Nibal,
Move Piped Equipment is the way to move connected pipe without losing the connection. If you are getting an error message that is telling you that a pipe segment has missing connected entities, and that it is deleting and aborting, then you must have removed one of the fittings on one side of that pipe.

Please see the links below on how to use the Move Piped Equipment tool, as well as what to do when you get that error message. And as always, take a look at our trainer videos on using specific tools.

Move Piped Equipment
Pipe Segment Has Missing Connected Entities
Trainer: Move Piped Equipment