Eccentric screw pump

Description

[0001] The invention relates to an eccentric screw pump with at least a stator, a rotor rotating in the stator, a pump housing (e.g. suction housing) connected to the stator (e.g. suction side) which has at least one inlet or outlet opening for the medium to be pumped, a connecting shaft driven by the drive and e.g. (detachably) connected to the drive, which rotates centrally around an axis under ideal conditions, and a coupling rod (preferably arranged in the pump housing) which is pivotally connected to the connecting shaft at the drive-side end and to the rotor at the rotor-side end and generates an eccentric movement of the rotor end when the connecting shaft rotates centrally.

[0002] Such an eccentric screw pump is used to pump a wide variety of media, and especially highly viscous liquids, in various industrial sectors. The liquids to be pumped can also contain solids, for example.

[0003] The stator preferably consists of an elastic or elastomeric material and is generally surrounded by a stator jacket or housing. The pump housing connected to the stator on the suction side is generally referred to as the suction housing, and the housing connected to the stator on the pressure side, for example, as the pressure port. However, it is also possible to operate the pump in the opposite direction of flow, in which case the suction housing (as the pump housing) would be located on the pressure side. Therefore, within the scope of the invention, the designation of the pump housing as the suction housing is independent of the actual flow direction. This is the housing located between the stator and the drive. The rotating connection, which simultaneously ensures eccentricity, between the drive or the centrally rotating connecting shaft and the eccentrically rotating rotor is achieved via a coupling rod, for example, located in the pump housing, which is...The drive-side joint connects the drive shaft to the rotor, and the rotor to the rotor via a rotor-side joint. Alternatively, the eccentricity can also be achieved through other means, i.e., without joints, for example, by a flexible or flexurally elastic connecting rod. A connecting rod, therefore, refers to an element that, through its articulated design or coupling, ensures the eccentricity of the rotor or enables or generates the eccentric movement between the centrally rotating connecting shaft and the rotor or its eccentrically rotating rotor end. The connecting rod can also carry one or more conveying elements, or conveying elements, such as a screw or transport screw, can be attached to the connecting rod. This is implemented, for example, in progressive cavity pumps designed as hopper pumps. The screw can be a hollow screw or a solid screw. The connecting shaft is also referred to as a plug shaft.It is generally connected directly or indirectly to the output shaft of the drive and serves as a connecting piece between the drive's output shaft and the power transmission components of the pump. The connecting housing, located between the pump housing (suction housing) and the drive, serves, for example, to accommodate, secure, and support the pump housing on the one hand and the drive on the other. This connecting housing is typically mounted on a base plate or directly on a foundation, supporting and carrying the pump housing's drive. Suspended configurations are also possible. In practice, a distinction is made between connecting housing designs that function as a "lantern" on the one hand and a "bearing stand" on the other. The connecting housing can always be designed as an open housing or at least as one that can be opened, meaning it is accessible from the outside through an opening. The sealing of the pump housing, or...The seal between the suction housing and the environment, or between the suction housing and the connecting housing, is achieved, for example, via a shaft seal. The connecting shaft is sealed with the shaft seal, thus creating a liquid-tight separation between the suction housing and the environment. The shaft seal can, for example, be designed as a mechanical seal.

[0004] Such eccentric screw pumps are known, for example, from DE 10 2014 112 552 A1, DE 10 2010 034 440 A1, WO 2009 / 024279 A1 and DE 10 2018 102 640 A1.

[0005] In practice, progressive cavity pumps and their components are subject to wear during operation, necessitating regular maintenance or repairs. Typical wear parts include the elastic stator and the rotor rotating within it. Wear also occurs in bearings (e.g., in the drive or gearbox) and joints. Therefore, it is known to monitor the wear of these components during operation by determining suitable parameters. For example, to monitor the stator condition, the flow rate can be recorded and compared with the respective rotor speeds. Similarly, the pump's back pressure can be determined in relation to its rotational speed. These known methods thus provide an indirect determination of the wear condition.

