giblitBlimey Ashokaa,
That list included everything except the kitchen sink (actually it included that as well ha ha ha)
As entertaining as that list was, I’m not sure I’ve ever seen any of those abbreviations on a P&ID !!
Now with regards to the original post, there isn’t a universal ‘standard’ for P&ID symbols.
Although PI will typically be a Pressure Indicator and TT will be a Temperature Transmitter , XI may be a pig signaller for one company or a corrosion coupon for another.
Rather than make an assumption it is always best to ask for the legend sheet that should be issued along with any P&ID’s.
I’ve fallen foul of assuming that something on a P&ID is one thing, only to find out later on that it’s something completely different that takes up 4 times as much room and should be located in an entirely different location !!