EP2699355B1 - Centrifuge and method for monitoring a torque - Google Patents

Description

The invention relates to a centrifuge according to the preamble of claim 1 and a method for monitoring a torque.

Decanters are known which are used for processing drilling mud. When processing such a sludge, also called drilling mud, a decanter is usually operated at a lower load than when processing other products. One reason for this is that in the event of a failure due to overload, the decanter must be disassembled and cleaned.

The DE 10 2006 028 804 A1 discloses a generic centrifuge with a drum and a screw, which are driven by a first motor and preferably a second motor, wherein a gear arrangement is arranged between motors and the drum and the screw, which has a plurality of gear stages, with torques in the four shafts first and the second gear stage are initiated and wherein a first and a second gear stage are driven on at least three shafts. The arrangement serves, among other things, to generate a differential speed between the drum and the screw.

In one embodiment, the DE 10 2006 028 804 A1 an uncontrolled drive is realized, in which a transmission input shaft is held. In this context, the possibility is described to implement a torque overload protection on the fixed shaft.

The DE 94 09 109 U1 discloses a centrifuge with two epicyclic gear stages combined to form a superposition gear. In one of the embodiment variants explained, an input of the epicyclic gear stages is recorded and a signal is determined at this input as a function of the torque on the worm. This signal can be used for monitoring, overload indication and / or damping measures

The FR 2 507 798 A1 discloses a solid bowl screw centrifuge with a torque overload safety device, which has a lever which is held via intermediate elements on a boom of a transmission input shaft. A lever end is held between two rollers, which are connected to a spring support via a double articulated arm. If the centrifuge is in operation, the lever presses against one of the two rollers, which are equipped with one Measuring device is connected. This measuring device determines the force exerted by the lever and, when a predetermined limit value is exceeded, issues a control command to a control device of the centrifuge which stops the inflow of product into the centrifuge. In the event of an excessive overload, the double articulated arm can buckle, whereby the fixation of the lever is released by the rollers. As a result, the gearbox input shaft of the centrifuge is no longer fixed or released.

The object of the invention is to provide a centrifuge which enables the drilling mud product to be processed in a particularly suitable manner.

The invention solves this problem by the subject matter of claim 1. According to its characteristics, the overload lever arm is detachably connected at one end radially to the axis of rotation of the transmission input shaft directly to the transmission input shaft or a part connected to it in a rotationally fixed manner, the overload lever arm having a receptacle at its free end which presses against a coupling means (54) and thus keeps the transmission input shaft at a standstill

The special design of the overload lever arm and its connection to the transmission input shaft simplify the design compared to the prior art.

Advantageous design variants are the subject of the subclaims.

The overload lever arm advantageously serves as a torque arm, which in the event of an overload is released from the transmission input shaft or the part connected to it in a rotationally fixed manner, such as an arm or a disk.

In this context, “normal operation” means that the torque acting on the overload lever arm is less than a predetermined first limit value. If this first limit value is exceeded, operating parameters are first changed in a suitable manner. For example, the product feed can be throttled.

If a second higher limit value for the torque is exceeded, the solid bowl centrifuge is switched off and moves to a safe state.

"Overload case" means that the torque increases to the extent that a compensation by influencing process parameters and even a shutdown can no longer be done in time. In this case, the overload lever arm compresses. This releases the transmission input shaft and the belt drive of the motor can no longer transmit torque to the worm or the drum via the transmission.

The overload lever arm is preferably designed as a cylinder / piston arrangement, which is designed in particular fluidically - pneumatically or hydraulically - in a telescopically resilient manner or has a mechanical spring element such as a helical spring.

In order to prevent an overload in good time before this condition is reached, the centrifuge has means for determining the momentary torque load on the cylinder / piston unit. These means can, for example, determine the change in length of the overload lever arm and / or determine the relative or absolute change in the tilting angle of the piston rod to a starting position. This information can be used to assess which operating state is currently in use.

