Wood Group – Amarinth deliver low NPSH pumping solution enabling Triton FPSO to meet OSPAR regulations

Space constraints and low NPSH

The project demanded ten high specification pumps to pump the produced water. These had to have a small enough footprint so that they could squeeze within the tight space constraints of the Triton vessel. The lack of decks also restricted the headroom available meaning that the pumps had to operate with a low Net Positive Suction Head (NPSH) leaving them prone to cavitation (where gas bubbles in the liquid rapidly collapse producing a shock wave) which can shorten the life expectancy of the impellers and other components.

In addition to these technical constraints, with a risk and reward prime contact in place, Wood Group required a tight 26-week delivery schedule to avoid the hefty penalties that would be levied if the operator did not meet the OSPAR deadline.

Drawing on their wealth of experience in delivering bespoke pumping solutions, Amarinth were chosen by Wood Group as the only company able to meet the performance requirements within the space constraints, achieve the low NPSH and deliver all of this to the tight schedule demanded. ISO9001 was a given and suppliers to Wood Group had to be registered with First Point Assessment Ltd, the oil and gas supply chain database used as the key tool by oil & gas purchasers to identify and select current and potential suppliers when awarding contracts or purchase orders.

Sophisticated hybrid design

To achieve the dimensional space constraints the Amarinth design was a hybrid based on its proven ‘C’ series heavy duty ISO 5199 chemical pump, but incorporating up-rated API 610 bearing brackets. The pumps were fitted with sophisticated ‘upstream pumping’ (USP) mechanical seals manufactured by John Crane that utilise seawater to provide a supply of cool, clean buffer fluid to the seal faces to ensure reliable operation on this abrasive media. ATEX compliancy was achieved along with complete material traceability. The pumps were delivered with a comprehensive bespoke documentation set.

Significant reduction in oil released

On commissioning the pumps performed flawlessly enabling the filtration system to reduce the oil released from 40ppm to just 3ppm, which is below the new OSPAR regulations. Amarinth has since been engaged in similar demanding projects in the North Sea with Maersk , ConocoPhillips and Shell.