Types of grab cranes overview: Clamshell crane, Bucket crane, Orange peel grab crane

Grab crane, the common name grab crane, English name: Grab crane / grabbing crane. Grab cranes are cranes equipped with grabs. They are widely used in ports, docks, station yards, mines, etc. to load all kinds of bulk cargo, logs, minerals, coal, sand and gravel materials, earth and stone.

Types of grab cranes

The grab crane is an automatic material picking machine. Its grabbing and unloading materials are operated by the ship unloader driver and no need auxiliary personnel, thus avoiding the heavy labor of the workers, saving auxiliary working time and greatly improving the Loading and unloading efficiency. Grab cranes are generally classified into bridge grab cranes, gantry grab cranes, and folding arm grab cranes. Usually, grab cranes are referred to as folding arm type grab cranes, such as log cranes.

Grab cranes can be classified according to crane type, grab type, and driving method.

Crab crane types based on crane designs

According to crane designs, the grab cranes can be classified in the overhead grab crane, gantry grab crane and folding arm grab crane.

Bridge grab crane

Overhead grab crane - Dongqi bridge crane and eot crane

Bridge grab cranes are dedicated to bulk and granular materials.

The conventional configuration of the bridge grab crane: the cab is controlled by the driver's cab, and the cab is divided into two types: closed and un-closed. Each mechanism adopts a winding type lifting motor and resistance speed regulation.

Lifting equipment grab bridge crane working duty: A6, A7, working environment 20 ° C ~ +40 ° C This model is not recommended for use in explosion-proof, insulation requirements of the working environment.

Lifting equipment grab bridge cranes are available for other configurations

• There are two types of parallel and vertical main beams in the direction of opening and closing of the grab;
• The lifting weight includes the weight of the grab;
• When the lifting trolley has a rain cover, the top size limit is H+h;
• The total amount of outdoor cranes and the maximum wheel pressure should be increased by 5%.
• The two types of conductive angled steel and safety sliding line are available for selection;
• This crane has two kinds of standard trolleys and weighing trolleys;
• According to needs can be equipped with sugar cane grab, garbage grab, wood grab and other types of grippers;
• Grab is divided into: single rope grab, double rope grab, electric grab, and target set grab.

Single beam grab crane and double beam grab crane

Mainly refers to bridge cranes, which are divided into single beam grab cranes and double beam grab cranes according to the number of beams. The function is the same as the bridge grab crane. More on single girder overhead crane and double girder overhead crane.

Gantry type grab crane

The gantry type grab crane is mainly used in outdoor fixed goods yards for transportation of mines, coal, wood, etc.

Folding arm grab crane

Usually, grab cranes are referred to as folding arm type grab cranes, such as log cranes.

Based on loading materials

According to the loading and unloading object, it is divided into round wood hanging, sugar cane falling and so on. However, with the development of science, China has developed a multi-purpose grab crane.

Classified according to the loading materials, the crane grabs are generally grouped into the following types:

Clamshell grab crane

Clamshell grab crane - Dongqi overhead crane 

It is suitable for loading various bulk cargo, minerals, coal, sand and gravel materials, earth and stone, etc. in ports, docks, station yards, mines, etc. It can also be used in earth and stone excavation, foundation and trench excavation, road construction, rail laying and other projects.

Multi-petal orange peel grab crane

Orange peel grab crane for scape handing - Dongqi scrap handling crane

Scrap steel extraction and refining for steel mills. More on scrap handling crane.

Wastes handling grab crane

Waste and garbage handling grab crane -  Dongqi eot crane 

Bulk waste, waste refining, handling and handling at work, garbage disposal sites and construction sites, car recycling yards for car dismantling, refining and recycling, tooth replacement, and high hardness wear-resistant steel to ensure The long service life. Check more on Bucket crane for waste and garbage handling. 

The valve shell can be selected according to different working environments; the fully closed valve shell, the semi-closed valve shell, the wide side flap shell and the narrow side flap shell.

Wood, log, pipes handling grab crane

The wood grab is mainly used for the grasping and loading and unloading of logs, wood, pipes, drums and other objects of various specifications. It can be grabbed by a single grab or multiple picks, and can be used with cranes such as tower cranes and gantry cranes. Applicable to occasions such as log yards, dock unloading, etc. Check on Log handling crane and Pipe handling crane: clamp crane and magnetic crane

Straw bale handling grab crane

Straw bale grab is a material handling equipment specially developed for straw power plants. It mainly carries out unloading, stacking and feeding of straw bales. The working duty is high, adapting to the needs of the working environment of the straw tank of the power plant is humid, dusty, frequently used and uninterrupted work.

