LTZC Large-scale Marine Slewing Bearing Project Completed

I. LTZC Large-Scale Marine Vessel Slewing Bearing Project

The target application for this LTZC large-scale marine slewing bearing is the main crane slewing mechanism of a self-propelled offshore crane vessel. The required large-diameter slewing bearing must withstand the crane's axial loads, radial loads, and overturning moments while enduring strong offshore winds and the corrosive impact of seawater. These conditions place extreme demands on bearing quality, particularly given the difficulty and high cost of maintenance. To reduce costs and improve efficiency, the client required a marine slewing bearing solution featuring a long maintenance-free service life, high reliability, and superior resistance to seawater corrosion.

Challenges currently faced by the client regarding the slewing bearing:

Poor sealing performance allowed seawater and contaminants to easily penetrate the bearing interior, accelerating damage;

Severe salt-spray corrosion in the marine environment caused pitting and cracking on the bearing raceways and rolling elements;

Frequent start-stop operations and luffing (boom angle changes) subjected the bearing to high instantaneous impact loads, requiring the raceways and gears to possess excellent fatigue and impact resistance;

Limited installation space necessitated strict precision controls regarding end-face flatness, inner/outer diameter concentricity, gear backlash, and assembly preload ranges.

Upon receiving the client's technical requirements, the LTZC project team immediately initiated a detailed analysis of the specifications. A specialized technical team—comprising structural design engineers, materials engineers, heat treatment process engineers, and quality control engineers—conducted simulation and verification based on the client's load conditions, installation constraints, and the marine environment. Addressing the specific challenges and requirements, the team developed an optimized design for the marine slewing bearing. This design successfully passed the technical review at the client's headquarters, and production was officially launched.

II. LTZC Exercises Strict Quality Control to Ensure the Quality of Large-Diameter Marine Slewing Bearings

1. Procurement of High-Quality Raw Materials

To meet the demands of marine operating conditions, the slewing bearing rings are manufactured from high-purity 42CrMo alloy forgings. Upon arrival, all forgings are accompanied by comprehensive inspection reports—including heat treatment and ultrasonic testing records—ensuring quality at the source.

2. High-Precision CNC Rough and Semi-Finish Machining

Utilizing the facility's large-scale CNC vertical lathes and CNC turn-mill centers, LTZC performs rough and semi-finish machining on the inner and outer diameters, end faces, and mounting threaded holes of the large rings. To address the risk of deformation caused by machining stress in extra-large diameter workpieces, multiple aging stabilization processes are implemented to gradually relieve internal stresses.

3. Precision Grinding, Gear Finishing, and Comprehensive Dimensional Inspection

Gears undergo precision hobbing and grinding processes. Strict control over tooth alignment errors, tooth profile errors, and gear backlash ensures smooth operation, reduced noise, and minimized impact loads during the bearing's rotation.

Following finishing, the Quality Inspection Department conducts a full dimensional inspection. Parameters such as end-face flatness, inner and outer diameters, raceway curvature, mounting hole positional accuracy, and gear precision are recorded individually to generate a final product dimensional inspection report.

4. Anti-Corrosion Treatment and Sealing System Assembly

Based on the client's operating environment, the marine slewing bearings utilize a C5-M heavy-duty marine anti-corrosion scheme. This involves a multi-layer coating process: surface sandblasting, followed by zinc-rich primer, intermediate coat, and a specialized marine topcoat. Coating thickness is strictly controlled in accordance with offshore equipment standards. A combined labyrinth and double-lip seal structure effectively blocks the ingress of seawater, salt spray, and moisture, significantly delaying grease degradation and raceway corrosion. During assembly, seawater-resistant grease is used, and the bearing is assembled to precise design clearance specifications. Multiple 360° rotation flexibility tests are conducted to ensure smooth operation and eliminate issues such as binding or abnormal rotational noise. Upon completion of all manufacturing processes for the large-diameter slewing bearing assembly, LTZC conducted an internal pre-acceptance inspection. Once all test parameters met the required standards, a comprehensive technical documentation package—including raw material certificates, forging flaw detection reports, heat treatment reports, hardness test reports, finished product dimensional inspection records, magnetic particle inspection reports, anti-corrosion coating inspection reports, and factory test records—was compiled for delivery to the customer. Following on-site verification by the customer's third-party inspector, all specifications were confirmed to meet technical requirements, marking the official completion of the LTZC large-scale marine vessel slewing bearing project.