CN114599952A

CN114599952A - Method for monitoring a sealing element of a fluid-operated roller device and roller device

Info

Publication number: CN114599952A
Application number: CN202080062518.1A
Authority: CN
Inventors: A.许内肯斯
Original assignee: Andritz Kuesters GmbH
Current assignee: Andritz Kuesters GmbH
Priority date: 2019-09-04
Filing date: 2020-08-12
Publication date: 2022-06-07
Also published as: DE102019123658A1; WO2021043553A1

Abstract

The invention relates to a method and a fluid-operated roller (4, 19, 42), wherein a sealing element (11, 12, 28, 29, 47) is acted upon by a pressurized operating fluid, wherein the pressure of the operating fluid is influenced by means of a pressure valve (17, 30, 48), and wherein the volumetric flow of the operating fluid flowing through the pressure valve (17, 30, 48) is detected in order to detect wear of the sealing element (11, 12, 28, 29, 47).

Description

Method for monitoring a sealing element of a fluid-operated roller device and roller device

Technical Field

The invention relates to a method for monitoring a sealing element of a fluid-operated roller, in which method the sealing element is loaded with an operating fluid under pressure, wherein the pressure of the operating fluid is influenced by means of a pressure valve. Furthermore, the present invention is directed to a fluid operated roller with internal push lift and/or deflection compensation (mit inerem Hub und/oder durchbieggausgleich), comprising: at least one fluid support element with a sealing element and/or at least one pressure chamber with a sealing element, and at least one pressure valve, by means of which the pressure acting on the at least one support element and/or the at least one pressure chamber can be influenced.

Background

Fluid-operated rollers with internal displacement lift and/or deflection compensation are typically provided with dynamic sealing elements inside the roller. In particular compressed gas or pressurized liquid, in particular hydraulic fluid, can provide the fluid pressure. For heated, deflection-controlled rollers, hot oil is also used.

Such rollers with internal displacement lift and/or deflection compensation are usually designed as so-called "plunger support rollers (stempeltste Walzen)" or as so-called "floating rollers (schwimmende Walzen)". They usually comprise a stationary support frame on which a roller shell is rotatably mounted.

For the plunger support rollers, a plurality of radially guided support elements in the form of piston/cylinder units are usually arranged distributed along the length of the supporting frame. The dynamic sealing element is formed by a piston seal which seals the piston in a cylinder chamber provided in the bearing block for receiving the piston, in order to prevent the operating fluid supplied to the cylinder chamber from flowing out. Such a roller is known, for example, from DE 29503126U 1.

For floating rolls, a pressure chamber is usually provided between the carrier frame and the roll shell, which pressure chamber is charged with an operating fluid, so that hydraulic support forces can be transmitted from the carrier frame to the shell. This pressure chamber, hereinafter also referred to as "first pressure chamber", is sealed with respect to a leakage chamber, hereinafter also referred to as "second pressure chamber", via a longitudinal seal and an end seal. The longitudinal seal and the end seal constitute a dynamic sealing element. Such a roller is known, for example, from WO 2004/097110 a 1.

For trouble-free operation of such a roller, it is necessary: leakage that typically occurs in dynamic sealing elements does not exceed a maximum allowable limit. This maximum permissible limit is also mainly dependent on the effective power of the device providing the fluid pressure. During operation of such a roller, it is often necessary to be able to position the roller with a certain force against a counter-tool, which is usually likewise designed as a roller. This force is also referred to as line force. When the leakage becomes large, the amount of operating fluid that must be delivered to the plunger to support the roller cylinder chamber or the dancer first pressure chamber in order to maintain the line force is increased. If this operating fluid quantity cannot be provided, for example because the hydraulic pump for this purpose has insufficient available power, then a pressure drop in the respective cylinder chamber or in the respective first pressure chamber must ensue. The line force characteristic and/or the line force as a whole therefore changes, as a result of which production faults can subsequently result. If the operating fluid pressure in the cylinder chamber or the first pressure chamber continues to drop, this can even lead in extreme cases to mechanical collisions of the rotating roller shell with the supporting frame, which can then lead to damage or even destruction of the roller. Furthermore, especially the roll surface may also be damaged due to uneven distribution of the line forces.

