In some standards this structure is commonly used:
is to be
are to be
- 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: ?
- 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.