Degassing centrifugal apparatus with sensor

1. A degassing centrifugal apparatus comprising

a rotatable hollow rotor connected to a stationary fluid inlet at one end portion and a stationary liquid outlet at the opposite end portion, and having a gas exhaust for removing gas from the center thereof,

said apparatus having at said inlet end portion means for rotating said fluid and directing it to the inner wall of said rotor, characterized in that the apparatus further comprises a rotatable sensor arranged to measure the layer thickness of a liquid rotating in said apparatus

said means for rotating said fluid comprises a first impeller and wherein said apparatus further comprises a second impeller at said outlet end portion,

said apparatus further comprising a shaft extending from outside of the rotor into said outlet portion,

wherein the sensor is attached to the second impeller or to the shaft.

2. An apparatus according to claim 1 , wherein said degassing centrifugal apparatus is a degassing centrifugal pump.

3. An apparatus according to claim 1 , wherein the sensor is attached to the rotor and the sensor is placed in the center of the rotor.

4. An apparatus according to claim 1 , wherein the sensor is arranged to measure the mutual capacitance of said liquid layer and said sensor.

5. An apparatus according to claim 1 , wherein the sensor is arranged to measure a distance to said liquid layer by means of light beam measuring.

6. An apparatus according to claim 1 , wherein the sensor is arranged to measure a distance to said liquid layer by means of ultra sound measuring.

7. An apparatus according to claim 1 , further comprising converting means arranged to convert the measured signal into a digital or frequency signal.

8. An apparatus according to claim 7 , wherein the converting means is an electronic measurement card.

9. An apparatus according to claim 7 , wherein the converting means is attached to the second impeller or to the shaft.

10. An apparatus according to claim 7 further comprising means for transferring the measured signal from the sensor to the converting means.

11. An apparatus according to claim 10 , wherein the means for transferring the measured signal is one of the following: a transmitter-receiver pair arranged to transfer the signal over an air interface, a transmitter-receiver pair arranged to transfer the signal through an intermediate material, or a transmitter-receiver pair arranged to transfer the signal through direct contact.

12. An apparatus according to claim 11 further comprising means for transferring the digital or frequency signal from converting means to a stationary signal processing means.

13. An apparatus according to claim 12 , wherein the means for transferring the digital or frequency signal comprises a radio transmitter implemented in the converting means and a radio receiver in the stationary signal processing means.

14. An apparatus according to claim 13 , wherein the stationary signal processing means comprises receiving means and means for determining the liquid layer thickness.

15. An apparatus according to claim 14 , wherein the stationary signal processing means further comprises means for transferring the digital or frequency signal from receiving means to means for determining the liquid layer thickness.

16. An apparatus according to claim 12 , wherein the stationary signal processing means comprises receiving means and means for determining the liquid layer thickness.

17. An apparatus according to claim 16 , wherein the stationary signal processing means further comprises means for transferring the digital or frequency signal from receiving means to means for determining the liquid layer thickness.

18. An apparatus according to claim 12 , wherein the stationary signal processing means comprises receiving means and means for determining the liquid layer thickness.

19. An apparatus according to claim 18 , wherein the stationary signal processing means further comprises means for transferring the digital or frequency signal from receiving means to means for determining the liquid layer thickness.

20. An apparatus according to claim 1 further comprising rotatable and stationary coils arranged to transfer inductive signal.

21. An apparatus according to claim 1 , wherein the apparatus further comprises means for conducting power from a stationary power supply to the sensor.

22. An apparatus according to claim 1 , wherein the sensor is arranged to measure the distance of the liquid layer from the sensor.

23. An apparatus according to claim 1 , wherein said hollow rotor has a length to diameter ratio which is at least 2:1 and wherein at least half of the rotor length is arranged to rotate with a dry outer surface.

24. An apparatus according to claim 23 , wherein said length to diameter ratio of said hollow rotor is preferably between 3:1 and 10:1.

25. An apparatus according to claim 1 , wherein said stationary liquid outlet comprise a stationary pump housing surrounding less than half of the rotor.

26. An apparatus according to claim 1 , wherein the rotatable sensor is arranged to measure the liquid layer thickness on the inner wall of said rotor.

27. An apparatus according to claim 1 , wherein the apparatus is arranged to separate a gas from the fluid flowing in a pulp or papermaking process.

28. An apparatus according to claim 1 , wherein the fluid is backwater in a papermaking process.

29. An apparatus according to claim 1 , wherein the signal indicating a measured liquid layer thickness is transmitted from the sensor to a stationary signal processing means via an air interface.

30. An apparatus according to claim 29 , wherein the sensor comprises a radio transmitter to transmit the measured signal through the air interface and the stationary signal processing means comprises a radio receiver to receive the transmitted measurement signal.

31. A degassing centrifugal apparatus comprising

a rotatable hollow rotor connected to a stationary fluid inlet at one end portion and a stationary liquid outlet at the opposite end portion, and having a gas exhaust for removing gas from the center thereof,

said apparatus having at said inlet end portion means for rotating said fluid and directing it to the inner wall of said rotor, characterized in that the apparatus further comprises a rotatable sensor arranged to measure the layer thickness of a liquid rotating in said apparatus,

wherein the rotatable sensor is arranged to measure the thickness of a liquid ring in pumping zone.