Xiaobai asks for advice, how to draw PID in this process?
Thread Content
I have been doing crafts for more than a year, and now I plan to study the standard drawing method of PID diagrams. Now I am studying the 20505 standard... Can I ask the experts, how to draw the following process? I thought about it for two days and didn't think of the correct way to draw it. The general process is like this. Two thermal resistors measure the temperature of the hot gas. Valve 202 is normally closed, and valve 201 is open at 100%. When the temperature exceeds 500°C, the opening of 201 is reduced through the interlocking of valves 201 and 202, and valve 202 is opened to provide cooling to ensure that the temperature is controlled at around 500°C. Thank you all.
Just draw an interlocking signal line for cascade control.
Can you send a screenshot? I don’t understand. Do you mean that I can just connect TIC 201 and 202? Also, is the drawing method of my double thermal resistor correct? We use PLC for control.
I don't fully understand your intention, so I drew a simplified diagram according to my own opinion, but left out the valve and instrument parts. The letters you use have the following meanings. If they are wrong, the picture is wrong: R--record, S--switch, A--alarm. The sub-range control used is based on the Baidu principle. The values in the sub-range block diagram can be changed according to your intention. The diagram only represents the principle. Big question about your picture: 1. Are there any requirements for the total gas flow rate? The current control method completely abandons the control of quantity and aims entirely at reaching the temperature, and the temperature after the tee point. The temperature before the tee point cannot be controlled by adding cold flow. 2. Can dual resistors solve the failure problem? If one reading is 400 and the other is 600, how do you determine which one is accurate? Without the third data for reference, it is impossible to determine which one is invalid.