A two-petal grab is a bulk material handling spreader designed for use with cranes. This device consists of two hinged shells that open and close, driven by either mechanical wire ropes or an electro-hydraulic system. Users employ it to grasp, lift, and release materials. The device is suitable for the loading and unloading of bulk materials such as coal, ore, sand, and gravel.
The clamshell grab bucket is a spreader designed for the handling of bulk materials. It features a capacity range of 0.5 to 20 cubic meters, a grab width of 1 to 2.4 meters, and a self-weight of 5 to 17 tons. This double flap clamshell grab bucket can be driven by either hydraulic or electro-hydraulic systems, enabling the device to perform the grabbing, transporting, and unloading of bulk materials within a single lifting cycle.
A clamshell grab is a crane spreader consisting of two symmetrically hinged shells. It captures and encloses bulk materials through a closing action, generating a gripping force that typically exceeds 150 kN. This enables a single crane to perform the loading, transfer, and unloading of bulk cargo without the need for manual intervention. Modern clamshell grabs integrate hydraulic cylinders or electro-hydraulic drive units directly into the grab frame, achieving a closing speed of 8 to 12 seconds and a filling efficiency exceeding 90%. Typically, this device is mounted on bridge cranes, gantry cranes, or port cranes, and can be used directly in conjunction with standard crane hook blocks.
The structural shell is fabricated from high-strength steel conforming to GB/T 700 (Q235B) or GB/T 1591 (Q345B), providing a yield strength of 235–345 MPa. Its working class can reach levels M5 through M8.
Our double-flap grab bucket comes in different types and configurations to suit specific lifting needs and usage scenarios. These include a hydraulic grab bucket and an electric-hydraulic grab bucket. Let’s take a look at the most common types:
Hydraulic equipment draws power from the crane’s onboard hydraulic power unit (HPU) via a rotary distribution valve. It provides continuous gripping force without the need for a built-in power source, thereby keeping the self-weight within a low range (5 to 10 tons), even with a gripping capacity of up to 10 cubic meters. This feature significantly shortens the cycle time for repetitive loading and unloading operations in ports. Additionally, its open-loop hydraulic circuit design facilitates simple and seamless integration with the vast majority of overhead and gantry crane systems.
The electro-hydraulic model contains a self-contained electric motor and hydraulic pump inside the upper frame, eliminating the need for external hydraulic lines. Power is supplied via a trailing cable or wireless radio-frequency remote with ±10 m control range. Therefore, it suits ship-unloaders, floating cranes, and multi-purpose overhead cranes where installing HPU pipework is impractical. The motor-pump unit operates at an ambient temperature range of −20 °C to +50 °C, and the integrated variable-displacement pump enables energy savings of up to 25 % compared with fixed-displacement alternatives. However, the self-contained drive adds 2–4 t to the unit’s self-weight, which must be accounted for in crane safe working load calculations.
The VOITTO crane double flap clamshell grab bucket incorporates design features that align with FEM 1.001 Annex II fatigue class requirements.
This clamshell grab bucket is suitable for the handling of various bulk materials, with a loading rate ranging from 300 to 1,200 tons per hour. The specific value depends on the material density and the crane’s lifting capacity.
Ports and Marine Terminals: Users equip port cranes with clamshell grabs to transport and handle coal, iron ore, and grain.
Mining and Quarrying: Underground and open-pit mining operations frequently utilize clamshell grabs with capacities ranging from 6 to 20 cubic meters. Operators use these to retrieve ore, limestone, and phosphates from stockpiles.
Construction and Demolition: Smaller-capacity grabs, ranging from 0.5 to 4 cubic meters, are typically employed in this sector. Users commonly utilize them for trench excavation, handling recycled concrete rubble, and loading aggregates into the hoppers of concrete mixing plants.
The following parameters apply to the standard VOITTO double clamshell grab bucket range. Custom configurations outside these ranges are available upon engineering review.
| Parameter | Value / Range |
|---|---|
| Capacity | 0.5 – 20 CBM |
| Grab Width (jaw opening) | 1.0 – 2.4 m |
| Grab Self-Weight | 5 – 17 t |
| Shell Material | Q235B / Q345B |
| Drive Type | Hydraulic / Electro-hydraulic |
| Closing Time | 8 – 12 s |
| Ambient Temperature | −20 °C to +50 °C |
| Duty Classification | M5 – M8 |
| IP Rating (bearings) | IP67 |
| Swivel Rating | 200 % of self-weight |
VOITTO is a leading manufacturer of crane spreaders in China. Since 2003, VOITTO Crane has provided customers in over 60 countries worldwide with products featuring technical certifications that meet international standards. With years of accumulated experience, we are committed to providing customers with full-process customized lifting solutions.
For detailed technical specifications or industry-specific solutions, please feel free to contact us.
Alan
Crane Solutions Specialist · Voitto Crane
Specialized in Overhead Crane, Gantry Crane, Jib Crane, Port Crane & EOT Crane export solutions. 10+ years helping global clients with pre-sales consultation, capacity selection and site-specific configurations.
For coal (bulk density ≈ 0.8 t/m³) at 500 t/h with a 4-minute crane cycle, a 10 CBM grab captures approximately 8 t per lift, yielding 480–520 t/h.
The grab is suspended from the crane hook via a hardened swivel hoist ring (rated 200 % of grab self-weight). Electro-hydraulic models additionally require a trailing power cable routed through the crane’s festoon or energy-chain system, typically 380 V / 50 Hz, 3-phase, as a result needing coordination with the crane’s electrical designer.
Yes. For cohesive materials, VOITTO configures the shells with wider-aperture tooth profiles and a higher closing-force cylinder (up to 200 kN) to prevent material bridging. Moreover, the replaceable hardox 450 cutting lips are available in a flat-blade profile specifically engineered for clay, sludge, and wet sand.
The duty classification follows FEM 1.001 Annex II, rated M5 through M8 depending on utilisation class and load spectrum. The CE Declaration of Conformity under Machinery Directive 2006/42/EC is the primary legal document for import into EU member states; GB/T 14560 governs acceptance in China.
Our pre-sale team provides consultations, tailoring solutions to your needs and environment.
Offer customization options for lifting capacity, span and lifting height etc. to meet specific needs.
Real-Time Progress Updates: Weekly reports and PM communication.
Pre-Delivery Testing: 100% load & safety checks, detailed reports.
3-5 years warranty and free replacement for non-manufacturing defects.
24/7 online support and on-site assistance for crane issues.
Yes, lifting capacity, span, height, structure type, and hoist options can be customized to match specific working conditions.
We offer comprehensive after-sales service, including regular maintenance, rapid technical support, and spare parts supply. The standard warranty period is 1 year, with options for extension based on your needs.
Yes, international shipping and export support are available for global customers.
Transit time varies depending on many factors, including the destination of the goods, distance, shipping method and shipping service provider, etc. Generally speaking, international shipping may take about a month.
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