Page 154 - Shale Shakers Drilling Fluid Systems
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SHALE SHAKER SCREENS 137
Early shale shaker screens required durability. can significantly increase shaker performance and
This demand was consistent with the shaker de- screen life.
signs and solids removal philosophies of their Manufacturers employ different geometric-
period. These shakers could only remove the large shaped apertures in their screen panel design.
coarse solids from the drilling fluid while the sand Some of the more common panels are square,
trap, reserve pit, and downstream hydrocyclones rectangular, hexagonal, or oval shapes. The aper-
removed the bulk of the drilled solids. tures in the panels can vary from 1-in. to 3-in.
Changes in drilling fluids, environmental con- squares, 2-in. x 6-in. ovals, 7-in. x 33-in. rect-
straints, and a better understanding of solids/ angles, to 1.94-in. hexagons.
liquid separation have modified the role of the The panels can be flexible (built of thin gauge
shale shaker. Generally, the more solids removed metal or plastic) so they can be stretched over
at the flow line, the higher the effectiveness of crowned shakers. They can also be flat and built
downstream equipment. The results include re- from heavy-gauge mechanical tubing for installation
serve pits that can be smaller (or eliminated alto- as panels on flat-decked (non-crowned) shakers.
gether), lower clean-up costs, and increased drill- Regardless of configuration, the function of
ing efficiency. the panel is to provide mechanical support for the
As important as the mechanical aspects of newly fine mesh screen cloth bonded to it, and at the
designed shale shakers may be, improvements in same time occlude as little potential flow area as
screen panels and screen cloth have also signifi- possible with the supporting grid structure.
cantly increased shaker performance. Older shak- Some screened panels are made with no sup-
ers have benefited from these improvements, as port grid at all, but simply by bonding the finer
well. Two design changes have been made to ex- mesh(es) cloths directly to a coarser backing wire
tend the economic limit of fine-screen operation: using a heat-sensitive adhesive. Essentially this
becomes a hook strip design, with certain sup-
1. A coarse backing screen to support the fine port refinements.
mesh cloth(s), and Pretensioned screen panels help address two of
2. Tensioned cloth bonded to a screen panel the three original design goals: capacity and screen
(pretensioned screen panel) life. The remaining goal of easy identification/
comparison is a function of the screen cloths used
in today's panel designs and better labeling tech-
Coarse Backing Screen niques to display important performance variables.
Today, fine screen cloth (s) is reinforced with a
coarse backing screen. This backing screen pro- Hook Strip Screens
tects the fine mesh screen from being damaged
and extends life. The backing screen also provides Hook strip screens are also available. Because
additional support for heavy solids loading. of the superior life characteristics of the panel
mount units, they have been relegated to a mi-
nor role on linear motion machines, although they
Panels are used extensively on circular and elliptical mo-
tion machines. Proper tensioning (and frequent re-
The most important advance in screen panel tensioning) of all screen types is good screen
technology has been the development of preten- management and can significantly increase screen
sioned screen panels. Although similar panels life. Individual manufacturer's operation manuals
have been used on mud cleaners since their in- should be consulted to obtain the proper installa-
troduction, earlier shakers did not possess the en- tion methods and torque requirements, where appli-
gineering design to allow their use. With the ad- cable, for specific screens/panels.
vent of linear motion machines, the pretensioned
screen panels extended screen life and permitted
more routine use of 200+ mesh screens. Bonded Screens
These panels consist of a fine screen layer(s)
and a coarse backing cloth layer bonded to a sup- Several types of bonded screens are available.
port grid. The screen cloths are pulled tight, or The repairable perforated plate screen has one
tensioned, in both directions during the fabrication or more layers of fine mesh cloth bonded to a
process. This ensures that every screen begins sheet of metal or plastic with punched, patterned
with the proper tension. Correct installation pro- holes. Perforated plate designs are available in
cedures and post-run retightening of screen panels various opening sizes and patterns. Additional
