Laserfiche WebLink
Preliminary Design Memorandum <br /> Silt Pumping Plant Rehabilitation <br /> results in higher pumping energy and costs over the life of <br /> the project. <br /> Dual(suction and discharge) interconnected priming tanks.A two section <br /> tank system or single tank with suction and discharge compartments is utilized to <br /> provide priming water to the pump much like a self-priming pump. The suction <br /> tank provides water to the impeller upon startup which creates a vacuum to lift the <br /> water from the sump. The pump discharge is directly piped to the discharge tank <br /> which is fitted with a check valve at the tank outlet. Upon pump shutdown,the <br /> water in the discharge tank empties into the suction tank so that the tank is fully <br /> charged with water for the next pump start. The required tank sizes are directly <br /> related to the volume of suction line that must evacuated by the vacuum action. <br /> Separate priming tanks would be required for each pump. <br /> Advantages: <br /> • Automatic self-priming. <br /> • Reliability is reported to be very high as there are few <br /> moving parts. <br /> • Pump efficiency is not impacted. <br /> Disadvantages: <br /> • Commercial product is no longer in production thereby <br /> requiring a custom,prototype design. <br /> • Requires floor space adjacent to the pumps that may restrict <br /> access to the pumps. <br /> • A few additional minor losses are introduced into the <br /> system curve that will consume a small amount of energy <br /> over the life of the project. <br /> • Sticks could accumulate in the suction tank and require <br /> cleaning. <br /> • If sized too small,prime will not be achieved. <br /> Vacuum priming system. A vacuum priming system consists of single or duplex <br /> vacuum pump(s),a receiver, a vacuum header, a priming valve for each pump and <br /> a control system.Typically,the priming vacuum pump is sized only on the <br /> volume that must be evacuated and time desired to fill the suction piping,pump <br /> casing and discharge piping to the discharge valve. Air infiltration is not <br /> considered when sizing the vacuum pump because any leakage into a well <br /> maintained system is inconsequentially small. In simple systems,the vacuum <br /> system is always actively connected to each pump and all pumps are primed and <br /> ready to start at any given time. In more complex systems,the control system <br /> 16 <br /> FOR OFFICIAL USE ONLY <br />