Page 170 - Shale Shakers Drilling Fluid Systems

SOLIDS CONTROL EQUIPMENT 153

Hydrocyclone troubleshooting:

symptom: Probable Cause(s) and/or Action:
Some cones continually plug at apex • Partially plugged feed inlet or outlet; remove cone and clean
out lines
• Check shaker for torn screens or bypassing
• Possibly increase apex size
Some cones losing whole mud in • Plugged cone feed inlet allowing backflow from overflow
a stream manifold
Low feed head • Check centrifugal pump operation—RPM, voltage, etc.
• Check shaker for torn screens or bypassing
• Check for line obstructions, solids settling, or partially closed
valve

Cones discharge dry solids • Increase apex size and/or install more cones
Vacuum in manifold discharge • Install anti-siphon tube

Increasing solids concentration in • Insufficient cone capacity; solids may be too small; use finer
drilling fluid shaker screens

Heavy discharge stream • Overloaded cones; increase apex size and/or install more cones
High drilling fluid losses • Cone apex too large; reduce size
• Check for centrifuge cyclone discharge
• Reduce cone sizes
Unsteady cone discharge, varying • Air or gas in feed line
feed head
Aerated mud downstream of • Route overflow into trough to allow air break-out
hydrocyclone

Hydrocyclones must be relied on to remove the The advantages of hydrocyclones are simple
majority of these solids. In this case, the shale design, no moving parts, easy maintenance, and
shaker protects the hydrocyclones from oversize good separation ability.
particles that may cause plugging. The disadvantages are the inability to handle
Hydrocyclones should be designed to provide flocculated materials and a limited separation of
maximum removal of solids with a minimum ultra-fines.
loss of liquid. There should be sufficient hydro- It is impractical to desand or desilt a mud con-
cyclones arranged in parallel to process all drilling taining appreciable amounts of barite. Silts and bar-
fluid arriving into the additions region of the mud ite have about the same size range. The majority
tank system. of barite particles are between 2 and 44 microns;
Hydrocyclones produce a wet discharge com- however, some range between 44 and 74 microns
pared to shale shakers and centrifuges. Underflow and, unfortunately, 8 to 15% range between 0 and
density alone is not a good indicator of cone per- 2 microns.
formance since finer solids have more associated A desander median cut falls between 25 and 30
liquid and the resultant slurry density is lower than microns. A desilter median cut falls between 10
for coarser solids. As the solids content increases, and 15 microns. Since much of the barite falls
separation efficiency decreases and the size of above these cuts, it is discarded along with the silt
particles that can be separated increases. and sand.