Abstract: A rotary anti-scaling device comprises a pair of substantially identical halves connected together at a relative displacement of 180.degree. about a central transverse axis through the halves to form a unitary spike. Each half includes a central body portion with a central, transversely-extending bore therethrough permitting rotation of the unitary spike on an associated mounting bar, one or more projections extending from opposed ends of each body portion and at least one of the body portions having means formed thereon for co-operating with an adjacent spike to locate said spike in a position displaced angularly about its transverse axis relative thereto.