Page 140 - Shale Shakers Drilling Fluid Systems

SHALE SHAKER SCREENS 123

manufacturers have simplified the selection by This means the XF180 screen could pass more
offering several cloth series such as market grade flow. The screen life of the XF180 will most likely
(MG), tensile bolting cloth (TBC) and extra-fine be shorter than the TBC 165 since the wire diam-
(or ultra fine) wirecloth (XF) as shown in Tables eter of the XF180 cloth is 30.5 microns and the
6-1 through 6-3. Notice in Table 6-1 that a mar- TBC165 is 48.3 microns.
ket grade 80 cloth (MG80) has an opening size of The National Bureau of Standards has a sieve
178 microns, whereas in Table 6-2 a tensile bolt- series that is often used to describe screen open-
ing 80 cloth (TBC80) has an opening size of 224 ing sizes. The opening size of this test series plots
microns. The MG80 cloth has a smaller opening uniform increments on semi-log paper, making it
size than the TBC80 because the market grade ideal for use in plotting particle-size distributions.
cloths' heavier wires take up some of the open- Shaker screens used in the industry may be as-
ing space. As a result, a MG80 cloth can remove signed an Equivalent National Bureau of Standards
smaller solids than a TBC80. Furthermore, as a Sieve mesh count according to their opening sizes
result of the larger wires, the MG80 cloth will be as shown in Table 6-1.
more resistant to abrasion and will last longer. From the discussion above, it should be clear
The major drawback is that the MG80 cloth will that mesh count alone does not specify the screen
allow about half the flow rate of the TBC80. As opening size. As a result, if mesh count is used,
shown in Table 6-4, the screen conductance (abil- it must be accompanied by a designation of wire
ity to transmit fluid) for the TBC80 cloth is 3.88 diameter, such as Market Grade (mesh count) +
kilodarcy/mm, whereas for the MG80 it is 1.91 mesh count, Tensile Bolting Cloth + mesh count,
kilodarcy/mm. Similar comparisons can be made or National Bureau of Standards Test Sieves equiva-
between the separation/fluid conductance of the lent mesh count.
TBC cloths relative to the XF cloths. For instance, Opening size is used to measure separation per-
a single layer of XF180 screen cloth has almost the formance, but percent open area of a single-lay-
same opening size as a single layer of TBC 165. ered screen does not indicate liquid throughput.

TABLE 6-1. Market Grade Wire Cloth
Wire Diameter Opening
Open Area
Mesh Inches Mm. Inches Microns (%)
8x 8 .028 .710 .0970 2464 60.2
10 x 10 .025 .640 .0750 1905 56.3
12 x 12 .023 .584 .0600 1524 51.8
14 x 14 .020 .508 .0510 1295 51.0
16 x 16 .018 .457 .0445 1130 50.7
18 x 18 .017 .432 .0386 980 48.3
20 x 20 .016 .406 .0340 864 46.2
30 x 30 .012 .305 .0213 541 40.8
40 x 40 .010 .254 .0150 381 36.0
50 x 50 .009 .229 .0110 279 30.3
60 x 60 .0075 .191 .0092 234 30.5
80 x 80 .0055 .140 .0070 178 31.4
100 x 100 .0045 .114 .0055 140 30.3
120 x 120 .0037 .0940 .0046 117 30.9
150 x 150 .0026 .0660 .0041 105 37.4
180 x 180 .0023 .0584 .0033 84 34.7
200 x 200 .0021 .0553 .0029 74 33.6
230 x 230 .0018 .0457 .0026 66 34.3
250 x 250 .0016 .0406 .0024 63 36.0
325 x 325 .0014 .0356 .0017 44 30.0