METHOD AND DEVICE FOR CONDITION MONITORING OF A PISTON ROD SEAL SYSTEM OF A PISTON COMPRESSOR

Description

[0001] The invention relates to a method and a device for monitoring the condition of a piston rod sealing system of a piston compressor. State of the art

[0002] Document DE202014102844U1 discloses a piston rod packing for a piston compressor. Such piston rod sealing systems are used, for example, to seal the compression chamber of a piston compressor against ambient pressure. A reciprocating piston rod is connected on one side to a drive and on the other side to a piston of the piston compressor. The piston rod passes through the piston rod sealing system, so that the pressure between the compression chamber and the environment is reduced within the piston rod sealing system. To achieve a high sealing effect or low leakage for the piston rod sealing system, such a pressure packing preferably includes frictional sealing elements whose sealing surfaces bear against the piston rod and are therefore subject to wear. Such piston rod sealing systems have the disadvantage that their leakage increases depending on the operating time.Operators of such piston compressors require safe operation during a long operating time of, for example, at least 8000 hours continuously, without the leakage in the piston rod sealing system having an unacceptably high value, or without the sealing elements exhibiting high wear, breakage or even elastic-plastic deformation. Description of the invention

[0003] The object of the invention is to develop a method and a device that allow for more reliable operation of a piston compressor.

[0004] This problem is solved by a method comprising the features of claim 1. Claims 2 to 10 relate to further advantageous method steps. The problem is further solved by a monitoring system comprising the features of claim 11. Claims 12 to 14 relate to further advantageously configured devices.

[0005] The problem is solved in particular by a method for condition monitoring of a piston rod sealing system of a piston compressor comprising a compression chamber, wherein a gas is compressed from a suction pressure to a final pressure in the compression chamber of the piston compressor, wherein the piston rod sealing system comprises at least two chamber rings arranged successively in a longitudinal direction, each with at least one sealing element arranged therein, wherein a piston rod running through the sealing elements and the chamber rings is moved back and forth in the longitudinal direction and sealed by the sealing elements, wherein the piston rod sealing system has an inlet side and an outlet side, wherein the pressure of the compression chamber is applied to the inlet side, and wherein a differential pressure occurs between the inlet side and the outlet side, wherein the differential pressure that occurs has a static pressure component and a dynamic pressure component.wherein the dynamic pressure component is changed as a function of the crank angle, wherein a leakage gas is located in the chamber rings, wherein at least the dynamic pressure component of the leakage gas is measured in the piston rod sealing system, and wherein a change of state of at least one of the sealing elements is determined from a change in the dynamic pressure component as a function of time.

[0006] The problem is further solved in particular by a method for condition monitoring of a piston rod sealing system of a piston compressor, wherein the piston rod sealing system comprises at least two chamber rings arranged successively in a longitudinal direction, each with at least one sealing element arranged therein, wherein a piston rod running through the sealing elements and the chamber rings is moved back and forth in a longitudinal direction and sealed by the sealing elements, wherein the piston rod sealing system has an inlet side and an outlet side between which a differential pressure occurs, wherein the differential pressure that occurs has a static pressure component and a dynamic pressure component, and wherein a leakage gas is located in the chamber rings, wherein at least the dynamic pressure component of the leakage gas is measured in the piston rod sealing system.and wherein a change in the dynamic pressure component as a function of time determines a change in the state of at least one of the sealing elements.

[0007] The problem is further solved in particular by a monitoring system for the condition monitoring of a piston rod sealing system of a piston compressor, wherein the piston compressor comprises a piston and a compression chamber, wherein a gas can be compressed from a suction pressure to a final pressure by means of the piston in the compression chamber, wherein the piston rod sealing system comprises at least two chamber rings arranged successively in a longitudinal direction, each with at least one sealing element arranged therein, wherein a piston rod movable back and forth in the longitudinal direction passes through the sealing elements and the chamber rings, wherein the piston rod is connected to the piston, wherein the piston rod sealing system has an inlet side and an outlet side, wherein the pressure of the compression chamber is applied at the inlet side.wherein at least one pressure sensor is provided for measuring at least the dynamic pressure component of a leakage gas located in the chamber rings, and wherein a storage and evaluation device stores a plurality of measured dynamic pressure components, and wherein the evaluation device monitors a change in the dynamic pressure component as a function of time, and derives from this a change in the state of at least one of the sealing elements.

