SEALING ARRANGEMENT

Abstract

A method for controlling a sealing arrangement for a shaft including: setting a first pressure inside a first annular hollow core of a first annular seal element arranged around the shaft, wherein the first seal element includes a first annular elastic casing surrounding the first annular hollow core and the first annular elastic casing; setting a second pressure inside a second annular hollow core of a second seal element arranged around the shaft, wherein the second seal element includes a second annular elastic casing surrounding the second annular hollow core; monitoring the first pressure inside the first annular hollow core and/or the second annular hollow core; and adjusting the first pressure inside the first annular hollow core and/or the second annular hollow core to adjust sealing of the shaft by the first annular seal element and/or the second annular seal element.

Claims

1. A method for controlling a sealing arrangement for a shaft comprising: setting a first pressure inside a first annular hollow core of a first annular seal element arranged around the shaft, wherein the first seal element includes a first annular elastic casing surrounding the first annular hollow core and the first annular elastic casing; setting a second pressure inside a second annular hollow core of a second seal element arranged around the shaft, wherein the second seal element includes a second annular elastic casing surrounding the second annular hollow core; monitoring the first pressure inside the first annular hollow core and/or the second annular hollow core; and adjusting the first pressure inside the first annular hollow core and/or the second annular hollow core to adjust sealing of the shaft by the first annular seal element and/or the second annular seal element.

2. The method according to claim 1, further comprising monitoring wear of the first seal element and/or wear of the second seal element using an electric circuit element.

3. The method according to claim 1, further comprising scheduling the first seal element or the second seal element for replacement based on the monitoring of the first pressure and/or second pressures.

4. The method according to claim 1, wherein the first annular elastic casing includes an outer layer of braided material.

5. The method according to claim 1, wherein the first annular seal element includes a valve connected to an inlet port for supplying a fluid to the first annular hollow core, and the setting of a first pressure includes supplying the fluid to the first annular hollow core.

6. The method according to claim 5, wherein the fluid is a gas.

7. The method according to claim 1, further comprising pressurizing a fluid space between the first annular seal element and the second annular seal element.

8. The method according to claim 7, wherein the pressurizing the fluid space includes pressurizing the fluid space to a pressure greater than a threshold pressure.

9. A control system for controlling a sealing arrangement comprising a control device connected to at least one measurement and actuator module and configured to perform the method of claim 1.

10. A computer program product comprising computer readable program code that when executed by a processor causes carrying out the method of claim 1.

11. A method for controlling a sealing arrangement around a shaft, wherein the sealing arrangement includes: an outer annular structure with an inner surface extending around the shaft and facing an outer surface of the shaft; a first annular seal element between the inner surface of the outer annular structure and the outer surface of the shaft, the first annular seal includes a first annular elastic casing and a first annular hollow core within the first annular elastic casing, wherein the first annular elastic casing includes a first sidewall extending outward radially relative to a rotational axis of the shaft and a first inner surface in sliding contact with the outer surface of the shaft; a second annular seal element between the inner surface of the outer annular structure and the outer surface of the shaft, the second annular seal includes a second annular elastic casing and a second annular hollow core within the second annular elastic casing, wherein the second annular elastic casing includes a second sidewall extending outward radially relative to the rotational axis and a second inner surface in sliding contact with the outer surface of the shaft, and the second sidewall faces the first sidewall along a direction parallel to the rotational axis, and an annular fluid space around the shaft and defined by the first sidewall, the second sidewall, the inner surface of the outer structure and the outer surface of the shaft and/or a gland mounted on the shaft, and the method comprises: pressurizing the first annular hollow core of the first annular seal element; pressurizing the second annular hollow core of a second seal element; and adjusting the pressure in the first annular hollow core to adjust sealing of the shaft by the first annular seal element.

12. The method of claim 11, further comprising: monitoring the pressure in the second annular hollow core, and adjusting the pressure in the second annular hollow core to adjust sealing of the shaft by the second annular seal element.

13. The method of claim 11, wherein the first seal element includes a first electric circuit element, wherein the first electric circuit is on or in the first inner surface of the first annular elastic casing, and the method further comprising: monitoring conductivity of the first electric circuit element during rotation of the shaft, and detecting an electrical short in the first electric circuit element based on the monitoring of the conductivity in the first electric circuit element.

14. The method of claim 13, wherein the second seal element includes a second electric circuit element, wherein the second electric circuit is on or in the second inner surface of the second annular elastic casing, and the method further comprising: monitoring conductivity of the second electric circuit element during rotation of the shaft, and detecting an electrical short in the second electric circuit element based on the monitoring of the conductivity in the second electric circuit element.

15. The method of claim 11, wherein the first seal element includes a first electric circuit element, wherein the first electric circuit is on or in the first inner surface of the first annular elastic casing, and the method further comprising: monitoring conductivity of the first electric circuit element during rotation of the shaft, and determining that the first seal element is to be replaced based on a change in the conductivity of the first electric circuit element.

