mining the dead sea | feature stories Horizontal Wave Force 1.50 to 1.75 tons 1.90 tons/m2 of the jetty Uplift Pressure Calculated wave loads Mud and soft sea bed layer extending down between 20 and 30 m atop the solid layer salt rock Geotechnical conditions Pile length varied between 40 and 50 m Project design The pumps’ large hydraulic power, the large flow conveying capacities of the twin pipelines, the 4-pump intake system in this project, create a massive inertia. If not guarded, such a large inertia leads to pressure surges - over and under pressures during starting/stopping of the pumps or changes in steady flow conditions; the pumps could be destroyed or one of the pipelines could burst. The pumping system underwent extensive surge analyses and hydraulic modeling to determine the discharge valves closing and opening time in case of pressure surges. Design and numerical stimulation determined the size, number and location of the anti-vacuum valves to be installed on the twin pipelines in order to prevent their collapse during sudden stoppages. Road design A new road and jetty design allows access of a 220-ton mobile terrain crane and a 50-ton lowboy trailer truck for dismantling the pumps or parts of them, transporting them to the workshop for routine maintenance, and any repair work to the intake station. • Ground motions for a rare, intense - maximum credible earthquake at the site, considering structural foundation was inelastic while having adequate reserve strength to avoid collapse. Vibration monitoring • The pumps’ supporting structure is treated as a flexible foundation with inherent vibration frequencies that must not coincide with or come within +/- 20 % of the rotating and vibrating frequency of the pumps • Extensive finite element modeling is carried out to ensure that the pumps and structure vibrating frequencies will not coincide with or approach within +/- 20 % of each other Electrical design The main design objective for PS3’s electrical needs is an efficient system delivering electrical power to the pumps while accounting for two constraints that could result in a substantial voltage dip on the motor terminals during pumps start-up: • 34 km separating the intake pumping station from the nearest power supply source • 5-MW rating requirement (4X5 MW for all four pumps) Early in the design stage, the study performed to determine the most preferable way to start the pumps with acceptable voltage dip and effective cost evaluated three alternatives: (1) the use of medium voltage variable frequency drives; (2) the use of autotransformers; and (3) the use of direct on-line starting. Advanced modeling recommended the use of 11-kV motors starting them directly on-line with capacitor banks to compensate for the heavy motor inductive load. The model optimizes the transformers’ special design and various transmission lines and power cables sizing requirements using advanced load flow analysis, short circuit calculations, and motor starting analysis. Stuctural load considerations • Four pumps totalling 836 tons -209 tonsX4 - plus the load of the vertical down thrust forces during operation • Two pipelines weighing 7.8 tons/m plus the load of the hydraulic thrust at direction changes • Mobile crane - dispatched to the tip of the jetty for maintenance or repair operations - may reach over 300 tons • Operating lowboy trailer could weigh up to 75 tons Seismic loading modeling conditions to IBC 2006 code • Ground motions with reasonable likelihood of not being exceeded at the site during the jetty’s lifecycle while considering elastic structural response 39