Open Access Open Access  Restricted Access Subscription or Fee Access

Study and Checking of Adequacy of Pinion Stiffness for Jacking Systems of Self Elevating Units during the Conversion Jobs

Bh. Nagesh, I.N. Niranjan Kumar, N. Madhu Latha

Abstract


Jacking systems are used to elevate and lower the hull of self-elevating units in the elevated condition and to raise and lower the legs in the floating condition. In one of a conversion job of a Jack-up Rig from MODU to MOPU, which has been considered here as a case study, in which during conversion it has been identified that the inadequacy of the pinion stiffness could be one of the causes of impending future failure of the rig when installed as a future offshore platform. The hull of the unit is maintained stationary in the elevated condition by means of a holding mechanism. The same mechanism is used to maintain the legs stationary in the floating condition. It is therefore, necessary to have a thorough check of the entire jacking system and identify the pinion stiffness for the jacking system. In this paper, a meticulous checking procedure has been shown to identify the adequacy of the pinion stiffness. The Finite Element Method is used to determine the stresses and strains in various support sections of the jacking system of legs, by modelling the entire structure in SACS modelling and FE analysis software which is extensively used in offshore industry. The analyses have been done on the existing leg lattice structure of a three legged drill rig with spud cans which had been undergoing conversion process from Mobile Offshore Drilling Unit (MODU) to Mobile Offshore Production Unit (MOPU) for installation at Mumbai High.

Full Text:

PDF

References


REFERENCES

ABS Rules for Building and Classing Offshore Installations.

Guidelines for Site Specific Assessment of Mobile Jack-up Units. SNAME T&R 5–5A.

API. RP-2A, WSD, Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms: Working Stress Design. 21st Edn. Dec 2000; Suppl.1–3.

Ohta T, Yamauchi H, Toriumi M. Design Method of Leg Structure of Jack-Up Rigs. NKK Corporation, Engineering Research Centre, Kawasaki, Japan. 1st International Offshore and Polar Engineering Conference, Edinburgh, United Kingdom. 1991; Vol-I.

ABS. Guidance Notes for Dynamic Analysis of Self Elevating Drilling Units. USA: ABS; Jan 2004.

Bh Nagesh, Niranjan Kumar IN. Study on the Failures of Leg Lattice Structure When Offshore Drill Rigs are Being Converted from Mobile Offshore Drilling Units (MODU) to Mobile Offshore Production Units (MOPU). IJIRD. Aug 2016; 5(7): 198–210p.

Bh Nagesh, Niranjan Kumar IN. An Investigation into the Failure of Leg-Lattice Structure of a Jack-Up Rig in Relation to Site Specific Condition, Using Finite Element Method, When Elevated Load of the Rig has Been Increased. IJIR. Sep 2016; 2(9): 1232–1239p.

Bh Nagesh, Niranjan Kumar IN. An Investigation into the Failure of Pinion Holding Capacity, Joint Cans of a Leg Structure, and Preload Tank Capacity of a Jack-up Rig by using Finite Element Method. IJST. Aug 2016; 4(8): 17–25p.

Bh Nagesh, Niranjan Kumar IN. Investigation on the Overturning Stability of a Jack up Mobile Offshore Production Unit by Site-Specific Analysis to Find a Solution to Avoid the Failure of Its Leg Lattice Structure. IJRASET. Oct 2016; 2(10).

Litvin FL. Application of Finite Element Analysis for Determination of Load Share, Real Contact Ratio, Precision of Motion, and Stress Analysis. Journal of Mechanical Design, Transactions of the American Society of Mechanical Engineers (JMD-TASME). 1996; 118(4): 561–567p.

Welaya Yousri MA, Ahmed Elhewy, Mohamed Hegazy. Investigation of Jack-Up Leg Extension for Deep Water Operations. Department of Naval Architecture and Marine Engineering, Alexandria University, Egypt. Int J Nav Archit Ocean Eng. 2015; 7(2): 288–300p. http://dx.doi.org/10.1515/ijnaoe-2015-0020

Chien-Hsing Li, Hong-Shun Chiou, Chinghua Hung, et al. Integration of Finite Element Analysis and Optimum Design on Gear Systems. Finite Elem Anal Des. 2002; 38(3): 179–192p.


Refbacks

  • There are currently no refbacks.