[0006] Alternatively, DE 20 2005 008 989 U1 discloses an eccentric screw pump in which a sensor is assigned to the stator, measuring compressions and / or movements of the stator or the elastic material during rotor rotation. The sensor can be, for example, a pressure sensor or a force sensor integrated into the stator that registers stator compressions. Here, too, the primary purpose is monitoring stator wear.

[0007] Vibration measurements are used in practice to detect potential wear on the bearings and joints of pumps. This applies, for example, to centrifugal pumps, where vibration measurements are used to detect bearing damage.

[0008] Furthermore, DE 10 2005 019 063 B3 discloses a method for operating a progressive cavity pump to monitor different operating conditions, wherein preliminary tests are carried out on the progressive cavity pump for certain negative operating conditions, the resulting specific damage frequency profile is stored and compared during the operating phase with an overall vibration profile that is taken from only one point on the progressive cavity pump. The sensor is located, for example, at the stator input.

[0009] Finally, DE 10 2015 112 248 A1 describes an eccentric screw pump with an adjustment mechanism for the stator-rotor system. At least one sensor determines the actual operating parameters of the stator-rotor system, and a control unit then actuates the adjustment mechanism based on these parameters. The wear condition is determined either directly via a sensor embedded in the stator's elastomer material or indirectly via the elastomer's reaction forces on other components. The sensor can measure, for example, the pump pressure, rotational speed, temperature, and / or flow rate.

[0010] JP2018021876A discloses an eccentric screw pump according to the preamble of claim 1.

[0011] Based on the prior art, the invention addresses the technical problem of further developing a known progressive cavity pump in such a way that damage, and in particular joint and / or bearing damage, of the pump can be detected in a simple and reliable manner.

[0012] To solve this problem, the invention teaches, in the case of a generic eccentric screw pump of the type described above, that at least two sensors are arranged in the area of ​​the connecting shaft for the detection or measurement of a runout deviation, which are arranged in different angular positions offset from each other by an angular offset and which each determine a movement profile of the connecting shaft in which the distance of the surface of the connecting shaft from the respective sensor is measured at different angular positions.

[0013] According to the invention, damage to the bearings (e.g., in the drive or its gearbox) and / or joints within the pump is not detected or monitored by conventional vibration measurement. Instead, the runout deviation of the connecting shaft or its (largely) centrally rotating portion is directly determined. The invention is based on the understanding that wear on bearings, guides, and / or joints increases the runout deviation of the ideally centrally rotating portion of the connecting shaft. Therefore, by measuring or monitoring the runout or runout deviation of the connecting shaft, wear on the bearings, guides, and / or joints of the pump can be quickly, easily, and very reliably detected.

[0014] Such a sensor is preferably designed as a non-contact sensor, e.g., a proximity sensor. It can preferably be an inductive proximity sensor. Alternatively, optical sensors, e.g., optical proximity sensors, can also be used. It is always possible to determine any potential runout of the connecting shaft, which ideally rotates concentrically with perfect concentricity, using such a sensor, preferably by measuring the distance between the surface of the connecting shaft, which has a circular cross-section, and the sensor. In ideal operation, the distance of the shaft surface from the sensor does not change during rotation, so the measured runout deviation – recorded over time – is zero. If damage or other factors occur, the sensor can be used to detect the runout deviation.If (increased) runout deviations occur due to wear on bearings, guides and / or joints, the sensor does not measure a distance that is constant over time and consequently over the angle of rotation, but rather the distance varies over time, with the time corresponding to the respective angular position of the connecting shaft at that time.

[0015] According to the invention, each of these two sensors measures a (separate) motion profile, i.e., the function of the distance over time and thus over the rotation angle of the connecting shaft. Combining two such measurements enables particularly reliable detection of runout deviations. With certain phenomena, a single sensor may not reliably detect a runout deviation. The use of two sensors (or optionally more than two sensors) improves the detection of runout deviations. Within the scope of the invention, the angular offset is at least 10° and / or a maximum of 180°. Preferably, the angular offset is at least 30° and / or a maximum of 150°. In practice, an angular offset of approximately 90° is advantageous.

