AU2011328429B2

AU2011328429B2 - Method and system for identifying damage to piston membrane pumps containing working fluids

Info

Publication number: AU2011328429B2
Application number: AU2011328429A
Authority: AU
Inventors: Peter Heinrichs
Original assignee: Mhwirth GmbH
Current assignee: Mhwirth GmbH
Priority date: 2010-11-12
Filing date: 2011-10-18
Publication date: 2016-02-18
Anticipated expiration: 2031-10-18
Also published as: EP2638288A1; WO2012062542A1; PE20140463A1; BR112013011648A2; ZA201302998B; CL2013001323A1; DE102010060532A1; CL2015003478A1; AU2011328429A1

Abstract

In a method and a system for identifying damage to piston membrane pumps containing working fluids, the pressure of the working fluid is measured during operation in relation to the time and compared with a desired value profile, and a signal is triggered if a predetermined deviation is exceeded.

Description

WO 2012/062542 1 PCT/EP2011/068186 Method and system for identifying damage to piston membrane pumps containing working fluids The invention relates to a method for identifying damage to piston membrane pumps containing working fluids. Piston membrane pumps are used for pumping liquids or gases. Their principle of 5 operation is similar to the piston pump, wherein however the pumped medium is separated from the drive by a membrane. The drive is therefore screened by this separating membrane from damaging effects of the pumped medium. The pumped medium is also separated from damaging effects of the drive. 10 With a piston membrane pump, the oscillating movement of the piston is transmitted to the membrane by means of a working medium. Water with a water-soluble mineral additive or, in particular, a hydraulic oil can be used as the working fluid. Accordingly, the volume which is filled by the working fluid is also referred to as the "oil reservoir". As a result of the constant volume of the oil reservoir between piston and membrane, 15 the movement of the piston directly causes a deflection of the membrane and thus generates suction and compression pulses. The method according to the invention and the system according to the invention are basically suitable for piston membrane pumps of this kind of any size and for any 20 application. In particular, however, the invention relates to piston membrane pumps which are intended for pumping sludge, also referred to as thick matter, in earthwork operations. Piston membrane pumps of this kind are designed for continuous use and must work reliably over long periods up to years, if possible without faults, as a replacement of a defective piston membrane pump is usually associated with 25 considerable effort and time due to its size. In addition, with these piston membrane pumps, damage to the membrane can have particularly serious consequences. This is because, on the one hand, if the membrane is damaged, the working fluid enters the membrane chamber and mixes 30 with the pumped sludge which necessitates laborious cleaning. On the other, sludge 2 is carried over into the oil reservoir, as a result of which the whole pump can be contaminated and the drive piston damaged. The invention is therefore based on the object of creating a method and a 5 system for identifying damage to piston membrane pumps containing working fluids, which damage can be identified before it assumes a level which necessitates an immediate shutdown of the piston membrane pump, or damage to the membrane occurs to an extent which leads to a mixing of working fluid and the medium, in particular the sludge, to be pumped. 10 This object is achieved by the method described in claim 1 and by the system described in claim 5. With the method according to the invention, the pressure of the working fluid 15 is measured during operation in relation to the time and compared with a desired value profile. A signal, for example a visual and/or acoustic warning signal, is triggered if a predetermined deviation is exceeded. The invention is based on the surprising knowledge that the occurrence of 20 damage is indicated by a significant change in the pressure profile of the working fluid. In particular, the pressure of the working fluid during a suction or compression cycle, which varies in a characteristic manner about a mean value in the case of an undamaged piston membrane pump, changes significantly when damage is indicated. Surprisingly, it has been shown that 25 the profile of the significant change even allows conclusions to be drawn relating to the type of damage which is beginning to show. The commencement of wear of a cross head bearing of the piston membrane pump, for example, therefore exhibits a characteristically different change of the value profile from the commencement of wear of a connecting rod 30 bearing. An imminent membrane tear again leads to a characteristically different change in the actual value of the pressure profile before a failure of the membrane occurs to a level which causes the working fluid to mix with the liquid to be pumped. 2532596v1 WO 2012/062542 3 PCT/EP2011/068186 When operating a new or at least an undamaged piston membrane pump, the desired value profile of the pressure of the working fluid is preferably recorded for a time which includes at least a plurality of suction and pump cycles. By forming a mean value, an optimum desired value profile can then be calculated and saved in 5 the data memory. The actual pressure values during a suction or compression cycle which are measured during the operation of the piston membrane pump are then compared with the desired profile of the suction cycle and the compression cycle respectively. 10 Upper and lower envelope curves, between which the profile with respect to time of the actual values during the operation of the piston membrane pump is expected, can be determined based on the recorded desired value data, which if necessary are averaged by means of superimposition. Tests have shown that damage is indicated when an empirically determined minimum number of actual values per unit time lies 15 outside the region between the envelope curves. The pressure data are preferably recorded with a frequency of approximately 1 to 8, particularly preferably approximately 4 kHz. Tests have shown that, on the one hand, a sampling rate of this kind leads to an adequate time resolution for reliable detection 20 of impending damage without, on the other hand, an overly large and therefore expensive storage medium being required for storing the data over a longer period and in the order of magnitude of one year. For storage purposes, the pressure data are preferably digitized with a 16-bit 25 resolution. According to the invention, the system according to the invention for identifying damage to a piston membrane pump with a working fluid in continuous operation according to an above method comprises a pressure sensor for measuring the 30 pressure of the working fluid during the operation of the piston membrane pump.

