Software simulates stresses in pumping platform

Ansys has announced that its simulation software has been used to build pumping station platforms in New Orleans.

Engineers charged with improving water drainage pumping capacity faced a number of design challenges.

Because the platforms are partially submerged, all design problems had to be identified and addressed before any construction began.

In addition, the project needed to be completed prior to the onset of hurricane season.

Work was contracted after hurricane Katrina devastated the Gulf Coast.

When Category Two hurricane Gustav hit in 2008, the platforms and pumps successfully kept flood waters in check, validating the accuracy of the Ansys simulation results.

When a hurricane or other major weather event hits, high-power pumping units must work at full capacity to drain excess water out of sub-sea level New Orleans.

The heavy equipment - turbine pumps, diesel engines, gearboxes and associated piping - produce vibrations and other stresses that can cause the massive platforms supporting the equipment to fail.

Mechanical Solutions (MSI), working for the platform design-build contractor Weston Solutions, used software from Ansys to simulate these stresses in the pumping platform along the 17th Street Canal, ensuring that the system would perform optimally during storms.

Simulation-driven design using Ansys software allows companies to determine potential problems early in the design phase, long before a structure or product is built.

In addition, many different design modifications can be rapidly simulated and the corresponding effects assessed.

William J Kelly, principal engineer at MSI, said: 'Our approach with every project is to bring value to the table by identifying and mitigating risk early on to reduce the potential for costly modifications after construction has been completed.

'By using software from Ansys to simulate the vibrational response of the platform, we were confident that the pumping system would perform optimally, and it did.

He added: 'In addition, engineering simulation helped us meet a rigid deadline by identifying issues early in the design process so that the platform could be completed before hurricane season.

MSI used its well-practiced design audit approach to characterise and predict the behaviour of the system's structural natural frequencies and vibration levels at various locations.

The team accounted for soil conditions expected to play a role in the system platform's vibrational response.

Engineers performed analyses to assess forces imparted to the platform by the diesel engines, gearboxes and pumps.

MSI also analysed frequencies up to 120Hz, which corresponded to the cylinder firing frequency for the diesel engines, and they accounted for rotating imbalance loads and phase conditions imposed by the gears and pump impellers.

The results indicated that the worst-case loading occurred when the imbalance loads of all 11 pumps were in phase.

Finally, MSI performed an acoustic evaluation of the discharge piping to assess the potential for acoustic resonance within the 9ft-diameter manifolds leading to the lake.

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