Could everyone please help explain what the logic in these PID diagrams means?
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I hope that those who are experts can help me resolve these doubts and answer my questions regarding the PID diagrams below: Figure 1: Figure 2: In both Figure 1 and Figure 2, it is a shut-off valve, but they differ in design – one has an electromagnetic actuator while the other does not. As I understand it, a shut-off valve with an electromagnetic actuator can be fully closed; but without such an actuator, isn’t it more likely to leak? Or can leaks be avoided simply by using a plunger-type diaphragm head? Furthermore, are the shut-off valves in Figure 1 and the solenoid valves in Figure 2 both controlled by PLC programming? It seems that by looking at the flowcharts I have, any valve labeled as an “XV” shut-off valve uses this type of instrument symbol. In Figure 2, the solenoid valve-controlled element should be understood using the logical programming symbol “I”, which implies a sequential connection; however, for the “E” in Figure 1, after checking various sources, it seems to refer to voltage. Could it be that the element in Figure 2 should be interpreted as current? Is there anyone who can help me explain in detail the specific meaning of the gauge symbols in Figures 1 and 2? There’s also Figure 3 below; I’m not quite sure what it means either. Figure 3:
This post was last edited by ylb913 on 2018-6-22 07:10. 1. Refer to HG/T 20505-2014 on the functional indicators and graphic symbols for process measurement and control instruments; first, look at Table 5.3.2 to understand the meaning of the graphic symbols for the instrument connections. It can be seen that Figure 1 represents an electric valve, while Figure 2 represents a pneumatic valve. Since Figure 1 shows an electric valve, then E undoubtedly represents electricity, electric drive ； The I inside the diamond symbol can be found on page 29; I18506 represents interlocking. 2. Next, refer to Table 5.1.2 to understand the meaning of the graphic symbols for instruments and their functions; the dashed and solid lines inside circles or squares convey different meanings. Looking at Table 4.1.1, the code letters go without saying. 3. The tightness of a valve when closed depends on the performance of the valve itself.
Is it a fire interlock, a level high/low interlock, or a value interlock?
The poster’s question is not clear! ! ? Figure 1 is the reset button, Figure 3 is 3 select 2
HG/T 20505 is quite detailed and can be used as a reference. I also had many doubts in the past, and there are slight differences among different design institutes. However, once you understand the basic descriptions and structural framework specified in the standards, it becomes not difficult at all