-Shale Shakers:the first line of defense for a properly designed solids control equipment has been and will continue to be, the shale shaker. Without proper screening of the drilling fluid during this initial removal step, reduced efficiency and effectiveness of all downstream solids control equipment in the system is assured. The downstream hydrocyclones will simply be overloaded beyond their designed capacity.The shale shaker, in various forums has played a prominent role in solids control systems for several decades. The two main shale shakers utilized in the utility industry are:1.Elliptical, “unbalanced” design;2.Linear “straight line” design.
Vibrating Mechanism-the purpose of vibrating the screen in solids control equipment is to tumble the solids particles to separate fluids from solids and increase through put capacity. This vibrating action causes rapid separation of whole mud from the oversize solids, reducing the amount of mud lost with the solids.
For maximum efficiency, the solids on the screen surface must travel in a predetermined pattern. For example; some devices use elliptical motion and others use Linear motion to increase efficiency. The combined effect of the screen and vibration, result in the separation and removal of oversized particles from drilling mud.
Hydrocyclones-Hydrocyclones have become important in solids control equipment because of their ability to efficiently remove particles smaller than the finest mesh screens. They are also uncomplicated devices, which make them easy to use and maintain.
A hydrocyclone consist of a conical shell with a small opening at the bottom for the underflow discharge, a larger opening at the top for liquid discharge through an internal“vortex finder”and a feed nozzle on the side of the body near the wide (top) end of the cone.
Desanders-Desanders are hydrocyclones larger in diameter than 5”. Desanders are installed down stream from the shale shaker. The desander removes sand size particles and larger drilled solids, which have passed through the shale shaker screens. These solids are discarded along with some liquid into the waste pit. The clean mud is then discharged into the next pit ready to be run through the desilters.
Desilters- A desilter uses smaller hydrocyclones usually 5” or smaller. The smaller cones enable desilters to make the finest particle size separation of any full flow solids control equipment. Removing particles of 15 microns and larger. Multiple cones are normally used in this application to obtain the required GPM you need for your solids control equipment.
Mud Tank Separation-There are many ways to configure your mud tanks below your solids control equipment. The most common practice requires three sections. Under your shale shaker you have the first section known as the sand trap where the mud to be pumped from this section goes through your Desander. This cleaned mud is then dumped into the second section known as a silt tank. The mud is picked up then pumped through your Desilters. The Desilters dumps the cleaned mud into the third section, know as the clean mud or mixing tank. This will be picked up by the pump to be pumped back into your bore hole.
Centrifugal Pumps-Another important aspect of a well engineered solids control equipment is the use of centrifugal pumps which not only mix the mud to be pumped down the bore hole, but also provide the feed pressure and volume required to operate the hydrocyclones. Maintenance of these pumps is essential to the operation of your solids control equipment.