Case study

Fast-track replacement pre-filtration system for sulphate reduction plant (SRP)

Oil & Gas


Process Internals


Floating Production, Storage  & Offloading Facility (FPSO)


Seawater membrane protection


Oil & Gas

The problem

Process engineers on the FPSO had concerns over the performance of membrane pre-filtration on their onboard sulphate reduction plant (SRP). Filter cartridge change-outs were being done every two-three days, and each housing took 24 hours to execute a change of cartridges. Aside from the vast cost of all the filter cartridges, the operational challenges posed by such frequent and lengthy cartridge replacements were significant.

Further investigation revealed a number of serious issues. The filter housings were undersized for the task in hand, resulting in a very high flux rate for seawater service which is guaranteed to lead to shorter filter life.

The filter internal assembly did not adequately support the cartridges as they should have done. This was limiting the maximum differential pressure at which the cartridges could be operated. It was well below their intended dirty values, resulting in underutilised cartridge dirt holding capacity. Due to inadequate internals design, some cartridges would inevitably rupture, necessitating disassembly of the internals and manually cleaning out of the cartridge debris on each cartridge change-out.

The solution

Our solution was to supply replacement internal assemblies which could be bolted in to replace the existing ones. As well as supporting the cartridges properly, it was also possible to increase the number of cartridges fitted by better arrangement, resulting in a 20% increase in filtration area. Delivered ahead of schedule, the client was able to fit the replacement internals with no modifications to the filter vessels required.

Super duplex internals being taken out of its crate

The results

The improvements were dramatic. Our solution reduced filter cartridge change-out frequency from two-to-three days to two weeks, with change-out time itself cut from 24-five hours. Alongside using our filter cartridges at a cheaper unit price than the original fitted ones, the solution delivered a 90% reduction in cartridge spend, paying back the capital investment in under a month. At the same time, maintenance hours were reduced as far as possible given the constraints of the poorly designed original housings.

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