Wear of the dynamic sealing elements generally increases with increasing operating time. In addition, accidental contamination can also lead to a loss of the sealing function of the dynamic sealing element, so that the prediction of the achievable operating time is not practically reliable. In particular with heated floating rolls, in which the operating fluid is preheated in order to increase the temperature of the roll jacket, temperature-induced undesirable deposits can occur which impede the sealing action of the sealing element and/or increase the difficulty of the necessary adjustment movement thereof. Furthermore, an unintended reduction in the power of, for example, a hydraulic pump provided for supplying the operating fluid can also lead to the above-mentioned consequences.

In practice it has been shown that: the pressure loss with the consequences exemplified above often occurs suddenly and unexpectedly to some extent, resulting in production stoppages. In this case, a complicated troubleshooting is first required. Typically, component failures are first eliminated in the regulated path that is necessary to provide the desired pressure and the required amount of operating fluid. Typically, it is necessary to check IP converters, pressure reducers, pressure regulating valves, servo valves, etc. Only if it is ensured that a fault in the regulating path component is ruled out can it be concluded that the cause of the pressure loss is in the dynamic sealing element. Then, in order to accurately determine and eliminate the failure, the rollers must be removed and a backup roller installed. In the case of heated rollers, it is also generally necessary to bleed off the heat-carrying fluid (in most cases the operating fluid). The auxiliary equipment required for roll change, such as tools, transport equipment and backup rolls, must be prepared first. Thus, there is often a lengthy shutdown and production stoppage associated with the sudden occurrence of an unexpected leak.

Loading such a roller with pressurized operating fluid can be achieved in different ways:

1. pressure regulation in the inflow (Vorlauf): in this case, a pressure which has already been set is supplied to the cylinder chamber of the plunger support roller or to the first pressure chamber of the dancer roller. For plunger-supported rollers, leakage typically corresponds to the sum of leakage of the piston seal and leakage between the support element and the roller tube. For a dancer, the leakage generally corresponds to the sum of the leakage of the end seals and the longitudinal seals of the pressure chamber. In particular, the pressure regulation can be carried out via various valves. For example, proportional valves should be mentioned first. If the proportional valve is used, the oil pressure is measured, the measured actual value is compared with a predefined setpoint value, and the difference between the actual value and the setpoint value is applied to a control module which actuates the proportional valve. The control module changes an adjustment signal for the proportional valve based on the difference (also referred to as the trim offset). If, for example, a pneumatic pressure regulator is used, an air pressure, which is provided by the IP converter and fed to the pneumatic pressure regulator, can be determined, for example, by the system control from the measured actual value/setpoint difference.

2. Pressure regulation in reflux (rtuklauf): in particular for heated dancers, it has proven to be possible to carry out the pressure regulation in the return flow from the first pressure chamber. In this case, an operating fluid volume flow which is as constant as possible (for example, provided by a hydraulic pump) is first fed to a first pressure chamber, flows through the first pressure chamber, then flows through a pressure valve, via which the directly or indirectly adjustable pressure drops, and finally flows through a second pressure chamber (also referred to as "leakage chamber"). Such a valve can in principle be any component which is suitable for generating a pressure drop by changing the throttle cross section. Particularly preferably, the valve is a pneumatically operated pressure regulator which balances a pneumatic pressure, which can be specified, in particular, by the system control, with the pressure drop in the roller volume flow. The pressure regulator is also referred to below as "differential pressure regulator". In principle comparable pressure regulation is also used in so-called "CS rolls". This CS roller has two first pressure chambers, which each have an inflow and a return. Each return flow passes through a pressure valve. The operating fluid flowing back from the pressure valve merges with the leakage flow which may be present.

Disclosure of Invention

The object of the present invention is to provide countermeasures by means of which the risk of accidental failure of the roller due to sudden pressure loss is greatly reduced.

This object is achieved by a method having the features of claim 1 and by a roller having the features of claim 8. The subject matter of the dependent claims is some preferred developments of the inventive method and of the inventive roller.

