Solids control comparison
Desander vs Desilter: what's the difference?
Both are hydrocyclones and both sit downstream of the shakers, but they cut at different particle sizes and play different roles in the solids-control train. Here's how to tell them apart and run them right.
A desander uses large cones (typically 6"–12") to strip out sand-size solids down to about 45–74 µm. A desilter uses small cones (typically 4"–5") to make a finer cut, removing silt-size solids down to about 15 µm. The desander runs first; its overflow feeds the desilter.
| Feature | Desander | Desilter |
|---|---|---|
| Cone size (I.D.) | 6"–12" (large) | 4"–5" (small) |
| Cut point (removes down to) | ~45–74 µm (sand-size) | ~15 µm (silt-size) |
| Position in train | After shaker/degasser, before desilter | After the desander |
| Flow per cone | ~500 gpm at 75 ft head (10" cone) | ~80 gpm at 75 ft head (4" cone) |
| Job | Strip the bulk sand load first | Make the final fine cut |
| Plugging tendency | Lower — larger apex | Higher — small apex plugs more easily |
| Weighted mud (with barite) | Use with caution | Not recommended — discards barite |
What a desander does
The desander is the coarser of the two hydrocyclone banks. Pressurised mud enters each cone tangentially; centrifugal force throws the heavier solids to the wall, where they spiral down and discharge at the apex, while clean fluid rises through the vortex finder. Large cones (6" and up, commonly 10") give a high throughput and a coarse cut, so the desander handles the bulk of the sand-size load and protects the finer equipment downstream.
What a desilter does
The desilter works on exactly the same principle but with smaller cones (usually 4" or 5"). The smaller diameter raises the centrifugal force near the apex and lowers the cut point, so the desilter makes the finest particle-size separation of any full-flow solids-control equipment — down to roughly 15 µm. Because each small cone passes much less flow (~80 gpm at 75 ft head), a desilter uses many cones in parallel to handle rig flow.
How they work together
Run them in series: shaker → desander → desilter. The desander's overflow should be routed to the desilter's suction tank so the desilter only has to make the fine cut on already-desanded mud. Both banks need their own dedicated, correctly-sized centrifugal pump feeding ~75 ft of head, and both should show a light spray at the apex — a rope means the cones are overloaded or plugging.
The weighted-mud rule
Neither bank is run on weighted (barite) mud the way they are on unweighted mud. Barite is roughly 4.2 SG and sized below the cyclone cut, so a desilter in particular will throw expensive barite out with the drilled solids. On weighted systems the fine cut is handed to the centrifuge instead, and a mud cleaner (cyclones over a fine screen) is used to recover barite while discarding drilled solids.
Frequently asked
What is the main difference between a desander and a desilter?
Cone size and cut point. A desander uses large cones (6"–12") to remove sand-size solids down to about 45–74 µm; a desilter uses small cones (4"–5") to remove silt-size solids down to about 15 µm. The desander runs first and feeds the desilter.
Which comes first, the desander or the desilter?
The desander. The order is shaker → desander → desilter. The desander strips the coarse sand load, and its overflow is routed to the desilter, which makes the finer cut.
Can I run a desilter on weighted mud?
No — a desilter is not recommended on weighted (barite) mud because it discards barite along with the drilled solids. On weighted systems the fine cut is made by the centrifuge, and barite is recovered with a mud cleaner.
What micron size does a desander remove?
A desander typically removes solids down to roughly 45–74 µm (sand-size), depending on cone size, mud properties and feed pressure.
What micron size does a desilter remove?
A desilter typically removes solids down to about 15 µm (silt-size) — the finest cut of any full-flow solids-control equipment.
Why does my cyclone discharge a rope instead of a spray?
A rope-shaped underflow means the cone is overloaded or starting to plug. Aim for a light spray: check feed head, apex size and the solids load, and open or replace the apex if needed.
- Desander ~45–74 µm, desilter ~15–44 µm; pairing & efficiency — Drilling Bucket ↗
- Desilter 4"/5" cones, finest cut ~15 µm, plugging & weighted-mud caution — ScienceDirect ↗
- Desander 500 gpm/cone, desilter 80 gpm/cone at 75 ft head — H-Screening ↗
- Desander overflow routed to desilter suction; not for weighted mud — DrillingForGas ↗
Figures are typical field values and vary with mud properties, equipment design and operating conditions — always confirm against your OEM data and the current standard. From SC DrillTech · independent & vendor-neutral.