Methods which work with a torque overload protection and which switch off the inlet at a first limit value are already part of the prior art. However, the method according to the invention can be used to prevent the overload situation even more reliably by specifying a total of two limit values, the operating parameters being changed when a first limit value is reached or exceeded, and being switched off when a second limit value is reached or exceeded. Only when the overload safety device is triggered does the elaborate cleaning of the centrifuge, in particular the screw, become necessary. This can include prevented by the new step of timely shutdown.

The use of the method in the processing of drilling mud has proven to be particularly useful, since the processing of drilling mud leads to the occurrence of unforeseen conditions that lie outside the normal operation of the centrifuge. A more differentiated monitoring of the torque by specifying a first and a second limit value can surprisingly reduce the percentage of an overload that occurs.

Figur 1

eine schnittartige, schematische Darstellung einer Vollmantelschneckenzentrifuge;

Figur 2

eine Vorderansicht einer Vollmantelschneckenzentrifuge;

Figur 3

eine Detailansicht eines Überlasthebels aus Fig. 2 und

Figur 4a)-4c)

Teilansichten der Vollmantelschneckenzentrifuge aus Fig. 2 und 3 in verschiedenen Betriebszuständen.

The invention is explained in more detail below using an exemplary embodiment with reference to the accompanying drawings. They show:

Figure 1

a sectional, schematic representation of a solid bowl centrifuge;

Figure 2

a front view of a solid bowl screw centrifuge;

Figure 3

a detailed view of an overload lever Fig. 2 and

Figure 4a) -4c)

Partial views of the solid bowl centrifuge Fig. 2 and 3rd in different operating states.

The Figures 1 to 3 show a solid bowl screw centrifuge with a rotatable drum 1 with preferably a horizontal axis of rotation D and a rotatable screw 2 arranged inside the drum 1, which has a centrifuge drive 3 for rotating drum 1 and screw 2. The drum is arranged between a drum bearing 4a, 4b on the drive side and a drive bearing facing away from the drive.

The centrifuge drive 3 has a motor 5 and a gear arrangement arranged between the motor 5 and the drum 1 and the screw 2.

The gear arrangement comprises, for example, a single gear, a so-called planetary gear 6, with three or more gear stages 7, 8, 9, which are connected downstream of the motor 5, the first two gear stages 7, 8 and the third gear stage 9 in the embodiment selected here the two axial sides of the drive-side drum bearing 4a are arranged. Alternative configurations e.g. with all gear stages 7, 8, 9 inside or outside the drum bearing 4a (relative to the drum 1) can also be realized.

The design of the gear 6 is such that a differential speed can be set between the speed of the drum 1 and the speed of the screw 2 during operation.

The first gear stage 7 and the second gear stage 8 of the transmission 6 are each designed in the manner of a planetary gear, the first gear stage 7 forming a type of preliminary stage and the second gear stage 8 forming a type of main stage, both of which are arranged in a common housing 12. The first and second gear stages 7, 8 are designed as epicyclic gears, with the housing 12 also being driven, which in turn drives the drum 1, which is connected to the housing 12 preferably in a rotationally fixed manner via a hollow shaft 13.

The first gear stage 7 has in the housing 12 a sun gear 14 on a sun gear shaft 15, planet gears 16 on planet gear axes 17, which are combined to form a planet gear carrier 33, and an outer ring gear 18.

The second gear stage 8 also has - likewise inside the housing 12 - a sun gear 19 on a transmission input shaft 20, also known as a sun gear shaft, planet gears 21 on planet gear axles 22 which are combined to form a planet gear carrier 40, and an outer ring gear 23.

The motor 5 drives directly (not shown) or indirectly (via a first belt transmission 24 with a pulley 25 on its motor shaft 26, a belt 27 and a pulley 28, which rotatably with the housing 12 and the planet wheel axes 17 of the planet gears 16 of the first gear stage 7 is coupled, so that it also forms the planet carrier 33), the housing 12 and the planet gears 16. The pulley 28 can also be formed in one piece with the housing 12 or on its outer circumference.

