Method for regularly determining maintenance time

Abstract

The invention relates to a method for periodically determining the maintenance time of a submersible machine. Wherein the method comprises the following steps during each periodic determination:-updating at least one of said calendar time from the implementation of maintenance and said run time from the implementation of maintenance by:-monitoring a first operating parameter (OP1) affecting the calendar time from the implementation of maintenance; -comparing the first operating parameter value (OP1) with a default first operating parameter value (D-OP1), where a deviation in the comparison provides a calendar time adjustment factor proportional to the deviation; -adjusting the calendar time from implementation of the maintenance based on the calendar time adjustment factor; and-monitoring a second operating parameter (OP2) affecting the remaining run time of the machine; -comparing the second operating parameter value (OP2) with a default second operating parameter value (D-OP2), wherein a deviation in said comparison provides a run-time adjustment factor proportional to the deviation; -adjusting the runtime from the implementation of the maintenance on the basis of the runtime adjustment factor; and thereafter setting the run time of the machine from the implementation of the maintenance to the shortest one of the calendar time from the implementation of the maintenance and the run time from the implementation of the maintenance.

Description

Technical Field

[0001] The present invention generally relates to the field of methods for monitoring and controlling the operation of submersible machines (e.g., pumps and mixers), which are configured to pump, transport, and / or mix liquids containing solid substances, slurries, clear water, etc. In addition, the present invention relates to the field of methods for monitoring and controlling the operation of submersible pumps (e.g., sewage / wastewater pumps and drainage / dewatering pumps), which are particularly configured to pump liquids containing solid substances (e.g., sewage / wastewater, biomass slurries, drilling mud, clear water, etc.). In addition, the present invention relates to the field of methods for monitoring and controlling the operation of submersible mixers, which are particularly configured to transport / mix liquids (e.g., wastewater / sewage, biomass slurries, clear water, etc.).

[0002] Submersible machines can also operate in liquids that do not contain solid substances, and it should be noted that submersible machines must not be submerged during operation, but can be dry-mounted and / or partially submerged. Therefore, the term "submersible" only defines that the machine can be immersed in a liquid without being damaged, and submersible machines can be wet-mounted and / or dry-mounted, and are of the submersible type in both applications / installations.

[0003] The present invention specifically relates to a method for periodically determining the maintenance time of a submersible machine (i.e., the remaining time until maintenance is carried out), wherein the machine is associated with the calendar time until maintenance is carried out and the operating time until maintenance is carried out for each periodic determination, and the operating time until maintenance is carried out is based on the remaining operating time before maintenance is required and the historical utilization rate of the machine. Background Art

[0004] All such submersible machines need to be maintained from time to time, mainly due to wear, in order to maintain good efficiency and ensure the expected correct operation.

[0005] Today, maintenance intervals are in most cases the so-called fixed maintenance intervals, and are determined based on the maximum calendar time until maintenance is carried out (i.e., an interval with a fixed duration). The operator plans and implements maintenance for the machine before the end of the maximum calendar time until maintenance is carried out. In some complex facilities, the fixed maintenance interval may be shortened if the longest operating time between maintenance is reached before the end of the maximum calendar time until maintenance is carried out. For example, the maximum calendar time until maintenance is set to two years, and the longest operating time is set to 4000 hours of operation, and maintenance is carried out when one of these two thresholds is reached. Of course, different machines and different applications have appropriate maximum calendar times until maintenance is carried out and longest operating times, but these thresholds are fixed for a specific machine and application, and can be periodically updated after each maintenance is carried out.

[0006] In addition, it is conceivable that these machines also have different alarm functions, and due to unplanned downtime caused by different reasons, additional / urgent maintenance will be triggered between unplanned maintenance. These reasons may be imbalance and temperature rise.

[0007] Therefore, there is always a situation where scheduled / fixed maintenance is too early as a safety measure to prevent unplanned downtime, or too late as an emergency measure due to unplanned downtime.

[0008] Scheduled maintenance is costly, but unplanned maintenance is even more costly, and the processing / operation of pumping stations, treatment ponds, etc. will be affected by unplanned downtime, resulting in problems such as overflows and improper treatment.

