HDD is a quite common way for pipeline works in cities or for pipelines across the rivers or so. This word is short for horizontal directional drilling. Just as other drilling, the drilling mud is to be used for HDD and the drilling mud should be well treated and prepared for reuse. A complete mud cleaning system for HDD always includes following steps for separation:

1. Shale shaker. In many mud cleaning systems or so called solids control systems, the shale shaker is always the first step for separation. It is used to remove most of particles and also the largest particles. In those 2 systems GN recently made for SINOPEC, the shale shakers are GNZS703F. This shaker model is quite popular in HDD projects and also used for oil and gas solids control systems. It has a screen area of 2.63 square meters provided by 3 pieces of shaker screens each sized 1250*700mm.
2. Mud cleaner. In fact, in an HDD mud cleaning system, there are always desander cones and desilter cones. Desander cones are of 10 inch diameter, which is used for removal of particles larger than 40 microns. And the desilter cones are of 4 inch diameter for removal of particles larger than 20 microns. A mud cleaner is a combination of desander cones and desilter cones, with a shared underflow shaker for drying.
3. A mud mixing hopper is a must for a HDD mud cleaning system, which is used for adding the loss components into the recycled drilling mud in order to prepare the drilling mud for the future drilling. A mud mixing hopper has a hopper and a centrifugal pump, the hopper can be located together with pump by the mud tank, or on tank top with the centrifugal pump on tank bottom.
4. A decanter centrifuge, which is not a must but quite efficient in high configuration systems. A middle speed centrifuge like GNLW452D is used to remove particles from 5 to 7 microns. And a high speed centrifuge is used to remove particles from 2 to 5 microns.
Welcome to consult GN for more information.