Machines and machine parts; machines for mixing and/or metering substances, in particular chemicals, in particular flocculants and/or polymers, into fluids, suspensions or sludges, in particular for the chemical conditioning of sludges before dewatering and/or for the treatment, in particular the disintegration and/or homogenisation and/or cleaning and/or dewatering, of liquids, suspensions or sludges, in particular sewage sludge, industrial sludge, mining sludge and/or sludges for disposal o...