Wear and tear

Audrey Leon spoke with DNV GL’s Michiel van der Geest about its new joint industry project regarding wear acceptance criteria for jacking systems. Currently 13 companies have signed on to the project, which aims to provide criteria for better assessing self-elevating units.

Photo from iStock.

In late November, DNV GL announced it would begin a new joint industry project (JIP) on the heels of its last project to provide recommended practices for jacking system maintenance and inspectional; the JIP occurred from 2013-2014. Guidelines were published in September 2014. The new JIP aims to simplify further an area that is already complex.

“Defining maximum limits of wear across all parts of a jacking system is technically complex,” says Michiel van der Geest, product manager offshore classification, DNV GL - Maritime. “It not only involves the interaction of all elements of the system, including the different materials applied, but also relevant operational and maintenance strategy considerations,” he said at the time the JIP was announced. OE spoke with him to learn more about the new JIP and what to expect.

OE: How did the new JIP come about?

van der Geest.

This recent JIP has a history in a successful joint industry project we executed in 2013-2014 resulting in a recommended practice on Jacking System Maintenance and Inspection (ref DNVGL-RP-0075). The project group realized that, even though we met our project aim, we needed to stay proactive and try to bring the jackup industry forward. As such, we have developed a series of workshops/conferences in further explaining the recommendations.

In one of these workshops, in Houston in September 2015, an issue was raised on acceptable wear limits and the unclear situation around these. This lack of clarity gives way to unnecessary discussions, time loss and cost for follow up analyses.

After a constructive discussion during the workshop (attended by main rig owners as Paragon, Rowan, Seadrill and Noble, but also an original equipment manufacturer (OEM) as Friede & Goldman) we took the idea further and decided to propose a JIP.

OE: Who is involved in the JIP?

At this moment, we have confirmed engagement from drilling contractors, such as: Noble Drilling, Rowan, Paragon, National Drilling Co., Shelf Drilling (supported by Aggrego), and UMW. OEM designers: GustoMSC, Friede and Goldman, NOV-BLM and Siemens AG. And service suppliers: AllRig (in partnership with Ali & Sons), David Brown and Zentech. In all 13.

OE: What will the JIP evaluate and what does DNV GL hope to accomplish?

The project will evaluate all relevant elements of the load path, from the spud-can through the legs, jack gear and rack chock to the jacking house with a focus on wear and the related effects on load and wear of other components of the jacking system.

In addition, we’ll have an operational view in considering relations to maintenance strategy and (acceptable) operational limitations.

At the end, we and our project partners’ aim for documenting the relevant design arguments, considerations and calculations to define wear acceptance criteria. Ideally, we produce a process flow with an overview of all relevant arguments which can be used by all industry partners to define the acceptable wear for a unit on a case-by-case basis.

OE: What is your approach to the project?

The first step is to collect relevant technical considerations relevant for the determination of maximum allowable wear limits; this includes, but are not limited to topics such as, listing of (typical) geometry and material of racks and pinions, different pattern of wear and tear, allowable contact stresses and failure analysis, wear and related effects on other components.

The second step is to describe the trade-offs to be made in accepting wear level vs. effects on asset to higher wear rates, operational limitations and availability.

The third step aims to define guidelines and approaches to define acceptance criteria given a set of operational choices and constraints. The result of this approach should be a process description making it clear how one should define acceptance criteria for a specific unit, for specific operational considerations.

OE: What other benefits are there for including the jacking system in a predictive maintenance campaign?

This must be in further reducing maintenance cost. Being able to assess the conditions of the system and knowing the remaining wear margins gives the possibility to further focus and plan the maintenance activities and reduce downtime / maintenance periods even more.