WO 2012/062542 4 PCT/EP2011/068186 The pressure sensor is connected to a data-processing device which records discrete actual values of the pressure with a predetermined read-out frequency and stores them as a function of time in an actual value data memory. 5 Further, the system according to the invention comprises a desired value data memory in which the profile with respect to time of pressure data of an undamaged piston membrane pump is stored. In addition, a data-processing device is provided which includes a calculation routine which matches an upper and lower envelope curve, the distance between which can be specified, to the desired values and 10 checks whether the actual values lie between the two envelope curves and generates an alarm signal if a defined number or rate of deviating actual values is exceeded. The data-processing device is designed in such a way that the read-out frequency is 15 between 1 and 8, preferably 4 kHz. If the piston membrane pump is a pump for pumping sludge, then the pressure sensor preferably has a measuring range of approximately minus 5 to plus 400 bar. Basically, the pressure sensors used must have measuring ranges such that the 20 pressure of the working fluid to be expected in operation lies within the measuring range. If the pump is a multiple piston membrane pump, a separate pressure sensor is preferably provided for each working volume. 25 The invention will now be explained in more detail with reference to the attached drawings. In the drawings: Fig. 1 shows a longitudinal section through a piston membrane pump which is 30 intended for pumping sludge; Fig. 2 shows the section II in Figure 1 in an enlarged representation; WO 2012/062542 5 PCT/EP2011/068186 Fig. 3 shows the pressure of the working fluid as a function of time in a time interval comprising two pressure and two suction cycles for an undamaged piston membrane pump; s Fig. 4 shows the pressure profile in relation to time for imminent membrane damage; Fig. 5 shows the pressure profile for a suction cycle with torn membrane; 10 Fig. 6 shows the pressure profile with cross head bearing damage; Fig. 7 shows an enlarged individual representation of the pressure profile in the middle of the suction cycle in Fig. 6; 15 Fig. 8 shows the pressure profile with connecting rod bearing damage, and Fig. 9 shows the pressure profile in the second suction cycle shown in Fig. 8 in an enlarged individual representation. 20 Although not discernible in the drawing, the piston membrane pump designated in Fig. 1 as a whole by 100 is designed as a triple-piston membrane pump. Fig. 1 shows a longitudinal section through the middle part of the pump. The two further parts of the pump are designed correspondingly. 25 The piston membrane pump 100 shown is intended for pumping sludge. It comprises a motor-driven crankshaft 1, on the central crank pin 2 of which a connecting rod 3 is mounted with the help of a connecting rod bearing 4 which is designed as a roller bearing. A cross head 5 is mounted on the other end of the connecting rod 4 by means of a cross head bearing 6, which is likewise designed as a roller bearing. The 30 cross head 5 comprises sliding shoes 7 which act as its linear mounting in the sliding bearing walls 8.

