Monitoring melt pump metering

　　The melt running gear metering pumps need to be a certain degree of monitoring. Observed an important indicator of the outlet pressure , including the suction pressure , outlet pressure difference , the motor current , and the pump shaft seal of the gear temperature .

　　Since the head of the output pressure as the flow rate varies , and therefore the outlet pressure should be constant . In general , fluctuations in outlet pressure must not exceed ± 10psi . Fluctuations usually belong transmission problem , you need to adjust the transmission parameters of the motor technician . If the melt gear pump metering severe wear , will cause such a problem. A suction pressure change of the reaction extruder output changes. Although the main function of the melt metering pump is a gear to eliminate these fluctuations, the fluctuation range control is limited . Even melt gear pump metering the amount of polymer continuously to keep the output constant , the melt temperature will change. Since the suction pressure to maintain a stable screw speed will change , thereby causing the melt temperature fluctuations. Melt temperature fluctuations will directly lead to changes in the nose melt flow and product size.

　　Fluctuation range ideal suction pressure must not exceed ± 100psi, preferably ± 50psi. If volatility exceeds this value, the flow will cause the nose to change. For this reason , the need to reduce the sensitivity of the extrusion machine motor responsive to pressure fluctuation . This is usually proportional control , and bandwidth by increasing the pressure to make the extrusion detection electromechanical machine has this feature. If this method is not able to control fluctuations to a minimum , it is likely that the extruder own problems , which will have to be analyzed separately .

　　The power required to rotate the gear pump should be constant . Even the occurrence of several amperes of current change during the driving , but also means that there is a problem. This may be a simple parameter setting problem , it could be the pump , gearbox or drive shaft inside the mechanical problems, or suction pressure is too volatile

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