clamshell grab
Enable an AI agent to recognise a clamshell grab, assess its suitability and condition, and determine whether a proposed material-handling operation is supported by its configuration and evidence.
Bundle → Layer → Finding → Questions Filled
6 bundles · 11 layers · 17 findings · 27 questions
Shell capture and retention The paired-shell geometry that admits, encloses, retains and releases material.
Paired-shell identity
Recognise the attachment through its enclosing surfaces and their relative movement.
Enclosing shell pair
Record evidence that two opposed shells form the carrying cavity, including features that distinguish them from tines or gripping jaws.
- Which two moving shell surfaces form the material-carrying cavity? definition
- What observed geometry distinguishes this attachment from an orange-peel grab, grapple or single-body bucket? boundary
Material-contact geometry
Describe the shell features governing entry into material and its subsequent retention.
Edges, gaps and drainage
Record cutting edges, teeth, closure gaps and deliberate openings against the intended material and retention requirement.
- What edge profile, teeth, drainage openings and closed-shell gaps does this configuration have? measurement
- For the intended particle size and moisture condition, what evidence supports acceptable retention or drainage? provenance
Closing drive and control How power, ropes and linkages produce shell movement and how that movement is controlled.
Actuation path
Trace the mechanism from its external input to shell movement.
Drive and transmission
Identify the actual drive arrangement and its ropes, cylinders, sheaves or linkages without presuming a universal mechanism.
- What mechanism opens and closes the shells, and which components transmit the closing effort? definition
- What documented rope arrangement, hydraulic supply or electrical supply is required? measurement
Command and failure behaviour
Relate commands and loss of services to actual shell behaviour.
Closure control and holding
Record how closure is commanded, how its completion is established and what maintains the loaded state.
- How can an operator or agent distinguish commanded closure from achieved closure or a material obstruction? measurement
- What does the documentation require when power, hydraulic pressure, rope tension or a control signal is lost? action
Carrier and payload envelope The attachment interfaces and combined limits governing a supported lift.
Attachment and services
Establish compatibility between the grab configuration and the proposed carrier.
Verified carrier interface
Record suspension or mounting details, applicable reeving and service connections with their supporting compatibility evidence.
- Which suspension or mounting interface and, where applicable, rope reeving arrangement does this grab require? definition
- Which manufacturer documents support use with the proposed carrier and service configuration? provenance
Volume and mass limits
Separate cavity volume, grab self-mass and allowable contents.
Material-dependent load check
Evaluate expected contents using a stated volume basis, material bulk density and filling assumption, then check the applicable load limits.
- What are the documented capacity, self-mass and permitted material payload for this configuration? measurement
- Given the material density, expected filling and carrier capacity at the planned operating position, is the proposed load within all applicable limits? action
Grabbing and discharge cycle Observable states and material behaviour during filling, transfer and emptying.
Material engagement
Assess whether the grab can reach and capture the intended material under the proposed conditions.
Capture suitability
Relate opening dimensions and shell features to material accessibility, particle size and resistance to closure.
- Do the opening dimensions and working clearances permit engagement with the material at the proposed location? measurement
- What evidence shows that this configuration can close effectively through the intended material without prohibited forcing or obstruction? provenance
Transfer and emptying
Assess retention during movement and release into the receiving space.
Retained and released material
Record spillage, incomplete opening and residual material separately from the commanded operating state.
- What observations establish that the captured material remains contained during the proposed transfer? measurement
- If material bridges, adheres or remains after opening, what documented clearing procedure is permitted? action
Integrity and use restrictions Grab-specific deterioration, maintenance requirements and evidence governing continued use.
Wear and load-path condition
Inspect the structures and moving components that support and retain the load.
Inspection and rejection evidence
Associate observed shell, edge, pivot, linkage and drive-component condition with documented inspection and rejection criteria.
- What wear, cracking, distortion, excess clearance or leakage is present in the shell assembly and applicable closing components? measurement
- Which documented limits determine whether the observed condition requires adjustment, repair or withdrawal from service? provenance
Safe intervention and applicability
Establish supported maintenance actions and the requirements applicable to the particular configuration and use.
Isolation and operating authority
Record shell-support and energy-isolation procedures together with applicable manufacturer restrictions and verified conformity requirements.
- How must the shells be supported and relevant rope loads, hydraulic pressure or electrical energy controlled before inspection or maintenance? action
- Which standards, issuing bodies, inspection obligations and conformity records apply to this grab configuration, jurisdiction and intended service? provenance
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these check these first hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these kinds and varieties hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these real-world use hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these typical measurements hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these failure modes and hazards hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these regional variation hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of clamshell grab this model covers, and on what evidence? provenance
Classifiers Filled
- Family
- Thing Registry
- Category
- Physical world and living systems
- Entry kind
- thing
- Plane
- PHY
- Domain
- PHY.OBJ
- Other names and narrower kinds
- Hammergrabs
What it is Filled
A clamshell grab is a lifting or excavating attachment with two opposed, hinged bucket shells that close around loose material to contain it during lifting and open to discharge it.