In the method according to the invention, the operating fluid volume flow through the pressure valve is detected directly or a variable from which the operating fluid volume flow through the pressure valve can be inferred is measured. The detection of the volume flow or the variable takes place continuously or at certain predefined time intervals. From the time profile of the measured volume flow, the state of the sealing element is inferred. In the case of pressure regulation in the inflow, the increase in the volume flow rate can be evaluated as an indication that the leakage is large, in the case of pressure regulation in the backflow, the decrease in the volume flow rate can be evaluated as an indication that the leakage is large, and the roller or its sealing element should be repaired.

If the operating fluid pressure required for this purpose is not accidentally built up when the fluid-operated roller is put into operation, it can be determined on the basis of the detection of the operating fluid volume flow through the pressure valve according to the invention: whether there is a defect in the supply of pressurized operating fluid (e.g. a malfunction of the pressure regulator, pump, etc.), which, if so, would detect no or only an unexpectedly low volumetric flow; alternatively, the cause of whether the pressure has not been built up is due to a damaged sealing element, if this is the case, an unexpectedly high volume flow will be detected in the case of an inflow pressure regulation and an unexpectedly low volume flow will be detected in the case of a return pressure regulation. Troubleshooting may include: firstly, determining whether a differential pressure regulator works; or whether, for example, an incorrect control pressure is provided; or whether there is a mechanical fault in the regulator. This can be determined, for example, by a displacement sensor in the following respects: the valve is completely stationary or abuts an end stop.

For example, the volume flow to the hydraulic support element of the plunger support roller or to the first pressure chamber of the dancer can be detected directly by means of a flow sensor. For this purpose, the flow sensor can be connected to a supply line for the operating fluid.

Alternatively or additionally, the position of the pressure valve can also be monitored and the volume flow can be inferred from the position. For this purpose, the valve position can be observed or converted into an evaluation parameter proportional to the volume flow.

For floating rollers, the volumetric flow of the operating fluid is usually supplied first to a first pressure chamber of the roller, then to a pressure valve and finally to a second pressure chamber of the roller (also referred to as a leakage chamber), wherein the pressure valve is used to set the pressure difference between the first and second pressure chambers. Since the roller is usually supplied with an almost constant operating fluid volume flow, the valve position in the return flow can be detected to detect a leak rise between the first and second pressure chamber, which indicates an increased wear of the sealing element. If the valve is to be closed in order to maintain the necessary pressure difference, it can be concluded that the internal leakage is rising.

Alternatively or additionally, it is also possible, if the pressure difference in the first and second pressure chambers is correlated with the valve travel of the pressure valve, to measure this valve travel and compare it with a predefined valve travel. From the unexpected difference, it can again be concluded that the leakage between the first and second pressure chambers has risen and that the sealing element has worn.

Alternatively or additionally, the operating fluid volume flow into the cylinder chamber or into one or more first pressure chambers can likewise be measured. In the case of pressure regulation in the return flow, the volume flow flowing out of the first pressure chamber or chambers is measured.

The fluid actuated roller with internal displacement lift and/or deflection compensation includes: at least one fluid support element with a sealing element and/or at least one pressure chamber with a sealing element; and at least one pressure valve, by means of which the pressure acting on the at least one support element and/or the at least one pressure chamber can be influenced, according to the invention the roller comprises means by which the volumetric flow of the operating fluid flowing through the pressure valve can be detected. Upon detection of the volume flow, the wear development of the sealing element can be deduced by comparison with a reference value (which is stored, for example, in an electronic data memory).

The device by means of which the volumetric flow of the operating fluid through the pressure valve can be detected preferably comprises at least one flow meter.

In addition or as an alternative to this, the device which is able to detect the volumetric flow of the operating fluid through the pressure valve may comprise a measuring device for detecting a measured variable from which the volumetric flow of the operating fluid can be inferred.

The fluid actuated roller of the present invention preferably includes first and second pressure chambers and is configured such that the operating fluid flows first through the first pressure chamber and then through the second pressure chamber. Preferably, the pressure valve is configured as a differential pressure regulator, which functions to: the operating fluid is sent to a first pressure chamber which is at a higher pressure than a second pressure chamber (also referred to as a "leakage chamber"). The differential pressure regulator preferably comprises a valve body displaceable away from a closed position. The distance displaced from the closed position is referred to as the valve stroke. It is then preferred that the roller further comprises a differential pressure measuring device which detects the difference between the fluid pressures present in the first and second pressure chambers.