16. The method of claim 15, wherein the second seal element includes a second electric circuit element, wherein the second electric circuit is on or in the second inner surface of the second annular elastic casing, and the method further comprising: monitoring conductivity of the second electric circuit element during rotation of the shaft, and determining that the first seal element is to be replaced based on a change in the conductivity of the first electric circuit element.

17. The method according to claim 11, further comprising pressurizing the annular fluid space between the first annular seal element and the second annular seal element to a pressure greater than a threshold pressure.

18. The method according to claim 11, further comprising: monitoring a pressure in the first annular seal element, and determining that the first annular seal element is to be replaced based on the pressures obtained from the monitoring of the pressure in the first annular seal element.

19. A method for monitoring a sealing arrangement around a shaft, wherein the sealing arrangement includes: A method for controlling a sealing arrangement around a shaft, wherein the sealing arrangement includes: an outer annular structure with an inner surface extending around the shaft and facing an outer surface of the shaft; a first annular seal element between the inner surface of the outer annular structure and the outer surface of the shaft, the first annular seal includes a first annular elastic casing and a first annular hollow core within the first annular elastic casing, wherein the first annular elastic casing includes a first sidewall extending outward radially relative to a rotational axis of the shaft and a first inner surface in sliding contact with the outer surface of the shaft; a second annular seal element between the inner surface of the outer annular structure and the outer surface of the shaft, the second annular seal includes a second annular elastic casing and a second annular hollow core within the second annular elastic casing, wherein the second annular elastic casing includes a second sidewall extending outward radially relative to the rotational axis and a second inner surface in sliding contact with the outer surface of the shaft, and the second sidewall faces the first sidewall along a direction parallel to the rotational axis, and an annular fluid space around the shaft and defined by the first sidewall, the second sidewall, the inner surface of the outer structure and the outer surface of the shaft and/or a gland mounted on the shaft, and the method comprises: pressurizing the first annular hollow core of the first annular seal element; pressurizing the second annular hollow core of a second seal element; monitoring conductivity of a first electric circuit element during rotation of the shaft, wherein the first electric circuit element is on or in the first inner surface of the first annular elastic casing; detecting an electrical short in the first electric circuit element based on the monitoring of the conductivity in the first electric circuit element, and determining that the first annular seal element is to be replaced based on the electrical short detected in the first electric circuit element.

20. The method of claim 19, further comprising: monitoring conductivity of a second electric circuit element during rotation of the shaft, wherein the second electric circuit element is on or in the second inner surface of the second annular elastic casing; detecting an electrical short in the second electric circuit element based on the monitoring of the conductivity in the second electric circuit element, and determining that the second annular seal element is to be replaced based on the electrical short detected in the second electric circuit element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:

[0026] FIG. 1 shows a schematic cross-sectional view of a sealing arrangement according to an example embodiment of the present invention;

[0027] FIG. 2 shows a further schematic cross-sectional view of a sealing arrangement according to an example embodiment of the present invention;

[0028] FIG. 3 shows a schematic three-dimensional view of a sealing arrangement according to an example embodiment of the present invention;

[0029] FIG. 4 shows a schematic cross-sectional view of a seal element according to an example embodiment of the present invention;

[0030] FIG. 5 shows a schematic block view of a sealing arrangement control system according to an example embodiment of the present invention; and

[0031] FIG. 6 shows a flow chart a sealing arrangement control method according to an example embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows a schematic cross-sectional view of a sealing arrangement 100 according to an example embodiment of the present invention. The sealing arrangement 100 is depicted at an end and around a shaft 30 of a disc filter unit. In an embodiment, the filter unit is a rotary filter unit of a white liquor plant, such as a white liquor filter or a lime mud filter. The sealing arrangement 100 comprises at least a first, or outer, seal element 10a and at least a second, or inner, seal element 10b. The first 10a and a second 10b seal element are arranged concentrically around the shaft 30. In an embodiment, the arrangement comprises at least one further seal element (not shown). The arrangement 100 comprises a fluid space 60 between the first 10a and the second 10b seal element. The fluid space 60 is filled with a fluid, in an embodiment water, for increasing the sealing effect and for flushing the seal surfaces while preventing solid particles from wearing down the seal elements. In an embodiment, the pressure of the fluid in the fluid space 60 is controlled, or adjusted, for example by adjusting the flow of the fluid into the fluid space 60, to a suitable pressure. In an embodiment, the fluid pressure in the fluid space 60 is larger than the pressure inside the rotary filter.

