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I have a schematic for some gas lines in a wafer processing unit. One of the symbols which occurs is a circle with an x in it that has the left and right quarters filled in to form two black triangles. (I've attached a drawing.)

From context, i can tell that these represent valves to allow or block flowing of the gas. However i would like to find this symbol in some guide to give a more exact interpretation of the meaning, and just to have an authority that i can cite to.

I have not found the symbol in the context of a gas line schematic in any online reference.

Where, and how, can i look?

circle with two black sectors

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  • $\begingroup$ A simple search for « pipeline symbols » gives : wermac.org/documents/symbols_iso.html. And that was the second result ... $\endgroup$ – Solar Mike Apr 8 '18 at 6:32
  • $\begingroup$ @SolarMike Thanks for the reference! I looked at the 74 symbols on that page and none seemed to match the symbol i'm looking for. Could you please give me the name of the matching one? (Maybe i just don't understand when two symbols are deemed equivalent.) Thanks! $\endgroup$ – dan Apr 8 '18 at 21:21
  • $\begingroup$ You did ask for "where, and how, to look" so I gave you an example of the words I searched for and an example result... there were many others. It could be a symbol defined by that particular discipline or manufacturer... $\endgroup$ – Solar Mike Apr 9 '18 at 7:44
  • $\begingroup$ Do I understand you correctly that you look at a P&ID? $\endgroup$ – mart Apr 9 '18 at 11:43
  • $\begingroup$ The first sheet of the set of P&IDs should be a symbol legend and explanation of the numbering system. Do you have the whole set or just one sheet? $\endgroup$ – Mark Apr 9 '18 at 12:23
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Normally you look at the relevant industrial code. I believe in most parts of the world this would be DIN EN ISO 10628-2 - Diagrams for the chemical and petrochemical industry -- Part 2: Graphical symbols. Your sombol is not included.

Next step would be to look at the relevant ASME code (I beleive the ASME provides the relevant code here, not working in the americas I'm not sure). I don't have that available and I'm not sure valves are drawn that differently in ASME P&IDs. This page references some non-ISO 10628 compliant symbols, but the valves look like in the ISO code.

So the last step is to ask wether the company providing the drawing has an internal standard they use, for whatever reason.

Edit to paraphrase Mark's comment: Sometimes, the first sheet of the set of P&IDs has a symbol legend and explanation of the numbering system.

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  • $\begingroup$ This answers the question, literally and in detail, so i'm obliged to accept i think. (And it is useful information besides. :) ) $\endgroup$ – dan Apr 10 '18 at 3:06
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From my experience in bridges, I would expect that to represent a borehole: google image result.

Perhaps this isn't a pipeline-specific symbol, but a general engineering symbol. I can well believe that boreholes would have been taken to sample the soil/strata before a pipeline is constructed.

In my googled image, it appears with the letters BH next to it to, to signify BoreHole. In my experience there are often also numbers to correlate it with a table of borehole results, e.g. it might say "BH 10436". Are there any letters/numbers near your symbol which could be part of it?

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  • $\begingroup$ This is useful information as well, but i can only accept one answer. (And based on your idea about adjacent letters, i think that in this particular schematic the symbol refers to air operated valves. So not so authoritative but good enough. Thanks for your answer.) $\endgroup$ – dan Apr 10 '18 at 3:27

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