[0008] The problem is also solved in particular by a monitoring system for the condition monitoring of a piston rod sealing system of a piston compressor, wherein the piston rod sealing system comprises at least two chamber rings arranged successively in a longitudinal direction, each with at least one sealing element arranged therein, wherein a piston rod movable back and forth in the longitudinal direction passes through the sealing elements and the chamber rings, wherein the piston rod is connected to a piston, wherein the piston rod sealing system has an inlet side and an outlet side, and wherein a pressure sensor is arranged at at least one of the chamber rings for measuring at least the dynamic pressure component of a leakage gas located in the chamber rings, and wherein a storage and evaluation device stores a plurality of measured dynamic pressure components.and wherein the evaluation device monitors a change in the dynamic pressure component as a function of time, and derives from this a change in the state of at least one of the sealing elements.

[0009] The inventive method for monitoring the condition of the piston rod sealing system of a piston compressor has the advantage that the condition of the piston rod sealing system, or the wear of the sealing elements located in the piston rod sealing system, can be monitored in a simple, cost-effective, and very precise manner. Monitoring can be carried out, for example, at predetermined intervals, such as every few days, and particularly preferably continuously, by monitoring the condition of the sealing elements, for example, several times per minute or several times per day. With a prescribed continuous operating time of, for example, at least 8000 hours, this means that the piston rod sealing system is continuously monitored for approximately one year.The condition monitoring system according to the invention uses measured values ​​to determine the sealing effect of at least one sealing element and preferably the sealing effect of a plurality or all sealing elements of a piston rod sealing system, so that the condition of the respective sealing element and preferably the individual condition of each sealing element with regard to its sealing effect can be determined. The condition monitoring system according to the invention also has the advantage that a partial or complete failure of one or more of the sealing elements can preferably be predicted based on the respective determined condition and preferably detected with a sufficiently long lead time, so that the monitoring system can advantageously issue a warning or condition message even before a complete failure of the sealing elements, thus providing sufficient lead time for planning maintenance of the piston rod sealing system.The operational reliability advantageously gained through the condition monitoring according to the invention also allows the piston rod sealing system to be operated maintenance-free for a period of more than 8000 hours, if desired. On the other hand, serious failures of the piston rod sealing system, such as a break or elastic-plastic deformation of a sealing element, can also be clearly detected, and maintenance can therefore be scheduled accordingly. Preferably, the remaining period of reliable operation of the piston rod sealing system before maintenance becomes absolutely necessary can also be calculated.

[0010] In the inventive method, the condition or sealing effect of the sealing elements arranged in a piston rod sealing system of a piston compressor is measured. The piston compressor comprises a reciprocating piston and a compression chamber, wherein the piston acts on the compression chamber such that a gas in the compression chamber is compressed from a suction pressure to a final pressure. The piston rod sealing system comprises at least two chamber rings arranged successively in a longitudinal direction, each with at least one sealing element arranged therein, wherein a piston rod, extending through the sealing elements and the chamber rings and connected to the piston, is moved reciprocating in the longitudinal direction and sealed by the sealing elements.The piston rod sealing system has an inlet side and an outlet side, with the pressure of the compression chamber applied at the inlet side, and a differential pressure occurring between the inlet and outlet sides. Preferably, an external pressure or ambient pressure, preferably 1 bar, is applied at the outlet side. The resulting differential pressure has a static pressure component, preferably the suction pressure, and a dynamic pressure component, the dynamic pressure component being changed depending on the position of the piston or the crankshaft angle of the crankshaft driving the piston or piston rod. A leakage gas is present in the chamber rings and, if applicable, in the spaces between two chamber rings; the pressure of this gas can be measured or determined with a suitable sensor.Since the static pressure is a constant or very slowly changing pressure, the same static pressure preferably exists in the interior of all the chamber rings, as the static pressure is preferably reduced at the last sealing element facing the outlet side. Since all chamber rings preferably have essentially the same static pressure, no indication of the condition of an individual sealing element can be derived from the static pressure when using sealing elements designed as friction sealing rings. According to the invention, the pressure acting between the inlet side and the outlet side of the piston rod sealing system is divided into the static pressure and a dynamic pressure. The condition of a sealing element can be derived from the dynamic pressure.Of the friction-type sealing elements arranged in the piston rod sealing system, those facing the inlet side experience wear first because essentially the entire dynamic pressure is exerted on one of these elements. Due to the increasing wear of the sealing elements from the inlet side towards the outlet side, the dynamic pressure is measurable further and further within the piston rod sealing system, or in other words, the dynamic pressure penetrates deeper and deeper into the piston rod sealing system. Unlike static pressure, the behavior of the dynamic pressure provides valuable information regarding the condition of the individual sealing elements within the piston rod sealing system.It is particularly advantageous to use, measure and / or calculate only the dynamic pressure of the piston rod sealing system in order to derive the state or a change of state of at least one of the sealing elements and preferably a plurality of the sealing elements by observing the values ​​as a function of time.

