The invention provides an apparatus (10) for removing magnetic particles (53) from a liquid flowing from an oil or gas operation and method of use. The apparatus (10) comprises a plurality of magnet assemblies (20), each having a first condition in which an operable part is active to attract magnetic particles (53) to the magnet assembly (20), and a second condition in which the operable part is inactive and magnetic particles (53) are not attracted to the magnet assembly (20). A drive mechanism (13) moves the magnet assemblies (20) between exposure to a flow path of from a liquid (40) flowing from an oil or gas operation and a collection location (54). An activation means (36) moves the magnet assemblies (20) between the first condition and the second condition.