Having questions about control valves?
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In the process flow diagram, do FV, LV, and TV refer to the flow control valve, level control valve, and temperature control valve, respectively? What are the differences in their working principles? Can I take a look at the drawings and site plans for these three control valves there? In my process flow diagram, the pipelines connected to FV, LV, and TV all have flow meters attached to them. FV is interlocked with the flow meter, while LV and TV are each interlocked with their respective thermometers and level gauges. So how do LV and TV regulate the level and temperature? What is the purpose of the flow meters connected to their pipelines?
All control valves are the same; the only difference is that the signal source for determining the valve opening degree is flow rate, liquid level, or temperature
The control signal sources are liquid level and temperature. Adjusting the control valve and flow meter based on this should provide an intuitive indication of your adjustments
No matter what type of control valve it is, there’s no difference – they’re all just valves. It’s simply that, in terms of manufacturing processes, specific names are given to certain parameters in order to control them – such as flow rate, temperature, or pressure. Additionally, as you mentioned, even if the level control valve is interlocked with the liquid level, a flow meter is still used to monitor the actual flow rate, because we need to know how much fluid is being added. If you want to know, just add it; it’s just for the manufacturing process.
Let’s take a look at the image above Why is there also a flow meter connected behind the temperature control valve? Is it the flow rate of the cooling or heating medium?
The flow control valve is linked to the flow rate; the temperature control valve regulates the valve opening based on temperature. The liquid level also serves to control the valve opening by being linked to the liquid level. As for the flow meter, it serves only as a monitoring device. For example, the valve can operate in either direct or reverse mode, and the flow rate provides a more intuitive way of monitoring this. Additionally, in the event of a malfunction in the valve, the flow rate can be used for self-diagnosis
The same type of valve is named differently depending on the object it acts on
All of these methods achieve control of liquid level and temperature measurement by adjusting flow rate. The flow rate is an easy-to-understand parameter, but the ultimate goals are things like liquid level and temperature.
FV, LV, and TV indicate the naming (tag number) of the control valve; as for what type of control valve it is, a different choice must be made depending on the process conditions, and different control valves have different structures. I’m not quite sure what “FV and flowmeter interlock” means; it would be helpful to have an image.