[0011] Leakage gas present in the piston rod sealing system causes a static and / or dynamic pressure drop in the individual sealing elements of the piston rod sealing system. This leakage gas has a static pressure component and a dynamic pressure component. According to the invention, a change in the dynamic pressure component is monitored as a function of time, and from this change, a conclusion can be drawn about the change in condition of at least one sealing element, wherein this change in condition is typically caused by a change in the sealing, for example by wear, breakage, or elastic-plastic deformation of the sealing element. Brief description of the drawings

[0012] The drawings used to illustrate the exemplary embodiments show: Fig. 1 a schematically simplified longitudinal section through a piston compressor; Fig. 2 a longitudinal section through a piston rod sealing system; Fig. 3 a pressure curve at the inlet of the piston rod sealing system as a function of the crank angle; Fig. 4 the suction pressure and the dynamic pressure in successively arranged chamber rings with new sealing rings; Fig. 5 the suction pressure and the dynamic pressure in successively arranged chamber rings with sealing rings that partially show wear; Fig. 6 a longitudinal section through another piston rod sealing system; Fig. 7 another example of condition monitoring of a piston rod sealing system; Fig. 8 a dynamic pressure curve as a function of the crankshaft angle; Fig. 9 another example of condition monitoring of a piston rod sealing system; Fig.10. A schematically simplified longitudinal section through another embodiment of a cylinder with piston and piston rod sealing system.

[0013] In principle, identical parts in the drawings are provided with the same reference numerals. Ways to implement the invention

[0014] Figure 1Figure 1 shows a piston compressor 1 for compressing a gas, comprising a horizontally extending cylinder 2 and a piston 3 movable within the cylinder 2 in the longitudinal direction L or in the direction of the cylinder 2. The piston compressor 1 also includes a piston rod 16, a piston rod sealing system 12, a crosshead 17 with a linear guide 18, a push rod 19, a crank 20, and a drive shaft 21. In the illustrated embodiment, the piston 3 is designed to be double-acting and includes sealing rings 4 and a guide ring 5, wherein the piston 3 divides the interior of the cylinder 2 into a first interior space 6 and a second interior space 7, or a first compression chamber 6 and a second compression chamber 7, each of which has an inlet valve 8, 9 and an outlet valve 10, 11.The cylinder 2 is connected to the housing 15 via an intermediate piece 14, in which the piston rod sealing system 12 is also arranged. At least one sensor 26 is arranged in the piston rod sealing system 12 to detect pressure at least at one point within the piston rod sealing system 12. A monitoring device 22 detects, via a signal line 24 and an additional sensor (not shown in detail), for example, the displacement s(t) of the piston 3 in the cylinder 7 as a function of time t, the displacement s(t) of the piston rod 16 as a function of time t, or a rotation angle α(t) of the drive shaft 21 as a function of time t. The monitoring device 22 also detects the value of the at least one sensor 26 for measuring the pressure in the piston rod sealing system 12 via the signal line 25.

