Issues regarding n-hexane and the flow rate of the inverter
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Help: Our facility previously used frequency converters to control the speed of the pumps in order to regulate the flow rate of n-hexane. It worked well at first, as it operated in automatic mode throughout, but after 3 years, problems have arisen with the flow rate! 1. At present, with the pump speed being adjusted manually, the slower the pump speed, the higher the flow rate; sometimes, when it reaches a certain level, this can cause the air circuit breaker to trip. On the other hand, when the pump speed is increased, the flow rate decreases, even if only slightly! It’s also very unstable; automatic mode is even worse. Nowadays, automatic mode isn’t needed at all! 2. When the flow rate changes, the pump pressure also changes. Based on the pump’s output volume and my experience, the high flow rate indicated by the flow meter is likely not that high in reality! Help: 1. Why does the pump trip when a high flow rate is indicated, even if the outlet valve is not adjusted to a smaller or larger position? 2. Why do the above problems occur? Now, it is planned to upgrade by installing electrical automatic valves, without using frequency converters anymore! In other words, the opening degree of the automatic valve is controlled by setting the flow rate, thereby ultimately controlling the flow rate of n-hexane! (Our workshop currently has such excellent results from this kind of modification.) The n-hexane we use in our workshop needs to be heated; the temperature should be between 59 and 65 degrees! To save energy, there is currently a flasher for returning workshop steam water at the outlet of the solvent pump, followed by a solvent heater! Question: If automatic valves are to be installed, where is the most reasonable and scientific location for them? What needs to be noted? I hope the experienced masters can give me plenty of guidance! ! ! Thank you so much! ! !
1. Based on your description, it’s possible that there’s an error in the way the frequency converter and motor speed are configured in the automatic settings – specifically, the direction of their interaction is incorrect. As a result, when more power is needed, the speed decreases. If the automatic setting has a positive deviation, the speed will keep decreasing; if it has a negative deviation, the speed will keep increasing. This is likely why automatic mode cannot be used； 2. The main reason for tripping is still overcurrent protection ； 3. Electrical automatic valves are definitely much more effective than those you have now, but one needs to know how to set the PID parameters; if they aren’t set properly, the valve cannot operate in automatic mode. The installation location can be chosen after heating; it doesn’t matter much. The drain valve should be placed at the lowest point of the control valve. Hope this is useful to you