WO 2012/062542 6 PCT/EP2011/068186 One end of a piston rod 9 is fixed to the cross head. The other end of the piston rod 9 carries a piston 10 which works in a cylinder 11. The bottom dead centre is shown in Fig. 1. 5 The cylinder 11 opens out into a working fluid volume 12 which is filled with a working fluid, usually a hydraulic oil. The working fluid - also referred to as the oil reservoir - which is not shown in the drawing fills the working volume up to a membrane 13 which is arranged in a membrane chamber 14. 10 The membrane chamber comprises an inlet 15, which is shown at the bottom in the drawing, and to which an inlet non-return valve 16 is flanged. It is designed in such a way that it opens when the sludge to be pumped flows in the direction of the arrow P1. 15 On the side opposite the inlet 15, the membrane chamber 14 comprises an outlet 17 to which an outlet non-return valve is flanged. It likewise opens when the sludge to be pumped flows in the direction of the arrow P2. A rotational actuation of the crankshaft 1 leads to the working fluid moving 20 backwards and forwards in the working fluid volume 12 and therefore the membrane being deflected alternately to the right or to the left as shown in Fig. 1 and 2. A deflection to the left leads to a closing of the outlet non-return valve and to a sucking in of sludge through the open inlet non-return valve 16. This pump phase is referred to as the "suction cycle". The subsequent displacement of the piston to the right as 25 shown in Fig. 1 and 2 leads to a closing of the inlet non-return valve 16 and a discharge of a volume 18 of sludge corresponding to the cylinder capacity via the now open outlet non-return valve 18 while displacing the membrane to the right as shown in Fig. 1 and 2. 30 As can be seen particularly in Fig. 2, a pressure sensor 20 is arranged on an elbow 19 which forms part of the working fluid volume 12. It communicates with the working fluid volume 12 and is designed in such a way that it can be used to measure the pressure of the working fluid as accurately as possible at a 4 kHz sample rate.

WO 2012/062542 7 PCT/EP2011/068186 As has been shown only schematically in Fig. 2, the pressure sensor is connected to a data processing device 21. This records actual values of the pressure at the 4 kHz sample frequency and stores them as a function of time in a data memory. Further, 5 the data-processing device 21 comprises a desired value data memory in which the profile with respect to time of pressure data of an undamaged piston membrane pump is stored. Finally, the data-processing device is provided with a calculation routine which 10 matches an upper and lower envelope curve, the distance between which can be specified, to the desired values and checks whether the actual values lie between the two envelope curves. If a defined number or a defined rate of deviating actual values is exceeded, the data-processing device generates a signal at a signal output 22. 15 Pressure data recorded on a piston membrane pump of this kind have a profile as shown in Fig. 3 for example. It can be clearly seen that the pressure data during a suction cycle - shown at the bottom - and during a compression cycle - shown at the top - oscillate about a mean value in a characteristic manner. The profile with respect 20 to time of the pressure for an undamaged membrane pump is reproduced in Fig. 3. Fig. 4 shows how the characteristic pressure profile changes when damage to the membrane is indicated. A plateau-shaped minimum can be clearly seen at the end of the suction cycle shown on the right in Fig. 4. This could already be identified before 25 a complete tear, which would cause a mixing of working fluid and sludge, occurred. The measurement of the pressure profile shown in Fig. 4 can therefore be used to be able to stop the piston membrane pump before greater damage occurs. For clarification, the pressure profile for a completely torn membrane is shown in Fig. 30 5. As Fig. 6 and 7 and Fig. 8 and 9 show, other damage also characteristically changes the pressure profile of the working fluid, for example in a suction cycle. Fig. 6 and 8 WO 2012/062542 8 PCT/EP2011/068186 show larger, high-frequency pressure variations at the beginning of a suction cycle which indicate damage to the cross head bearing. On the other hand, the larger high-frequency variations of the pressure at the end of the suction cycle over a longer period which are shown in Fig. 8 and 9 signal damage to the connecting rod 5 bearing. By comparing the pressure actual values of the working fluid determined during operation with empirically determined characteristic pressure profiles for particular types of damage which are stored in the data-processing device 21, these can be 10 detected with the help of the method according to the invention before total failures of the piston membrane pump occur. Consequential damage can therefore also be effectively avoided with the method according to the invention and the system according to the invention.