[0015] Figure 2Figure 1 shows a longitudinal section illustrating an embodiment of a piston rod sealing system 12 comprising six chamber rings 12a, each chamber ring 12a delimiting an inner cavity, a so-called chamber K, on ​​its outer surface. The piston rod sealing system 12 has an inlet side E, which, as shown in Figure 12, Figure 1The inlet side E is visibly oriented towards the interior 6 or the compression chamber 6 of the cylinder 2 and has an outlet side A opposite it, where atmospheric pressure is typically present. The inlet side E is preferably arranged adjacent to the compression chamber 6 and preferably forms a boundary of the compression chamber 6, so that the compression chamber 6 and the piston rod sealing system 12 are fluid-conducting via the inlet side E. Starting from the inlet side E, the piston rod sealing system 12, as illustrated by way of example, comprises six chamber rings 12a arranged successively in the longitudinal direction L, wherein the first four chamber rings 12a form a first chamber K1, a second chamber K2, a third chamber K3 and a fourth chamber K4, in each of which a sealing element 12b is arranged, each sealing element 12b comprising a sealing ring 12e, a support ring 12c and a cover ring 12d.The sealing elements 12b could also be designed differently. A pressure sensor 26 is arranged between the third and fourth chambers K3, K4 to measure the pressure of the leaking gas in the space between the third and fourth chambers K3, K4, with the pressure in the inner cavity of the fourth chamber K4 corresponding to this pressure. A second pressure sensor 26a is also arranged in the third chamber K3 to measure the pressure of the leaking gas in this chamber K3. The pressure sensors 26, 26a are connected to the control device 22 via electrical lines 25, 25a. Downstream of the fourth chamber ring 12a with chamber K4, a fifth and sixth chamber ring 12a are arranged to the left, each containing two locking rings 12j in its chambers K. The fifth chamber ring 12a also includes a leakage gas channel 12g, which opens into the environment at atmospheric pressure, so that this outlet can be referred to as the exit side A.The piston rod 16 passes through the locking rings 12j, the sealing elements 12b, and the chamber rings 12a. The piston rod sealing system 12 also includes a partial housing 12h. The piston rod sealing system 12 is arranged in the intermediate piece 14 and connected to the drive housing 15. The sealing elements 12b are designed as wear-prone friction rings whose sealing surfaces bear against the surface of the piston rod 16 to achieve very low leakage. To ensure that the high sealing effect of the sealing elements 12b is maintained during operation for as long as possible, the sealing elements 12b are designed such that their sealing surfaces remain in contact with the piston rod 16 as completely as possible despite progressive wear, thus minimizing the passage area for leakage gas. The sealing elements 12b therefore exhibit wear compensation. The piston rod sealing system 12 according to... Figure 2comprises a series connection of four such gas-tight sealing elements 12b, each sealing element 12b being arranged in a separate chamber ring 12a. Another embodiment could, in contrast to the embodiment according to Figure 2 , have no leakage gas channel 12g, wherein in the last two chamber rings 12a arranged on the left, sealing elements 12b are arranged instead of the locking rings 12j, so that the outlet side A, as in Figure 2 shown, located on the left in the area of ​​the piston rod 16.

[0016] Figure 3Figure 1 shows an example of a possible pressure profile of the pressure in the first compression chamber 6, also referred to as cylinder pressure DK or differential pressure DK between the inlet side E and the outlet side A, during operation of the piston compressor 1, as a function of the crankshaft angle. The differential pressure DK is caused by the fluid compressed by the piston 3 within the cylinder 2. A fluid to be pumped is drawn in by the piston 3 at a suction pressure DA and compressed in the cylinder 2 to a final pressure DE. During this suction and subsequent compression process, the pressure at the inlet side E of the piston rod sealing system 12 exhibits the illustrated profile of the cylinder pressure DK or differential pressure DK as a function of the crankshaft angle α.The outlet side A and the leakage gas channel 12g exhibit, for example, the pressure of a subsequent compression stage or, in the present example, an ambient pressure DU of 0 bar. The pressure occurring in the piston rod sealing system 12 can, as in . Figure 3The pressure components shown can be divided into a static pressure component DS and a dynamic pressure component DD. The static pressure component DS is preferably equal to the suction pressure DA. The dynamic pressure component DD is the pressure component that changes with time or with the crank angle, where the dynamic pressure component DD at the inlet side E corresponds to the difference between the cylinder pressure DK applied to the piston rod sealing system 12 and the suction pressure DA or the static pressure DS. The static pressure component DS is the difference between the suction pressure DA of the compression stage under consideration and the pressure DU applied at the outlet side A, where in this example the pressure DU corresponds to atmospheric pressure, so that the static pressure component corresponds to the suction pressure DA.