[0016] Of particular importance in an eccentric screw pump is the fact that a concentric movement of the drive is converted into an eccentric movement of the rotor or rotor end via the so-called connecting rod. The runout deviation is measured in the section of the drive train that rotates concentrically, preferably on the last cylindrical part of the rotating train (viewed from the drive side) that is (still) rotating concentrically. Within the scope of the invention, this concentrically rotating cylindrical part, or part with a circular diameter, is referred to as the connecting shaft. This connecting shaft is connected at its end opposite the drive to the connecting rod and consequently to the part that no longer rotates concentrically.

[0017] Of particular importance is the fact that, in progressive cavity pumps, in addition to the disturbances caused by wear of bearings, guides and / or joints, further disturbances arise from the direct contact between the rotor and stator. However, the measurement according to the invention relates directly to the concentricity, so that other disturbances do not interfere with the detection.

[0018] Preferably, the sensor(s) – relative to the axial extent of the pump – are arranged between the drive-side end of the connecting shaft and a coupling-side shaft seal, e.g., a mechanical seal. The progressive cavity pump has an (additional or separate) connecting housing between the pump housing or suction housing and the drive, wherein the connecting shaft is arranged at least partially within this connecting housing. Such a connecting housing can be designed as a lantern or a bearing support. The two sensors are arranged or attached in or to this connecting housing, i.e., in or to the lantern or the bearing support. From a design perspective, it is possible to integrate the sensors into the cover plates on the lantern or the bearing support. The connecting housing can be a partially open housing, the openings of which can be closed with one or more cover plates.The sensors can be connected to such cover plates. However, the sensor(s) can also be connected to permanently installed parts of the junction box.

[0019] Overall, the eccentric screw pump according to the invention enables the early detection of wear on bearings, guides, and / or joints in a simple manner. This allows for better planning of maintenance, repairs, and other servicing. Unplanned downtime can be reduced or avoided, thus increasing system availability. The detection method according to the invention is characterized by very low susceptibility to interference. In particular, it is less susceptible to disturbances in the pump's environment than, for example, vibration measurements. While vibration measurements, for instance, can also react to disturbances that may be caused by stator wear, the measurement of runout deviation according to the invention in the area of ​​a centrally rotating part enables targeted and unaffected detection of runout deviations.

[0020] The invention relates not only to the progressive cavity pump itself, but also to a method for operating such a progressive cavity pump. According to the invention, the described sensors determine a movement profile of the connecting shaft for different angular positions by determining or measuring the distance of the (circular or cylindrical surface) of the connecting shaft from the respective sensor. Consequently, according to the invention, any runout deviations are monitored during operation of the progressive cavity pump using the sensors according to the invention. .

[0021] It is within the scope of the invention that the determined or measured values, i.e., the values ​​measured by the sensors (e.g., distance values ​​representing a runout deviation), are compared with previously stored reference values, and that if a predefined deviation is exceeded, a message (error message) is generated and / or displayed and / or transmitted. In the simplest case, therefore, no feedback of a possible tolerance exceedance to the pump or the pump control is provided; instead, simple condition monitoring takes place, which indicates an intolerable runout deviation, e.g., visually and / or audibly. In a possible further development, however, a combination with a pump control is also possible, so that the pump is operated and / or switched off depending on the measured values ​​or on a comparison of the measured values ​​with stored reference values.In preferred embodiments, however, the monitoring serves to detect damage early, e.g. joint damage or bearing damage, in order to better plan subsequent maintenance work, so that immediate feedback to the pump control is not required.

[0022] Wear on joints, bearings, or guides includes, among other things, wear in the joints that connect the connecting rod to the rotor on one side and to the connecting shaft (e.g., a stub shaft) on the other. Such wear can lead to runout. The same applies to wear on bearings or guides, which includes, for example, the guides in the area of ​​the shaft seal (e.g., a mechanical seal). Wear can also be detected in the bearings within the drive or its gearbox. Wear on the connecting rod, which is located between the rotor and the connecting shaft, also results in runout of the connecting shaft and is thus detected.

