The weight of the grab of the crane depends on the type, volume, material and design of the grab. Generally speaking, the weight of the grab should be less than the rated lifting capacity of the crane to ensure safety and efficiency.

Weight calculation method of grab:
Volumetric method: according to the geometric volume of the grab and the volume weight of the material, calculate the weight of the grab material, plus the weight of the grab itself.
Gravimetric method: put the materials grabbed five times into a container, weigh the total weight, divide by 5, and then compare with the designed grab weight, which is the grab full rate.
The calculation formula for the weight of materials lifted by crane:
-Lifting capacity=theoretical value of crane × 3 ÷ (horizontal distance between the lifted component and the crane × 0.75) [^10^]
Introduction to hydraulic and mechanical grab
The hydraulic grab itself is equipped with an opening and closing structure, which is generally driven by hydraulic oil cylinder. The hydraulic grab composed of multiple jaw plates is also called hydraulic claw. Hydraulic grab is widely used in hydraulic special equipment, such as hydraulic excavator, hydraulic lifting tower, etc.

The mechanical grab itself has no opening and closing structure. It needs external force to realize opening and closing, such as wire rope, chain, etc. The mechanical grab is generally composed of two or four symmetrical jaw plates. The common types are single rope, double rope, four rope and electric.
How to select the appropriate crane grab?
It is very important to select a proper grab, because it will affect the efficiency and safety of the crane.
Before selecting grab, you need to consider the following aspects:
Construction environment: different environmental conditions, such as temperature, humidity, wind, etc., will affect the performance and life of the grab. You need to select a grab with strong adaptability, wear resistance and corrosion resistance according to the actual situation.
Material type: different materials have different density, particle size, shape and other characteristics, and will have requirements on the volume, shape, jaw plate, etc. of the grab. You need to select the appropriate grab type according to the characteristics of the material, such as spherical grab, orange petal grab, etc.
Crane tonnage: the rated lifting capacity of the crane determines the maximum load of the grab. You need to select appropriate grab volume and dead weight according to the tonnage of the crane to ensure the lifting capacity and safety factor.