[0017] Figure 4 shows an example of condition monitoring of the piston rod sealing system 12 according to Figure 2 The first chamber ring 12a forms chamber K1, the second chamber ring 12a chamber K2, the third chamber ring 12a chamber K3, and the fourth chamber ring 12a chamber K4. In the Figure 4 In the illustrated example, a pressure sensor 26, 26a is arranged in each of the four chambers, with the aid of which the pressure in the respective chamber can be measured. The pressure sensors 26, 26a can be arranged in a variety of ways to measure the pressure in the respective chamber, for example also inside the chamber ring 12a, or outside the chamber ring 12, with a fluid-conducting connection to the respective chamber. Figure 4The figure shows, for each of the four chambers K1, K2, K3, K4, the static pressure DA in the respective chamber and the maximum pressure Dmax, which is composed of the static pressure component DS and the dynamic pressure component DD. In the example shown, the static pressure component DS corresponds to the suction pressure DAa. The pressure Dk or differential pressure Dk curve is fundamentally dependent on the crankshaft angle or the piston position as a function of time. The maximum pressure Dmax occurring in the respective chamber K1, K2, K3, K4, or the sum of the static pressure component DS and the dynamic pressure component DD, depends, however, on the sealing effect or the condition or wear of the respective sealing elements 12b.The piston rod sealing system 12 exhibits a high maximum pressure D Max only in chamber K1 when new, because the entire dynamic pressure component DD is sealed at the first rubbing sealing element 12b, which is located in chamber K1. With increasing operating time, the sealing elements 12b are subject to wear, which, as shown in . Figure 5 As shown, the maximum pressure D Max can penetrate from the inlet side E into further interior spaces K2, K3, K4 of chamber rings 12a, or propagate from the inlet side E into these further chambers K2, K3, K4, so that in the individual chambers K1 to K4, for example, the pressure in Figure 5 The maximum pressures D Max shown can be measured. The condition of the piston rod sealing system 12 can now be monitored, for example, in the following ways: A) The pressure of the leaking gas is measured in a single chamber, namely in chamber K4, which is furthest from the inlet side E. As long as the pressure measured therein essentially corresponds to the suction pressure DA, it can be concluded that at least one of the sealing elements 12b arranged upstream towards the inlet side E in chambers K1, K2, K3 is fulfilling its sealing function, so that no increased pressure is measured in chamber K4. From this, it can be concluded that the dynamic pressure component DD is sealed by one of the sealing elements 12d located in chambers K2, K3, or K4, and preferably completely sealed. In the exemplary embodiment according to Figure 5In chamber K4, an increased maximum pressure Dmax is measured, from which it can be concluded that all sealing elements 12b arranged in chambers K1, K2, and K3 are no longer able to achieve a complete seal due to wear. B) The pressure of the leaking gas is measured in each of the chambers K1, K2, K3, and K4, so that, in addition to the value of the maximum pressure amplitude Dmax in each chamber, a mutual comparison of the dynamic pressure components DD of the individual chambers K1 to K4 is also possible, or rather, the distribution of the pressure in the individual chambers. The in Figure 5The distribution shown indicates that the sealing elements 12b in chambers K1, K2, and K3 already exhibit considerable wear due to the measured, increased maximum pressure Dmax, and that the dynamic pressure component DD is essentially only sealed by the sealing element 12b located in chamber K4. C) The following are particularly revealing: Figure 5The measurement results shown are valid if they are measured daily over a longer period, for example, a month or a year, and the measurement results are stored, and if the changes in the measurement results over time are analyzed. With increasing operating time of the piston rod sealing system 12, the maximum pressure Dmax measured in the individual chambers K1, K2, K3, and K4, or the dynamic pressure component DD, that is, the difference between the maximum pressure Dmax and the static pressure DA, starting from chamber K1, will increase towards the outlet side A, so that the values ​​in Figure 5 The measurement results shown indicate which of the sealing elements 12b and to what extent the individual sealing elements 12b still contribute to the sealing, or is derived from Figure 5It is evident to what extent the individual sealing elements 12b are already worn. Or, in other words, the maximum pressure Dmax or the dynamic pressure component DD penetrates deeper and deeper into the piston rod sealing system 12, or into the subsequent chambers K2, K3, and K4, starting from chamber K1, as the operating time increases. Thus, a change in the condition of the sealing elements 12b can be determined from this change in the dynamic pressure components DD in the individual chambers as a function of time. The condition of the piston rod sealing system 12, and in particular the condition or wear of the individual sealing elements 12b, or at least of one of the sealing elements 12b, can therefore be determined very precisely.observable, so that, for example, it can be determined whether the piston rod sealing system 12 is still sealing reliably, or it can be extrapolated how long the piston rod sealing system 12 is expected to continue sealing reliably, or it can be estimated which of the sealing elements 12b and preferably also by what point in time the individual sealing elements 12b should be replaced or serviced.

