SUMMARY

Pipeline hydraulic and transient studies assisted the design of facilities to increase the capacity of the Saudi Aramco East/West pipeline system. The capacity of pumps and the power of their combustion gas turbine (CGT) drivers limited existing pipeline throughput. The hydraulic capacity increased by 50%. Hydraulic studies identified additional pipeline looping and pumping capacity to be added to the pipeline system. Transient studies predicted that operational upsets, such as a trip of a pump station, cause excessive surge pressures in the pipeline system. New surge relief stations and an increase in capacity of existing surge relief stations was mandated to protect the pipelines at the higher flow rates. The surge studies identified the optimum location of six surge relief stations. Pump station trips are highly disruptive to normal pipeline operations. A trip of a pump station at flow rates above 70% of design capacity may cause surge relief stations to operate, downstream pump stations to trip on low suction pressure, and upstream pump stations to trip on high discharge pressure. Pipeline flow rates reduce to zero as a result of these cascading series of events. Transient studies identified pump station operating strategies to minimize pump station trips and maximize pipeline throughput at high flow rates. Following an upset, a Supervisory Control and Data Acquisition (SCADA) computer system transmits commands to Distributed Control System (DCS) computers located at the pump stations and pressure reducing stations. The SCADA and DCS computers invoke a series of actions to minimize the effects of upsets. Set point changes, implemented by the DCS computers, adjust pressures and power levels. They prevent the pipeline transient pressures from exceeding the relief set points of the surge relief stations and the trip set points of the pump control systems by reducing the speed of the CGT driven pumps. Relief valves at surge relief stations do not open and the remaining pump stations continue to operate. An additional series of SCADA and DCS improves control of the pipelines communication failure and pump station operations.

INTRODUCTION

Actions during by pass The Saudi Aramco East/West Crude Pipelineconsists of two pipelines originating at AbqaiqPlants and terminating at Yanbu crude oil terminal. Crude oil storage tanks located at an initiating pump station receive the Arabian Light crude transported from Abqaiq Plants. Eleven pump stations transport the crude oil to Yanbu. The eleven pump stations are similar except for infrastructure and other support facilities.

1.0 COMPUTER MODELING OF THE EAST/WEST PIPELINE SYSTEM
1.1 SOFTWARE PACKAGES

Several software packages assisted studies of the pipeline system during four phases of the project. The four phases encompassed hydraulics and surge studies during Conceptual Analysis, the Design Basis, Project Proposal, and Detailed Engineering. Simulation Sciences Inc. software package PIPEPHASE, and Scientific Software Intercomp Inc. software package TLNET assisted hydraulics analysis. Stoner Associates Inc. software package LIQT, and the Scientific So&are Intercomp Inc. software package TCON assisted surge studies. The software packages TCON and PIPELINE SIMULATOR also assisted control systems analysis during rampdown studies.

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