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https://nap.nationalacademies.org/catalog/27432/critical-issues-in-transportation-for-2024-and-beyond

SURGE PROTECTION DESIGN FOR THE CITY AND COUNTY OF SAN FRANCISCO WATER TRANSMISSION SYSTEM

The City and County of San Francisco were concerned about the ability of their water transmission system's ability to withstand pressure surges resulting from the unplanned operation of their system flow control valves and their two primary pump stations, Lake Merced and Baden. Flow Science Incorporated was hired to determine the extent of the surges in the system and recommend alternatives to keep the maximum hydraulic gradelines within the system below 130% of the maximum static pressure within the system. The analysis showed that the loss of power to the two pump stations created surges in the system that raised the maximum HGL elevations within some of the main transmission pipelines well in excess of 130% of the maximum static pressure that was used as the upper limit for allowable pressures. The existing surge protection that was installed at the Lake Merced pump station did little to lower these pressures due to the configuration of the surge tank connection. It did however change the problem from a waterhammer problem to a surge problem. Protection was to be designed to prevent the maximum HGL elevations from exceeding the 130% of maximum static pressure threshold. However, it was determined through a series of simulations with various protection measures that this would not be feasible. The best solution would be to limit the pressures as close as possible to the allowable level. The surge protection alternative that was determined to provide the most protection to the system was the installation of a 28.3 cu m (1000 cu ft) surge tank on the discharge side of the Lake Merced pump station and a 610-mm (24-in.) surge relief valve on the suction side of the Lake Merced pump station. The surge relief valve is designed to work in combination with the existing surge tank at this location. At the Baden pump station a 127.4 cu m (4500 cu ft) surge tank was required on the discharge side of the pump station and a 42.5 cu m (1500 cu ft) surge tank was required on the suction side of the surge tank. The installation of the surge protection measures described above were predicted to provide the system with protection that would keep the maximum pressures as near to the 130% of the maximum static pressures for the system as possible.

Language

  • English

Media Info

  • Features: Figures;
  • Pagination: p. 103-112

Subject/Index Terms

Filing Info

  • Accession Number: 00760372
  • Record Type: Publication
  • ISBN: 0784403724
  • Files: TRIS
  • Created Date: Mar 2 1999 12:00AM