Paper No. 79
A. L. Lewis, F. R. Szenasi and D. R. Roll, Pumping Technology, The Journal of Advanced Fluid Handling, A Putnam Publication, Volume 2, No. 1, June 1998, pp. 27-31.
During startup and commissioning of two stock pumps in a pulp mill, violent vibrations took place in the associated piping systems. Figure 1 shows one of the two pumps as installed. Over time, the piping and its supporting structures sustained major damages, included a ruptured pipe, cracks in masonry supports, failures of diagonal cross bracing in the column and beam support structures, and fastener failures on the pipe rack. These events resulted in production delays and safety issues which were of great concern to the owner of the systems. Initial analysis indicated that the pumps were performing properly, so attention turned to the piping system. Several modifications were made to better anchor the pipe and stiffen its support structures, but no significant reduction in the vibrations resulted.
A field test and analysis of the nature of the vibrations was undertaken to determine their source. The pulsation frequencies measured were well below any of the normal pump-related frequencies so the pump was not considered to be the source of the problem. The pulsation at vane passing frequency was measured at 1 psi peak-peak (approximately one-third of one percent of developed head) which is normal for a pump of this type.