barite recovery

Functions of decanter centrifuge speed for VFD and PLC system

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Decanter centrifuge is widely used for drilling rig mud system; it can be used from barite recovery, fine solids separation, as well as for waste management. It is utilizing different speed to vary G force and to separate different size solid particles from drilling fluids. In this case, centrifuge G force is very important for the performance.  

How to change decanter centrifuge speed for VFD and PLC system

It is actually differential speed what decides G force. Differential speed have relationship with bowl speed, gearbox input speed and the gearbox ration. Gearbox ration is usually a fixed figure for a certain decanter centrifuge model. Below is the relationship of them:

Differential Speed = ( Bowl speed – Gearbox input speed) / Gear Box Ration

 Take GNLW363VFD decanter centrifuge as an example, Gear Box Ration=57. Blow speed and gearbox input speed (conveyor speed) is changeable; they can be set on the PLC touch screen of the VFD centrifuge.  

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So Gearbox input speed=Bowl Speed – 57×Differential Speed= Small Motor Speed transferred to gearbox by belt, in some occasions, it is also called conveyor speed.

 Below we see 2 examples

Case 1) Bowl speed=3200RPM, and Differential Speed=30RPM

Gearbox Input speed=3200-57×30=1490RPM ,

Case 2) Bowl speed=1200 RPM, differential speed=35 RPM

Gearbox Input Speed= 1200-57×35= -795RPM it is a negative number.

Above situation, you can see, sometimes the gear box speed is  a positive number, that means small motor running according to the Arrow on the belt cover. Watching from feeding tube side the small motor rotation is Anticlockwise.

The motor speed is changed for some condition. GN brand VFD centrifuge have program to control the motor speed and motor direction. It can changed automatically when necessary.

 

 

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1500HP land drilling rig usually match 2000bbls mud system. The mud system will have complete full 4 stages solids control equipment and with 5 steps separation process.

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Equipment included in 1500 hp land drilling rig mud system:

1) First stage solids control – Shale shaker GNZS594E / GNZS703E linear motion, 3 each

2) The second & third stage solids control – Mud cleaner GNZJ594E-3S-16N / GNZJ703E-3S16N, 1 each

3) Vacuum degasser GNZCQ360 to remove gas from drilling mud before enters into mud cleaner desander / desilter cone.

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4) The fourth stage solids control – Decanter centrifuge, 2 each

 One decanter centrifuge GNLW452S in middle speed for barite recovery.

 Another decanter centrifuge GNLW363 in high speed to separate the low gravity mud.

5) Jet mud mixing & shearing mixing system, with GN high efficiency centrifugal pump and shear pump for chemical shearing and mixing.

6) 7 each Mud tanks: shale shaker tank, decanter centrifuge tank, suction tank, mixing tank, shearing tank, storage tank 1 or 2 each

Above is the standard 2000bbls mud system for 1500 hp land drilling rigs. GN Solids Control can make customized mud system per user’s special requirements. If you need more information of other size land drilling rig mud system, you can visit GN website or send mail to vivi@gnsolidscontrol.com