EVA Series Installation Operation and Maintenance Manual

EVAprevent this condition from occurring, it is necessaryto maintain approximately 10 psi (0.7 bar)back pressure against the pump. This can beaccomplished through the installation of a backpressure valve in the discharge line. Typically, thevalve should be located near the pump. However,back pressure valves for large pumps with longand extremely small discharge lines may have tobe installed near the point of discharge into theprocess (to minimize siphoning tendencies).2.7.2 Pulsation DampenersAn accumulator, surge chamber, surge suppressor,or pulsation dampener should be used with theback pressure valve in the discharge line to absorbthe flow peaks between the pump and the backpressure valve. Without the pulsation dampenerthe valve mechanism will snap open and close withthe surge from each pump stroke. The pulsationdampener will allow the back pressure valve tooscillate about a partly-closed position, thus minimizingwear on the valve. Discharge line pulsationdampeners offer the further advantage of limitingthe flow and pressure variations characteristic ofthis kind of pump. Installing a properly sized pulsationdampener will improve pump performance andmay reduce system costs dramatically by permittingthe substitution of smaller piping. Please contactMilton Roy Company for further information onpulsation dampeners.2.7.3 Safety Valves and Priming ValvesMotor-driven positive displacement pumps candevelop excessive discharge pressures longbefore thermal overload devices interrupt the motorelectrical circuit. To prevent a blocked dischargeline from causing damage to the pump, piping, orprocess equipment, install a safety valve in thepump discharge line. This valve is designed andsized to handle system flow rates and pressuressafely while resisting corrosion by the process liquid.To aid in pump start-up, it is advisable to install apriming valve on the discharge side of the liquidend.2.7.4 Shut-off ValvesProvide shut-off valves in both suction and dischargelines next to the pump. Locate dischargeline shut-off valve downstream from the inlet connectionof the safety valve. Figure 2 shows recommendedvalve locations.2.8 ELECTRICAL CONNECTIONSDo not forget to connect the earth terminal on themotor to the equipment earth conductor.Ensure that the electrical supply matches the pumpmotor nameplate characteristics. Connect themotor in accordance with the instructions and connectiondiagrams on the motor (or in the motor terminalbox).The electrical protection installed for the motor(fuse or thermal protection) must be suitable for themotor's rated current.6