In addition, the first motor 5 drives the (hollow) shaft 15 for the sun gear 14 of the first gear stage 7 directly or indirectly (for example via a second belt drive 29 with a pulley 30 on its motor shaft 26, a belt 31 and a pulley 32).

The ring gear 18 is also coupled via a spacer to a ring gear 23 of the second gear stage 8 to form an intermediate shaft 39 in a rotationally fixed manner or is designed in one piece with the latter.

The planet gear axles 22 of the planet gears 21 of the second gear stage 12 drive an intermediate shaft 41 to the third gear stage 9 via the planet gear carrier 40, which drives the worm 2 (as a single or again multiple output gear stage) (only indicated schematically here).

Between the housing 12 and the intermediate shaft 41, a differential speed that can be set by the first and the second gear stage 7, 8 can be realized, which is determined on the one hand by the speed of the transmission input shaft 20 of the second gear stage 8 and on the other hand by the speed of the intermediate shaft 39.

To set the differential speed, the transmission input shaft 20 is set to zero in the present exemplary embodiment. This arrangement can also be referred to as a zero point drive.

The speed of the intermediate shaft 39 is determined by the speed of the sun gear shaft 15 of the sun gear 14 of the first gear stage 7 and is therefore also dependent on the output speed of the (drum) motor 5.
Both the sun gear shaft 15 and the housing 12 have a rotational speed other than zero, the rotational speed of the housing 12 being fixedly coupled to the rotational speed of the sun gear shaft 15.

It is also advantageous that the two first gear stages 7, 8 are arranged within the common (rotatable) housing 12, since this can be implemented inexpensively and is compact.

The first gear stage 7 forms a kind of preliminary stage, which acts with the second gear stage 8 as a kind of superordinate primary gear stage.

According to the arrangement of the Fig. 1 and 2nd a dynamically rigid connection to the rotating system is possible due to the preliminary stage located outside the drum bearing 4a on the drive side.

The first two gear stages 7, 8 can, however, also be arranged completely together (possibly with further stages) between the drive-side drum bearing 4a and the drum 1 or, relative to the drum 1, outside the drive-side drum bearing 4a.

As an advantage of the constructions, it should also be mentioned that the dependence of the differential speed on the slip and on the load condition of the decanter is low. By changing the belts or pulleys, the specified differential speed range can be set in a simple manner.

It can be seen here that the differential speed can be preset by exchanging the belt pulley of the belt transmission, the differential speed being changeable within the given ranges during operation by regulating or controlling the motor 5.

With this construction, there is no speed reversal, which in combination with a planetary gear of conventional design leads to a leading worm. By holding the now free transmission input shaft 20 of the second transmission stage 12, a drive which is preset but is not regulated during operation can be realized. The torque is measured here on the fixed shaft and an overload safety device 45 is implemented.

The structural design and the mode of operation of the overload protection device 45 are described in more detail below.

The transmission input shaft 20 points in Fig. 1 and 2nd at its free end a washer 46. On this disk 46, an overload lever arm 47 is supported outside the axis of rotation D. This overload lever arm 47 can be designed in different ways and, in its function as a torque arm, prevents the transmission input shaft 20 from rotating.

In a preferred embodiment, the overload lever arm 47 is designed as a cylinder / piston unit or as a compression spring with a cylinder housing 49 and a piston rod 50 that is linearly movable thereto. A force in the manner of a restoring force is exerted on the piston rod 50, in particular a spring force or a pressure by a fluid, e.g. a gas or a liquid. If a force acts on the piston rod 50, it moves relative to the cylinder housing 49.

In the embodiment of the Fig. 2 the overload lever arm is, for example, a pneumatic cylinder, which opposes the force which the worm transmits to the pneumatic lever via the disk, a restoring force by a gas pressure.

The overload lever arm exerts a restoring force against the direction of rotation R of the drum 1 and the screw 2 during operation of the centrifuge and uses this force to keep the transmission input shaft 20 at rest.

