A foam is created when a mass of gas bubbles is evenly distributed throughout a quantity of liquid, in such a way that the gas occupies almost all of the final volume, surrounded by the liquid in the walls of the bubbles. If the liquid then sets solid, a very porous mass is created, which […]
Somewhat akin to the capsule filter in operating principle, although very different in construction and operating conditions, are many of the filters used to remove contaminants from the flow of molten polymer on its way to an extrusion nozzle. The filtration of plastic melts presents a considerable challenge, and sets of standards have had to […]
Similar in principle to the cartridge filter, by virtue of being used until full of collected solids and then cleaned or discarded, are the small in-line capsule filters, much used in laboratories and the small-scale production processes of the lifescience industries. These are made entirely, both housing and filter medium, of a polymer suitable to […]
The sintered (thermally bonded) materials will normally be made into tubular shapes, by moulding or isostatic pressing, before sintering, and these shapes will be self-supporting, so there is no need for a core (unless required in the forming process). These shapes can then be considered as candles rather than cartridges, a single element in its […]
The cartridges with thick media are intended to work by depth filtration, and their contaminant loading capacity is an important feature of their usability. Thick media will often be graded so as to have an increase in density towards the centre of the cartridge, thus improving their depth filtration behaviour. Once the maximum load has […]
The thin media can be any material that may be produced in sheet form, but a flat sheet wrapped around the central core would not be a very efficient filter element, because the ratio of filtration area to housing volume would be too small. The available area can be greatly increased by pleating the flat […]
The cartridges consisting of a single piece of filter medium are made from a perforated cylindrical core, of metal or stiff plastic, onto which the material of the filter medium is placed or formed. There are two basic types of integral media cartridges, depending upon which primary filtration mechanism is operating: thin media, which work […]
Several attempts have already been made in this Handbook to classify a type of filter, only for examples to be shown of filter types that cross the filter type classification boundary. The difficulty of precise classification is nowhere so apparent as in the types of filter elements known as cartridges, and therefore with the types […]
There is much confusion over the precise meaning of the term ‘candle filter, ‘ so let it be said that, in the present context, a candle filter is a process filter, mainly used for the recovery of process residues from liquid streams. It almost always has a vertical cylindrical housing, inside which a multitude of […]
The filter pocket is just as its name implies: two rectangular sheets of filter medium, placed side-by-side, joined together at three edges, the fourth being open. Pockets are used almost exclusively for air cleaning, in which function they act, literally and metaphorically, as an extension of the panel filters described in Section 3J: several pockets […]
