METHOD FOR CONDITION MONITORING A DEVICE AND APPLIANCE

Description

[0001] The invention relates to a method for monitoring the condition of a device for conveying thick material.

[0002] DE 10 2014 205 042 A1 discloses a hydraulic cylinder with ultrasonic sensors for measuring the motion of a piston, which is linearly mounted in a housing, wherein the piston separates a first and a second cylinder chamber from each other. The first and / or the second cylinder chamber is at least partially filled with a hydraulic fluid.

[0003] DE 198 06 544 A1 discloses a method for measuring the operating characteristic of an electromagnetic proportional control valve.

[0004] EP 1 437 178 A2 discloses a pumping device for powders.

[0005] EP 3 336 050 A1 discloses a forklift truck with a control unit for regulating the movement of a piston rod of a hydraulic cylinder and an associated method.

[0006] EP 2 123 594 A1 discloses a lifting vehicle with a speed control, wherein the lifting vehicle is hydraulically operated.

[0007] WO 2015 / 195246 A1 discloses a method for speed control of a hydraulic actuator.

[0008] US patent 2019 / 072118 A1 discloses a fluid delivery system with a hydraulic fluid source and a hydraulic cylinder that is fluidically coupled to the hydraulic fluid source and that has a piston that is movable between a first and a second end position.

[0009] The invention is based on the objective of providing a method for monitoring the condition of a device for conveying thick material, which enables reliable condition detection.

[0010] The method according to the invention serves for condition monitoring of a device for conveying viscous materials, for example in the form of liquid concrete. The device can, for example, be a concrete pump.

[0011] The device features a conventional first drive cylinder for receiving hydraulic fluid, for example in the form of hydraulic oil.

[0012] The device further comprises a conventional first drive piston, which is movably arranged, in particular longitudinally movably, in the first drive cylinder.

[0013] The procedure involves the following steps.

[0014] Determining the velocity of the first drive piston, particularly in the longitudinal direction of the first drive cylinder. The determined velocity can be the instantaneous velocity of the drive piston, which can be determined continuously or only at specific positions of the drive piston. Additionally, a velocity profile of the first drive piston can be determined. The first velocity can be determined, for example, using a conventional displacement measuring system that can determine the position of the first drive piston. The first velocity can then be calculated by differentiating the time of the determined position. Alternatively, the first velocity can be determined based on the stroke time between two defined points of the drive cylinder.

[0015] Calculate the difference between the measured velocity of the first drive piston and its expected velocity. The expected velocity is, for example, the velocity the first drive piston should theoretically have under fault-free operation, particularly at a given position. The expected velocity can be determined, for example, by knowing the properties of the device, such as piston geometries, cylinder geometries, known or measured drive flow rates, etc., or it may be known a priori.

[0016] Determining a fault condition of the device or of components of the device as a function of the difference or amount of the difference between the determined speed of the first drive piston and the expected speed of the first drive piston.

[0017] If the speed is derived from the lifting time, the lifting time and / or the change in the lifting time compared to the expected values ​​can serve as an error criterion.

[0018] Typically, the first drive piston and the first delivery piston each perform a purely translational, oscillating movement with a specific stroke.

[0019] With regard to the aforementioned conventional elements of the device, reference should also be made to the relevant technical literature.

[0020] According to one embodiment, the fault condition is determined when the difference between the measured speed of the first drive piston and the expected speed of the first drive piston exceeds a defined threshold. Alternatively or additionally, the fault condition is determined when a time-dependent change or derivative of the difference between the measured speed of the first drive piston and the expected speed of the first drive piston exceeds a defined threshold. The defined threshold can be an absolute or a relative value.

[0021] For example, a fault condition can be determined if the difference between the measured speed of the first drive piston and the expected speed of the first drive piston exceeds a predefined percentage of the expected speed or the measured speed. The predefined percentage could, for example, be in a range between 0.1% and 10% of the expected speed or the measured speed. Similarly, a fault condition can be determined if the rate of change or derivative of the difference between the measured speed of the first drive piston and the expected speed of the first drive piston per unit of time, for example, 60 seconds, exceeds a predefined percentage of the expected speed or the measured speed.The specified percentage value can, for example, be in a range between 0.1% and 10% of the expected speed or the measured speed.

