The exact meaning of “interlock” in instruments.
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As a common example, a temperature gauge is installed on the reaction vessel, while an adjustable valve and a stop valve are placed on the steam pipeline of the vessel’s jacket. 1. The temperature signal from the reactor is sent directly to the control valve, which adjusts its opening degree in order to regulate the steam flow and thus control the temperature of the reactor. Is this approach referred to as temperature \"interlock\" control using a valve? 2. The temperature signal from the reactor is sent directly to the control valve; when the temperature is high, the control valve closes immediately. Is this phenomenon referred to as temperature‑based \"interlock\" of the control valve? 3. The temperature signal from the reactor is transmitted to the DCS control center; upon detecting that the temperature is too high, the DCS control center automatically controls the valve to close it. Some people say that the usage of “interlocking” is incorrect, so I’m asking here. Is there a difference between case 3 and case 2? Is the method of control direct or indirect? Thank you
The first one is a temperature control loop that does not require interlock; the second and third ones involve interlocks, and the interlocking can be achieved through hardwiring or using ordinary controllers, as well as DCS, PLC, or SIS
Items 1 to 4 above can all be referred to as generalized control (Control). In a narrow sense, it can be divided into Regulation and Interlocking ； Regulate refers to continuous adjustment within safe limits, with the aim of keeping the process parameters at the set point ； Interlock is an emergency intervention measure taken when process parameters reach safe limits or other emergencies occur ； As for whether to use conventional instruments, relays, DCS, PLCs, or other devices, it’s just a matter of different tools being used.
1, is called cascade control. Both 2 and 3 are interlocks; 2 belongs to a hard interlock, while 3 belongs to a DCS interlock. 3 belongs to the DCS system, and 2 belongs to the SIS system.
This post was last edited by qifangwei on 2019-6-20 at 11:11. 1 refers to control, which is usually PID single-loop regulation or cascade control; 2 and 3 represent interlocks – it’s better not to use the term \"interlocking\", as this term tends to imply mutual interlock rather than interlocking in general
What I understand by interlock is an automatic alarm switch. . . . The control unit collects the measurement signals, makes a decision, and then generates drive signals to cause the actuator to move to either a fully open or fully closed position. . . . Interlocking means connecting automated sensing elements and actuation units in a closed loop to enable switching actions.
The first one is called interlocking; that is regulation. 2,3 are interlocked.
The first one is called interlocking; that is regulation. 2,3 are interlocked.
Interlock switch valve for high and low temperatures