I have a question regarding chemical engineering metrology
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The company wants to implement an automatic dosing system. Is it more precise to use a chemical metering pump for dosing or a flow meter for controlling the dosage? Are there any other better methods? Dear experts, please help.
Actually, this depends on the accuracy requirements of your process. Taking our process as an example: (for low flow rates) 1. For applications where high accuracy is not required, when treating water by adding scale inhibitors and disinfectants, a metering pump is sufficient； 2. For applications requiring high precision: flow meters are used, along with metering pumps; (and some also come equipped with a calibration system) ； If the flow rate is high, only a flow meter is used; no metering pump is employed ；
In most cases, using a flow meter for control is sufficient to meet the requirements. Flow meters can be divided into those that measure volumetric flow rate and those that measure mass flow rate; volumetric flow meters are the more commonly used type, as mass flow meters are too expensive and generally not used. Flow meters have a minimum flow requirement; when the flow rate is below 1 cubic meter per hour, ordinary flow meters can no longer be used, and in such cases a metering pump must be employed instead. Of course, a flow meter with a low flow rate can also be used, but there are few manufacturers of such devices in China at present; not only are they expensive, but they are also difficult to maintain. Next are the general procedures and methods for flow control.
This post was last edited by zxg.wylton on 2017-7-19 09:06. It’s a bit misleading: 1. Electromagnetic flowmeters can measure flow rates as low as 00018 m3/h; they are the most cost-effective type of flowmeter. 2. Mass flow meter: It can measure flow rates as low as 0.045 t/h. 3. The inlet part of the mass flow meter is expensive; domestic versions, however, are not costly. We have used several units under normal operating conditions, and they perform very well. 4. The flow meters mentioned above perform well and are basically maintenance-free. For example, we have been using Yokogawa electromagnetic flowmeters for over a decade, yet we have never even touched them properly.
It is recommended to use a scale, as it is more accurate. Metering pumps are prone to failure; if the outlet gets blocked, the metering pump is likely to be damaged.
Check the requirements. Weight should take into account errors as well as the equipment. It has high requirements for installation. If it is a metering pump, there are also high-precision imported metering pumps available. Then there are mass flow meters. In any case, selection is very important
Stop talking nonsense. For automatic dosing in water treatment, metering pumps are usually used – why use flow meters? Flow meters have latency in their control logic; it’s much better to have a metering pump that can stop immediately when instructed to do so. Of course, this applies to the situation of adding chemicals at low flow rates; for higher flow rates, a flow meter is still necessary.