It is then particularly preferred if a displacement sensor is provided, which detects the valve stroke. If the valve stroke is changed to maintain a pressure differential of the operating fluid in the first and second pressure chambers, this can indicate a change in the leakage condition, and as a result the state of the sealing element can be inferred.

Alternatively or additionally, such a roller can comprise a flow meter, by means of which the operating fluid volume flow into one or more first pressure chambers and/or the operating fluid volume flow through the second pressure chamber can be detected directly. An increase in the measured flow rate indicates increased wear of the sealing element. If the roller has a flow meter by means of which the volume flow out of the first pressure chamber can be detected, a drop in the measured flow rate indicates that the wear of the sealing element is progressing.

The flow meter may, as is particularly preferred, comprise a venturi nozzle, a metering orifice, a standard nozzle and/or a pitot tube and is integrated in or connected to a line through which the operating fluid flows in a suitable manner.

Drawings

The invention will now be further illustrated by means of the purely schematic drawing. In the drawings:

fig. 1 shows a twin-roll calender with a roll belonging to the prior art, which roll is shown partly in section;

FIG. 2 shows a partial region, also shown partially in section, of a first embodiment of the roll of the invention;

FIG. 3 shows a second embodiment of the roller according to the invention in a view comparable to FIG. 2, an

Fig. 4 shows a twin-roll calender with a third embodiment of a roll according to the invention in a diagram comparable to fig. 1.

Detailed Description

The calender, designated as a whole by K1 in fig. 1, comprises a calender frame 1 in which a roller 2 is mounted rotatably about an axis a1 via a roller bearing 3.

Calender K1 also comprises a roller 4, which is designed as a floating roller. It comprises a support frame 5 supported against rotation, which is mounted on the calender frame 1 via a lifting cylinder 6 and can be moved towards and away from the roll 2.

The roller 4 furthermore comprises a roller sleeve 7 which is mounted rotatably about an axis a2 on the supporting frame 5 via a rolling bearing 8.

In the operating position shown in fig. 1, the roller 4 is positioned against the roller 2, and the roller shell 7 forms with the roller 2 a roller gap 9 through which a material web, for example, paper, nonwoven, textile or film, is guided during operation for the treatment thereof.

In order to be able to counteract the deflection of the roller 2 between the roller bearings 3 and the deflection of the roller shell 7 between the roller bearings 8 due to the dead weight and in particular due to the forces acting on the roller shell 7 in the roller gap 9, the roller 4 is designed as a so-called "floating roller". It comprises a first pressure chamber 10, which is formed between the supporting frame 5 and the roller shell 7 on the side facing the other roller 2. The first pressure chamber is sealed off via sealing elements configured as a longitudinal seal 11 and an end seal 12 from a second pressure chamber 13, which is also referred to as a "leakage chamber".

The support frame 5 has a first channel 14 which opens from both end sides into the first pressure chamber 10 and a second channel 15 which opens from the end side into the second pressure chamber 13.

A hydraulic pump P is provided which is connected via a supply line 16 to a first channel 14 shown on the right in fig. 1. It serves to supply an operating fluid, for example hydraulic oil, to the first pressure chamber 10 at a constant volume flow. The operating fluid passes from the pressure chamber 10 via a first channel 14 shown on the left in the figure to a pressure valve configured as a pressure regulator 17 and from there to a second channel 15 shown on the left in fig. 1. Through which the operating fluid is led to the second pressure chamber 13, from where it reaches the pressureless reservoir R of operating fluid via the second channel 15 and the line 18 on the right in fig. 1. The differential pressure regulator 17 causes the pressure of the operating fluid flowing through it to drop, so that the operating fluid in the first pressure chamber 10 maintains a higher pressure than in the second pressure chamber 13. The differential pressure determined by means of the differential pressure regulator 17 is selected in such a way that the pressure acting on the roller shell 7 from the inside in the first pressure chamber 10 results in: the gravitational and linear forces (from the roll gap) acting on the roll shell 7 directed towards the supporting frame 5 and the deflection of the roll 2 are compensated for so that the roll gap 9 has an at least substantially constant gap height over its length (total length).