[0033] The shaft 30 rotates around its axis, as shown with an arrow in FIG. 1. The direction of rotation is not decisive. Furthermore, the shaft 30 reciprocates in an axial direction as shown with an arrow in FIG. 1. The combined rotation and reciprocation places high demands on the sealing arrangement 100. Using traditional sealing, the seal elements would have to exert a large pressing force causing large friction. Furthermore, should the shaft 30 not be perfectly round, as it is expensive and difficult to manufacture perfectly round shafts especially in case of hollow shafts as in an embodiment used in the rotary filter unit, the sealing could be compromised. It is further to be noted that the interior of the filter unit is pressurized and contains alkaline material making the operating environment demanding.

[0034] Accordingly, the first 10a and the second 10b seal element are adjustable, i.e. the sealing effect is controlled by pressurizing the seal elements 10a, 10b with pressurized fluid, in an embodiment gas, such as air, through pressure valves 18a, 18b. The internal pressure of the first 10a and the second 10b seal element is individually adjustable, i.e. the pressurization need not be at the same level for both. In an embodiment, the internal pressure of the first 10a and/or the second 10b pressure element is set to correspond to ambient pressure. The adjustable pressure provides for an adjustable sealing effect, i.e. the pressure of the first 10a and second 10b seal element is adjusted in such a way as to provide a sealing effect in each operating situation. The pressure in the fluid space 60 is in an embodiment adjusted relative to the pressure of the first 10a and second 10b seal element. in an embodiment, the pressure in the fluid space 60 is lower than the pressure of the first 10a and second 10b seal element. In an embodiment, the fluid to the fluid space 60 is supplied via a hydraulic accumulator in order to ascertain the sealing effect of the fluid in case of disruption in fluid supply. FIG. 1 further shows the placement of the first 10a and second 10b seal element. The first seal element 10a is in an embodiment positioned between the outer shell 20 and gland 40 of the filter unit. The second seal element 10b is in an embodiment positioned between the gland 40 and the interior of the filter unit. Although the first 10a and second 10b seal element have been depicted as having a same size, i.e. diameter and inner cross-sectional diameter, the first 10a and the second 10b seal element in a further embodiment have different sizes. In an example embodiment, the diameter of the first 10a and second 10b seal element, i.e. the diameter of the shaft, is 1300 mm.

[0035] The sealing arrangement 100 may for the shaft 30 may include at least a first seal element 10a arranged around the shaft 30; at least a second seal element 10b arranged around the shaft 30, wherein the first 10a and second 10b seal elements include adjustable seal elements, wherein the first 10a and second 10b seal elements include, respectively, an outer shell 14a, 14b of elastic material and a hollow core 12a, 12b, wherein the hollow core 12a, 12b of the first 10a and/or the second 10b seal element(s) is pressurized with a fluid for an adjustable sealing effect.

[0036] FIG. 2 shows a further, enlarged with respect to FIG. 1, schematic cross-sectional view of a sealing arrangement according to an example embodiment of the present invention. FIG. 2 shows the first 10a and second 10b seal elements. In an example embodiment, the seal elements comprise ExSeal-seal elements. Each seal element 10,10b comprises an outer shell 14a, 14b and a hollow core 12a, 12b. In an embodiment, the outer shell 14a, 14b comprises elastic material. In an embodiment, the outer shell 14a, 14b comprises a layer of elastic material, such as rubber, and an outer layer resistant to wear and tear, for example an outer layer of braided material.

[0037] The hollow core 12a, 12b of the first 10a and the second 10b seal element is pressurized with a fluid, in an example embodiment gas, such as air. The fluid is directed inside the first 10a and second 10b seal element, respectively, through a nipple, or valve, 18a, 18b. The valves 18a, 18b are connected, respectively to an inlet port 16a, 16b for supplying the fluid for pressurizing the seal elements 10a, 10b through the outer shell of the filter unit.

[0038] In an embodiment, as depicted in FIGS. 1 and 2, the valves 18a, 18b and the inlet ports 16a, 16b are positioned in a direction perpendicular to the axis of the shaft around which the seal elements are placed. In a further embodiment, depicted in FIG. 3, the valves 18a, 18b and the inlet ports 16a, 16b are positioned in a direction parallel to the axis of the shaft around which the seal elements are placed. in a still further embodiment, the positioning of the valves 18a, 18b and the inlet ports 16a, 16b is different for the first 10a and the second 10b seal element.

[0039] FIG. 3 shows a schematic three-dimensional view of a sealing arrangement according to an example embodiment of the present invention. FIG. 3 shoes the first seal element 10a and the second seal element 10b around a shaft 30. FIG. 3 shows also the seams 15a, 15b of the first 10a and second 10b seal element. The seal elements 10a and 10b are in an embodiment not unbroken rings, but formed into a ring from a tube closed at both ends thereof and attached at those ends at the seam 15a, 15b. FIG. 3 further shows the inlet ports 16a, 16b of the first 10a and second 10b seal element respectively. In the embodiment of FIG. 3, the tubing of the inlet port 16b of the second seal element 10b has been arranged in the seam 15a of the first seal element 10a.

