slings are used to lift a
basket the total load or rating is not 12 tonne ( 4 x 3 = 12 )
The actual rated load of 4 x 16mm slings is 6.4 tonne
Single leg slings are used in one direction or at one angle only
4 leg slings normally work at angles from 0 – 90 degrees that’s
why the SWL are different
Assembly's / Single Leg Slings
Assembly's / Single Leg Slings

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Safe Use of Slings
Safe Use of Slings
Misconception that two single leg slings can be used to
double the weight.
Two 10 Tonne slings do not make 20 tonne
Its almost imposable to manufacture two slings the same
length and if two slings are used together one sling will
take more of the weight than the other. This is not good
rigging practice.

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How do we know the weight of an item
How do we know the weight of an item
Data Plate
Hard Stamped
Load Cell / Crane load indicator
Manifested weight
Ask Manufacturer
Manual
Old lifting plans
Calculation ( Density of Materials )

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Tare weight
Safe working Load
Gross Weight

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Can you guess the weight
Can you guess the weight
Well, we lifted one that looked the same
I think it weight is 10te
He told me it weighed 6te
I have been doing this for years ( trust me )

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Selection of equipment
Selection of equipment
How do you pick the equipment to use
Who picks the equipment to use
Should you carry out a pre-use check on the equipment
What must be marked on the equipment
1. Identification Number
2. SWL
3. Colour Code

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Load Charts
Load Charts

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Crane Hooks
Crane Hooks

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Summary
Summary
If you don’t know the Safe Working Load ASK
Always use the correct equipment