The differential pressure regulator 17 is pneumatically operated. The level of the applied pneumatic control pressure PS is a measure of the desired value of the pressure difference between the first pressure chamber 10 and the second pressure chamber 13. During operation of the roll 4, the control pressure PS is predetermined by the system control PLC. The pressure with which the lifting cylinder 6 is acted upon during operation is also predetermined by the system control PLC in order to be able to set the line force present in the roll gap 9 to a desired value.

The embodiment of the roller 4 shown in fig. 1 additionally comprises a differential pressure gauge 50, by means of which the differential pressure value Pdiff falling at the differential pressure regulator 17 is detected. An unexpected drop in the actual differential pressure value may indicate: more operating fluid from the first pressure chamber 10 reaches the second pressure chamber 13 around the differential pressure regulator 17 and may mean that the sealing elements are completely damaged, which may require immediate shut down of the calender.

An embodiment of a further developed roller 19 according to the invention is partly shown in fig. 2. The roller 19 is also a floating roller, which comprises a support frame 20 supported in a rotationally fixed manner and a roller shell 21 mounted rotatably about the support frame. In the roller 19, a roller shell 21 is mounted and supported on the outer side of a support frame 20. For this purpose, a bearing cage (Lagerdom)22 is provided on the support frame 20, which bearing cage comprises an enlarged-diameter region 23. In this region 23, a rolling bearing 24 is provided, which acts externally on a region 25 of smaller diameter of the roller shell 21.

The roller 19 also comprises a first pressure chamber 26 and a second pressure chamber 27, also called leakage chamber. The first and

second pressure chambers

26, 27 are in turn formed between the support frame 20 and the roller shell 21 and are separated from one another by sealing elements, including longitudinal seals 28 and end seals 29.

In fig. 2, only the left-hand region of the roller is shown, in which a differential pressure regulator 30 is arranged. It goes without saying that the area of the right side of the roller 19, which is not shown in the figures, can be constructed in a similar manner and mounted on the outside of the support frame. Except that no differential pressure regulator is provided and the operating fluid is fed to the first pressure chamber 26 and discharged from the second pressure chamber 27, for example, as described with reference to fig. 1.

The structural design and the principle of operation of the roller differential pressure adjuster 30 of the present invention will now be described:

the differential pressure regulator 30 comprises a valve body 31 which comprises a first valve disk 32, a second valve disk 33 and a connecting member 34 which connects the two

valve disks

32, 33 to one another. The first valve disk 32 is arranged in a pneumatic cylinder 35 which can be acted upon by a control pressure PS acting on the first valve disk 32. In the embodiment shown in fig. 2, the pneumatic pressure generates a force that presses the valve body 31 to the right. The valve body 31 is provided movably relative to the support frame 20 and the bearing housing 22 in the longitudinal direction of its connecting member 34. A channel 36 is provided in the support frame 20, which opens into the first pressure chamber 26 and in which an operating fluid is held, which has the pressure PD present in the pressure chamber 26. At its other end, the passage 36 opens into a hydraulic chamber 37, which can be closed or opened by the second valve disk 33. In the open state, the hydraulic chamber 37 is in fluid connection with a return channel 38 leading into the second pressure chamber 27.

The valve body 31, the pneumatic cylinder 35 and the hydraulic chamber 37 are designed such that the second valve disk 33 closes the hydraulic chamber 37 outward, in particular against the return channel 38, when the force acting on the second valve disk 33 from the hydraulic pressure PD in the first pressure chamber 26 is smaller than the force acting on the first valve disk 32 on the basis of the pneumatic control pressure PS. If the first pressure chamber 26 is now (as in the exemplary embodiment shown in fig. 1) supplied with operating fluid, for example, at a constant volume flow, a hydraulic pressure builds up in the first pressure chamber 26 and thus in the hydraulic pressure chamber 37, which increases until the valve body 31 opens the hydraulic pressure chamber against the force acting on the first valve disk 32 by the control pressure PS and the operating fluid can flow through the return channel 38 into the second pressure chamber 27 and from there into the pressureless operating fluid reservoir. Therefore, the differential pressure Pdiff of the operating fluid in the first pressure chamber 26 and in the second pressure chamber 27 can be influenced by changing the control pressure PS.