The force which acts on the overload lever arm through the transmission input shaft is measured by a load cell 51 which is fixed on the overload lever arm 47. The measurement can be carried out in various ways, for example by measuring the change in length of the elements of the overload lever arm that are movable relative to one another or by measuring the angle of the lever arm to the base or frame on which it is fixed. In the case of one Pneumatic cylinders (gas pressure springs) can also measure the gas pressure.

Depending on the force determined, various control commands can be issued. If a predetermined limit is slightly exceeded, the inflow of product into the centrifuge can be throttled or stopped completely. By determining the torque during operation of the centrifuge, the drive power of the motor 5 or the intake power of the product can thus be regulated, for example, so that the centrifuge can be operated up to its performance limit.

For this purpose, the load cell 51 outputs a signal which is passed on to a computing unit 52 and is compared with a limit value or limit value. In the present example, the load cell 51 is arranged in a compact manner directly on the overload lever arm 47 or integrated therein.

At its free end facing the disc, the overload lever arm 47 has a receptacle 53, here for example a metal clip, which presses against a coupling means 54, preferably a bolt of the disc 46, and thus keeps the transmission input shaft 20 at a standstill.

When the centrifuge is in operation, the force is measured which acts on the overload lever arm and the torque is determined from this. If the solid bowl screw centrifuge is in normal operation, the drilling mud is clarified. This clarification takes place by feeding drilling mud into the centrifuge. In the centrifugal field of the centrifuge, the drilling mud is converted into a liquid phase and a solid phase, which are discharged from the centrifuge through various processes.

As soon as a first limit value is reached or exceeded, the overload lever arm remains in its original position, however operating parameters are changed. The inlet is preferably switched off and a safe state is thus generated.

If a second limit value of the torque M is reached or exceeded, the centrifuge will be switched off and move to a safe state. The overload lever arm remains in its original position even when the second limit value is reached or exceeded.

Only in the event of an emergency or overload, in which the torque in the transmission and thus the force on the overload lever arm increases so quickly that it would not be possible to switch it off quickly enough, does the piston rod 50 of the overload lever arm 47 spring in a linear movement A and loosen during the rotation of the transmission 6 in a concerted tilting movement B from the transmission input. The increase in torque is dM / dt.

If a predetermined limit value for the increase in the torque dM / dt is exceeded and the force on the overload lever arm increases too quickly, then this releases itself from the transmission input. This is shown schematically in the Figures 4a-4c shown. The release of the overload lever arm from the transmission input corresponds to the triggering of a torque overload protection.

The piston rod 50 has a receptacle 53 on the end which is rigidly connected to the piston rod 50 or is formed on the end of the piston rod 50.

The receptacle can preferably be formed in the form of a groove 58 with a shoulder 59 for guiding the bolt 54. As in Fig. 3 is shown, the bolt 54 of the washer 46 rests in the groove 58 of the receptacle 53.

The disc 46 exerts a force in the direction of rotation R of the drum 2 on the bolt 54 when the centrifuge is operating.

If the piston rod 50 dips into the cylinder housing 49 of the overload lever 47, the disk 46 is decoupled from the overload lever arm 47 and moves in the direction of rotation R. When uncoupling, the bolt 54 is released from the groove 58 of the receptacle 53 during the rotational movement, which leads to decoupling the disk 46 and the screw 2 connected to it. The overload lever arm is arranged pivotably about the pivot pin 55 of a tilt joint 61. By decoupling the transmission input shaft 20 is free and rotates with.

The present invention has the advantage that an emergency stop and thus cleaning of the worm and renewed decoupling of the overload lever arm is only necessary when the third limit value is reached, ie in the event of a fault. In addition, an optimal utilization of the centrifuge is achieved by the force measurement or the determination of the torque and the operating parameters coordinated with it, such as the drive power of the motor 6.

