Screening surfaces used in solids control equipment are generally made of woven wire screen cloth, in many different sizes and shapes. The following characteristics of screen cloth are important in solids control applications.
Screens may be constructed with one or more layers.Non-layered screens have a single layer, fine-mesh, screen cloth (reinforced by coarser backing cloth) mounted on a screen panel. These screens will have openings that are regular in size and shape. Layered screens have two or more fine mesh screen cloths, usually of different mesh (reinforced by coarser backing cloth), mounted on a screen panel. These screens will have openings that vary greatly in size and shape.
To increase screen life, especially in the 120-200 mesh range, manufacturers have incorporated two design changes:
A coarse backing screen to support fine meshes
Pre-tensioned screen panels
The most important advance has been the development of pre-tensioned screen panels. Similar panels have been used on mud cleaners since their introduction, but earlier shakers did not possess the engineering design to allow their use successfully. With the advent of modern, linear-motion shakers, pre-tensioned screen panels have extended screen life and justified the use of 200-mesh screens at the flow-line. The panels consist of a fine screen layer and a coarse backing cloth layer bonded to a support grid shown in the picture below. The screen cloths are pulled tight, or tensioned, in both directions during the fabrication process for proper tension on every screen. The pre-tensioned panel is then held in place in the bed of the shaker.
Today, fine screens may be reinforced with one or more coarse backing screens. The cloth may also be bonded to a thin, perforated metal sheet. This extra backing protects the fine screen from being damaged and provides additional support for heavy solids loads. The screens equipped with a perforated plate may be available with several sizes options for the perforation to allow improved performance for a given situation.