Vibration analysis of vibration sensitive site

Construction was planned for a new building whose contents would be sensitive to any external vibration for example, due to variations in traffic volume and weight of vehicles using the site or the adjacent main road.  The objective of the work was to undertake a series of induced vibration tests and ambient vibration monitoring tests.  The information from each test was collected using various pieces of data acquisition equipment and analysed using Fourier Transforms.  The resulting information was used to determine the soil strata beneath the proposed site and was also used to determine whether or not the vibrations would cause a problem with the intended future use of the building.

D C White & Partners were invited to inspect the condition of the drying drums at a water authority's Sludge Treatment Facility.  The main area of interest was the retro-fit of the new flexible middle drum mounting modifications that had been proposed by D C White & Partners Ltd.  The new mountings had been in service for over a year and it was desirable to assess their performance to date.  In addition to this inspection work thickness measurements were taken to assess the wear rate at the outlet end of the drums.  The feed chute and general condition of the furnace was also assessed for each line.

The flexure support plate assemblies were all in good condition and appeared to be functioning correctly.  There had been zero defect detection in the welds associated with this modification and the actual flex plates showed no indication of breakdown or fatigue damage.  Concern was raised regarding the amount of wear experienced  at the outlet end of the drum.  Further investigation was undertaken, possible causes were postulated and a number of solutions were given.

Click here to view drum manufacturer's web page showing a picture of the drum and part of the plant

Pump Manufacturer

Initially, DC White and Partners Ltd performed a design analysis for a vertical water pump for use in Iran.  That study was completed in November 2004 with the outcome that a potential vibration problem for the pump was identified.

After a meeting with pump manufacturer, DC White and Partners Ltd. were asked to investigate possible means of altering the design of the pump, to resolve any vibration issues which would hinder the performance/functionality of the pump.

DC White & Partners Ltd. investigated possible solutions and performed supporting calculations and analyses for the pump assembly.  The proposed solution is the addition of an additional shaft bearing which would affect the characteristics of the pump structure in such a way that resonant frequencies are moved away from the running speed of the pump.

Finally, the pump manufacturer requested that a frequency analysis be run on the pump model in its shortened form to represent the setup that would be used for testing purposes.  The results of this analysis showed that there were no resonant natural frequencies coinciding with the pump running speed.