In scope
- Opposed shells, cutting edges, pivots and linkages that enclose and release material
- Rope-operated, hydraulic or other documented opening and closing arrangements
- Suspension or mounting interfaces and required carrier services
- Grab capacity, self-mass and material-dependent payload limits
- Capture, retention, discharge and observable operating states
- Grab-specific wear, inspection, maintenance and operating restrictions
Out of scope
- The complete crane, excavator or other carrier and its structural design
- Bulk-material classification and properties beyond their relevance to grab suitability
- Site-wide lifting plans, traffic management and exclusion-zone administration
- Hoppers, stockpiles, vessels and transport systems receiving the load
- Orange-peel grabs, grapples and conventional digging buckets as separate attachment kinds
Why it exists Filled
Enable an AI agent to recognise a clamshell grab, assess its suitability and condition, and determine whether a proposed material-handling operation is supported by its configuration and evidence.
Distinguishing features Filled
- Material is captured between two opposed shell-like halves that move toward one another to form a carrying cavity.
- The load-bearing enclosure is formed by shells rather than the multiple separated tines characteristic of an orange-peel grab.
- Material capture depends on the relative closing movement of the two shells, distinguishing it from a conventional single-body bucket.
- The working surfaces enclose loose material rather than relying primarily on narrow jaws gripping an individual object.
- The attachment has an identifiable opening and closing mechanism and carrier interface; neither the carrier nor a complete unloading installation is itself the grab.
What robots and AI may and may not do Filled
Must not
- Swing or open a loaded grab over people.
- Exceed the crane's rated load including the grab's own weight.
- Use a grab to lift people or for loads it was not designed for.
- Dredge in protected waters without the required permits.
Only with a human decision
- Lifting operations near people, power lines or in confined spaces.
May
- Operate a clamshell grab on cranes or excavators the agent is authorized to control.
- Inspect shells, hinges, ropes and hydraulics before work and report defects.
- Log loads and cycles for maintenance records.
Moral aspects Filled
- Falling material from an open grab can kill workers below.
- Dredging disturbs sediment and aquatic habitats.
Who is affected
- Workers on the site
- Dock and ship crews
- Aquatic ecosystems
Owners Filled
Steward
The operator of the crane or dredging plant.
Links to other meta-models Filled
parent
- Q141142065 - registry parent class
What else AI and robots need to interact with it Filled
Identity and identifiers required Filled
- Vercy registry: vr.tr.clamshell-grab
- Wikidata: Q2896329 (https://www.wikidata.org/wiki/Q2896329)
Direct properties required Filled
- Actuation arrangement: Rope-operated; externally supplied hydraulic; electrohydraulic; other documented arrangement
- Shell configuration: Shell profile, edge or tooth arrangement, drainage openings and closure details
- Nominal volumetric capacity: m³, with the manufacturer's capacity definition
- Grab self-mass: kg, identifying the included equipment and configuration
- Permitted material payload: kg or t, with configuration and operating restrictions
- Material compatibility: Supported material classes linked to bulk density, particle size, cohesion and abrasiveness
- Working geometry: Maximum opening, shell width, closed height and relevant clearances in mm or m
- Carrier compatibility: Documented compatible suspension or mounting interfaces, reeving arrangements and service requirements
- Service requirements: As applicable: hydraulic pressure in bar or MPa, flow in L/min, electrical supply in V and Hz, rope requirements in manufacturer-specified units
- Shell and load state: Open; closing; closed; opening; obstructed; unknown, paired with empty; loaded; residual material; unknown
- Mechanical condition: Observed condition of edges, shells, pivots, linkages and applicable ropes, sheaves or hydraulic components
Recognition required Filled
- Two hinged scoop-shaped halves hanging from ropes or a hydraulic arm.
- Seen on cranes at docks, scrap yards and dredgers.
Capabilities and actions required Filled
- Identify the grab configuration from shell geometry, actuation and attachment evidence.
- Check compatibility with a proposed carrier and its available services.
- Estimate a candidate material payload and compare it with documented grab and carrier limits.
- Assess whether the shell geometry supports capture, retention and discharge of the intended material.
- Interpret operating observations to identify incomplete closure, obstruction, leakage or retained material.
- Determine which inspection, maintenance or operating restrictions apply before further use.
Hazards and failure modes required Filled
- Worn ropes or hinges can drop the load.
- Material can spill from a partly closed grab.
Standards and interfaces required Filled
- Directive 2006/42/EC on machinery, European Union.
Context of use required Filled
- A clamshell grab is used with compatible lifting or excavating machinery to collect, move and discharge loose bulk material.
- It is encountered in ports, stockyards, dredging operations and construction sites handling materials such as sand, gravel or sediment.
- Its suitability depends on the material, operating environment and compatibility with the supporting machine.
Sources Filled
- Wikidata item Q2896329: clamshell grab - identity and sense of the item
- Wikipedia (de): Zweischalengreifer - general description of the item
Open questions
- Does the registry intend this entry to include both suspended clamshell grabs and rigidly mounted clamshell attachments, and does an existing Vercy world model already cover that scope?
- Which manufacturer sources establish representative capacity, mass and dimensional ranges separately for bulk handling, excavation and dredging configurations?
- Which standards and conformity requirements apply to each actuation arrangement and jurisdiction, and which obligations belong to the carrier rather than the grab?
- What configuration-specific evidence establishes behaviour after loss of power, pressure or rope tension and the permitted response to incomplete closure?
- Which measured wear limits and material-retention criteria distinguish ordinary serviceable grabs from configurations intended for fine, wet or environmentally sensitive material?
Machine files
Provenance
thing registry research (pass 2) · unreviewed
Built from: models/things/publications/thing-q2896329/spec.json