[0023] The invention will now be explained in more detail with reference to the drawings, which merely illustrate exemplary embodiments. They show Fig. 1 shows a simplified side view of an eccentric screw pump, Fig. 2 shows an enlarged section of the object. Fig. 1 Fig. 3 shows a modified embodiment of an eccentric screw pump in a simplified side view, and Fig. 4 shows a section of the object according to Fig. 3 in a perspective view.

[0024] The figures each depict an eccentric screw pump, which in its basic structure comprises a stator 1, a rotor 2 rotating within the stator 1, and a drive 3 for the rotor 2. A pump housing 4, referred to as the suction housing 4, is connected to the stator 1 (e.g., on the suction side). A housing part connected to the stator 1 at the opposite end (e.g., on the discharge side) is referred to as the connection port or discharge port 5. The pump housing 4 has an inlet opening 6 (or, depending on the operating direction, an outlet opening) through which, for example, the medium to be pumped is supplied. This medium is conveyed from the pump housing 4 via the stator / rotor 1, 2 to the discharge port 5. The drive 3 is equipped with an output shaft (not shown) which is connected to a connecting shaft 9. In this embodiment, this connecting shaft 9 is designed as a plug-in shaft 9.In the exemplary embodiment, the rotor 2 is connected to the connecting shaft 9 via a rigid connecting rod 10. The connecting rod 10 is connected to the connecting shaft 9 via a drive-side joint 11 and to the rotor 2 via a rotor-side joint 12. Thus, the connecting rod 10 and the joints 11 and 12 enable the eccentric movement of the rotor 2 and / or the rotor end 7. The drive therefore acts on the connecting shaft 9, which, under ideal conditions, rotates concentrically about an axis R. The eccentric movement of the rotor end 7 is generated via the connecting rod 10. However, it is also possible to use embodiments without joints, for example, by making the connecting rod elastic. Such an embodiment is not shown. The (elastic) connecting rod can also be formed integrally with the rotor and thus constitute one end of the rotor.Furthermore, embodiments in which the connecting rod is equipped with one or more conveying devices, e.g., a screw which can be designed as a hollow screw or a solid screw, are also generally covered. Such connecting rods carrying a screw are implemented, for example, in progressive cavity pumps in the form of hopper pumps. This particular embodiment is not shown in the figures. However, the explanations in the figure description apply equally to the aforementioned, but not shown, embodiments.

[0025] A connecting housing 14 is arranged between the pump housing 4 and the drive 3. In the embodiment shown, this connecting housing 14 is Figuren 1 and 2designed as a so-called lantern. The connecting shaft 9 is arranged at least partially within this connecting housing 14. To ensure a liquid-tight separation of the pump housing 4 from the environment or from the drive 3, the connecting shaft 9 is sealed with a shaft seal 13, which can, for example, be designed as a mechanical seal.

[0026] According to the invention, at least two sensors 15, 16 are arranged in the area of ​​the connecting shaft 9 for detecting or measuring a runout deviation. These sensors are arranged in different angular positions offset from each other by an angular displacement and determine a movement profile of the connecting shaft 9 for a predetermined angular position by measuring the distance of the surface of the (cylindrical) connecting shaft 9 from the respective sensor 15, 16 at different angular positions. In the illustrated embodiment, two sensors 15, 16 are provided, arranged in different angular positions offset from each other by an angular displacement. In this embodiment, the angular displacement is approximately 90°. The sensors 15, 16 are, for example, designed as non-contact, inductive proximity sensors.

[0027] Under ideal conditions, the connecting shaft 9 – driven by the drive 3 – rotates centrally around its axis of rotation R. Since it has a circular cross-section, the distance of its surface from the fixed sensor 15, 16 does not change during rotation. Therefore, measuring this distance as a function of time, and consequently the angular position of the shaft 9, results in a constant signal. In practice, however, a runout deviation occurs, depending on the wear condition of various pump components. This runout deviation causes the sensor 15, 16 to measure different distances for different angular positions of the connecting shaft during operation. Using the sensor 15 or 16, or using the sensors 15, 16, a runout deviation can therefore be determined very easily and reliably, and this runout deviation can be used to infer the wear condition.For example, the measured values ​​can be compared with stored reference values, so that if a predefined deviation is exceeded, an error message is generated, displayed, and / or transmitted. The pump can be equipped with a (not shown) visual indicator. Alternatively or additionally, acoustic signals can be generated. The signal can also be transmitted to a pump controller, and the display can be managed by the controller. The sensors can be powered and / or the signals processed by a pump controller (e.g., a PLC).

