| Abstract: | Flow control for small metering pumps with continuous and pulsating flow. Metering of small flows with high discharge pressure is performed mainly by displacement metering pumps. The necessary mass-flow control shows problems with pulsating piston- or diaphragm metering pumps. A survey explains the presently available continuous and discountinuous methods of mass- and volume flow control. Special investigations have been performed with differential scales and mass flow meters based on the Coriolis- and the thermal principle. The differential weighing method shows good accuracy down to minimum mass flows of 0.1 kg/h. This method is expensive and requires vibration protected installation. The Coriolis flow meter, applicable over a similar range, precisely integrates the pulsating signal, but requires damping or signal averaging for regulation purposes. Thermal flow meters prove rather sensitive to temperature fluctuations. Under stable conditions and with proper calibration this principle may be applied to flows even below 0.1 kg/h. |
