The pin attachment comprises anchor for securing to the body of the sweeper, and a head portion including a number of fingers each having a tip end surface which is inclined with respect to the direction of movement of the sweeper. The fingers are divided into first and second groups, the first group having their tip end surfaces inclined in one direction and the second group having their tip end surfaces inclined in a direction opposite to the first group. The fingers are substantially frustoconical. The pin attachment is secured to the body of the sweeper to project along a radius of the pipe when in use.
