Nuclear Industry - Star Filters
NW Total Engineered Solutions have been working alongside the Nuclear Industry for many years, helping to devise solutions to a wide variety of unique problems. NW Total are regularly involved in a whole host of activities such as procuring / manufacturing bespoke systems, pumps, and valves. Back in 2009 NW Total were approached by a large Nuclear Re-Processing Plant to come up with a solution to a historic problem they were having within their Powder Handling Reactors.
The existing Stainless Steel Star Filters installed in Powder Handling Reactors were not functioning correctly due to various design flaws and system problems. The purpose of these Filters is to allow air to escape from the Reactor whilst not allowing any powder through, however during use excess powder was found to be permeating through the existing Filters and into the pipework/ducting beyond. Our investigations found the filter mesh size to be the most likely cause of the problem.
With NW Totals background and experience in undertaking specialist machining and fabrication projects working to stringent standards, they were approached to work in partnership with a well-established filter design & testing company. The task was to design a replacement Star Filter taking into account the problems with the functionality of the existing units.
This unit was re-designed using cylindrical Filter Tubes rather than Fins, while keeping within the space envelope of the existing Filters. Cylindrical Tubes were preferred as thanks to the inherent strength of this shape, additional internal strengthening is not required. As the internal strength of the original oval shaped fins proved to be the main drawback of the previous design, this new design feature also reduced the manufacturing costs.
The Filter Tubes are built from a woven stainless steel mesh. The mesh is manufactured using five layers with the top layer performing the primary filtration and the other four layers providing the necessary support and strength.
The original design utilised pipes and plates to make the manifolds on either end of these filter assemblies. However, to reduce the amount of welding required and improved the overall integrity of these units, we re-designed the manifolds so they were completely machined from solid bar.
A prototype of this filter was then manufactured, followed by a month of rigorous testing utilising an Alumina Test Dust to replicate the product used on-site. The test rig itself was custom built and the design ensures that the orientation of the filter assembly closely replicates it’s installation within the Powder Handling Reactor on-site.
The tests carried out included a Dust Loading Test, Back Pulse Test at various pressures and an Overall Efficiency Test. Following the successful testing of this Filter an order was placed for 16 complete units which all underwent and passed filter efficiency testing using the same test rig as previously. All 16 of the Star Filters have now been installed and are working correctly.