ANSYS Mechanical Enterprise 2020 R1 was used to undertake a FEA substantiation of an eductor for a flotation vessel to ASME VIII.
Company
The project was undertaken for Morris Ejector Technologies Ltd, who are a UK OEM with a global supply network and are specialists in venturi equipment and specialise in custom designed venturi products such as eductors, mixing eductors, jet pumps, thermocompressors, air ejectors, vacuum ejectors, inline steam heaters and desuperheaters. The End client was MODEC, headquartered Japan and a global leader in providing competitive floating solutions for the offshore oil and gas industry.
The Eductor is being used as part of an Induced Gas Flotation (IGF) vessel for water treatment.
Background
An eductor is a type of pump which works on the ‘venturi effect’ to pump out air, gas or liquid from a specified area. An eductor requires only a motive fluid or driving fluid for its operation, which allows it to be used at any part of the ship including hazardous areas. When the driving fluid is passed through the eductor at the required capacity, a low pressure is created inside it. This low pressure or vacuum enables the eductor to suck liquid or gas from a certain area. This liquid or gas is pumped out through the driving fluid discharge.
The Eductor assessed here, is used on a ship where tidal and manoeuvre loads can be extreme. Therefore, not only is the eductor subjected to high temperature and pressure, it also has to withstand significant pipe flange forces and moments due to the movements of the ship.
Project Scope of Work
As experts in the assessment of pressure vessels to ASME code using FEA, Mechanika were commissioned to provide a full stress analyses of the eductor to ASME VIII and provide a structural substantiation report, which would then be reviewed by all parties in the supply chain, prior to manufacture.
Analysis
Accurately extracting stresses using a linearized stress method in-line with ASME, requires sound modelling and a high-quality mesh in the areas where stresses are reported. The areas of high stress were meshed with quadratic hexahedral elements and mesh convergence was performed until less than 5% convergence was achieved.
Internal pressure and pipe end loads were assessed along with individual nozzle loads as stipulated in ASME VIII.
Sections were created through the high stress regions so that a path could be selected for post processing and extracting the linearized stresses.
Outcome
The structural report has been reviewed and accepted by Morris Ejector Technologies Ltd and MODEC and the eductor has been approved and commissioned for manufacture and use on the vessel.
