German Rander & Co pumps, Rander & Co models, Rander & Co prices

Rander & Co pumps are mechanical devices that meter the delivered liquid. They are often used in complete chemical dosing systems and are therefore also called dosing pumps. They are a special type of positive displacement pump that can meet various strict process requirements, with flow rate steplessly adjustable within the range of 0-100 to %, used for transporting liquids (especially corrosive liquids).

Rander & Co pump structure and classification

The pump consists of three parts: motor, transmission box, and cylinder body. The transmission box components consist of a cam mechanism, stroke adjustment mechanism, and ratio worm gear mechanism; the tappet stroke is adjusted by rotating the adjustment handwheel, thereby changing the diaphragm extension distance to achieve flow rate adjustment. The cylinder body components consist of the pump head, suction valve group, discharge valve group, diaphragm base, etc. Dosing metering pumps can be divided into motor-driven and solenoid-driven types according to the drive. For motor-driven metering pumps, flow rate adjustment can be achieved by using a frequency converter to change the motor speed, or by adjusting the piston stroke. Install a servo motor (ATE), rotate left and right to adjust the angle, increasing or decreasing the piston stroke. Solenoid-driven flow rate adjustment changes the reciprocating frequency of the diaphragm. It can accept pulse frequency from a flow meter or analog signals of 4 to 20mA, and can also accept analog 4 to 20mA signals from water quality instruments, with the controller adjusting the dosing. Flow rate can be adjusted manually via buttons, or the dosing amount can be controlled by a controller (PID).

Rander & Co pump working principle

The motor drives the worm shaft via a coupling, and the worm gear reduces speed to make the main shaft and eccentric wheel rotate. The eccentric wheel drives the tappet to reciprocate within the guide tube. Together with the diaphragm, a vacuum is gradually formed in the pump chamber through the action of the check valve, opening the suction valve and drawing in liquid; when the diaphragm moves to the forward dead center, the suction valve closes, the discharge valve opens, and the liquid is discharged under the push of the diaphragm. The pump forms a continuous, pressurized, quantitative discharge of liquid through reciprocating motion with a certain adjusted stroke. Pump flow rate adjustment relies on rotating the adjustment handwheel, which drives the adjustment screw to rotate, thereby changing the distance between tappets and determining the flow rate by changing the diaphragm's moving stroke within the pump chamber. The scale on the adjustment handwheel determines the diaphragm stroke, with an accuracy of 95 %.

Rander & Co pump precautions

1) What important matters should be noted when operating a dosing system? Injection point pressure, stroke frequency, suction lift height, altitude, and chemical corrosiveness. 2) When the metering pump outlet is at atmospheric pressure, what methods can improve the pump's repeatable metering accuracy? Installing a valve spring on the metering pump discharge valve can improve repeatable metering accuracy, but the most effective improvement method is to install a back-pressure valve at the end of the pipeline. 3) How to adjust the back-pressure valve? When there is pressure at the suction end of the metering pump, the pressure at the discharge end must be at least 1bar higher than the suction end pressure. Never exceed the maximum working pressure of the metering pump. 4) If the transported liquid is not water, how is the suction lift height calculated? Divide the rated suction lift height of the metering pump by the specific gravity of the metered liquid. 5) How to set the safety valve pressure? The safety valve pressure can be adjusted within the rated working pressure range of the metering pump and must not exceed the maximum working pressure of the metering pump. The safety valve is designed to prevent overpressure operation of the metering pump. For example, if the maximum working pressure of the metering pump is 3bar, the safety valve pressure should be set to 3bar, or lower, to ensure normal operation of the metering pump. Overpressure operation is one of the main causes of metering pump damage. 6) How to select the appropriate volume for a pulse dampener? Multiply the metering capacity per stroke of the metering pump (ml) by 26 to obtain the minimum volume (ml) of the pulse dampener required to reduce pulsation by 90 %. 7) Under what circumstances is flooded suction used? When the metered liquid is volatile; when the metered liquid has a high specific gravity; when a high stroke frequency is required; when the metering pump operates at high altitudes; or when field applications require large storage tanks and self-priming by the metering pump is not feasible. 8) Can you provide some recommendations regarding metering pump head selection? What problems usually arise concerning chemical corrosion of pump heads/seals, and how can they be avoided? Problems with metering pump heads usually occur when metering acids, chlorine, fluorides, and hydrogen peroxide. Due to different chemical concentrations and operating temperatures, it is difficult to determine the specific pump head material. When metering fluorides, we recommend choosing Viton sealed PVC pump heads. For most chlorination applications, it is best to choose EPDM sealed NP (plexiglass) pump heads. For metering hydrogen peroxide mixtures, only PTFE sealed PTFE pump heads or stainless steel pump heads can be selected. For metering concentrated hydrochloric acid, Viton sealed plexiglass pump heads are usually selected. For metering concentrated sulfuric acid, PTFE sealed PTFE pump heads can be selected. Chemical manufacturers will provide relevant recommendations, or consult the ProMinent chemical resistance chart to determine the compatibility of chemicals with contact materials. 9) What influencing factors must be considered when metering liquids with the pump head? The main factors to consider are liquid viscosity, specific gravity, vapor pressure, and temperature.

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