[0022] The device further comprises a conventional drive pump designed to generate a flow rate of hydraulic fluid to move the first drive piston in the first drive cylinder. Reference is made in this respect to the relevant prior art. The expected velocity is then calculated as a function of the generated flow rate, taking into account typical known geometries and associated volumes of the hydraulic system.

[0023] The device is a device for conveying viscous material and further comprises: a conventional first conveying cylinder for receiving and discharging viscous material, a conventional first conveying piston which is movably arranged in the first conveying cylinder, in particular longitudinally movable, a conventional first piston rod which is attached to the first drive piston and to the conveying piston for coupling the movement of the first drive piston and the first conveying piston, a piston seal which, in a defect-free or intended state, in conjunction with the first drive piston, seals a first volume or a drive pump-side volume in the first drive cylinder against a second volume or a rocking volume in the first drive cylinder, and a rod seal which, in conjunction with the first piston rod, seals the first drive cylinder against the surroundings of the device.In this case, the fault condition in the form of a defect in the piston seal and / or in the form of a defect in the rod seal is determined depending on the difference formed between the determined speed of the first drive piston and the expected speed of the first drive piston.

[0024] According to one embodiment, the method comprises the following further steps: introducing a drive pump-side drive volume flow and determining the fault condition in the form of a defect in the piston seal during the introduction of the drive pump-side drive volume flow as a function of the difference formed between the determined speed of the first drive piston and the expected speed of the first drive piston.

[0025] According to one embodiment, the method comprises the following further steps: introducing a rocker-side drive volume flow and determining the fault condition in the form of a defect in the rod seal during the introduction of the rocker-side drive volume flow as a function of the difference formed between the determined speed of the first drive piston and the expected speed of the first drive piston.

[0026] According to one embodiment, the device for conveying viscous material further comprises: a second drive cylinder for receiving hydraulic fluid, a second drive piston movably arranged within the second drive cylinder, a second delivery cylinder for receiving and discharging viscous material, a second delivery piston movably arranged within the second delivery cylinder, and a second piston rod attached to the second drive piston and the second delivery piston for coupling the movement of the second drive piston and the second delivery piston. Within the first drive cylinder, the first drive piston separates a first volume (i.e., a volume on the drive pump side) from a second volume (i.e., a rocking volume). Similarly, within the second drive cylinder, the second drive piston separates a first volume (i.e., a volume on the drive pump side) from a second volume (i.e., a rocking volume).The rocking volume in the first drive cylinder and the rocking volume in the second drive cylinder are connected via a rocker link for the exchange of hydraulic fluid, such that the first drive piston moves in opposite phase to the second drive piston. In this case, the velocity of the second drive piston is determined, where the expected velocity of the first drive piston equals the determined velocity of the second drive piston. In other words, the determined velocity of the first drive piston is compared with the determined velocity of the second drive piston, and a fault condition is determined if the determined velocities differ by more than a predetermined amount, or if the rate of change of the difference in the determined velocities exceeds a predetermined amount.If wear on piston or rod seals can be ruled out, a deviation in piston speeds may also indicate a fault / wear in the remaining hydraulic system (especially the hydraulic pumps).

[0027] According to one embodiment, hydraulic fluid is fed into or drained from a rocking volume. This rocking volume comprises the rocking volume in the first drive cylinder, the rocking volume in the second drive cylinder, and a volume of the rocking connection. The feeding or draining is carried out such that the possible or maximum stroke of an oscillating movement of the first and second drive pistons reaches a desired dimension. The rocking connection causes the first and second drive cylinders to perform oscillating movements in opposite phases, the respective maximum stroke of which depends on the rocking volume. Consequently, the stroke can be adjusted by changing the rocking volume.

