Vibrations were registered and measured on site, while in operations in the Middle East. It was found that as the valve was being opened, there was an audible buzzing noise that could be heard. Confident that the valve design was not to blame, Glenfield approached IDAC to conduct a FEA analysis on the valve. In reviewing the results of the analysis, Glenfield hoped to show the Water Authority that the valve was indeed functioning and that the fault lay in other area, perhaps in an upstream butterfly valve designed by another manufacturer.
The analysis was performed using ANSYS DesignModeler for the geometry modifications and parameterization, whilst ANSYS Simulation was used to set up, solve and post process the linear static analysis.
The 3D geometry of the valve was supplied by Glenfield in acis (.sat) format. The geometry consisted of a horizontal vessel, 4 holding clips, a support ring and a gas box. The inlet device rested on 4 clips whilst the gas outlet system was supported on a supporting ring.
The frequencies measured on-site and the frequencies and mode shapes of the FE model (that are closest to the measured values) were compared. The measured frequencies should be lower than their corresponding modelled frequencies (if they exist), because the modelled frequencies have no damping; the inclusion of damping in the model tends to decrease the frequency. However, there may be other factors that could negate this effect (e.g. material properties, geometric inconsistencies), so, the frequencies that are above and below the measured frequencies - within a certain range (roughly +/- 30 [Hz] to 50 [Hz]) were reported. The three figures above show the mode shapes closest to on-site frequency measurements for the 75% open condition.
For each of the 3 flow conditions (100%, 75% and 50% open) suitable candidates for the frequencies measured at all 3 locations (ILR Outlet, ILR Top and BFV Inlet) were identified.
Having determined that there were candidates for all 3 flow conditions, a CFD analysis was run for each and the resulting pressure distributions applied as the loads for the 3 static structural analyses and the 3 harmonic response analyses. The figure to the left shows the Velocity contours for 100% Open condition.
The static structural analyses for the 3 conditions show that the maximum deflections occurred at the centre of the orifice plate, the largest of which is approximately 0.5mm. Deflections in the main body of the valve were found not to exceed 0.1mm.
The harmonic response analyses were carried out with a constant damping ratio of 0.01. Responses in the main body of the valve for the 100% open and 75% open conditions were found to be below 1.2mm. The largest response occurred in the orifice plate at the 50% open condition.