[0009] Object of the Invention

[0010] The present invention aims to avoid the above-mentioned disadvantages and deficiencies of the previously known methods for periodically determining the maintenance time of submersible machines and to provide an improved method for periodically determining the maintenance time of submersible machines.

[0011] The main object of the present invention is to provide an improved method for periodically determining the maintenance time of submersible machines of an initially defined type such that maintenance is carried out when needed, i.e., neither too early nor too late. Therefore, the object of the present invention is to extend the maintenance interval as much as possible while minimizing the risk of unplanned downtime or completely avoiding the risk of unplanned downtime. Summary of the Invention

[0012] According to the present invention, the main object is at least achieved by an initially defined method having the features defined in the independent claims. Preferred embodiments of the present invention are further defined in the dependent claims.

[0013] According to the present invention, there is provided a method for periodically determining the maintenance time of a submersible machine, wherein the method comprises the following steps during each periodic determination:

[0014] - Updating at least one of the calendar time to maintenance and the running time to maintenance by the following steps:

[0015] - Monitoring a first operating parameter (OP1) that affects the calendar time to maintenance,

[0016] - Comparing the first operating parameter value (OP1) with a default first operating parameter value (D-OP1), wherein the deviation in the comparison provides a calendar time adjustment factor proportional to the deviation,

[0017] - Adjusting the calendar time to maintenance based on the calendar time adjustment factor, and

[0018] - Monitoring a second operating parameter (OP2) that affects the remaining operating time of the machine,

[0019] - Comparing the second operating parameter value (OP2) with a default second operating parameter value (D-OP2), wherein a deviation in the comparison provides a running time adjustment factor proportional to the deviation,

[0020] - Adjusting the running time until maintenance is performed based on the running time adjustment factor,

[0021] - Thereafter setting the maintenance time of the machine to the shorter of the calendar time until maintenance is performed and the running time until maintenance is performed.

[0022] Thus, the present invention is based on the inventors' insight that it is advantageous to be able to adjust and adapt the maintenance time, i.e., to employ a dynamic maintenance interval rather than a fixed maintenance interval. The general concept of a dynamic maintenance interval is to extend or shorten the calendar time until maintenance is performed and / or the running time until maintenance is performed according to the nature / characteristics of the actual operation of the diving machine. The nature / characteristics of the actual operation of the diving machine are determined by monitoring one or more operating parameters and comparing the operating parameter value with a default operating parameter value.

[0023] Thereby, both the calendar time until maintenance is performed and the running time until maintenance is performed are extended or shortened according to the nature / characteristics of the actual operation of the diving machine.

[0024] According to embodiments of the present invention, an operating parameter (OP1) that affects the calendar time until maintenance is performed is the temperature of the machine.

[0025] Thus, an increase in the machine temperature (e.g., due to unsatisfactory cooling effects caused by external dirt, internal blockages, increased power consumption, etc.) will directly affect the aging of the internal components / elements of the machine.

[0026] According to embodiments of the present invention, an operating parameter (OP1) that affects the calendar time until maintenance is performed is the machine vibration level when the machine is inactive.

[0027] Thus, the machine vibration when the machine is inactive / idling (i.e., not operating) is harmful / has a negative impact on the machine because, for example, lubrication is not properly distributed, resulting in misalignment of the rolling elements of the bearings and improper distribution of forces, and the internal components / elements of the machine may be damaged.

[0028] According to embodiments of the present invention, an operating parameter (OP2) that affects the running time until maintenance is performed is the operating speed of the machine.

[0029] Therefore, increasing the operating speed puts stress on the machine and directly affects the aging / wear of the internal components / elements of the machine.

