Reasons and significance for using control valves in interlocks
Thread Content
Gentlemen, while reviewing the drawings recently, I noticed that some control valves are equipped with interlocks, and I don’t quite understand this. Control valves are generally used for control purposes; why is interlocking also required? There is a cut-off valve interlock in the diagram. If it is only for interlock purposes, a cut-off valve will suffice; if it is used for regulation, a control valve will do. What is the purpose of using an interlock with a control valve for this?
Control valves are used in interlocks primarily to ensure system safety and the stability of process control. Interlocking means that the operation of the control valve depends on the status of other devices or parameters in the system. Its purpose can be: 1. Protection: to prevent equipment damage or safety accidents caused by incorrect operation of the control valve. For example, if the liquid level is too low, it may cause the pump to run dry; in such cases, interlocks can ensure that the control valve opens or closes under safe conditions. 2. Process control: Ensure operations are carried out under specific process conditions. For example, in chemical reactions, the addition of certain materials requires strict control over flow rate and pressure; these parameters can be precisely controlled through interlocked control valves. 3. Efficiency optimization: When multiple process units are operating simultaneously, the interlock of control valves can help coordinate the operations between these units, thereby optimizing the efficiency and response speed of the entire system. Through the interlock of control valves, the process can be controlled more precisely, enhancing the safety and reliability of the operation. .
This interlock might work like this: for example, in a steam-heating scenario, the opening degree of the control valve is adjusted using temperature control, and a temperature interlock is also in place – the control valve is closed when the temperature reaches the set upper limit, and it is opened when the temperature falls below the set value; meanwhile, the shut-off valve is closed at extremely high temperatures.
It is used to control process parameters such as liquid level, temperature, and pressure
Can’t this be achieved directly through control? When the temperature is reached, the valve opening becomes 0. Why is an interlock needed?
Bro, what I mean is: can’t the control valve be opened and closed based on the process parameters? Does it have to rely on interlocks for that? In other words, an opening degree of 0 or 100 can be achieved through control
The control valve can be combined with a temperature transmitter to enable automatic temperature regulation through a DCS or PLC.
The interlocked component is the shut-off valve; the control valve is not interlocked, but the signal wires are drawn in the same manner. Mainly, one should refer to the textual description of the control logic.
I’ve seen it; it’s a control valve with interlock functionality integrated into the SIS. The SIS is rated at level 1, and this approach is used to reduce costs by eliminating the need for an additional shut-off valve
The control valve interlock is a dynamic balance interlock, while the shut-off valve interlock is a static two-end locking mechanism