HDT Develops OpenAire Filter Systems for the U.S. Army Advanced Chemistry Laboratory (ACL)

When the U.S. Army needed radial flow gas filtration systems for their new Advanced Chemistry Laboratory (ACL) they turned to HDT Global’s Engineering Services (formally New World). With an earlier product release, HDT Global had demonstrated an aluminum filter system with unparalleled performance characteristics. To meet the stringent requirements of the ACL, HDT Global would need to redesign, build, and test a stainless steel variant.

Filtration systems for the ACL would provide scientists with an unprecedented level of safety while working with toxic chemical warfare agents. Although gas filtration systems are used for collective protection (ColPro) applications, none of the “off-theshelf” systems satisfied the stringent performance standards needed for the ACL.

Customer requirements included:

  • Fully-welded, air-tight, stainless steel construction
  • Right-angle flow to allow filter servicing without entering the flow stream
  • Superior airflow uniformity from filter-to-filter for uniform gas adsorption
  • Modular design allowing for scaling in length, width, and height Engineering methods applied:
  • Mechanical design, 3D solid modeling, and tolerance stack-up analyses
  • Finite Element Analysis (FEA)
  • Computational Fluid Dynamics (CFD)
  • Production engineering

Approach: The project began with the development of product and system definitions. Initial design work focused on solid modeling and structural FEA to develop both the gas filter housings and the overall framework in which they would mount. With a requirement that the filter systems withstand a differential pressure of 20.0 inches of water, gauge, FEA was essential in predicting mechanical deflections and determining the optimal size and location of reinforcing members.

A key part of the engineering design process was to conduct dimensional tolerance analyses to determine the necessary length of the filter housings (cylinders). With this information, the filter housings were designed so that all gas filters – regardless of manufacturing tolerances – would mount securely within the filter housings.

HDT Global used CFD extensively to validate air flow uniformity and eliminate flow restrictions. This allowed the performance of the systems to be understood prior to manufacture and testing. The principal concern was that air flow uniformly through each of the filters for optimum gas adsorption. Flow uniformity was demonstrated by evaluating air flow rates (mass flux) from housing-to-housing as well as from filter-to-filter within housings. These flow simulations provided both information to optimize the design and sufficient evidence to allow a decision to proceed with manufacture.

Although engineering was an important and necessary part of this project, the end goal was to manufacture 18 filter systems (having 144 filter housings) for the ACL. Throughout the design phase, HDT Global worked with manufacturing partners to ensure that the resulting design would be not only suitable for manufacture, but as cost effective as possible. With the engineering design nearly complete, a prototype system was built to confirm the manufacturing methods and techniques. This was a valuable step, and allowed for the customer to provide valuable feedback prior to the commitment to manufacture.

Results:

  • Designed, manufactured, and tested stainless steel filtration systems for the ACL.
  • Provided design assurance prior to manufacture using simulation software.
  • Applied advanced methods of welding and fixturing to eliminate heat-related effects, such as warping.
  • Performed dimensional validation of manufactured systems using digital coordinate measuring machines (CMM).
  • Standardized the design of a stainless steel filter system for use in exhaust gas or collective protection (ColPro) applications.

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