Reliability centred maintenance of Electric Overhead Traveling (EOT) cranes installed in the well intervention area: A case study for ConocoPhillips

Abstract

Material handling equipment is vital for support functions for oil and gas production facilities. On a production platform, cranes are mounted in several areas. E.g. for handling load between supply vessels and platform, and smaller cranes for internal material handling. Lifting of suspended loads on an offshore platform present a significant hazard, the probability of which increases considerably if the crane lacks robust inspection and maintenance routines. Older cranes on a production facility often do not have inspection and maintenance recommendation from the vendor since these were installed in a time when there was less focus on inspection and maintenance. The recommendations at times are ambiguous or were applicable only for initial one or two years of operations. During the years some of the manufacturers could be acquired by other companies, resulting in discontinuity of the crane model or production line, or the crane model could simply be specially made for the given platform. In the well intervention area of ConocoPhillips’ Ekofisk M four Electric Overhead Travelling (EOT) cranes are installed, two cranes with working load of 25 tonnes and two with working load of 15 tonnes, all manufactured by Dreggen specially made for ConocoPhillips and Ekofisk M. The cranes of interest were installed in 2004 and are almost exclusively used under well intervention campaigns. The campaigns require extensive usage of the cranes for 10 to 15 days every third months. The given period demands high reliability of the crane, down time in well intervention are not appreciated. Thus, a strict inspection and maintenance regime is needed. The inspection and maintenance instructions given by Dreggen recommend annual inspection and maintenance. The inspection and maintenance instructions are not aligned to the operational requirements. Few instructions, with little description are given on inspection and maintenance that exceed the annual demand. A need for further investigation into this subject had presented itself, thus, the problem text was formulated: how can the inspection and maintenance regime be enhanced to facilitate this particular use case? By utilizing reliability methodology such as Reliability Centred Maintenance (RCM) the cranes were analysed through looking at equipment history, boundary systems, breaking down the equipment structure, defining functions and identifying functional failures, failure modes and effects. Focusing on preserving functions to enhance the Preventive Maintenance (PM) program. The analysis presented a suggestion to enhance the current PM program to facilitate the particular use case, and some recommendations for further work. Which in general terms was to live the PM program; implement RCM tasks, monitor, and report results, measure effectiveness and continuously make improvements to the PM program. To do this one will need to focus on preserving functions and identifying failure modes, and failure causes in the reported data.