Detailed Description
Marine Grab Crane — Same Machine, Hostile Environment
A land-based grab crane handles coal at a port terminal. A marine grab crane handles the same coal — but from a barge, floating crane, or self-unloading bulk carrier, with salt spray, constant humidity, and ship movement.
The cable faces the same mechanical demands (hoist + grab cycling) plus marine-specific threats:
- Salt spray corrosion: Tinned copper conductors throughout (not bare copper), stainless steel tensile core option
- Constant moisture: Sealed jacket-to-core interfaces prevent water wicking along conductor strands
- Ship classification: DNV GL, ABS, or Lloyds certification required — cable must be on the vessel's certified equipment list
- Halogen-free mandatory: Enclosed ship spaces — PVC cannot be used due to toxic HCl gas emission in fire
Construction for a Salt-Laden Duty Cycle
| Element | Specification |
|---|---|
| Conductor | Tinned copper (standard for marine), IEC 60228 Class 6 |
| Power cores | 10-120 mm² - hoist + grab motors |
| Control cores | 0.75-2.5 mm², 4-24 cores |
| Core insulation | EPR - moisture resistant, high dielectric |
| Tensile core | Galvanized steel or stainless steel (marine preferred) |
| Outer jacket | PUR TMPU - halogen-free, salt spray tested, DNV GL approved |
Power and control run in one cable: the hoist motor, the grab open and close motors and the limit switches are all supplied through a single marine-certified cable, which removes a second cable run and a second set of terminations from the crane.
Certification and Verification
- DNV GL, ABS and Lloyds approval - the documentation needed to place the cable on a vessel's approved equipment list
- Salt spray tested to IEC 60068-2-52 for 2 000 hours or more
- Halogen-free per IEC 60754-1 - mandatory for enclosed ship spaces and crew safety
- Rated 0.6/1 kV with a 3 500 V AC test voltage
- Operating temperature -40 °C to +80 °C
- Reeling duty: minimum D/d 10:1
Applications
- Floating grab cranes - barge-mounted bulk handling for port and coastal operations
- Cutter suction dredgers - ladder and spud grab crane power and control
- Shipboard grab unloaders - self-unloading bulk carrier crane cables
- Offshore platform cranes - certified marine grab crane for supply vessel loading
Combined Hoist and Grab Duty in One Cable
A grab crane uses two motions at the same time: the hoist that lifts the grab, and the open and close motors that operate the jaws. Both are fed from the same reeling drum, so the cable carries hoist power and grab power together with the control cores for the limit switches. Power conductors are sized from 10 to 120 mm², while control conductors run from 0.75 to 2.5 mm² in 4 to 24 cores inside the same sheath.
That combination is what allows a single certified cable per crane instead of two separate runs with two sets of terminations. Reeling duty is specified at a minimum D/d ratio of 10:1, and the EPR core insulation holds its dielectric strength in the humidity that a vessel deck or dredger ladder sees continuously.