How to Configure Hydrocyclones for Mud Desander and Desilter
Hydrocyclone setup is not just a matter of deciding how many cones to install. The cyclone size, the flow going through the manifold, the solids load, and the job each stage needs to handle all affect the final arrangement.
Two rigs can have similar pump capacity and still need different cyclone setups. What matters is how much mud actually reaches the cyclone stage and what needs to be removed from it.
Start With the Solids You Need to Remove
Mud desanders commonly use 8-, 10-, or 12-inch hydrocyclones for coarser drilled solids after the shale shaker. Mud desilters normally use 4-inch cones when finer solids need to be removed further down the process.
These are not interchangeable just because both are hydrocyclones. A larger cone can handle more flow, but it is not a replacement for a smaller cone when the job calls for finer separation.
This is one reason cyclone size should be tied to the solids removal duty, rather than selected from the rig size alone.
Use the Actual Flow to Size the Cone Bank
After choosing the cyclone size, look at the flow.
The number of cones should be based on the mud flow that will actually go through the cyclone manifold. The mud pump's maximum rated capacity is useful information, but it is not necessarily the flow the desander or desilter will see.
This is particularly important with 4-inch desilters. Several cones normally run in parallel, so the cone bank gets larger as the required flow increases. Depending on the application, a desilter may have 4, 8, 10, or more cones.
Do not size the bank right at its limit if the flow is expected to change during drilling. A little extra capacity gives the operator some room when conditions move away from the normal operating point.
When You Need Both Desander and Desilter
Whether both are needed depends on the solids left after the shale shaker.
If the main concern is coarse sand-size solids, a desander may be enough. If finer drilled solids also need to be controlled, a desilter is normally added after it.
A common layout is:
Shale Shaker → Desander → Desilter
The desander takes the coarser solids first. The desilter then works on the finer material that remains.
If fine-solids control is still poor, adding more desander cones is not necessarily the answer. First check whether the cyclone diameter and the duty of each stage are right for the job.
When a Mud Cleaner Makes More Sense
A mud cleaner puts the hydrocyclones and shaker together in one unit. This can be useful when the cyclone underflow needs to go straight to a screen and the installation needs to stay compact.
A mud cleaner can be fitted with desander cones, desilter cones, or both, depending on the required solids removal.
For a new system, this can make the equipment layout simpler. For a retrofit, things are usually less straightforward. The existing shaker, flow path, available space, and downstream equipment all need to be checked before deciding whether an integrated unit is the right fit.
In some installations, separate desander and desilter units are still preferable because they give the operator more flexibility.
A Few Sizing Points That Are Easy to Miss
Using the mud pump's maximum flow as the cyclone design flow is a common mistake. The flow through the solids control equipment can be quite different.
Another mistake is looking at cone quantity too closely. More cones give you more handling capacity, but they do not change the basic separation range of the cyclone itself.
Solids loading also matters. Two systems running at the same flow can put very different loads on the cyclone bank if the amount of drilled solids in the mud is different.
The rest of the solids control equipment should be checked at the same time. If the cyclone capacity is increased but the shale shaker or downstream equipment cannot keep up, the bottleneck simply moves.
What the Manufacturer Needs to Know
When asking for a cyclone recommendation, the most useful information is usually:
- Normal and maximum mud flow
- What solids need to be removed
- Expected solids loading
- Existing shale shaker and downstream equipment
- Available installation space
- New installation or retrofit
For an existing system, a simple layout drawing is often more useful than a long equipment list. It shows where the cyclone package will be installed, how the mud gets to it, and what equipment it has to work with.
The more closely the proposed setup matches the actual operating conditions, the less likely it is that the cyclone bank will be oversized in one area and undersized in another.