[0030] Further advantages and features of the present invention will become apparent from the following detailed description of other dependent claims and preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other features and advantages of the present invention can be more fully understood from the following detailed description of the preferred embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 is a schematic cross-sectional view of an exemplary submersible pump,

[0033] Figure 2 is a schematic cross-sectional view of an exemplary submersible mixer,

[0034] Figure 3 is a schematic graph of an adjustment factor corresponding to the machine temperature,

[0035] Figure 4 is a schematic graph of an adjustment factor corresponding to the machine vibration when the machine is inactive,

[0036] Figure 5 is a schematic graph of an adjustment factor corresponding to the operating speed of the machine, and

[0037] Figure 6 is a schematic graph of an adjustment factor corresponding to the machine vibration when the machine is active. DETAILED DESCRIPTION

[0038] The present invention specifically relates to the field of methods for monitoring and controlling the operation of submersible machines (e.g., pumps and mixers configured for pumping, transporting, treating, and / or mixing liquids). Figure 1 A schematic cross-sectional view of an exemplary submersible pump (generally labeled 1) is disclosed, and Figure 2 a schematic cross-sectional view of an exemplary submersible mixer or flow generator (generally labeled 2) is disclosed. Here, the machine is a general term, while the pump / mixer is a specific term, and it should be noted that for the machines related to the present invention, unless otherwise stated / explicitly stated, all disclosures related to the pump are applicable to the mixer, and vice versa.

[0039] The pump 1 can be composed of a submersible sewage / wastewater pump or a submersible drainage / dewatering pump. First, refer to Figure 1 .

[0040] The pump 1 comprises two main parts: a drive unit (generally denoted by 3) and a hydraulic unit (generally denoted by 4). In addition, the pump 1 is also connected to a control unit 5. The control unit 5 monitors and controls the operation of the pump 1. In the disclosed embodiment, the control unit 5 is integrated into the pump 1 and forms part of the pump, i.e., the control unit 5 is located in the top unit 6 of the drive unit 3 of the pump 1. According to an alternative embodiment, the control unit 5 is constituted by a separate / external member and is operatively connected to the pump 1, or the control unit 5 is a combination of internal and external elements. A cable 7 extending from a power source (e.g., the power supply network) supplies power to the pump 1, and the pump 1 includes a liquid-tight conductor 8 for receiving the cable 7. The cable 7 may also include signal lines for data communication between the pump and any external control unit. The control unit 5 includes a variable frequency drive (VFD). The control unit 5 is configured to implement the method of the present invention.

[0041] The submersible pump 1 is configured to be fully submerged, but it should be noted that the submersible pump 1 may be partially or fully above the liquid level during operation. According to the disclosed embodiment, the pump 1 is cooled by the liquid / medium around the drive unit 3, but the pump 1 may also or alternatively be cooled by a cooling device including a cooling jacket surrounding at least a part of the pump 1.

[0042] The hydraulic unit 4 includes an impeller 9 configured to convey / pump liquid. The hydraulic unit 4 includes a pump housing 10 defining a volute 11 (also referred to as a pump chamber). In addition, the hydraulic unit 4 includes an inlet opening 12 and an outlet opening 13, with the volute 11 located between the inlet opening 12 and the outlet opening 13. The impeller 9 is located within the volute 11 and is configured to cause the liquid to move from the inlet opening 12 through the volute 11 to the outlet opening 13 when the submersible pump 1 is operating. According to the disclosed embodiment, the impeller 9 is a so-called open impeller, but the present invention is also applicable to a pump 1 having a so-called closed impeller. The open impeller 9 includes an upper shroud, a hub, and one or more vanes extending from the shroud and the hub. The closed impeller includes a lower shroud, with the vanes extending between the upper shroud and the lower shroud.

[0043] The drive unit 3 includes a drive unit housing 14 that defines a motor compartment 15, an electric motor 16 disposed within the motor compartment 15, and a drive shaft 17 that is connected to the electric motor 16 and driven to rotate by the electric motor. The electric motor 16 includes a stator 18 and a rotor 19, wherein the drive shaft 17 is connected to the rotor 19 of the electric motor 16 in a conventional manner. The drive shaft 17 extends from the electric motor 16 of the drive unit 3 to the hydraulic unit 4, wherein an impeller 9 is connected to the drive shaft 17 and is driven to rotate by the drive shaft during operation of the submersible pump 1. Accordingly, the pump 1 is configured to operate at a variable operating speed [rpm] by a control unit 5 configured to control the operating speed of the pump 1. The operating speed of the pump 1 is more precisely the rotational speed (rpm) of both the electric motor 16 and the impeller 9 and corresponds to / relates to the VFD output frequency.

