Crane Vessel Hoist Block Segmentation for Inertia Reduction
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Solution Overview
Problem
The operation of crane vessels is hindered by the heavy main hoist lower block, which increases inertia and causes swinging, potentially leading to accidents and damage, especially in rough seas, due to its significant weight located near the end of the jib.
Innovation Solution
The main hoist lower block is assembled from a sheave block and a load attachment assembly, with a storage device for the load attachment assembly, and displacement means that can engage and disengage with the load attachment assembly, allowing it to be stored during auxiliary hoist operations, reducing the total weight and preventing swinging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the main hoist lower block is designed with extreme load capacity (tens to 300 tonnes), then the load attachment capability is improved, but the inertia of slewing operation increases and the block sways with respect to the jib
Solution Approach 1:
The main hoist lower block is divided into two separate components: the sheave block (containing sheaves) and the load attachment assembly (containing lowering weight and hoisting hook). This segmentation allows the heavy load attachment assembly to be detached and stored when not in use, reducing the weight participating in slewing operations while maintaining full load capacity when needed.
Solution Approach 2:
The load attachment assembly is extracted from the sheave block and stored in a dedicated storage device mounted on the hull. This extraction removes the majority of the dead weight from the slewing operation, significantly reducing inertia and preventing unwanted swinging during crane operations.
2Ease of operation
If the main hoist lower block remains assembled and close to the jib end, then the load attachment device is readily available, but the vessel rolls more due to increased rotating weight
Solution Approach 1:
A storage device is introduced as an intermediary structure mounted on the hull to hold the load attachment assembly when not in use. This separates the load attachment device from the rotating jib structure, eliminating its contribution to vessel rolling during slewing operations while keeping it accessible for when it is needed.
3Ease of operation
If the main hoist lower block is disassembled frequently, then the weight participating in slewing is reduced, but re-rigging time is required which reduces productivity
Solution Approach 1:
The load attachment assembly is pre-positioned in a storage device mounted on the hull, ready for quick attachment to the sheave block when needed. This preliminary positioning eliminates the need for complex re-rigging operations and reduces downtime between main hoist and auxiliary hoist operations.
Data Source
AI summary
A crane vessel including a revolving hoist crane and a method of using such a vessel are provided. The hoist crane includes a jib, main hoisting means and auxiliary hoisting means for raising and lowering a load. The main hoisting means include a main hoisting tackle with a main hoist upper block connected to the jib and a main hoist lower block. The main hoist lower block is assembled from a sheave block including the sheaves of the main hoist lower block and a load attachment assembly having the lowering weight and the main load attachment device. The crane vessel is provided with a load attachment assembly storage device for storage of the disassembled load attachment assembly and displacement means capable of engaging with and displacing the load attachment assembly while it is assembled to the sheave block and when the jib is supported by a jib rest.