the cleaning devices being entrained discrete elements, e.g. balls, grinding elements, brushes

Full Title

Cleaning hollow articles by methods or apparatus specially adapted thereto > Cleaning pipes or tubes or systems of pipes or tubes (apparatus for cleaning metal pipes by chemical methods C23G3/04) > Cleaning the internal surfaces; Removal of blockages > using cleaning devices introduced into and moved along the pipes > moved along the pipes by a fluid, e.g. by fluid pressure or by suction > the cleaning devices being entrained discrete elements, e.g. balls, grinding elements, brushes