riser main vs riser pipeline

riser main and riser pipeline both are nouns.

Word	Noun	Adjective	Verb	Adverb
riser main	Yes	No	No	No
riser pipeline	Yes	No	No	No

As nouns, riser main and riser pipeline are synonyms defined as:

Other synonyms of riser main include riser, riser pipe.

riser main (noun)	riser pipeline (noun)
a vertical pipe in a building	a vertical pipe in a building