Microtunneling - 20 MSSP (Hartford)
Derrick 20' Modular Slurry Separation Plant and DE-7200 Centrifuge
A contractor out of New Jersey is using a Derrick 20’ Modular Separation Plant and DE-7200 VFD high speed, decanting “Big Bowl” centrifuge in conjunction with a Herrenknecht AVN1800 Microtunneling Machine with 90” O.D on a project in Hartford, CT. The ground conditions in Hartford are primarily clay, at times 90% of the material is -200 mesh.
Before starting the project, the contractor consulted with Derrick Equipment Company and their local agents to insure the proper separation equipment was specified for these challenging ground conditions. It would be crucial for the contractor to have a means for handling the large chunks of clay at the front end of the plant and also plenty of centrifuge capacity downstream to handle the fine colloidal clays that are typically in the sub 2 micron range. It was decided that two Derrick Flo-Line Primers (Belt Scalpers) would handle the primary separation, while a DE-7200 centrifuge would be used to continually remove fine silts and clays on the tail end of the plant. Derrick FLC-2000 shakers and mud cleaners comprised the secondary and tertiary separations on the 20’ Modular Plant.
As anticipated, the majority of the separation work is being performed by the two (2) Derrick Flo-Line Primers (Belt Scalpers) outfitted with 5 mesh belts and DE-7200 centrifuge. The conveying action of the Primer removes the large, consolidated chunks of gumbo clay and other oversize material +5 mesh and above.
Clay solids that go into solution are removed downstream via the DE-7200 centrifuge and polymer mixing system. The high capacity, DE-7200 centrifuge eliminates the need for the contractor to haul off dirty, solids laden fluid. The polymer mixing system introduces polymer to the feed line of the centrifuge that helps the centrifuge capture fine particles down to 0 um and obtain the semi-clear effluent. The centrifuge is able to process a maximum of 15 t/hr of dry solids and when used in conjunction with a polymer mix system, can provide a semi-clear effluent at flow rates up to 120 gpm that is clean enough to dump down the sewer.
The combination of the separation plant and centrifuge allow the contractor to sufficiently clean their drilling fluid and maintain maximum tunnel production which can reach 100’ per 12 hour shift. This project is an excellent example of a tunneling contractor excelling in some of the most challenging ground conditions.
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