Wstter hammering one pipe system steam heat

We have had isdues in the riser pipe up on the 5th floor whete you hear real bad banging in the winter . Been asking the landlord for years to fix it . We were told the problem is most likely the basement nothing wS found up on our floor to cause this .so today plumber were here in the basement the open a wall on our section A . When we came home they threw this in the yard its pipingnthey cut out does anyone know what this is ? Is this where condensation is suppose to drip out