Design of Modifications for an Engineered Lift

OFFSHORE CRANES / PEDESTAL DECK CRANES / RAM LIFFING BOX BOOMENGINEERING
LOCATION  EMEA/ UK / SOUTHERN NORTH SEA
EQUIPMENT  OFFSHORE CRANES / PEDESTAL DECK CRANES / RAM LIFTING BOX BOOM
BRANDKENZ DHC12/180

Intro

During an upcoming TAR, our client hopes to utilize their deck crane for a special lift that exceeds the original safe working load. This provides substantial operational and financial benefits when compared to mobilizing a crane barge. Alatas was entrusted with the task of verifying suitability and designing the required modifications for the Pedestal Crane in preparation for the Special Lift.

BACKGROUND

Alatas has previously completed a load path inspection and engineering analysis, which highlighted some critical areas, including the following:

  1. Winch Frame

Due to the line pull applied to the hoist drum, the winch frame and crane chassis around the 4-off hold-down bolts were found to be highly stressed. Furthermore, material loss was noted.

  • Dead-End Padeye

Utilization was found to exceed acceptable limits when applying design loads calculated based on the relevant crane design code.

ALATAS’ SOLUTION

  1. Winch Frame Doubler Plates

Re-enforcement plates were designed to strengthen the structure around the bolted connection (Figures 1 and 2). A 3D CAD assembly was created, and FEA analysis was completed for a wide variety of load cases (Figures 3, 4, and 5). New Grade 10.9 bolts were utilized and torqued to a calculated value to ensure a slip-resistant joint was achieved (Figure 6). To aid ease of installation, the weight of each plate was kept below 10kg.

  • Dead-End Padeye

Conceptual design and initial analysis were completed on a cold work option (Clamp-on Frame) to negate the requirement for welding (Figure 7). Due to a range of limitations, such as total size and weight, working around existing boom ancillaries, and the maximum permissible pressure applied to the boom, it was agreed that this solution is not practical for this scenario. Therefore, a replacement weld-on pad eye was designed (Figure 8) and checked in ANSYS FEA (Figure 9). Fabrication Drawings, Assembly / Welding Drawings, and Installation steps were created.

Job Scope

  • Assess modifications required
  • Validate the feasibility of proposed solutions
  • Roughouts and Conceptual Design
  • Engineering Analysis by hand calculation and finite element analysis (FEA)
  • Detailed Design
  • Fabrication and Arrangement Drawings
  • Design Summary Report
Search

Share Article

Recent Posts

Scroll to Top