°®¶¹´«Ã½app

Design Assurance for Seawater Filtration Unit

°®¶¹´«Ã½app used CFD simulation to evaluate two variants of a proposed design for a seawater filtration unit, with the objective of limiting the potential for vibration within acceptable parameters. °®¶¹´«Ã½app was able to identify the best design option to meet MAHLE’s requirements.

Challenge

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, the possible design options were either to include:

• 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 implied a larger diameter unit and, since space was at a premium, maintaining the current footprint in a taller vertical unit was a more attractive option. However, longer filter elements would be increasingly prone to vibration.

Having worked successfully with °®¶¹´«Ã½app previously, amafiltergroup asked them to evaluate two variants of a proposed design from this perspective.

Solution

The most damaging flow-induced vibration typically occurs when organized vortex-shedding excites a natural frequency. The resonant frequency of filter elements was calculated from the details of their construction and supports. Excitation frequency is determined by flow across filter elements. Computational Fluid Dynamics (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.

MAHLE Industrial Filtration UK Ltd has worked with °®¶¹´«Ã½app on several previous occasions, where independent specialist knowledge, supported by the use of up-to-date computational techniques, was sought to support designs using conventional design processes.

MAHLE Industrial Filtration UK Ltd

Business 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.

°®¶¹´«Ã½app has always demonstrated a knowledgeable and professional understanding of our needs, and has 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