Summary:

There is no angular acceleration in the turn.

There is no change in speed in the turn.

There is a change in velocity in the turn.

There is centripetal acceleration in the turn.

The pipe applies a force to the mass to cause that centripetal acceleration. (F=ma)

The mass applies a matching reaction force to the pipe (Newton's 1st law).


If you disagree, look up "acceleration" and "velocity".