In some standards this structure is commonly used:

is to be


are to be


  1. Where external piping are to be connected to the vessel: ( to be continued).

Why don't we say simply:

Where external piping are connected to the vessel: ?


  1. Where the PLANT is to be constructed... (and we don't say: is constructed) ?

And regarding this issue the second question is : Copied sentences from STD : 1. Only to be used for instrument. ( and not it is used or should/shall/will be used) 2. All carbon steel bolting to be zinc coating (does it mean should be zinc coating???)-this sentence is mentioned as a note in certain code.

  • piping is singular, that's why. plural noun = are to be/singular noun =is to be. – Lambie Feb 3 '19 at 17:00

"Is connected" means where it is connected, like it's connected, right now. "Is to be connected" means where it will be connected, at some point in the future.

Before I started writing, there was a box on the page "was to be written". Once I started, it became where the answer "was being written", and when I finish it becomes the place the answer "was written". The little arrows to the left of my answer are to be clicked by those who wish to upvote it, or downvote it.

If it is "where the piping is to be connected", then the piping is not yet connected. The piping is not yet connected, the plant is not yet constructed, but you already know where they are to be connected, built, etc. Instructions such as those are giving instruction to do something to the area before the connection, building etc, generally in preparation.

It is also used to refer to cases. For example, the "external piping" example might be giving different instructions for installation of some equipment depending on whether or not external piping is to be connected. "If" would be clearer in that case, but "where" is used a fair amount, as is "when".

  • I think now it makes sense, thanks a lot, but what about the second part? All carbon steel to be zinc coating or only to be used for instrument, It feels like there is lack of a verb, like I explained above. I really appreciate it. – amir rezvanfar Feb 4 '19 at 10:12
  • In "only to be used" the verb is to use. – SamBC Feb 4 '19 at 12:21
  • If I want to translate it, may I say : All carbon steels should be zinc coating ? Or All carbon steels which are zinc coated? I mean is it imperative? Or it just gives you some details. The second sentence says: (This Item) should be used for instrument? Or it means : This item are used for instrument? I'll be extensively thankful 🌷 – amir rezvanfar Feb 5 '19 at 8:12
  • Should be zinc coated is the way it should be put. Carbon steel can't be zinc coating. "Only to be used for instrument" should be instruments, or possibly instrumentation. "An instrument" would also be grammatical, but is unlikely to be what they mean. – SamBC Feb 5 '19 at 8:26
  • But here is another example that now I'm reading: Plate to be joined by butt welding shall be matched accurately and retained in position during the welding operation. 'Plate to be joined' can't be placed by should be, and it's sort of a description "Plate which is joined by butt welding method" shall be matched accurately ... – amir rezvanfar Feb 5 '19 at 13:12

As Lambie says,

Where external piping are to be connected to the vessel.

is incorrect English. It should be:

Where the external piping is to be connected to the vessel.

That means

Where the external piping should be connected to the vessel.

It is an ellipsis, where a word is omitted but understood. It does not imply that the external piping actually is yet connected. It is a direction, rather than a statement of fact.

  • You missed the fact there's a colon and apparently more text after "Where external piping are to be connected", I think. The are is wrong, but there's no need to add a "the"; phrases like that are very common in instructions, standards etc. – SamBC Feb 4 '19 at 16:26

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