Tunneling - MSSP 1000



MSSP-1000 (1000 m3/hr Separation Plant)

The performance of a large diameter tunneling operation is directly related to the overall cleaning performance of the slurry separation system. Solids that remain within the slurry adversely affect slurry excavation processes. Benefits of proper and efficient separation of the drilled solids from a drilling fluid include:

• Increased Rate of Penetration (Production)
• Reduced Drilling Fluids Costs
• Reduced Water Usage
• Reduced Water Hauling Costs
• Reduced Hauling and Disposal Costs of Dirty Fluid
• Reduced Downstream Wear on Pumps, Plumbing, etc.

All of the above translates to increased production at reduced costs to the contractor.

In Kenmore, Washington, two (2) Derrick MSSP-1000 plants are each working with 5.7m wide Herrenknecht Tunnel Boring Machines that produce up to 1000 m3/hr (4400 GPM) of slurry each. The modular slurry separation plant is designed around 20’ and 40’ containers for quick setup and international transport.

Primary separation in the both plants are achieved by a Derrick C56 screening machine with low frequency, high amplitude motors. These machines are typically outfitted with high open area polyurethane screens with openings from 2.0mm to 10.0mm.

Secondary separation is performed by FLC-2000 high frequency screening machines that produce a G-force of 7.3 G’s of consistent acceleration. A desanding and desilting separation is achieved through a combination of 10” and 6” hydrocyclones that are mounted over more FLC-2000 screening machines outfitted with either polyurethane screen panels or Derrick’s patented Pyramid screens with corrugated, 3D openings.

The final stage of separation is achieved by three (3) Derrick DE-7200 VFD controlled decanting centrifuges that work continuously removing fine silts and clays which are extremely prevalent in the majority of the ground formations on this project. The centrifuges are set up to draw from either the active working tanks for each tunneling machine, or the “waste mud tank” which serves as a holding tank for future processing if necessary. The DE-7200 big bowl centrifuge can process up to 500 gpm and discharge 10-15 dry tons of solids per hour while making a cut point of approximately 5-10 microns. When flocculant is added to the centrifuge feed, a finer separation is achieved with a semi clear effluent that may be suitable for sewer discharge.

The separation plant is also composed of an operator control room, motor control center, mud laboratory, conveyors and stackers for solids stockpiling, flocculation dosing system, PTZ vision system, bentonite storage silos and dispensing system.
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