Longitude were contracted by Jurong Shipyard to perform a vibration study in order to reveal possible resonance problem in the drill floor of a Seadrill Jack up vessel.
Facts and Figures:
- CJ70II Jackup Type
- 89m Length
- 97m Breadth
- DNV Class
Longitude’s Scope of Work
A finite element model of the steel structures supporting and surrounding the drawworks was produced in order to calculate the acceleration frequency response of these structures. The excited vibration force was estimated based on the vibration velocity from “Dynamic Balancing Report of J2503 Drum”. The vibration response was then checked against NORSOK S-002 and ISO 10816-3 criteria.
The purpose of the study was to assess the natural frequencies of vibration of drill floor include some existing structure, acceleration and velocity amplitude of forced vibration were reported. This analysis was conducted by finite element modelling and post processing program “FEMAP” and performed the analysis using the program “NX-Nastran”.
The analysis shows that the vibration acceleration and velocity amplitude of drill floor structure resulted from draw works unbalance forces obtained from “Dynamic Balancing Report of J2530 Drum, October 25 2012” at the full speed 320 rpm satisfied the NORSOK S-002 vibration limit.