[0028] According to one embodiment, a fault condition is determined when the frequency of feeding or discharging exceeds a predetermined threshold. This predetermined threshold can be determined empirically, for example, through test series. For instance, frequencies less than or equal to one feeding or discharging per hour can be defined as fault-free, and frequencies greater than one feeding or discharging per hour can be defined as faulty. Alternatively or additionally, a fault condition of the device can be determined if a change or derivative of the feeding or discharging frequency over time exceeds a predetermined threshold. For example, a fault condition of the device can be determined if the change in the feeding or discharging frequency over time, such as every 60 seconds, exceeds a predetermined percentage of the expected or measured frequency.The specified percentage value can, for example, be in a range between 0.1% and 10% of the expected or measured frequency. Alternatively or additionally, a device error can be detected if the volume fed in or discharged exceeds a specified limit. This specified volume limit can be determined empirically, for example, through test series.

[0029] The invention is described in detail below with reference to the drawing. The drawing shows: Fig. 1 a device according to the invention for conveying thick material.

[0030] Fig. 1 Figure 1 shows a device 1 according to the invention for conveying viscous material DS. The device 1 can, for example, be a concrete pump.

[0031] The device 1 has a first drive cylinder 10a for receiving hydraulic fluid HF.

[0032] The device 1 further comprises a first drive piston 11a, which is arranged to be longitudinally movable in the first drive cylinder 10a.

[0033] The device 1 further comprises a first conveying cylinder 12a for receiving and discharging thick material DS in the form of liquid concrete.

[0034] The device 1 further comprises a first conveying piston 13a, which is arranged to be longitudinally movable in the first conveying cylinder 12a.

[0035] The device 1 further comprises a first piston rod 14a, which is attached to the first drive piston 11a for coupling the movement with the first conveying piston 13a.

[0036] The device 1 further comprises a second drive cylinder 10b for receiving hydraulic fluid HF.

[0037] The device 1 further comprises a second drive piston 11b, which is arranged to be longitudinally movable in the second drive cylinder 10b.

[0038] The device 1 further comprises a second conveying cylinder 12b for receiving and discharging thick substance DS.

[0039] The device 1 further comprises a second conveying piston 13b, which is arranged to be longitudinally movable in the second conveying cylinder 12b.

[0040] The device 1 further comprises a second piston rod 14b, which is attached to the second drive piston 11b for coupling the movement with the second conveying piston 13b.

[0041] The first drive piston 11a separates a drive pump-side volume V1 from a rocking volume V2 in the first drive cylinder 10a. Similarly, the second drive piston 10b separates a drive pump-side volume V1 from a rocking volume V2 in the second drive cylinder 10b. The rocking volume V2 in the first drive cylinder 10a and the rocking volume V2 in the second drive cylinder 10b are connected to each other via a rocker connection 60 for the exchange of hydraulic fluid HF, such that the first drive piston 11a moves in opposite phase to the second drive piston 11b.

[0042] The device 1 further comprises piston seals 15 which, in a defect-free state, seal the drive pump-side volumes V1 against the rocking volumes V2 in conjunction with the first drive piston 11a or the second drive piston 11b. Rod seals 16 are also provided, which, in conjunction with the first piston rod 14a or the second piston rod 14b, seal the first drive cylinder 10a or the second drive cylinder 10b against the environment.

[0043] The device 1 further comprises a drive pump 20, which is designed to generate the drive flow rates AVF of the hydraulic fluid HF. The drive pump 20 is connected via pump connections 30a and 30b to the drive pump-side volumes V1 for the movement of the first drive piston 11a in the first drive cylinder 10a or for the movement of the second drive piston 11b in the second drive cylinder 10b. The drive pump 20 can selectively supply a drive flow rate AVF either via pump connection 30a or pump connection 30b, so that either the first drive piston 11a or the second drive piston 11b moves to the right, with the other drive piston then moving to the left due to the coupling via the rocker connection 60.