[0044] The top unit 6 or the electronics / connection chamber is separated from the motor compartment 15 in a liquid-tight manner. The volute 11 is separated from the liquid-tight motor compartment 15 by a liquid seal chamber 20, thereby preventing the pumped liquid from reaching the motor compartment 15 along the drive shaft 17. Different housing parts of the pump 1 and the impeller 9 are preferably made of metal, such as aluminum and / or iron / steel.

[0045] Now referring Figure 2 , a mixer or flow generator 2 is disclosed, and the components of the mixer 2 corresponding to the components of the pump 1 are given the same reference numerals.

[0046] The mixer 2 is a submersible mixing machine and includes three main parts: a drive unit 3, a rotatable impeller / thruster 9, and a control unit 5. The control unit 5 monitors and controls the operation of the mixer 2. The drive unit 3 drives the thruster 9 to rotate, and the thruster 9 then pushes the liquid, i.e., provides a thrust to the liquid. The drive unit 3 and the thruster 9 are always part of the mixer 2, and in the disclosed embodiment, the control unit 5 is integrated into the mixer 2 and forms part of the mixer. In an alternative embodiment, the control unit 5 is constituted by a separate member and is operatively connected to the mixer 2. The mixer 2 is also commonly referred to as a mixing machine or a flow generator. In the disclosed embodiment, the mixer is configured to be fully submerged. It should be noted, however, that the submersible mixer 2 can be partially above the liquid level during operation. The mixer 2 is cooled by the liquid surrounding the drive unit 3.

[0047] A cable 7 extending from a power source (e.g., a power supply network) supplies power to the mixer 2, and the mixer 2 includes a liquid-tight electrical conductor 8 that receives the cable 7. The cable 7 can also include signal lines for data communication between the flow generator and an external control unit (not shown). The drive unit 3 includes an electric motor 16 and a drive shaft 17 that is connected to the electric motor 16 and is driven to rotate by the electric motor during operation of the mixer 2. The electric motor 8 conventionally includes a stator 18 and a rotor 19.

[0048] The electric motor 16 is located in the drive unit housing 14 and, in the disclosed embodiment, the thruster 9 is located in direct contact with the drive unit housing 14, which is a liquid-tight housing. However, in an alternative embodiment, the thruster 9 is located at a distance from the drive unit housing 14, i.e., the drive shaft 17 is visible between the drive unit housing 14 and the thruster 9.

[0049] The thruster 9 includes a hub 21 connected to the drive shaft 17 and a plurality of blades 22 connected to the hub 21, wherein the drive shaft 17 extends in the axial direction and each blade 22 extends in the radial direction from the base to the top. It should be noted that the blade 22 also has an extension in the axial direction, i.e., has a pitch, in order to generate a thrust on the liquid.

[0050] The control unit 5 is operatively connected to the electric motor 16 and is configured to monitor and control the operation of the mixer 2. The electric motor 16 is configured to be driven by the control unit 5. Thus, the control unit 5 is configured to control the rotational speed of the electric motor 16 of the mixer to be driven, for example, by controlling the frequency of the current operating the electric motor 16. According to the disclosed embodiment, the control unit 5 includes a variable frequency drive (VFD). Thus, the mixer 2 is configured to operate at a variable operating speed. The control unit 5 is configured to implement the method of the present invention.

[0051] The method of the present invention is used to periodically determine the maintenance time of a submersible machine, pump 1 or mixer 2. The maintenance time (i.e., the time remaining before maintenance is required / suggested in order to avoid unplanned downtime or at least to avoid inefficient operation of the machine) is equal to the shorter of the calendar time until maintenance is performed and the operating time until maintenance is performed. The calendar time until maintenance is performed is the required / suggested remaining time until maintenance is performed that is independent of the machine utilization rate. The utilization rate is expressed, for example, in terms of the number of hours per day the machine operates, the number of minutes per hour, etc. The operating time until maintenance is performed is based on the remaining operating time before maintenance is required and the historical utilization rate of the machine. Thus, the remaining operating time can be expressed, for example, in terms of the total number of hours, minutes, etc. that the machine can operate before maintenance is required / suggested. The remaining operating time, together with the historical utilization rate value of the machine, provides the required / suggested remaining time until maintenance is performed based on the utilization rate of the machine.