[0028] While Fig. 1 Figure 1 shows an embodiment of an eccentric screw pump in which the connecting housing 14 is designed as a so-called lantern. Fig. 2 A modified embodiment of an eccentric screw pump in which the connecting housing 14 is designed as a bearing support. In particular in Fig. 4 The two sensors 15, 16, offset by 90°, are visible in the area of ​​the bearing support 14. These sensors detect and monitor any runout deviation of the (not visible) connecting shaft 9 (plug shaft). Removable covers, e.g., cover plates 8, are visible on the housing 14, to which, for example, a sensor 16 may be attached. The sensor 15 is attached to a fixed part of the housing 14. The drive 3 is, in the embodiment according to Fig. 3 and 4 not explicitly shown. It can be connected to the shaft pin 17.

Claims

1. A progressive cavity pump having at least - a stator (1), - a rotor (2) rotating in the stator (1), - a drive (3), - a pump housing (4) connected to the stator (1) and having at least one inlet or outlet opening for the medium to be pumped, - a connecting shaft (9) which is driven by the drive (3) and which, when the pump is operating in an ideal manner, rotates centrally about an axle (R), - a coupling rod (10) arranged, for example, in the pump housing (4), of which the drive-side end is connected in an articulated manner to the connecting shaft (9) and of which the rotor-side end is connected in an articulated manner to the rotor (2) and which generates an eccentric movement of the rotor end (7) during a central rotation of the connecting shaft (9), - a connecting housing (14) arranged between the pump housing (4) and the drive (3), wherein the connecting shaft (9) is arranged, at least in regions, in the connecting housing (14) and wherein the connecting shaft (9) is provided with a shaft seal (13) which seals the pump housing (4) in a fluid-tight manner with respect to the connecting housing (14), characterised in that at least two sensors (15, 16) are arranged in the region of the connecting shaft (9) in order to detect or measure a concentricity deviation, these sensors being arranged in different angular positions offset with respect to one another by an angular offset and each of these sensors determining a movement profile of the connecting shaft (9) by measuring the distance of the surface of the connecting shaft (9) from the respective sensor (15, 16) at different angular positions, wherein the sensors (15, 16) are arranged or fixed in or on the connecting housing (14).

2. The progressive cavity pump according to Claim 1, characterised in that the angular offset is at least 10° and / or at most 180°, preferably 30° to 150°, for example approximately 90°.

3. The progressive cavity pump according to Claim 1 or 2, characterised in that the sensors (15, 16) are designed as sensors (15, 16) operating without contact, e.g. as inductive or optical proximity sensors (15, 16).

4. The progressive cavity pump according to one of Claims 1 to 3, characterised in that the sensors (15, 16) are arranged, with respect to the axial extent of the pump, between the drive-side end of the connecting shaft (9) and the coupling-side shaft seal (13).

5. The progressive cavity pump according to one of Claims 1 to 4, characterised in that the connecting housing (14) is designed as a lantern or as a bearing frame.

6. A method for operating a progressive cavity pump according to one of Claims 1 to 5, characterised in that one movement profile of the connecting shaft (9) at different angular positions is determined in each case by means of the two sensors (15, 16) by measuring the distance of the surface of the connecting shaft (9) from the respective sensor (15, 16).

7. The method according to Claim 6, characterised in that the movement profiles are measured continuously.

8. The method according to Claim 6 or 7, characterised in that the movement profiles or the values measured by means of the sensors (15, 16) are compared with stored reference profiles or reference values and in that an error message is generated and / or displayed and / or transmitted when a predefined deviation is exceeded.