In the classic weighted mud application the solids discharge (containing the majority of the weighting material) is returned to the mud system. The liquid effluent (containing the majority of the colloidal size solids) is discarded. As part of a“closed loopâ€, larger high capacity (75–250 GPM) decanting centrifuges (and sometimes standard centrifuges) are used to maximize fine solids removal. The coarser solids fraction is discarded in dry form, while the liquid and colloidal solids fraction is returned to the mud system.
Decanting centrifuges are becoming more popular for processing unweighted oil mud, especially if
1) the mud has been brought in from another location and may contain a large amount of fine drilled solids,
2) slow, hard drilling with a gradual buildup of ultra-fine solids is anticipated or
3) the liquid mud phase is valuable.
GN offers Decanting Centrifuge for unweighted mud applications.
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Published: 18 January 2014
Decanting centrifuges for oilfield applications were first introduced in the early 1950s. These early units were adapted from existing industrial decanting centrifuges. In the mid-1960s, a perorated rotor type machine was developed which does not perform like a pure decanter. Commonly called “barite recovery†centrifuges, these early designs were limited in capacity and application.
Today, the decanting centrifuge is even more important part of solids control. In addition, the increased use of low-solids mud and environmental dewatering applications require higher process volumes, greater clarification and solids capacity, and additional fine solids removal. Equipment selection is decided by site specific requirements. Proper system selection is the first step to effective solids control.
GN decanting centrifuge is purpose-built for drilling mud solids control in oilfield applications.
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Published: 11 January 2014
Decanting centrifuge is an import ant piece of equipment in mud solids control. Because of the environment regulation and high cost of drilling waste disposal, many CBM and HDD operator now prefers decanting centrifuges in their mud recycling system.
Also, as fluid costs increase, centrifuge use is highly recommended for reducing costs. The Australian client requires two set of GNLW363G decanting centrifuge to remove the supper fine solids to control the drilling mud density for reuse.
You can learn more about this Water Based Mud (WBM) Recovery System at GN solids news center.
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Published: 05 January 2014
According to Stokes Law, particle setting velocity is proportional to G-force. Since G-force increases with the square of bowl RPM, it is an important parameter of decanting centrifuge performance. G-force also increases linearly with bowl diameter. Figure 1 shows how solids removal efï¬ciency improves with increasing G-force. For a given particle size and fluid properties, there is a minimum G-force necessary to invoke settling. Although high G-force is desirable, the cost is proportional to the cube of the bowl rpm and there are similar economic limitations on bowl diameter as well. Thus, the required G- force must be obtained from a practical combination of speed and diameter. Most oilï¬eld decanting centrifuges have bowl dimensions from 14 to 28 inches in diameter and lengths from 30 to 55 in. Rotational speeds range from 1000 rpm to 4000 rpm, depending on the application. The more expensive, high “G†machines can provide up to 3,000 G’s.
Effect of G-Force on Separation (Higher G's Improve Separation Performance)
Note: however, that increasing G-force eventually reduces solids conveyance capacity due to torque limitations. As G-force increases, more solids are settled in the bowl and they adhere more tightly. More conveyor or torque is required to move the solids out. Once the torque limitations of the machine are reached, conveyance ceases.
G-Force for a Decanting centrifuges:
G’s = RPM2 x .0000142 x Diameter of Bowl (in inches)
High G-force decanting centrifuges are available from GN Solids Control.
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Published: 28 December 2013
The decanter centrifuge is used in weighted mud applications to recover valuable weighting material from mud which must be discharged due to unacceptable colloidal solids content. The decanter centrifuge settles out barite and coarse drilled solids which are returned to the active mud system to maintain density. The relatively clean centrate containing liquid and colloidal solids is discarded. These colloidal solids cause many drilling fluid problems, such as high surge/swab pressures and ECD, differential sticking and high chemical costs. Usually the value of the weighting agent in these mud systems makes it economic to recover the weighting agent from the whole mud before it is discarded.Ideally, the barite recovery process should remove only colloidal solids without losing the larger particle sizes used as weighting material.
Discarding potentially reusable barite increases barite use and drilling fluid cost. Barite losses can be reduced when the centrifuge makes the maximum liquid/solids separation. As discussed in the previous section, this means operating the decanter centrifuge at high G-force.
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Published: 22 December 2013
Cutting-edge research and product development is the soul of GN. Through trial and error, GN new generation decanter centrifuges finally come out. The mechanical design and electric control system are updated to a new high level.
Compact Mechanical Design
The primary motor and the secondary motor set at the one side and leave much room for operator to get access to rotating assembly. Collection box cover supporting system is installed with which much labor can be saved when opening the collection box and doing the maintenance.
VFD PLC Control Panel
In addition to the normal VFD (Variable Frequency Drive) Centrifuge. GN also developed DECANTER CENTRIFUGE controlled and monitored by a Programmable Logic Controller (PLC). Compared to other centrifuges, it requires fewer operating personnel and features automatic adjustment for different operating conditions.
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Published: 16 December 2013