Goose neck in a plant P&ID

[kakulec]

What is a goose neck and what is it used for? when do you use it? (I saw it in front of an absorber column)

[saplanti]

Where buried pipeline needs to go above ground a riser is used. In case this riser has a smooth bends for the pigging this riser is called goose neck riser.

There are similar application used for some vessels to drain. When the level is higher then the fixed level the system does automatically drain. The system has a vacuum breaker on the pipe in the vessel, the pipe goes to drainage with and omega shape of pipe. I guess you refer this as goose neck. It might be a local terminology.
You may find similar applications in the different industries.

If the referred application is not one of above so you need to provide more information and possibly a sketch to discuss further.