[0044] The drive pump 20 is controlled such that the drive piston 11a or 11b, driven via the active pump connection 30a or 30b, moves to the right until it reaches a desired reversal point. Due to the rocker connection, the other drive piston 11a or 11b then moves to the left until it reaches the opposite reversal point. The first drive piston 11a and the second drive piston 11b therefore each perform a purely translational movement, oscillating between two reversal points.

[0045] With regard to the components and functions described so far, which are known from the state of the art, reference should also be made to the relevant technical literature.

[0046] Position sensors 17a and 17b are provided for detecting the position of the drive cylinders 10a and 10b, respectively. The instantaneous velocity of the first drive piston 11a and the second drive piston 11b is determined by deriving the piston positions detected by the position sensors 17a and 17b over time.

[0047] A control unit 50 controls the operation of the device 1.

[0048] According to the invention, a speed of the first drive piston 11a and / or the second drive piston 11a is determined by means of the position sensors 17a and 17b respectively, then a difference is formed between the determined speed(s) of the first drive piston 11a and / or the second drive piston 11b and an expected speed of the first drive piston 11a and / or the second drive piston 11b, and finally an error condition is determined depending on the difference(s) formed.

[0049] For example, the error condition can be detected if the difference between the determined speed and the expected speed exceeds a corresponding measure, and / or if a change over time of the difference between the determined speed and the expected speed exceeds a corresponding measure.

[0050] The expected speed can be calculated, for example, as a function of the generated drive volume flow rate AVF.

[0051] The expected speed of one of the two drive pistons 11a or 11b can also correspond to the measured speed of the other drive piston 11a or 11b. In other words, the determined speed of the first drive piston 11a is compared with the determined speed of the second drive piston 11b, whereby the fault condition is determined if the determined speeds differ from each other by more than a predetermined amount, or if the change over time of the difference in the determined speeds exceeds a predetermined amount.

[0052] The fault condition corresponds to a defect in the piston seal(s) 15 and / or a defect in the rod seal(s) 16. For example, a defect in the piston seal(s) can be detected during the introduction of the drive pump-side flow rate AVF as a function of the difference between the measured velocity and the expected velocity. Similarly, a defect in the rod seal(s) 15 can be detected during the introduction of the rocker-side flow rate AVF as a function of the difference between the measured velocity and the expected velocity.

[0053] In the event that a stroke or reversal position of the drive pistons 11a or 11b does not correspond to the respective setpoint values, the stroke can be adjusted by adding or removing hydraulic fluid HF into a rocking volume formed by the rocking volume V2 in the first drive cylinder 10a, the rocking volume V2 in the second drive cylinder 10b, and a volume of the rocking connection 60. The addition or removal of hydraulic fluid HF into the rocking volume can be carried out using conventional components known from the prior art. These components are designated by reference numeral 18 for illustrative purposes.

[0054] In this case, an error condition can be determined if the frequency of feeding or draining and / or the volume fed or drained exceeds a predetermined limit.

[0055] The device may of course include further components known from the prior art, for example switching means for connecting the conveying cylinders 12a and 12b to a high-viscosity conveying line or a high-viscosity source, etc. Since these components are well known, their description will be omitted.

[0056] The inventive method for condition and wear detection can be supplemented by taking further parameters into account, for example, hydraulic pressure and / or the temperature of the hydraulic fluid. Additionally, a history of the measured parameters can be evaluated.

[0057] The invention makes it possible to determine the wear of components of device 1 and thus to warn of or prevent component failure. This increases the availability of device 1, as necessary maintenance can be planned in a targeted manner. Furthermore, the automated localization of wear can also significantly reduce maintenance costs.

