As the term is most commonly used in filtration technology, a screen serves two prime functions: as a large strainer, especially for water intakes and in wastewater treatment, and as a device for separating mixtures of solid particles into two or more sizes, either in the dry state or in liquid suspensions. In formal terms, […]
Perforated plate strainers provide coarse filtration down to about 150 um. For finer filtering, wire mesh elements are normally used in conjunction with perforated plate or other form of reinforcement, when this is necessary for added mechanical strength. Wire mesh strainers can provide filtration down to about 40m, but with reduced strength due to the increasingly […]
An obvious disadvantage of a permanent strainer of the types just described is the need to shut down the plant flow so that they may be cleaned. Where continuous operation is required in a pipeline service, duplex strainers can be used in an integral unit with the provision to isolate one element at a time […]
Permanent strainers are conventionally complete fittings, most commonly with a housing of Y-configuration, with a cylindrical strainer element (as in Figure 3.2 ). They can be used in both the horizontal and vertical planes, and are intended for applications where only a low concentration of contaminants is expected. The element is retained in its housing […]
Temporary strainers are intended for short periods of application, such as being fitted during the run-in period of a new system, or when restarting a pipeline system after shut-down and maintenance. They are intended to remove coarse debris particles present in the system. After a suitable period of use, they are removed (and can be […]
For a Handbook devoted to the removal of suspended contaminants, there is no better way to start than with the strainer, whose function is entirely that of protecting downstream items of equipment, or downstream processes, from the impact of impurities that may block narrow passageways or abrade sensitive surfaces. Strainers offer a simple method for […]
This first main section of the Handbook, which deals with fi ltration equipment, consists of a number of areas, each devoted to a type of fi lter. In accordance with the main theme of the book, more attention is paid to those fi lters used for clarification of gas or liquid streams than to those […]
Quite closely related to deep-bed filtration in principle is precoat filtration, which uses a bed of inert solids formed on the upstream surface of a relatively coarse filter medium to act as the actual medium. The most popular solids for this purpose are kieselguhr (diatomaceous earth) and perlite. These can only be used where the […]
The media used in deep-bed filters must be inert, resistant to fracture yet easily prepared in batches of graded particle size. Many different granular and crushed materials have been used to form the deep beds employed in the large gravity and pressure filters common to the water purification and sewage treatment industries. In addition to […]
The forms of filter media discussed in the previous parts in this section have all been constrained as pieces of material or structures. The remaining group of media materials, of particular interest to clarifying processes, are unconstrained (except by the walls of their containing vessel), being masses of coarse particulate substances, used as packed beds […]
