Powerful circles

Circular storage units for bulk goods require very little space and have a high storage capacity. A slewing scraper with a double-strand chain and wear-resistant scraper blades ensures that the stockpiled bulk goods are discharged again.

A technical challenge is the horizontal guiding of the scoops by means of centre guide rollers screwed onto the scraper. Vibrations here can cause problems with fastening. The German company SCHADE Lagertechnik has resolved this ­issue on an enormous circular lignite storage unit in the USA, using Nord-Lock wedge lock washers.

Engineer Klaus Lechte, Technical Order Processing at SCHADE Lagertechnik, explains the vibrations on the scraper boom: “We use a chain system in which the links run over sprockets. The polygon effect created here generates a push–pull tension, which is responsible for some of the vibrations.”

SCHADE Lagertechnik needed screw connectors that could not be loosened to secure the centre guide rollers. Nord-Lock supplied wedge locking washers with an enlarged outer dia­meter, which makes the connections absolutely secure. Nord-Lock securing system means that it is no longer necessary to weld the nuts into place or apply a high preload to the system, which could lead to plastic deformation. Nord-Lock offers the advantage of significantly lower tightening torques.

Customer: SCHADE Lagertechnik GmbH
Item: Circular storage unit for lignite
Length Of Scraper Boom: approx. 41 metres
Height: approx. 40 metres
Diameter: approx. 95 metres
Stacking/Unstacking: 2,200 t lignite/h