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Many of the specialist module suppliers for FPSO vessels turn to Amarinth for pumps that satisfy their demanding space and corrosion resistance requirements, in short lead times.

As a result of dwindling oil supplies, oil companies must find more cost-effective means of extracting resources in remote and deep-water areas not suited to traditional offshore rigs.

The use of floating production storage and offloading (FPSO) vessels has grown in popularity, but their demands for low volumes of highly specified pumps on short lead times pose major challenges to traditional equipment manufacturers used to selling much higher volumes to offset the investment made in high-specification pumps.

Oliver Brigginshaw, managing director of Amarinth, which specialises in the design, application and manufacture of pumps and associated equipment, explores how suppliers need to adapt if they are to tap into this growing market.

Oil has been produced from offshore locations since the 1950s.

Originally, oil platforms sat on the seabed, but as exploration has been forced to move into deeper waters and more distant locations, a more cost-effective means of extracting the oil was needed.

The first example of FPSO was simply a converted tanker tethered over a well site.

Later versions were then purpose-built with sophisticated ‘turret’ systems to allow the vessel to turn into the prevailing weather without tangling the umbilical hoses connecting the subsea well heads with the vessel.

Initially, this production technique was limited to oil, but now there is a new generation designed for LNG.

With advances in subsea production techniques, deep-water fields can now be developed economically using FPSO vessels that can deal with multiple subsea well heads without the cost previously associated with large fixed or jack-up platforms.

Once the field has been exhausted, the vessel can be towed to a new location or back to dry dock for maintenance or refitting.

The construction of an FPSO vessel breaks down into two sections: the hull and the topsides.

The hull is usually based on a standard tanker design and many of these are produced in shipyards based in Southeast Asia.

The topsides is where all of the oil or gas processing plant is located to clean up the oil before it can be exported.

These processes all require pumping solutions and typically involve the separating and compressing of the gas before stabilising the crude oil, followed by the dehydration of seawater and produced water ready for re-injection back into the well or disposal.

Finally, sand, solids and acid gas are removed.

In order to get the most life out of an FPSO vessel, newer ones are built to be adaptable to meet the requirements of the individual well location by virtue of the main pieces of process plant being manufactured as a modular design.

There are a number of specialist module manufacturers that have developed their businesses to service the FPSO market, such as: DPS for gas sweetening and filtration; Merpro for sand wash and filtration; Cyclotech for filtration and gas sweetening; and Petreco for gas compression and amine packages.

For all of this processing plant to operate reliably around the clock, the pumps chosen by these specialist manufacturers have to be designed to withstand a harsh environment, from the acidic composition of the oil and gas through to highly abrasive sand.

In addition to meeting the specific technical demands, however, each of the process plant manufacturers faces a common and major challenge in procuring the right equipment – lead time.

The target time to fit out an FPSO vessel is often less than 52 weeks from start to finish and, out of that, the time given over to the procurement of equipment can often be as little as 20 weeks.

Given the specialist nature of these vessels, the number of pumps they require for each project is small, but the specifications are often involved and so the support delivered from the larger pump suppliers can be sporadic as they usually work to larger volumes to create a viable business model.

The process module manufacturers also generally do not have rotating equipment specialists and, therefore, need guidance and support in the selection and application of pumps to meet the unique needs of each vessel, many of which have very limited space – headroom, in particular – which means that serious problems are likely to occur with such a low NPSH available environment.

For example, when Amerada Hess commissioned a sophisticated filtration system that would enable its Triton FPSO vessel located in the North Sea to meet OSPAR regulations, it had only 26 weeks to complete the work or face heavy penalties.

The lack of decks and, therefore, headroom in the vessel meant that the 10 high-specification pumps required to pump produced water had to operate with an extremely low NPSH, leaving them prone to cavitation, which could seriously shorten their working life.

To design a totally new pump was not possible and so, to meet the exacting requirements within the timescales, Amarinth developed a solution by uprating a heavy-duty ISO 5199 chemical pump to API 610 through the use of new bearing brackets and sophisticated upstream pumping mechanical seals that utilised the seawater to provide a supply of cool clean buffer fluid to the seal faces to ensure reliable operation on this abrasive media.

FPSO vessel operators also require flexible and timely support from their suppliers to deal with the many changes that can happen during the life of a contract.

In some cases, the final destination for an FPSO being fitted out is not known until well into the contract, meaning that last-minute alterations have to be made to suit the final operating environment.

Aker Floating Production posed such a problem when fitting one of its Smart FSPO vessels.

At the time, Amarinth was asked to supply the pumps.

Aker had no lease agreed for the vessel and so did not know which field the FPSO would be deployed to, nor the exact duty conditions of the pumps.

The initial requirement was for carbon steel pumps with single mechanical seals but, through the bid phase and even post order, the specifications altered rapidly.

Eventually, super duplex steel pumps were supplied with double mechanical seals to meet the requirements of Reliance Industries, which leased the vessel for use in India’s MA field in the Bay of Bengal.

Design changes continued until the last minute and the duty details were only issued weeks before final test.

Amarinth tuned the pumps to achieve the specified performance and pass final DNV witness tests successfully.

The final location of the vessel also produced the need for additional documentation in a format laid down by Reliance, all of which was delivered within the specified deadline.

Amarinth have purposely designed all of its pump series to ensure that bespoke versions of its high-performance API 610 pumps could be produced.

This thinking also enables small quantities of its pumps to be manufactured in sophisticated materials with minimal impact on lead times.

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