Introduction to hydraulic grabs:

 

　　A hydraulic grab is a working device that uses a hydraulic power source to supply power to hydraulic cylinders, thereby driving the opening and closing of two combined buckets or multiple jaws to grab and unload bulk materials. A grab composed of multiple jaws is also called a grab claw.

     　Classification

 

　　Classification by shape

 

　　By shape, they can be divided into clamshell grabs and orange-peel grabs. The former consists of two complete bucket-shaped components, while the latter consists of three or more jaws.

 

　　Classification by drive mode

 

　　By drive mode, they can be divided into two major categories: hydraulic grabs and mechanical grabs.

 

　　(1) Hydraulic grabs

 

　　Hydraulic grabs are equipped with an opening and closing structure, generally driven by hydraulic cylinders. A hydraulic grab composed of multiple jaws is also called a hydraulic claw. Hydraulic grabs are widely used in hydraulic special equipment, such as hydraulic excavators and hydraulic lifting towers.

 

　　Hydraulic grabs specially designed for excavators are divided into two types: slewing and non-slewing. Non-slewing grabs use the oil circuit of the excavator bucket cylinder and do not require additional hydraulic valve blocks or pipelines; slewing grabs require an additional set of hydraulic valve blocks and pipelines for control.

 

　　Applications of hydraulic grabs specially designed for excavators:

 

　　1. Foundation pit excavation for building foundations, deep pit excavation, and loading of mud, sand, coal, and crushed stone.

 

　　2. Especially suitable for excavation and loading on one side of trenches or confined spaces.

 

　　3. Suitable for loading and unloading of ships, trains, and trucks.

 

　　(2) Mechanical grabs

 

　　Mechanical grabs are not equipped with an opening and closing structure and are usually driven externally by ropes or connecting rods.

 

　　1. Rope grabs

 

　　(1) Double-rope double-jaw grabs and double-rope multi-jaw grabs;

 

　　(2) Four-rope double-jaw grabs and four-rope multi-jaw grabs;

 

　　(3) Single-rope ground-contact opening double-jaw grabs and single-rope ground-contact opening multi-jaw grabs.

 

　　Main parameters of grabs: ① Rated lifting capacity —— 3.2 t to 63.0 t; ② Grab capacity —— 0.20 m3 to 60.0 m3. 2. Hydraulic grabs (1) Without power source —— double-jaw hydraulic grabs and multi-jaw hydraulic grabs; (2) With power source —— double-jaw hydraulic grabs and multi-jaw hydraulic grabs. Suitable materials for grabbing: ① Double-jaw grabs —— bulk materials with particle size ≤ Ф30 mm, such as coal, yellow sand, small ore lumps (powder), etc.; ② Multi-jaw hydraulic grabs —— bulk materials with particle size > Ф30 mm, such as various large ore lumps, block rocks, scrap steel, garbage, straw, etc. Main parameters of grabs: ① Rated lifting capacity —— 3.2 t to 30.0 t; ② Grab capacity —— 0.10 m3 to 60.0 m3

 

　　3. Special grabs (1) Timber grabs (single-rope, double-rope, four-rope, electric). Suitable materials for grabbing: long logs; (2) Leak-proof grabs (single-rope, double-rope, four-rope, hydraulic, electric). Suitable materials for grabbing: grain, fertilizer, cement, etc.; (3) Straw grabs (single-rope, double-rope, four-rope, hydraulic, electric). Suitable materials for grabbing: crop straw, etc.

 

　　4. Dredging grabs (double-rope, four-rope double-jaw with teeth). Suitable materials for grabbing: underwater mud and sand, loose rock, coral reefs, low-density clay, etc.

 

　　5. Wireless remote control grabs (double-jaw, multi-jaw). Suitable materials for grabbing: ① Multi-jaw grabs —— bulk materials with particle size > Ф30 mm, such as various large ore lumps, block rocks, scrap steel, garbage, straw, etc.

 

     　　Manufacturing of hydraulic grabs

 

　　Hydraulic grabs are hydraulic structural component products, composed of hydraulic cylinders, buckets (jaws), connecting columns, bucket lug plates, bucket lug sleeves, bucket teeth, tooth seats, and other parts. Therefore, welding is the most critical manufacturing process for hydraulic grabs, and welding quality directly affects the structural strength and service life of hydraulic grabs. In addition, the hydraulic cylinder is also the most critical driving component.

 

　　Hydraulic grabs are special industry equipment accessories and require special equipment for efficient and high-quality operation, such as CNC plasma cutting machines, bevel milling machines, plate rolling machines, welding positioners, boring machines, hydraulic test benches, etc.