Roller cement mill

The outlet/inlet cylinders in a roller cement mill are operated around the clock. Accordingly, serious leaks start to appear around the piston rod packing after only three to four months. Montanhydraulik Repairs and Service worked out a solution that quadrupled the cylinder's useful service life.

Driven by a 2,000 kW electric motor, the mill drum feeds cement clinker, slag or limestone from the neighbouring open-cast mine underneath the mill roller. During the grinding process, the cylinder packings must be proof against the rapid, short-stroke swerving movements with high pressure peaks, as caused by stones in the feedstock. To cap it all, the various different feedstock types are ground at varying pressure levels: this generates temperatures of up to 100 °C and significantly reduces the service life of the packings. Under unfavourable operating conditions, correspondingly high rates of leakage can occur in a matter of weeks. A situation that the factory owner wanted to change. 

The steps taken during the cylinder repair process are outlined below. Instead of using steel, Montanhydraulik Repairs and Service manufactured a new packing adapter bushing from bronze, which exhibits minimal clearance on the cascaded triple-seal system. The fitting tolerance was also reduced for the new guide bushing, also manufactured from bronze. To achieve this, the bushing was installed in the cylinder head using an interference fit (shrunk-fit using liquid nitrogen). Following this, rod guide tolerance was adjusted to match the rod's tolerated diameter by rotating the guide bush to its final position.