The standard contains safety requirements for the design and construction of unloaders mounted in stationary round silos for silage and similar materials. It applies to electrically powered, slowly rotating unloaders located above the stored silage surface. It describes measures for the elimination or reduction of hazards for which specific requirements for unloaders, as defined in clause 3 and Annex B, are necessary. In addition, it gives information to be provided by the manufacturer on safe working practices. The document only deals with the hazards generated by the silo unloader and not with those of the silo system itself (for example, hazards arising from generated gases). This document does not refer to noise and fire hazards and hazards related to the foreseeable misuse. The document does not deal with technical requirements for installation or removal of the unloader from one silo to another. The environmental aspects have not been considered in this document. This document applies primarily to machines which were manufactured after the date of issue of this document.