Published: Friday, August 15, 2014

Seifert Technologies, was recently involved in a project that had us evaluating a client’s existing pump skids.  We gathered load and constraint information,lifting parameters and installation criteria. After reviewing all of the data, our engineers ran a Finite Element Analysis, using Autodesk Simulation (Algor), on the existing structure for stress and deflection.  Each component of the skid and hydraulic tank assembly was modeled as a separate volume for FEA meshing.  The volumes were meshed individually in separate groups to permit selective viewing in the results.  However, Algor analyzed the model as though there were welded connections at the volume interfaces.  This current skid design has been used for several years, in static locations, without any issues and based on the static load the skid was viable for its intended use. However, when moving the skid from one location to another, which is now required, the stress and deflections at the lifting points exceed normal safety limits.  When lifted, the acceleration of the skid and attached components amplifies the load by a factor of 1.5G.  This would have created a failure during onsite skid installation, as seen in the model to the left.  

The engineers at Seifert Technologies redesigned the stand with proper connections and reinforcements in the high stress areas (right) and the design was approved for use in the field.

Our analysis also showed that the current skid would impart deflection into any components that are mounted to the skid, such as the fluid tanks.  These tanks were welded to the skid frame, creating rigid connections, and when the skid was lifted to be moved, any deflection in the skid would also be imparted on the tank.  This caused the tanks to buckle when the skid was lifted (left).  

We incorporated sliding, non-rigid tank mounting connections to alleviate the lifting stress, therefore eliminating tank buckling (right).

One other issue was discovered with this design when were viewed all of the data.  When tanks were welded to the top of skid, temperature variations between the fluid and ambient temperatures would create stresses over 45,000psi at the weld points causing stress fractures (left).  The high stresses in the contact areas are mostly due to the fact that the tank needs to expand in each direction about CG.  Since the skid is welded to the tank, the tank can’t move and expand, creating stress risers. The solution that was used to solve the deflection issue was also used to solve the problem with temperature variations.

Dave Schumacher is a graduate of Stark State College of Technology,with continued education in Engineering Technology. Dave graduated from Perry High School and is a long standing resident of Stark County.

Dave Schumacher is a valued member of the Seifert Engineering team with over 20 years of experience at Seifert Technologies.    Amongst other projects, his work on the development of an Oscillating Cylinder Test Stand acquired a US Patent#7,231,820.  He continues to work on solving equipment problems for Seifert clients.   He is proficient in utilizing FEA, Parametric design programs like Visual Basic, Pro/E, and Pro/Programs.

Dave is a member of SME (Society of Manufacturing Engineers)and has served as a chairman in previous years.  He was also a Junior Steward of the Clinton Masonic Lodge #47 from 2000-2003.

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