WO 2012/062542 9 PCT/EP2011/068186 List of references: 100 Piston membrane pump 1 Crankshaft 5 2 Crank pin 3 Connecting rod 4 Connecting rod bearing 5 Cross head 6 Cross head bearing 10 7 Sliding shoes 8 Sliding bearing wall 9 Piston rod 10 Piston 11 Cylinder 15 12 Working fluid volume 13 Membrane 14 Membrane chamber 15 Inlet 16 Inlet non-return valve 20 17 Outlet 18 Outlet non-return valve 19 Elbow 20 Pressure sensor 21 Data-processing device 25 22 Signal output

Claims

1. A method for identifying damage to piston membrane pumps (100) containing working fluids, wherein the pressure of the working fluid is 5 measured during operation in relation to the time and compared with a desired value profile, and that a signal is triggered if a predetermined deviation is exceeded, wherein the desired value profile is recorded for the operation of an undamaged piston membrane pump and stored in a data memory, 10 and in that upper and lower envelope curves, between which the profile with respect to time of the actual values during the operation of the piston membrane pump is expected, are determined based on the recorded desired value data, and that the signal is generated when a minimum number of actual values per unit time lies outside the region between the envelope 15 curves.

2. The method as claimed in claim 1, wherein a conclusion is drawn about the type of damage from the profile with respect to time of the deviations between desired and actual values. 20

3. The method as claimed in any one of claims 1 to 2, wherein the pressure data are recorded with an approximately 1 to 8, particularly preferably approximately 4 kHz rate. 25

4. The method as claimed in any one of claims 1 to 3, wherein the pressure data are preferably digitized with a 16-bit resolution.

5. A system for identifying damage to a piston membrane pump which contains a working fluid in continuous operation according to a method as 30 claimed in any one of claims 1 to 4, wherein the system includes a pressure sensor for measuring the pressure of the working fluid during the operation of the piston membrane pump which is connected to a data-processing 2532582v1 11 device which records actual values of the pressure with a predetermined read-out frequency and stores them as a function of time in an actual value data memory, that a desired value data memory, in which the profile with respect to time of 5 pressure data of an undamaged piston membrane pump is stored, is provided, and that the data-processing device includes a calculation routine which matches an upper and lower envelope curve, the distance between which can be specified, to the desired values and checks whether the actual values lie 10 between the two envelope curves and generates an alarm signal if a defined number or a defined rate of deviating actual values is exceeded.

6. The system as claimed in claim 5, wherein the read-out frequency is between 1 and 8, preferably 4 kHz. 15

7. The system as claimed in claim 5 or 6, wherein the pressure sensor has a measuring range of approximately minus 5 to plus 400 bar.

8. The system as claimed in any one of claims 5 to 7 for a plurality of 20 multi-chamber piston membrane pumps containing working fluid volumes, wherein a separate pressure sensor is provided for each working fluid volume. 253258201