THE BASIC RIGGING PLAN
1. Who is responsible for the rigging
2. Calculate the weight of the load
3. Find the center of gravity
4. Selecting accessories
a. What is the sling angle
b. Calculate the sling leg length
c. Calculate the sling SWL
d. Selecting shackles
How to calculate the weight of the load?
The cargo weight (Weight Factor)
1.Weighted X 1.03
2.Manufactured X 1.05
3.Calculated X 1.1
4.Estimated X 1.2
How to calculate the weight of a load?
The safety Factor(operation factor)
•Onshore operation X 1.1
•Inshore operation X 1.15
•Offshore operation X 1.3 MSAH
Example
Cargo basket has a name plate stamped 3000 KG Gross weight
SO,
The load is 3000 kg weighted
Step(1) = 3000 * 1.03 (weight factor)= 3090 kg
Step(2) = weight of basket + weight of riggers(hook + slings, shackles, ) = 3090 + 1.0 (for example) = 4090 kg
Step(3) = 4090 * 1.3 (operation factor for offshore operation) = 5317 kg
SO, all your plan should designed on 5317 kg as the weight of the basket also, the minimum crane capacity at this point must be 5317 kg.
How to calculate the weight of a load?
1.Knowing the load density
2.Calculate how it’s weight in kg per cubic m
OR, you can use the tables directly
But, first you must know it’s volume.
How to calculate the weight of a load?
Volumes of common shapes
Example
•Aluminum block has the dimensions
•Length= 5 m, width= 2 m, thickness= 0.1 m
•Weight = 5 * 2* 0.1 * 2.7 = 2.7 tonne
N.B
How to find the center of gravity
Example
The weight of the load is 8000 KG
To find the center of gravity use the simple mathematics equation
6000 / (6000+2000) = 0.75 = 75%
The center of gravity is between the two centers shifted 75 % to the heaviest side
How to find the center of gravity
Example
The weight of the load is 11000 KG
To find the center of gravity use the simple mathematics equation
8000 / (8000+3000) = 0.73 = 73%
The center of gravity is between the two centers shifted 73 % to the heaviest side
4. Selecting accessories
MSAH.
1. Risk assessment.
2. Simple drawing to clarify the operation.
3. State the sequence of operation step by step.
1. Risk assessment
•Lifting supervisor to inspect the lifting accessories and assure the actual weights of the cargo measured by the crane is matching with the lifting plan.
•Lifting supervisor to check the Integrity of loads and associated equipment.
•crane operator to carry out pre-check/inspection of the crane.
•Banksman is the only authorized one to signal the crane operator as per pre-job safety meeting.
2. Drawing for the operation
3. sequence of operation(step by step).
•Mention all personal involved with the job (one crane operator, one banksman, two riggers, etc…)
•Lifting supervisor and lifting team review the lifting plan and risk assessment.
•Lifting supervisor check all lifting accessories and ensure the color code.
•Banksman instruct riggers to attach the accessories to the load as the plan said.
•Banksman give signal to crane operator to position the crane hook to a suitable height where the riggers can connect the slings. Banksman give signal to the crane operator to start hoisting up to take slack of slings and position the hook in center of gravity of the load.
•Banksman give signal to the crane operator to start hoisting up the load about 15 cm from ground to check balance.
•If the load balanced, banksman give signal to the riggers to connect two tag lines to control swinging of the load.
•Banksman give signal to the crane operator to start lifting the load and swinging it to it’s final position.
•After double check the landing are is clear, the banksman give signal to the crane operator to start lowering the load to it’s final position.
•Banksman give signal to the riggers to detach the lifting gears from the load.
•Cease and tidy work site.
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