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AutoCad

AuotCad is most commonly used sotwares for all engineering descipline.
Specifically for piping here are two softwares
Cadworx Pipe, generates Isometrics and BOQs, It has built in piping specifications and there are no. of other options
Cad Pipe it is almost similar to Cad Worx pipe
Omer

Microstation still has quite a strong hold on the process piping, especially in the UK on petrochemical projects