As is clear from the above-described operating principle and from fig. 2, an increased leakage between the first pressure chamber 26 and the second pressure chamber 27 results in: the valve body is moved to the right at a constant control pressure PS to maintain a pressure difference PDiff existing in the two pressure chambers. In the embodiment of the roller according to the invention shown in fig. 2, a displacement sensor 39 is provided for detecting this movement, with which the valve travel H or the corresponding position of the valve body 31 can be detected. The operating principle of the displacement sensor 39 can be, for example, inductive, the actuator of which can be adjusted by a spring. Accordingly, its output signal HS (which characterizes the corresponding valve travel characteristic) can likewise be analog, for example as a current in the milliamp range, the magnitude of which depends on the valve travel.

Thus, by monitoring the output signal HS of the displacement sensor 39, the increased state of leakage between the first and

second pressure chambers

26, 27 can be detected by measuring the valve travel, from which it can be inferred that the sealing elements separating the first and

second pressure chambers

26, 27 from each other are wearing out more heavily.

Fig. 3 shows a second embodiment of the roller according to the invention in a view comparable to fig. 2. Only the differences of the second embodiment from the first embodiment will be described below. To avoid repetition, reference is made to the detailed description of the embodiment of fig. 2. Like reference numerals designate corresponding parts.

In contrast to the roller 19, the roller 40 shown in fig. 3 does not detect the valve travel H or the position of the valve body 31 of the differential pressure regulator 30, but rather measures the operating fluid flow through the channel 36 which connects the first pressure chamber 26 to the differential pressure regulator 30. For this purpose, a flow meter 51 is provided, which comprises a cross-sectional constriction in the channel 36 in the form of a venturi nozzle 41. The resulting pressure difference PA/PB, which is caused by the pressure in the relatively untapered channel due to the reduced cross section, is measured, in such a way that the volume flow V through the channel 36 can be detected. If the volume flow drops unexpectedly, it can also be concluded that the leakage between the first and second pressure chambers is increasing, and that the wear of the sealing elements separating the first and

second pressure chambers

26, 27 from each other is increasing.

Fig. 4 shows a view comparable to fig. 1 of a calender K2, comprising a roll 42 according to the invention, which is a fourth embodiment. The roller 42 is a so-called plunger-supporting roller. It has a support frame 43 which, in a manner known per se and not shown in the figures, carries a plurality of support elements 44 which are guided radially on the support frame 43 and are designed in the form of piston/cylinder units. The support element 44 acts on a roller sleeve 45 which is mounted rotatably on the bearing bracket 43 via a rolling bearing 46. To control the deflection of the rollers 42, each of these support elements is loaded with operating fluid provided by the pump P. By means of the pressure valve 48 assigned to each respective support element 44, the pressure P1.. P8 is set individually, respectively, at which pressure each support element 44 is loaded with operating fluid. According to the invention, the volumetric flow Q1... Q8 of the operating fluid fed to the individual support elements 44 is additionally measured by means of a flow meter 49. From the unexpected rise, it can be concluded that the wear of the sealing element 47 of the respective support element 44 is progressing.