Vibrations or resonance vibrations may occur while the centrifuge is operating or stopping. These can be damped by damping feet 56 and damping plates 57, so that the centrifuge does not transmit any vibrations to a machine frame 60 or the surface. The operation of the centrifuge can additionally be set and monitored by means for determining vibrations 62, for example a vibration sensor.

Reference list

1

drum

2nd

slug

3rd

Centrifuge drive

4th

Drum bearing

5

engine

6

Planetary gear

7

Gear stage

8th

Gear stage

9

Gear stage

12th

casing

13

Hollow shaft

14

Sun gear

15

Sun gear shaft

16

Planet gears

17th

Planetary gear axles

18th

Ring gear

19th

Sun gear

20th

Transmission input shaft

21

Planet gears

22

Planetary gear axles

23

Ring gear

24th

Belt transmission

25th

Pulley

26

Motor shaft

27

belt

28

Pulley

29

Belt drive

30th

Pulley

31

belt

32

Pulley

33

Planet carrier

39

Intermediate shaft

40

Planet carrier

41

Intermediate shaft

45

Overload protection

46

disc

47

Overload lever arm

49

Cylinder housing

50

Piston rod

51

Load cell

52

Arithmetic unit

53

admission

54

bolt

55

Swivel pin

56

Cushioning feet

57

Damping plate

58

Groove

59

shoulder

60

Machine frame

61

Tilt joint

62

Means for determining vibrations

D

Axis of rotation

R

Direction of rotation

A

Linear motion

B

Tilting movement

Claims (12)

1. A solid bowl screw centrifuge for the processing of drill sludges, having a rotatable drum (1) and a rotatable screw (2), wherein the centrifuge has a drive device for driving the drum and the screw with a drive motor and a gear arrangement for generating a differential rotational speed between the drum (1) and the screw (2) during the operation of the centrifuge, wherein a gear input shaft (20) of the gear arrangement is fastened in a rotationally fixed manner by means of an overload lever arm (47) triggerable in a torque overload event, characterized in that the overload lever arm (47), spaced apart at one end radially with respect to the axis of rotation of the gear input shaft, is releasably connected directly to the gear input shaft (20) or to a part connected in a rotationally fixed manner to said shaft, wherein the overload lever arm comprises a receptacle (53) at its free end which presses against a coupling means (54) of the gear input shaft (20) and thus keeps the gear input shaft (20) stationary.
2. The centrifuge according to claim 1, characterized in that the overload lever arm (47) is supported with its other end on a machine stand.
3. The centrifuge according to claim 1, characterized in that the overload lever arm (47) is configured as a compression spring unit of variable length.
4. The centrifuge according to claim 1 or 2, characterized in that the overload lever arm (47) is designed as a piston/cylinder unit.
5. The centrifuge according to one of the preceding claims, characterized in that the overload lever arm (47) is designed as a torque support, wherein the coupling means (54) is provided, which in an overload event can be released from the receptacle (53) on the gear input shaft or on the rotationally fixed part.
6. The centrifuge according to one of the preceding claims, characterized in that the part connected to the gear input shaft (20) is a pulley or an arm segment extending in the radial direction.
7. The centrifuge according to one of the preceding claims, characterized in that the overload lever arm (47) is of telescopic form.
8. The centrifuge according to one of the preceding claims, characterized in that the piston/cylinder unit is designed as a fluidically or mechanically acting spring element.
9. The centrifuge according to one of the preceding claims, characterized in that the centrifuge has means for the damping of oscillations (56, 57) of the centrifuge on a machine stand (60) and/or a foundation.
10. The centrifuge according to one of the preceding claims, characterized in that the overload lever arm (47) is fastened at an end remote from the gear input shaft to a machine stand (60).
11. The centrifuge according to one of the preceding claims, characterized in that the centrifuge has means for determining the torque acting upon the piston rod (50).
12. The centrifuge according to claim 11, characterized in that the means for determining the torque load (51) upon the piston rod (50) is designed as a load cell.

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