The main turning hardware between the crane and the load.
APP: Dry & Subsea Lifting
Offshore crane Component
STANDARD: up to 400t
Swivels are used in Lifting, Mooring & Anchoring applications, and consequently are considered critical lifting component from safety point of view because is the main turning hardware between the crane and the load.
The main difference between Swivel Hook and Hook Block are pulleys: swivel hook does not need sheaves and the main reason is because there are certain lifting operations where straight lifting is necessary with enough weight and protection to turn.
The key component of the Swivel Hook is the COVER: this part is protecting inner machined parts, bearing and thread to guarantee a full turning and proper rotation of the load, and at the same time is giving the necessary weight to avoid rope outlet and crane incidents. Weight and rotating are the main functions of swivel.
Regularly this kind of products are used in Offshore environments, where swivels could have two main purposes:
For SUBSEA LIFTING, the crane is regularly located top site, even if recently semi-submergible and submergible cranes are being designed and installed. This kind of Offshore cranes regularly do subsea operations even if there are dry cranes too: most of them they do in shallow water, but others do deep water for e.g maniffols recovery, seabed pipeline maintenance or repair… being possible to do operations up to 4.000m subsea. For this application regularly Swivel Hooks are used.
For LONG TERM MOORING LINE, main technology to fix floating structures into the seabed, forged swivels are a great product to link two chains, chain with rope, rope with sling… or any technology used for floating structures mooring lines. Recently other technologies beside steel chain are being used and recommended by installation companies based on two criterias:
* Weight of mooring line in deep water.
* Cost of commissioning & installation.
Mooring Line is being a combination technology in recent projects, combining steel with fiber products: steel chain, steel wire ropes, synthetic ropes and textile slings. Combination of all 4 technologies is reducing commissioning costs and reducing weight. Hooks and other links are in between different technologies to ensure a permanent steel-fiber, steel-steel or fiber-fiber join or linkage. For this application regularly Eye-Eye and Eye-Clevis Swivels are used.
In both cases, with hook or without hook, swivels are working submergible and to avoid salty water getting into the inner parts, cover part and sealings are used to guarantee a long life time. Additionally when operation is held in deep water, outer & inner pressure difference is a big issue and sealings are a key factor to avoid any problem and guarantee the bearing is rotating correctly.