The maintenance and upkeep of a vessel’s structure is crucial in ensuring the safety of those on board. This specifically applies to fatigue cracks present on structural components such as the hull and boundary tanks. Shipowners and operators must ensure fatigue cracks are repaired as soon as possible to preserve asset integrity, seafarer safety, and cargo while also meeting regulatory and class requirements.
While the occurrence of cracks has been central to vessel repair and maintenance for many years, the initial cause of this common phenomenon is often unknown. Current opinion suggests that factors influencing the development of cracks could include vibration, fatigue, corrosion, and extreme loads.
Furthermore, new stress points are emerging as a result of the recent uptick in retrofitting and refits required to deliver compliance with the increasingly stringent environmental regulations. For example, installing a scrubber on a vessel to ensure compliance with the International Maritime Organization’s global sulphur limit has potentially added stress and strain to the existing structure; exposing previously unseen structural weaknesses because of different weight loads which cause cracks in new and unusual areas.
Although the cause of cracks on vessels varies greatly, it is imperative that all cases are repaired as soon as possible to prevent the cracks from developing further – if left untreated, these cracks could cause catastrophic failure.
For many years, gouging and rewelding or crop and renewal techniques have been universally regarded as the conventional way to repair cracks on vessels. While effective, these approaches have limitations, such as considerable time and budget commitments to complete extensive steel renewal and the heightened risks related with the necessary traditional “hot work” to repair cracks.
Despite the risk, as well as time and economic limitations, the ongoing use of these methods continues to prevail. This is mostly due to support by ease of acceptance from class societies, a lack of appetite for change from conservative shipowners, and the desire from yards to preserve their ‘bread and butter’ income from steel renewal work.
However, a permanent, alternative solution to repair vessel crack does exist. The use of structural composites, such as sandwich plate systems (SPS), offers a new, mature repair and prevention solution that is safe and non-disruptive. Structural composites also deliver improved strength compared with conventional steel structures. Notably, this method is intrinsically safe as SPS can be applied using ‘no hot work’ techniques and can also be carried out by riding squads alongside a vessel or while a vessel is in dry dock. For on-station below the water line or on floating production storage and offloading vessels, structural composites eliminate the need for dive boats and cofferdams which further reduces the associated risk of such activities and increases the safety of those working out at sea.
Given the heightened pressure on shipowners to find new ways to reduce their operating expenses, class societies offering greater support, and vessel owners looking to uphold and enhance the maritime industry’s rigorous safety standards, the case for an overhaul in traditional crack repair techniques has never been more compelling.