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Design Assurance for New Seawater Filtration Unit Design using CFD

amafiltergroup manufactures large first-stage seawater filtration units for various duties on offshore platforms. To handle increased flow rates for new installations, Wilde was asked to evaluate two variants of a proposed design.

amafiltergroup manufactures large first-stage seawater filtration units for various duties on offshore platforms. A filtration unit comprises a set of long cylindrical filter elements operating in parallel, mounted inside a vertical vessel. To handle increased flow rates for new installations, design options are either more elements of the same shape and size, the same number of elements with greater diameter or the same number of elements with increased length. The first two options imply a larger diameter unit and since space is at a premium, maintaining the current footprint in a taller vertical unit is a more attractive option. However, longer filter elements would be increasingly prone to vibration. Having worked successfully with the Wilde Group before, amafiltergroup asked Wilde Analysis to evaluate two variants of a proposed design from this perspective.

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Internal View of Seawater Filtration Elements (Courtesy: MAHLE Industrial Filtration UK Ltd)

About Amafitergroup

Following the acquisition of amafiltergroup in July 2008 by MAHLE Industrial Filtration, amafilter become a product brand within the MAHLE Industrial Filtration organisation. MAHLE Industrial Filtration has been producing high-quality industrial filters for fluid technology, dust filtration, and process technology for many years.

The MAHLE Group is among the top 30 automotive suppliers globally and is the world market leader for combustion engine components, systems and peripherals. MAHLE employs approximately 45,000 employees in 100 production plants and 8 research and development centers. In 2008, MAHLE generated sales in excess of EUR 5 billion (USD 7.3 billion).

Approach

The most damaging flow-induced vibration is typically when organised vortex-shedding excites a natural frequency. The resonant frequency of filter elements was calculated from details of their construction and supports. Excitation frequency is determined by flow across filter elements. CFD was used to investigate internal flow patterns and, in particular, to estimate the flow velocity over filter elements at their most vulnerable location opposite the exit nozzle where velocities were at their highest. Estimates of vortex-shedding excitation frequency showed that one of the design alternatives carried a risk of resonant vibration of these elements, whilst the alternative design gave a healthy safety margin against this mechanism.

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Seawater filtration investigation including vortex-shedding prediction (Courtesy: MAHLE Industrial Filtration UK Ltd)

Benefits

By simulating equipment performance before manufacture, a potential failure mechanism, with its attendant costs, was identified and avoided, whilst confidence was enhanced in an alternative design. A better understanding of the internal flow pattern also identified the potential to reduce overall pressure drop with a further incremental design modification.

“Wilde have always demonstrated a knowledgeable and professional understanding to our needs, and have been able to quickly and thoroughly assimilate our requirements, and equally quickly produce the necessary results to support our design process and provide guidance on the solution(s) best suiting our needs commercially and technically.”

MAHLE Industrial Filtration

 

 

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