[0052] The historical utilization rate is, for example, an average value, a weighted average value, etc., and provides a good measure of the degree of future utilization of the machine. Thus, newer information about the historical usage rate may be more relevant than older information about the historical utilization rate.

[0053] The length of each period can be one second or more, one minute or more, one hour or more, etc.

[0054] At the start of each period, the machine is associated with the stored calendar time to implementation of maintenance and the stored running time to implementation of maintenance, and at the end of the period, the machine is associated with the updated calendar time to implementation of maintenance based on the calendar time consumed within the period and the updated running time to implementation of maintenance based on the running time consumed within the period. This method is correct and does not require adjustment of the maintenance plan when the machine is operating normally / optimally. However, when the operation of the machine deviates from the normal / optimal operation state, the maintenance plan must be adjusted according to the method of the present invention.

[0055] According to the method of the present invention, the following steps are implemented during each period determination:

[0056] - Update at least one of the calendar time to implementation of maintenance and the running time to implementation of maintenance by the following method:

[0057] - Monitor a first operating parameter (OP1) that affects the calendar time to implementation of maintenance,

[0058] - Compare the first operating parameter value (OP1) with the default first operating parameter value (D-OP1), wherein the deviation in the comparison provides a calendar time adjustment factor proportional to the deviation,

[0059] - Adjust the calendar time to implementation of maintenance based on the calendar time adjustment factor, and

[0060] - Monitor a second operating parameter (OP2) that affects the remaining running time of the machine,

[0061] - Compare the second operating parameter value (OP2) with the default second operating parameter value (D-OP2), wherein the deviation in the comparison provides a running time adjustment factor proportional to the deviation,

[0062] - Adjust the running time to implementation of maintenance based on the running time adjustment factor,

[0063] - Thereafter, set the maintenance time of the machine to be equal to the shorter of the calendar time to implementation of maintenance and the running time to implementation of maintenance.

[0064] Thus, during operation of the machine, pump or mixer, the control unit 5 monitors one or more operating parameters of the machine. Each operating parameter affects at least one of the calendar time until maintenance is carried out and the running time until maintenance is carried out. Each operating parameter has a default / rated operating parameter value, and this default / rated operating parameter value does not require adjustment of the maintenance time. That is to say, when the control unit 5 determines that the measured / monitored operating parameter value is equal to the corresponding default / rated value (without deviation), there is no need to adjust the calendar time until maintenance is carried out, the running time until maintenance is carried out, or the maintenance time. In other words, in this case, the adjustment factor is equal to 1.

[0065] In other cases, that is, when the control unit 5 determines that there is a deviation between the measured / monitored operating parameter value and the default / rated operating parameter value, the control unit 5 will establish an adjustment factor that is not equal to 1. The adjustment factor is proportional to the deviation and is different for all monitored operating parameters. If the adjustment factor provided by the deviation between the measured / monitored operating parameter value and the default / rated operating parameter value is greater than 1, the instantaneous operation of the machine is more favorable than normal operation, thereby extending the calendar time until maintenance is carried out and / or the running time until maintenance is carried out. If the adjustment factor provided by the deviation between the measured / monitored operating parameter value and the default / rated operating parameter value is less than 1, the instantaneous operation of the machine is less favorable than normal operation, thereby shortening the calendar time until maintenance is carried out and / or the running time until maintenance is carried out.

[0066] According to various embodiments, the ratio or relationship between the value deviation of a specific operating parameter and the corresponding adjustment factor is provided by a look-up table. According to other embodiments, the ratio or relationship is provided by a mathematical relationship / formula / curve as Figures 3 to 6 shown.

[0067] Therefore, such an embodiment includes monitoring one or more operating parameters that directly affect the running time until maintenance is carried out, and includes monitoring one or more operating parameters that directly affect the calendar time until maintenance is carried out.

[0068] According to a preferred embodiment of the present invention, the step of updating the running time until maintenance is carried out is implemented by the following sub-steps,

[0069] - Monitor a second operating parameter (OP2) that affects the remaining running time of the machine,

[0070] - Compare the second operating parameter value (OP2) with the default second operating parameter value (D-OP2), wherein the deviation in the comparison provides a running time adjustment factor proportional to the deviation,

[0071] - Adjust the running time until maintenance is carried out based on the running time adjustment factor, as follows:

[0072] - Adjust the remaining operating time based on the operating time adjustment factor, and

[0073] - Adjust the operating time until maintenance is performed based on the adjusted remaining operating time and the historical utilization rate of the machine.