[0018] Figure 7 Figure 12 shows another example of condition monitoring of a piston rod sealing system. Figure 7 The measured values ​​of the maximum pressure D Max of chambers K1 to K6 shown were measured on a piston rod sealing system 12, which, unlike the one in Figure 2 The illustrated piston rod sealing system has six chambers K1 to K6 arranged successively in the longitudinal direction L, each with a sealing element 12b arranged therein, wherein the sealing elements 12b, in contrast to the embodiment according to Figure 2 The piston rod 16 does not touch, or only touches slightly, so that at least a gap exists between the end face of the sealing elements 12b and the piston rod 16. With such a series connection of frictionless sealing elements 12b, the pressure difference is distributed in varying amounts across all chambers K1 to K6. The method according to the invention is also suitable for condition monitoring of such a piston rod sealing system 12. Figure 7 The values ​​U1 to U6 show the maximum pressure D Max in the respective chamber K1 to K6 of a piston rod sealing system 12 in new condition. Figure 7The values ​​V1 to V6 indicate the maximum pressure Dmax present in the respective chambers K1 to K6 after a certain operating period, for example, after 2000 operating hours. The change in the dynamic pressure component DD during this operating period, or the change in the condition of each sealing element 12b located in the respective chambers K1 to K6, is evident from the difference between the values ​​U1 and V1, U2 and V2, etc. Thus, the condition of the piston rod sealing system 12, or the condition of the individual sealing elements 12b within it, can be monitored. This allows, for example, the early detection of any necessary maintenance of the sealing elements 12b, ensuring both the safe operation of the piston rod sealing system 12 and determining a time window for required maintenance.

[0019] Figure 6shows a longitudinal section through another piston rod sealing system 12, comprising a first partial packing 12x and a second partial packing 12y. The first partial packing 12x comprises the same components as in Figure 4 The illustrated chamber rings 12a with chambers K8, K9, K10, K11 and frictional sealing elements 12b arranged in these chambers, each comprising a sealing ring 12e, a support ring 12c and a cover ring 12d. The piston rod sealing system 12 according to Figure 6The second partial packing 12y also comprises a leakage gas channel 12g and, downstream towards the outlet side A, two chamber rings 12a with locking rings 12j arranged therein. The second partial packing 12y comprises seven chamber rings 12a arranged successively in the longitudinal direction L, with chambers K1, K2, K3, K4, K5, K6, and K7, wherein a pressure-breaking ring 12i is arranged as a sealing element 12b in each of these chambers. Such a pressure-breaking ring 12i has the property that it does not completely seal the leakage gas in the longitudinal direction L, but that it reduces the amplitude of the dynamic pressure component DD. In the illustrated embodiment, a sensor 26 for monitoring the pressure in chamber K11 and a sensor 26a for monitoring the pressure in chamber K7 are arranged. Such an arrangement is, in turn, suitable for monitoring the condition of the piston rod sealing system 12 or the condition of the sealing elements 12b located therein. Figure 9Figure 1 shows the measured values ​​V7 and V11 of the maximum pressure Dmax in chambers K7 and K11 of a piston rod sealing system 12 in its new condition. Figure 2 shows the measured values ​​W7 and W11 of the maximum pressure Dmax in chambers K7 and K11 after, for example, 5000 operating hours. Figure 3 shows the measured values ​​X7 and X11 of the maximum pressure Dmax in chambers K7 and K11 after, for example, 10000 operating hours. These values ​​show that the piston rod sealing system 12 still functions reliably after 5000 operating hours. However, value X7 shows that the pressure-breaking rings 12i, or the second partial packing 2y, no longer provide sufficient sealing after 10000 operating hours, whereas the sealing effect of the first partial packing 12x still meets the requirements.

[0020] In a further advantageous embodiment, the piston rod sealing system 12 can be configured according to Figure 6Starting from the inlet side E, a pressure sensor 26a in the last chamber ring 12a with pressure breaker ring 12i arranged therein, therefore in chamber K7, and a pressure sensor 26 in the first chamber ring 12a with friction sealing ring 12e arranged therein, therefore in chamber K8, are arranged in order to detect the state or a change of state of the pressure breaker ring 12i arranged in chamber 7 in the best possible way.

[0021] In the Figures 4 , 5 and 7 In the illustrated embodiments, the pressure in the respective chambers K is monitored by measuring the maximum pressure present in each chamber. Instead of the maximum pressure, the pressure profile as a function of the crankshaft angle can also be measured. Figure 8The figure shows such a pressure curve DV as a function of the crankshaft angle. From the increase during the rising flank, the maximum value, the crankshaft angle at which the maximum value is reached, or the decrease during the descending flank, statements can also be made about the condition of the sealing elements 12b.

