The depth issue of PID graphs
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A few more practical questions: Should the U-shaped liquid seal on the pipeline be shown in the diagram? Without considering the liquid seal height, it merely indicates where a liquid seal is required, such as the return pipe below the condenser. Regarding the issue of the relative position of the devices. Suppose one reactor is on the second floor and another on the first floor, with pipes connecting them to allow direct material transfer; can the two devices be drawn side by side in the diagram? Building on the previous assumption, two reaction vessels, one upstairs and one downstairs, are used to produce one product, which is referred to as a set in this context. To increase production, multiple sets need to be arranged in parallel; is it necessary to draw them all? According to HG20519-92, the same number of sets of equipment can be represented by boxes; however, I feel that the concept of a \"set\" as defined here is different from that specified in the standard, since there are many pipelines connecting the various reactors. If it is omitted as a box, how should the pipeline number be handled? Also, please share your experiences on how to arrange elements so that the diagram looks more pleasing.
The U-shaped liquid seal on the pipeline should be indicated, with specific provisions in the condenser system unit mode. In the PID, the relative position of the equipment should be indicated, as specified in HG 20519-92. For the third issue, it can be represented by a box; however, the pipes that enter and exit the system must be shown, along with their corresponding pipe numbers
It is recommended that you carefully review the provisions regarding the content and level of detail for the layout design of chemical plant equipment in HG 20546.1-1992, as well as the unified regulations on the content and level of detail for the construction drawings in chemical process design as specified in HG20519-92； There are these two standards on the forum; you can go down and take a look
The liquid seal must definitely be indicated. As for the relative positions of the equipment, as long as there is no excessive deviation, that should be fine. Regarding the second question you mentioned, it’s sufficient to show a certain height difference in the diagram. For the third question, in our design offices we generally require that everything be depicted
Answer: 1. The U-shaped liquid seal needs to be shown in the diagram to emphasize it and draw attention to it; the height of the liquid seal depends on the operating pressure inside the equipment, so it may not need to be indicated. 2. Regarding the relative position of the devices: a parallel drawing method can be used on the PID ； Just indicate the direction of the materials. The elevation of the equipment is determined primarily based on the plan and elevation drawings. 3. All devices should appear on the PID, including devices with the same tag number. So all these sets of parallel reactor systems you mentioned should be drawn, along with their complete piping systems. 4. Pipeline numbers should be assigned in numerical order, from left to right, following the principle of first-in-first-out, with main pipelines coming before branch pipelines. 5. Regarding layout: parallel arrangement, symmetrical layout.
1. The liquid seal on the PID must be indicated. 2. If differences in level can be indicated, then do so; in addition to representing processes, PID should be improved as much as possible in other aspects as well. 3. It’s best to draw it out; after all, it’s just a copy, so there’s no need to redraw it if it’s not necessary – there’s no reason to take shortcuts. For the layout, it’s best to have one diagram per step, so it remains clear and easy to understand.