[0040] FIG. 4 shows a schematic cross-sectional view of a seal element according to an example embodiment of the present invention. FIG. 4 shows as an example the first seal element 10a and a skilled person understands that the structure and functionality of the second seal element 10b and any further seal element is, in an embodiment, similar. The first seal element comprises, as previously explained with reference to FIGS. 1-3, the hollow core 12a, the elastic outer shell 14a, the valve 18a and is attached to the inlet port 16a for providing the pressurizing fluid. In the embodiment, of FIG. 4, the seal element 10a further comprises at least one electric circuit element 50a configured for conducting electric current until broken. The electric circuit element 50 a comprises in an embodiment for example copper wire. The electric circuit element 50a is positioned in such a way in the outer shell 14a of the seal element 10a that as the seal element 10a is subjected to wear, the electric circuit element 50a will at some point break due to the outer shell being worn down or torn in use. In the event that the electric circuit element 50a breaks, it will no longer conduct electric current which can be detected and accordingly excessive wear of the seal element 10a is detected. In a further embodiment, the seal element 10a further comprises a temperature sensor embedded therein.

[0041] FIG. 5 shows a schematic block view of a sealing arrangement control system according to an example embodiment of the present invention. FIG. 5 shows the sealing arrangement 100 and the control means connected thereto. The controls system comprises a control device 500. In an embodiment, the control device 500 is a standalone control device configured to control the sealing arrangement 100, for example a local control device or a cloud-based control system. In a further embodiment, the control device 500 is integrated into a mill-wide control system.

[0042] The control device 500 is connected to measurement and actuator modules 510a,510b. In an embodiment, there is provided a measurement and actuator module for each seal element 10a, 10b separately. In a further embodiment, a single measurement and actuator module is provided jointly for all seal elements 10,10b. The measurement and actuator modules 510a,510b are configured to measure the pressure inside the first 10a and second 10b seal element of the sealing arrangement 100. Furthermore, the measurement and actuator modules 510a,510b are configured to operate the means for providing and adjusting the pressure inside the first 10a and second 10b seal element, such as valves. In a further embodiment, the measurement and actuator modules 510a,510b are configured to monitor the electric current conducted by the electric circuit element 50a in order to detect wear that has broken the electric circuit. In a still further embodiment, the measurement and actuator modules 510a,510b are configured to monitor the temperature of the seal elements 10a, 10b.

[0043] FIG. 6 shows a flow chart a sealing arrangement control method according to an example embodiment of the present invention. In an embodiment, the method according to an example embodiment of the invention is caused to be carried out by a processor, for example a processor of a control system or control device 500. At step 610 the pressure inside the at least the first 10a and/or the second 10b seal element is set as well as the pressure in the fluid space 60. In an embodiment, the pressures are set at predetermined pressure values. In a further embodiment, the pressures are set depending on the operating pressure of the filer unit in the operating situation at hand. In an embodiment, the pressure is set to a different value for the first 10a and the second 10b seal element. In an embodiment, the pressure inside the at least the first 10a and the second 10b seal element is substantially in the range of 0.5 to 4 bar, or 1.6 to 3 bar, as examples.

[0044] At step 620, the pressure inside the first 10a and/or second 10b seal element is monitored during operation. In an embodiment, the pressure is monitored in realtime, or intermittently. In an embodiment, the pressure is monitored with a pressure sensor. In a further embodiment, the pressure is monitored by monitoring the amount of fluid, e.g. air, needed to maintain the pressure. Should the pressure fall, or the amount of fluid needed to uphold it, the seal element 10a, 10b in question might be worn too much, in which case it will be scheduled for replacement at step 640. Pressure inside the first 10a and/or second 10b seal element is in an embodiment adjusted at step 610 also during operation, for example based on the operating situation or based on the measurement at step 620.

[0045] In an embodiment, the wear of the first 10a and/or the second 10b seal element is monitored using the electric circuit element 50a. In an embodiment, the wear monitor comprises an alarm that is triggered when the electric circuit element 50a does not conduct, i.e. the circuit is broken due to wear of the seal element in question. In such a case, the seal element is scheduled for replacement at step 640.

[0046] Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is providing effective sealing for a rotating and reciprocating shaft. Another technical effect of one or more of the example embodiments disclosed herein is the provision of effective sealing in an alkaline environment. Another technical effect of one or more of the example embodiments disclosed herein is enabling adjustment and monitoring of sealing efficiency. A still further technical effect of one or more of the example embodiments disclosed herein is a safer and more maintenance free sealing. Another technical effect of one or more of the example embodiments disclosed herein is an increased lifetime of the sealing.

[0047] If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the before-described functions may be optional or may be combined.

[0048] Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

[0049] It is also noted herein that while the foregoing describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.