About some graphic symbols in PID
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This picture was given to us by our boss, intending to copy someone else's work, so the information is very incomplete. The picture is also a PDF file, which is very blurry and many of them cannot be seen clearly. I can't ask anyone else about this, so I came to the forum to ask the experts. Ask the master for advice or provide some ideas or information for inquiry. There are 3 places marked in the picture. 1. This figure seems to be a box with a dotted line in the middle. I found two similar figures in HG/T20505. One is an integrated orifice plate and the other is a thermal mass flow meter. I feel it is more like an orifice plate, but I feel that if it is an orifice plate, there is a pump in front of the orifice plate. I don’t think so, or this is not an instrument. 2. I think this is a pump. I don’t know what kind of pump it is. There is an M written in a circle, which should be a motor. 3. This is the letter I in the middle of the diamond box. This is explained in HG/T20505 as a chain logic symbol. This means that the pump is logically controlled by DCS or PLC, right?
This post was last edited by Xiaoxiao Chemical Engineer on 2022-2-18 10:16 2 It looks like a pump with a check valve at the outlet. If 2 is a pump, then 1 is at the inlet of 2 and feels like a filter. Why not say 1 is a flow meter? If it is a flow meter, it will definitely be marked with an FI mark, like the thermometer TG next to it. There is no label FI here, so it is more like a filter. 3 is the interlock symbol you mentioned. When interlocked, motor 2 stops or starts.
Thank you for the ideas. Sometimes I just think about it myself and I can’t get around it.
There are two pumps, the outlet is a check valve, the flow direction is from right to left, the two inlets are filters, the flow diagram is like a circuit diagram. The interlocking symbol is right.
1. Filter 2, pump 3, motor signal interlock
This drawing is too rough, even the PDF file is not that crude! I haven't seen it for a long time. Two pumps are connected in parallel. 3 is a signal interlock. There are two sets of materials at the pump inlet, and the outlet can also be in two directions.
1 block looks like it should be the inlet filter； (Personally, it looks a lot like Figure 3) 2 is a pump, it does not refer to what type of pump it is. ； 3 is the chain signal, which generally refers to the parking chain for power failure protection.
The first is the interlocking logic logo, the second is the pump and motor symbols, and the third should be the flow meter or restriction orifice plate.