FILTER

A pressure filter is claimed as well as its porous, tubular, strainer element which fits inside the filter casing to leave an annular space between the two, the fluid to be filtered being delivered into the annular space and the filtrate being drawn off from the bore of the tubular element; the exterior surface of the element is given a rough, uneven texture and fluid delivered into the annular space is directed to flow along the exterior surface of the element. Both casing and element are pref. hollow, cylindrical. The rough surface is pref. made up of mineral particles such as sand bound by a synthetic resin such as polyurethane or an epoxy resin, the mineral particles being of at least two different grain sizes. The use of the filter to remove suspended solid particle from a liquid is also claimed, the loss of pressure through the element not exceeding 0.35 kg/cm2 and pref. being as low as 0.070 kg/cm2. High capacity filter for removing solid particles from fluids of low viscosity, partic. water and gas. Device has high capacity with very low pressure loss through filter. Filtrate volume delivered per unit area of filter surface is much higher than in previous, similar filters. All these benefits accrue from the turbulence imparted to the incoming fluid by being directed along the rough surface of the element.