Claims

1. Method for monitoring the state of a device (1) for delivering thick matter (DS), wherein the device (1) has: - a first drive cylinder (10a) for receiving hydraulic fluid (HF), - a first drive piston (11a), which is movably arranged in the first drive cylinder (10a), - a first delivery cylinder (12a) for receiving and releasing thick matter (DS), a first delivery piston (13a), which is movably arranged in the first delivery cylinder (12a), and a first piston rod (14a), which is fastened to the first drive piston (11a) and to the first delivery piston (13a) for coupled movement of the first drive piston (11a) and the first delivery piston (13a), - a piston seal (15), which, in the non-defective state, seals off a drive-pump-side volume (V1) in the first drive cylinder (10a) with respect to a swing volume (V2) in the first drive cylinder (10a) in conjunction with the first drive piston (11a), - a rod seal (16), which seals off the first drive cylinder (10a) with respect to an environment in conjunction with the first piston rod (14a), and - a drive pump (20), which is designed to generate a drive volume flow (AVF) of hydraulic fluid (HF) for moving the first drive piston (11a) in the first drive cylinder (10a), wherein the method has the steps: - determining a speed of the first drive piston (11a), - calculating a difference between the determined speed of the first drive piston (11a) and an expected speed of the first drive piston (11a), and - identifying a fault state in the form of a defect in the piston seal (15) and / or in the form of a defect in the rod seal (16) according to the calculated difference between the determined speed of the first drive piston (11a) and the expected speed of the first drive piston (11a), characterized by the step - calculating the expected speed according to the generated drive volume flow (AVF).

2. Method according to Claim 1, wherein the fault state is determined - when the difference between the determined speed of the first drive piston (11a) and the expected speed of the first drive piston (11a) exceeds an associated value, and / or - when a temporal change in the difference between the determined speed of the first drive piston (11a) and the expected speed of the first drive piston (11a) exceeds an associated value.

3. Method according to either of the preceding claims, wherein the method has the further steps: - introducing a drive-pump-side drive volume flow (AVF) and - identifying the fault state in the form of the defect in the piston seal (15) during the introduction of the drive-pump-side drive volume flow (AVF) according to the calculated difference between the determined speed of the first drive piston (11a) and the expected speed of the first drive piston (11a).

4. Method according to one of the preceding claims, wherein the method has the further steps: - introducing a swing-volume-side drive volume flow and - identifying the fault state in the form of the defect in the rod seal (15) during the introduction of the swing-volume-side drive volume flow according to the calculated difference between the determined speed of the first drive piston (11a) and the expected speed of the first drive piston (11a).

5. Method according to one of the preceding claims, wherein the device further has: - a second drive cylinder (10b) for receiving hydraulic fluid (HF), a second drive piston (11b), which is movably arranged in the second drive cylinder (10b), a second delivery cylinder (12b) for receiving and releasing thick matter (DS), a second delivery piston (13b), which is movably arranged in the second delivery cylinder (12b), and a second piston rod (14b), which is fastened to the second drive piston (11b) and to the second delivery piston (13b) for coupled movement of the second drive piston (11b) and the second delivery piston (13b), - wherein the first drive piston (11a) separates a drive-pump-side volume (V1) from a swing volume (V2) in the first drive cylinder (10a), - wherein the second drive piston (10b) separates a drive-pump-side volume (V1) from a swing volume (V2) in the second drive cylinder (10b), and - wherein the swing volume (V2) in the first drive cylinder (10a) and the swing volume (V2) in the second drive cylinder (10b) are connected to one another via a swing connection (60) for exchanging hydraulic fluid (HF) in such a way that the first drive piston (11a) moves in phase opposition to the second drive piston (11b), wherein the method has the further steps: - determining a speed of the second drive piston (11b), wherein the expected speed of the first drive piston (11a) is the same as the determined speed of the second drive piston (11b).

6. Method according to Claim 5, wherein the method has the further steps: - supplying or discharging hydraulic fluid (HF) to or from a swing volume, which is formed by the swing volume (V2) in the first drive cylinder (10a), the swing volume (V2) in the second drive cylinder (10b) and a volume of the swing connection (60) in such a way that a stroke of an oscillating movement of the first drive piston (11a) and the second drive piston (11b) has a desired value.

7. Method according to Claim 6, wherein the method has the further steps: - identifying the fault state when a frequency of the supply or discharge procedure and / or a temporal derivative of the frequency of the supply or discharge procedure and / or a supplied or discharged volume exceeds a specified value.