List of reference numerals

Calender base frame 1

2 roller

3 rolling bearing

4 rollers

5 supporting rack

6 lifting cylinder

7 roller sleeve

8 rolling bearing

9 roller gap

10 first pressure chamber

11 longitudinal seal

12 end seal

13 second pressure chamber

14 first channel

15 second channel

16 pipeline

17 differential pressure regulator

18 pipeline

19 roller

20 support rack

21 roller sleeve

22 bearing cage

Region 23

24 rolling bearing

25 region

26 first pressure chamber

27 second pressure chamber

28 longitudinal seal

29 end seal

30 pressure difference regulator

31 valve body

32 first valve disc

33 second valve disk

34 connecting member

35 pneumatic cylinder

36 channel

37 hydraulic chamber

38 return flow path

39 displacement sensor

40 rollers

41 Venturi nozzle

42 roller

43 support frame

44 support element

45 roller sleeve

46 rolling bearing

47 sealing element

48 pressure valve

49 flow meter

50 differential pressure gauge

51 flow meter

Axis A1

Axis A2

H stroke

HS signal

K1 calender

K2 calender

P hydraulic pump

PA pressure

PB pressure

P8 pressure

PS pneumatic control pressure

PDiff pressure difference

PD pressure

PL pressure

PS control pressure

PLC equipment control system

Q1.. Q8 volume flow

R reservoir

Claims

1. Method for monitoring a sealing element (28, 29, 47) of a fluid-operated roller, in which method the sealing element (28, 29, 47) is loaded with an operating fluid under pressure, wherein the pressure of the operating fluid is influenced by means of a pressure valve (30, 48),

the method is characterized in that:

the pressure valve (30, 48) is provided with a detection of the operating fluid volume flow through the pressure valve (30, 48) or a detection of a variable from which the operating fluid volume flow through the pressure valve (30, 48) can be inferred, and a state of the sealing element (28, 29, 47) can be inferred.

2. The method of claim 1, wherein: the volume flow is detected by means of a flow meter (49).

3. The method according to claim 1 or 2, characterized in that: the position of the pressure valve (30, 48) is monitored and the volume flow is inferred from the position.

4. The method of claim 1, wherein: the volume flow of the operating fluid is supplied firstly to a first pressure chamber (26) of the roller (19), then to the pressure valve (30) and finally to a second pressure chamber (27) of the roller (19), wherein the pressure difference in the first and second pressure chambers (26; 27) is set by means of the pressure valve (30).

5. The method of claim 4, wherein: the pressure difference (PDiff) in the first and second pressure chambers (26; 27) is dependent on the valve travel (H) of the pressure valve (30), which is measured and wear of the sealing elements (28, 29) is concluded when the valve travel changes in order to maintain the pressure difference (PDiff).

6. The method according to claim 4 or 5, characterized in that: the volumetric flow of the operating fluid into the first and/or out of the first pressure chamber (26; 27) is measured.

7. Fluid-operated roller (19, 42) with internal displacement lift and/or deflection compensation, comprising:

-at least one fluid support element (44) with a sealing element (47) and/or at least one pressure chamber (26, 27) with a sealing element (28, 29)

At least one pressure valve (30, 48) by means of which the pressure acting on the at least one support element (44) and/or the at least one pressure chamber (26, 27) can be influenced,

the method is characterized in that:

the roller (19, 42) comprises means by which the volumetric flow of the operating fluid through the pressure valve (30, 48) can be detected.

8. The roller according to claim 7, characterized in that: the apparatus includes at least one flow meter (49).

9. The roller according to claim 7, characterized in that: the device comprises a measuring device for detecting a measurement variable from which a volume flow of the operating fluid can be inferred.

10. The roller according to claim 7, characterized in that: the roller comprises a first and a second pressure chamber (26; 27) and is configured such that the operating fluid flows first through the first pressure chamber (26) and then through the second pressure chamber (27).

11. The roller according to claim 10, characterized in that: a differential pressure measuring device is provided which detects the difference between the fluid pressures present in the first and second pressure chambers (26, 27).

12. The roller according to claim 10, characterized in that: the pressure valve (30) is designed as a differential pressure regulator (30) having a valve stroke (H), which has a displacement sensor (39) that detects the valve stroke (H).

13. The roller according to claim 10, characterized in that: a flow meter (51) is provided, by means of which the volumetric flow of the operating fluid flowing through a channel (36) connecting the first pressure chamber (26) to the differential pressure regulator (30) and/or through a return channel (38) connecting the differential pressure regulator (30) to the second pressure chamber (27) can be detected.

14. The roller according to claim 13, characterized in that: the flow meter (51) comprises a venturi nozzle (41), a metering orifice, a standard nozzle, and/or a pitot tube.