Classified by drive: Hydraulic grab crane & Mechanical grab crane

According to the driving method, it can be divided into two types: hydraulic grab and mechanical grab.

Hydraulic grab crane

The hydraulic grab itself is equipped with an opening and closing structure, which is generally driven by a hydraulic cylinder. The hydraulic grab consisting of a plurality of jaws is also called a hydraulic claw. Hydraulic grabs are widely used in hydraulic special equipment.

Mechanical grab crane

The mechanical grab itself does not have an opening and closing structure, and is usually driven by a rope or a connecting rod. According to the operation characteristics, it can be divided into a double rope grab and a single rope grab. The most common one is a double rope grab.

The double rope grab has a support rope and an opening and closing rope which are respectively wound around the support mechanism and the reel of the opening and closing mechanism. The double rope grab is reliable, easy to operate, high in productivity and widely used. After adopting two sets of double ropes, it becomes a four-rope grab, and the working process is the same as that of the double rope grab. The Single rope grab: the same rope is used for the support rope and the opening and closing rope. The wire rope turns to support and open and close by special locking device. The winding mechanism of the single rope grab is simple, but the productivity is low, and it is rarely used in a large number of loading and unloading operations.

Protection device

Our protection devices generally includes lifting limit switch, travelling limit switch, weight limit switch, alarm device, over-current protection, under-voltage protection, phase fault protection, overheating protection, emergency stop button, buffer and so on.

• Precautions for handling the grab crane? Do not operate if one of the following conditions is true:
• Unloaded when the load is overloaded or the weight of the object is unclear;
• When the signal is not clear, it is not suspended;
• Bundling, hanging or unbalanced may cause the crane to hang when sliding;
• Do not hang when being hoisted or floating;
• Structures or components have defects affecting safety work or damage, such as failure of brakes or safety devices, damage to structural devices of hook nuts, and failure of wire rope damage to meet scrapping standards;
• Do not hang when there is an unclear buried object;
• Do not hang when lifting heavy objects;
• The work site is dim, and it is impossible to see the site, the suspended object and the command signal;
• The corners of the weight are not suspended when the bundled wire rope is unpadded;
• The molten steel (hot metal) is not suspended when it is overpacked.

Maintaining aspect

Due to the frequent use of grabs and the limited operation level of the unloader driver, the failure rate of grabs is very high. Factors influencing material wear include external factors and internal factors. External factors include load, sliding speed, abrasive hardness and geometric shape. The internal factors include chemical composition, carbide type, microstructure and so on.

Therefore, it is necessary to strengthen the inspection of these parts during the daily spot inspection. Meanwhile, the maintenance work of these parts should also be done well. In order to better manage the grab, ensure production and ensure safety, the scope of work and working procedures shall be based on the composition of personnel involved in the use, maintenance and repair of the grab.

The following are examples of daily operating and maintenance.

• The driver should meet the standard for refueling to ensure sufficient lubrication; If the refueling cannot be added, record it in time and report it to the inspection personnel or the technician in charge. It is required to keep a record of each refueling on the running log.
• For each major grab repair, the grab repair team must perform statistical work (including repair items, repair time, difficulties encountered during repair, summary of repair materials, etc.), set up special statisticians and record them in the grab management desk account.
• Before sending the power, check that the controllers should stop at zero position and the switches should be in correct position. All mechanism circuit breakers on the control cabinet are closed, and the railing door is closed.
• The driver should observe the use of the grab in real time during the operation. If there is any wear and tear on the chain, the quick joint, etc., the driver should refuel in time. In case of any other failure or suspected failure of the grab, stop the machine for inspection and timely report, and record it in the running log.
• The inspection personnel should ensure the timeliness, accuracy and effectiveness of the inspection of the grab, so as to strengthen the plan of replacement and repair of the grab.
• The principle of interchangeability shall be followed by if replacement parts are needed during the repair of grabs. If the assembly of other parts of the grab bucket is involved in the replacement process, the original assembly method should be avoided as much as possible.