[0022] It can prove advantageous to measure a temperature T at least at one point in the piston rod sealing system 12, in particular the temperature of the piston rod 16, for example with an infrared sensor. An intact, functional friction ring causes the piston rod 16 to heat up due to friction. Measuring the temperature at one point in the piston rod sealing system 12, especially on the piston rod 16, provides additional information about the condition of a sealing element 12b. Furthermore, a broken sealing element 12b and / or an elastically deformed sealing element 12 can also lead to heating of the piston rod 16, and this condition can be detected by measuring the temperature.

[0023] Figure 10Figure 1 shows a schematically simplified longitudinal section through another embodiment of a cylinder 2 with a double-acting piston 3, which divides the interior into a first compression chamber 6 and a second compression chamber 7. In contrast to the embodiment according to Figure 2, the following applies: Figure 1 An additional piston rod sealing system 12 is arranged on the front face of the second compression chamber 7, wherein the piston rod 16, in contrast to the embodiment according to Figure 1 , extending from the piston 3 in the direction of the longitudinal axis L, passes through the additional piston rod sealing system 12, and is slidably mounted in the direction of the longitudinal axis L. Thus, both piston rod sealing systems 12 have an inlet side E and an outlet side A, and at least one and preferably both piston rod sealing systems 12 can be operated with the condition monitoring method according to the invention.

[0024] In the illustrated example, the piston compressor 1 is always depicted as a horizontal piston compressor. However, the piston compressor could also run in a different direction and, in particular, could be designed to run vertically, with a vertically oriented piston rod.

[0025] All illustrated embodiments show a double-acting piston 3. However, the piston could also be designed as a single-acting piston, in that the cylinder 2 has only a single compression chamber 6.

[0026] A plurality of piston compressors 1 or a plurality of cylinders 2 could also be connected in series, for example 2, 3, 4 or 5, wherein the final pressure of the preceding cylinder forms the suction pressure of the following cylinder. In such a series arrangement, for example, the suction pressure DA of one of the cylinders could be 80 bar, and the final pressure DE of this cylinder could be 300 bar. At least one, and preferably all, of such series-connected piston compressors 1 or the series-connected cylinders 2 can be operated according to the inventive method or have the inventive device.

Claims

1. A method for monitoring the condition of a piston rod sealing system (12) of a reciprocating compressor (1) comprising a compression chamber (6, 7), wherein in the compression chamber (6, 7) of the reciprocating compressor (1) a gas is compressed from a suction pressure (DA) to a discharge pressure (DE), the piston rod sealing system (12) comprising at least two chamber rings (12a) arranged one after the other in a longitudinal direction (L) and each having at least one sealing element (12b) arranged therein, wherein a piston rod (16) ext,ending through the sealing elements (12b) as well as the chamber rings (12a) is moved back and forth in the longitudinal direction (L) by means of a a crank (20) being provided on a drive shaft (21) and is sealed by the sealing elements (12b), wherein the piston rod sealing system (12) has an inlet side (E) and an outlet side (A), wherein the pressure of the compression chamber (6, 7) is applied to the inlet side (E), and wherein a differential pressure (DK) occurs between the inlet side (E) and the outlet side (A), the differential pressure (DK) occurring having a static pressure component (Ds) and a dynamic pressure component (DD), wherein the dynamic pressure component (DD) is changed as a function of a crank angle of the crank (20), and wherein a leakage gas is located in the chamber rings (12a), wherein at least the dynamic pressure component (DD) of the leakage gas is measured in the piston rod sealing system (12), and wherein a change in the state of at least one of the sealing elements (12b) is determined from a change in the dynamic pressure component (DD) as a function of time.

2. The method of claim 1, characterized in that the static pressure component (DS) corresponds to the suction pressure (DA), and in that the dynamic pressure component (DD) is determined as the difference between the differential pressure (DK) and the static pressure component (DS).

3. The method of claim 1 or 2, characterized in that the sealing element (12b) is configured to be gas-tight by forming a friction seal ring (12e) that abuts the piston rod (16), the friction seal ring (12e) being worn by the friction occurring between the friction seal ring (12e) and the piston rod (16).

