Ship-to-ship transfers can be particularly economical when a vessel has multiple unload points throughout its journey, or when draught restrictions prevent it from entering port
SafeSTS is a ship-to-ship STS operation management company formed in Diss, UK in May 2010 by Future Marine Services. Since that time it has performed more than 1,900 STS transfers, totalling 460M barrels of oil. Earlier this year the company commenced STS operations in the Port of Spain in the Gulf of Paria, off the northwest coast of Trinidad; more recently, it opened SafeSTS Middle East FZE. The UAE office has undertaken five UAE STS transfers for two oil majors in its first six weeks of operation.
The first two transfers took place at the company's Khor Fakkan "C" Anchorage, whilst the next three were at its Fujairah "S" Anchorage; both anchorages are in the Gulf of Oman and a total of nearly 2,334,000 barrels of oil were involved in the five operations. SafeSTS Middle East regional director Capt Jagdeep Singh Sodhi said: "The company was formed to support the growing demand for STS transfers of the full range of petroleum products, and these first five operations involved black fuel oil, crude oil and gas oil.
Elsewhere, the Latin American region has experienced significant growth in STS operations, but as Reuters reports, there have also been some major failings. For example, Reuters found that even the most basic safety and operational statistics were not available in Brazil. Companies are required to report STS operations, but Reuters found gaps between local reports and those submitted to the Brazilian Navy, including at least one collision.
Safety at each stage of the process is paramount to an STS operation, which has been likened to a controlled collision. Key elements in the process are the fenders used to keep the vessels separated and damage-free. “A priority for a shipowner is the safety and security of their assets,” said Teekay Marine Solutions business development manager Ozlem Kir. “When two ships come together for an STS operation, you want the best fenders to protect your assets. Remember, these ships can be up to 330 m long and weigh 320,000 metric tons.”
“Safety at each stage of the process is paramount to an STS operation, which has been likened to a controlled collision”
Together with Trelleborg, Teekay has developed HALO fenders, which are premium pneumatic fenders that are fully compliant with the ISO 17357-1:2014 standard. They are made with an abrasion-resistant outer rubber layer that protects the inner rubber and tire-cord layers from external damage. The fenders are usually supplied in sets of four and are typically 3.3 m in diameter by 6.5 m long for oil transfers.
UK P&I senior loss prevention executive Capt David Nichol has investigated STS operational incidents, including a case where the cargo hose ruptured near the receiving vessel’s manifold, causing oil to spray on deck and overboard.
Capt David Nichol (UK P&I): The shuttle tanker crew should carefully inspect any STS hose supplied by the other vessel
“The investigation into the incident concluded that the failure of the hose was related to its condition, as there was no evidence the agreed pumping rate or pressure in the system was exceeded. Markings on the hose indicated it was last pressure-tested more than two years before the incident and no valid certificate of inspection and test could be produced on demand,” he noted.
“The crew should carefully inspect transfer hoses as far as safely accessible and request access to the hose documentation, cross checking that identification markings match up and protesting any defects or anomalies. Industry guidelines require that periodic tests of hoses are undertaken at intervals not exceeding 12 months,” explained Capt Nichol.
This incident, and the subsequent investigation report, demonstrate the need for all involved – operators, owners and crew – to ensure that this process is conducted safely and efficiently. It also illustrates the need for suppliers to ensure that they are playing a role in raising standards across the industry, contributing their expertise as much as their products. In any oil transfer process, equipment not only needs to improve efficiency while operating safely and being easy to operate, it must also exhibit resilience in the face of environmental challenges.
Typically, the EN 1765 standard is used to qualify STS hoses. However, the GMPHOM 2009 standard mandates tougher requirements, increasing resilience and service life beyond that which is typical. This higher level of assessment guarantees a superior level of certainty and confidence when it comes to STS transfers, in line with best practice regulations, with more accurate performance predictors including service life and resistance. Investing in a hose that meets this higher specification will improve operations, decrease maintenance, and ultimately result in fewer expensive replacements over a project’s life-span.
Trelleborg’s oil and marine hoses operation used this standard when developing a unique solution for STS transfer, the Kleline STS.
Due to the nature of their use, STS hoses can be subject to accidental kinks or crushes because of external forces; the Kleline STS hose is a dual-carcass design, using technology initially utilised for truck tyres and applied in the form of two carcasses made up of steel cables. The first carcass provides resistance to internal pressure, up to five times that of the working rated pressure (WRP), with the second carcass responsible for generating resistance to inherent STS stresses and loads.
A Kleline dual-carcass design STS hose in action (source: Trelleborg)
The hose also features a unique nipple-less design. In contrast to a standard nipple-hose design, there is no stiff metal connector in between different sections of the hose. The hose is more flexible, and the continuous inner liner and integrated gasket create a perfect sealing. The design means that there is no need for gaskets at each connection, increasing the simplicity of installation and resulting in a hose that can withstand stresses and strains for longer. A more flexible design also allows hoses to be built from fewer, longer segments, decreasing the number of connections needed.
A key consideration in any long-term STS operation is the impact of the controlled collision on the hull. UK-based James Fisher and Sons’ partner Fendercare has developed Strainstall, a hull stress monitoring system for FPSOs and other vessels that undertake long-term STS operations.
“Our hull stress monitoring solution is an essential piece of technology on a vessel of this nature, that is designed to remain at sea for many years whilst withstanding everything the ocean can throw at it,” explained Strainstall business manager Paul Downes. “Strainstall has been providing hull stress monitoring solutions for over 20 years with an extensive reference list and can provide a ‘from launch’ record of hull stress, enabling the operator to monitor vessel performance and calculate the fatigue life of the hull.”