AP200 desilters are capable of processing up to 240 stere per minute and can get do to cut point of approximately 35 microns. This equipment is designed to remove the sand and silt sized particles before they have a chance to break down even smaller.
The AP200 desilter is designed to save barite and remove low gravity solids larger than barite from weighted mud system. The Sand/Silt Separator hydro-cyclones will separate the low solid liquid slurry from the barite and larger than medium silt range particles. The barite and larger silt size particles will be directed on the screen surface to save barite and drilling fluid while the large silt size particles will go off the end of the screen.
On the unweighted mud systems the AP200 desilter paired with a hunter shaker will reduce the costs by reduced jetting, less chemical replacement and less replacement of water and/or oil. With the use of 325 mesh screens it is possible to remove solids to approximately 25-35 micron silt size particle.
Hydrocylone/Shaker combination has several design characteristics that justify its ability to remove sand and silt sized solids from the drilling fluid. The feed manifold is designed to ensure balanced feed pressure into the hydrocyclones. System balance is achieved by opening or closing individual control valves on each hydro cyclone, by lowering or raising the siphon tubes on each overflow tube, and/or increasing or decreasing the apex bushing size. Any of these adjustments can alter the GPM rate and handle most volume requirements. These adjustments can make particle interference, mud viscosity, and rejection volume less critical and enable the system to work more efficiently. The Triflo 8-4 Mud Cleaner can remove solids that are often found to be the cause of drill collar sticking and wear on mud pump expendables.
AP200 Desilter Operation
- The feed slurry of solids and liquid is fed through the inlet at a high velocity obtained by steady pressure of twenty-five (0.25-0.4)Mpa. The high velocity transmitted to the feed section creates a spinning velocity and resulting centrifugal forces. The vortex finder causes the stream to spiral downward towards the underflow solids discharge. Centrifugal force and inertia causes solids to settle outward toward the hydro cyclone wall, in a downward spiraling stream.
- The solids separate according to size and weight of the particles. In the density range of solid particles in drilling fluids, size is of far more influence than the variations in density so that basically the biggest particles settle first and fastest.
- The cone section narrows, inner layers of the downward spinning liquid turn back toward the overflow because of the increasing centrifugal forces near the center.
- In Aipu’s hydrocyclone, as the last of the liquid moves to the center and back upward toward the overflow, the downward spiraling solids continue out the apex, not being able to turn back because of their greater inertia and high downward velocity. Therefore, the actual solids removal at the underflow is by inertia, not by settling. The underflow rate and density varies with the volume and size of solids being separated to the underflow.
- The underflow from the fluids, even under extreme conditions, will be approximately 40 GPM and ordinarily under 30 GPM. This makes it possible to use fine mesh screen (150-200 mesh) to clean all of the mud returning from the bore hole. 200 mesh screens have openings of 74 microns and the 150 mesh screens have openings of 104 microns. Theoretically, particles smaller than these opening should remain with the mud and larger particles and would be carried off the end of the shale shaker.
- The AP200 desilter is operated at 0.25-0.4Mpa of pressure. A six (6) inch butterfly valve should be placed in the discharge line between the centrifugal pump and the manifold inlet. This valve would be used for adjusting the manifold pressure to 0.25-0.4Mpa.
- Each hydrocyclone has a two (2) inch butterfly valve located before the feed inlet. This valve permits the operator to turn off each hydrocyclone individually for system balance and removal of the hydrocyclone, without shutting down the entire system.
- The siphon rod, located on the top of the overflow tubes are an adjustment of the underflow. When the siphon tube is completely down, the air entering the apex bushing is increased and less drilling fluid is permitted to spray out the apex of the hydrocyclone.
- When a wetter underflow with finer solids is desired, the siphon tube should be raised. This adjustment will reduce the amount of air permitted through the apex and cause a wetter underflow to travel to the shaker screen. The distance the siphon tube should be raised will vary with the drilling conditions and no hard fast rule will apply.
- The apex nut and apex bushing are designed for easy removal when plugging becomes a problem and are adjustable to permit the required amount of spray discharge desired. When a smaller opening is necessary tighten the apex nut to the desired setting. The tighter the adjustment the less air permitted to enter the bottom of the hydro cyclone. At times when
plugging is a problem, the apex nut and the apex bushing can be removed. This may be necessary when drilling a surface hole or when large amounts of sand are present.
AP200 Desilter Maintenance
- The AP200 Desilter is a high performance piece of mud equipment and requires a regular maintenance program.
- Hydrocyclone wear and performance is highly dependent of the feed pressure and the conditions of the hydro cyclones. The pressure should never exceed 0.4Mpa, as more than 0.4Mpa will cause excessive wear on the hydro cyclones. Recommended pressure is between 0.25 and 0.4Mpa, however this will vary depending on the concentration of solids.
- Damaged or worn, hydrocyclones will not separate the fine drill solids from the drilling fluid and need to be checked periodically for wear.
AP200 Desilter Troubleshooting
Pressure at the manifold too low:
- Is the centrifugal pump impeller large enough to deliver at least 0.4Mpa?
- Is the centrifugal pump speed correct?
- Is the supply line from the centrifugal pump to the manifold six (6”) in diameter?
- Is the feed pump supplying any other piece of equipment?
- Is the supply line to the manifold plugged?
- Is the centrifugal pump suction plugged?
No underflow or too little underflow:
- Is the feed pressure at least 0.25 Mpa?
- Is the apex bushing plugged?
- Is the apex bushing closed too tightly?
- Are there fine-drilled solids in the mud?
- Is the valve to the hydrocyclone open?
- Is the centrifugal pump running?
Too much underflow:
- Is the hydrocyclone feed section or cone section damaged?
- Is the apex bushing in the hydro cyclone?
- Is the pressure too high?