4. The method of claim 1-3 , characterized in that the sealing element (12b) comprises at least one pressure breaker ring (12i) that does not seal completely.

5. The method according to one of claims 3 or 4, characterized in that the dynamic pressure component (DD) of the leakage gas is measured at least at that chamber ring (12a) which is arranged furthest away from the inlet side (E ) in the longitudinal direction (L).

6. The method according to one of claims 4 or 5, characterized in that the piston rod sealing system (12) comprises, starting from the inlet side (E ) in the longitudinal direction (L), a plurality of chamber rings (12a) with pressure breaker rings (12i) arranged therein and subsequently a plurality of chamber rings (12a) with friction seal rings (12e) arranged therein, and that the dynamic pressure component (DD) of the leakage gas is measured in the last chamber ring (12a) with pressure breaker ring (12i) arranged therein or in the first chamber ring (12a) with friction seal ring (12e) arranged therein.

7. The method according to one of claims 1-6, characterized in that the dynamic pressure component (DD) of the leakage gas is measured in a plurality of chamber rings (12a), and that the state of the sealing element (12b) located in the respective chamber ring (12a) is determined on the basis of the maximum amplitude (Dmax) measured in the individual chamber rings (12a).

8. The method according to claim 7 , characterized in that a maximum amplitude (Dmax1, Dmax2, Dmax3) of the dynamic pressure components (DD) present in the respective chamber ring (12a) increases from the inlet side (E ) towards the outlet side (A) with increasing operating time of the piston rod sealing system (12), and in that the state of the sealing elements (12b) located in these chamber rings (12a) is determined from the difference in the maximum amplitude (Dmax1, Dmax2, Dmax3) of two adjacent chamber rings (12).

9. The method according to one of the preceding claims, characterized in that a change in the dynamic pressure component (DD) is monitored for a period of at least 2000 hours and preferably for at least 8000 hours.

10. The method according to one of the preceding claims, characterized in that a temperature (T) is measured in the piston rod sealing system (12) at least at one point, in particular the temperature of the piston rod (16).

11. A reciprocating compressor (1) with a monitoring system, wherein the piston compressor (1) comprises a piston (3) and a compression chamber (6, 7), wherein a gas can be compressed by means of the piston (3) in the compression chamber (6, 7) from a suction pressure (DA) to a discharge pressure (DE), wherein the reciprocating compressor (1) furthermore comprises a piston rod sealing system (12) which comprises at least two chamber rings (12a) arranged one after the other in a longitudinal direction (L), each with at least one sealing element (12b) arranged therein, wherein a piston rod (16) which is movable back and forth in the longitudinal direction (L) by means of a a crank (20) being provided on a drive shaft (21) extends through the sealing elements (12b) as well as the chamber rings (12a), wherein the piston rod (16) is connected to the piston (3), wherein the piston rod sealing system (12) has an inlet side (E ) and an outlet side (A), the pressure of the compression chamber (6, 7) being applied to the inlet side (E), characterized in that at least one pressure sensor (26, 26a) for measuring at least the dynamic pressure component (DD) of a leakage gas located in the chamber rings (12a) is provided, and wherein a storage and evaluation unit (22) stores a plurality of measured dynamic pressure components (DD), and wherein the evaluation unit (22) monitors a change in the dynamic pressure component (DD) as a function of time and derives therefrom a change in state of at least one of the sealing elements (12b).

12. The reciprocating compressor with monitoring system according to claim 11, characterized in that said monitoring system determines the dynamic pressure component (DD) as the difference between the differential pressure (DK) and the static pressure component (DS).

13. The reciprocating compressor with monitoring system according to claim 11 or 12, characterized in that the sealing elements (12b) are designed as friction rings resting against the piston rod (16), and in that a pressure sensor (26) is arranged at least at the chamber ring (12a) arranged closest to the outlet side (A) for measuring at least the dynamic pressure component (DD) of a leakage gas located in the chamber ring (12a).

14. The reciprocating compressor with monitoring system according to one of the claims 11 or 13, characterized in that in the running direction (L) of the piston rod (16), starting from the inlet side (E ), sealing elements (12b) designed as pressure breaker rings (2i) are arranged first, and in that sealing elements (12b) designed as friction rings are arranged subsequently towards the outlet side (A), and in that in the longitudinal direction (L) at least one pressure sensor (26) is arranged between the pressure breaker rings (12i) and the sealing elements (12b) designed as friction rings.