Maintenance Improvements on Offshore Fuel Oil Terminals

Abstract

Two marine terminals for receiving heavy fuel oil for power plants of the Pacific Gas and Electric Co. have power plants of the Pacific Gas and Electric Co. have been in service at Monterey Bay and Estero Bay for many years. The moorings were designed for the T-2 class tankship. The layout of the Estero Bay terminal, which serves the Morro Bay power plant, is shown on Fig. 8. The Monterey Bay terminal serves the Moss Landing power plant, which is essentially a duplicate. For many years the maintenance program for each terminal involved an annual overhaul during which the mooring buoys and active mooring chain would be lifted aboard a derrick barge for cleaning, painting and replacement of worn chain and shackle pins. The submarine oil delivery hose would be inspected by a diver and sections would be interchanged to distribute wear. Any indication of damage would call for disassembly of the string of eight 24-ft lengths of hose and inspection on the deck of the barge. A vacuum test with plexiglass seal plates at each end is used to check for separation of the hose liner. On reassembly the hose and the pipeline to the plant are subjected to hydrostatic test. At this time the cathodic protection potential at the seaward end is checked also. potential at the seaward end is checked also. Over the years it was learned that the wear of the active dip section of the mooring chain resulted in 40- to 50-percent loss of chain section between overhauls. This substantial loss of strength was due principally to wave action and was more or less constant principally to wave action and was more or less constant regardless of the number of cargoes delivered. Because of the considerable cost of overhaul and the disturbing loss of chain strength a study was made of means of reducing the critical wear of the chain links. Analysis of the wear indicated that abrasive action of bottom sand stirred up by the incessant working of the dip section under the rise and fall of the buoys was a major factor. P. 562