Well screens are sleeve-like units fitted over the ends of intake pipes in water or oil wells. They well illustrate the nomenclature problem outlined at the start of this chapter in that they are relatively small and clearly act entirely by straining, yet they have always been called screens, and so are described here. In […]
All of the intake screens discussed so far have operated in a stationary mode (or at least stationary whilst screening). An important group of screens rotate, screening solids continuously through that part of the screen that is submerged, with accumulated solids carried on the surface of the screen out of the water, to a zone […]
A different form of stationary water intake from surface water sources, such as submerged intakes for power, pulp and paper, or petrochemical industries, uses cylindrical screens at the inlet of the intake pipe, in single or multiple designs, as shown in Figure 3.9. These can usually be optimized to accommodate any set of conditions. In […]
A wide range of screens is used for the removal of solids from water in large-scale water handling systems. Where water is pumped from rivers or lakes (or from the sea, either as feed to a desalination plant, or for cooling purposes), screens are employed on the intake side to protect the pumps from debris […]
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 […]