[0074] Therefore, adjust (i.e., increase or decrease) the remaining available operating time before maintenance is required / requested, and thereby the operating time until maintenance is performed can be determined based on the historical utilization rate and the updated remaining operating time.

[0075] According to various embodiments, the adjustment of the remaining operating time includes multiplying the remaining operating time by the operating time adjustment factor, and the adjustment of the calendar time until maintenance is performed includes multiplying the calendar time until maintenance is performed by the calendar time adjustment factor.

[0076] Now refer to Figure 3 , which discloses an illustrative example of the correlation between the adjustment factors of the operating parameters that have a direct impact on the calendar time until maintenance is performed. The operating parameter (OP1) that affects the calendar time until maintenance is performed is the temperature of the machine.

[0077] Figure 3 shows the correlation between the adjustment factor and the temperature of the bearing 23 of the drive shaft 17 of the machine (i.e., the lubrication temperature of the bearing 23). The function of the bearing 23 depends on the lubrication condition of the bearing 23, and lubrication is sensitive to elevated temperatures because an increase in temperature can cause premature aging and deterioration of the lubrication. The temperature of the machine can also alternatively be measured at the control unit 5 of the machine, the electric motor 16 of the machine, etc. Such measurements / temperatures may have a specific correlation with the temperature of the bearing 23, whereby the correlation between the adjustment factor according to Figure 3 and the temperature of the bearing 23 of the drive shaft 17 of the machine can be used, or such measurements / temperatures can have their own correlation with the adjustment factor.

[0078] According to Figure 3 , the X-axis contains the relative temperature with respect to the default / rated operating parameter value, i.e., the value on the X-axis is multiplied by the default / rated operating parameter value. The Y-axis contains the corresponding adjustment factor. When the machine temperature is equal to the default / rated temperature, the adjustment factor is equal to 1. According to the shown example, the correlation / curve graph can be defined by the following formula, where each term is rounded: Temperature adjustment factor = 0.72*T^4 - 1.06*T^3 - 1.24*T^2 + 0.19*T + 2.49.

[0079] Default / rated operating parameter value (D-OP1), i.e., the temperature of bearing 23 is equal to or higher than 80 degrees Celsius and equal to or lower than 100 degrees Celsius, preferably equal to or greater than 85 degrees Celsius and equal to or less than 95 degrees Celsius. In the disclosed embodiment, the default operating parameter value (D-OP1) is 90 degrees Celsius.

[0080] Now refer to Figure 4 , which discloses an example illustration of the correlation between adjustment factors of another operating parameter that has a direct impact on the calendar time until maintenance is carried out. The operating parameter (OP1) that affects the calendar time until maintenance is the level of machine vibration when the machine is inactive. The machine vibration when the machine is inactive / idling has a negative impact on the machine because the lubrication in bearing 23 is not properly distributed and thus the rolling elements of bearing 23 are misaligned and the forces are not properly distributed and bearing 23 may be damaged.

[0081] According to Figure 4 , the X-axis contains the true vibration of the machine measured in millimeters per second. The Y-axis contains the corresponding adjustment factor. When the vibration of the inactive machine is equal to the default / rated vibration, the adjustment factor is equal to 1. The default / rated operating parameter value (D-OP1), i.e., the vibration of the inactive machine is 0 mm / s.

[0082] According to the example shown, the correlation / curve graph can be defined by the following set of formulas, where the terms are all rounded:

[0083] Inactive vibration adjustment factor (vibration range from 0 mm / s to 5 mm / s) =

[0084] -0.02 * VR + 1

[0085] Inactive vibration adjustment factor (vibration range from 5 mm / s to 10 mm / s) =

[0086] -0.016 * VR + 1.669

[0087] Inactive vibration adjustment factor (vibration range from 10 mm / s to 15 mm / s) =

[0088] -0.02 * VR + 0.3

[0089] Inactive vibration adjustment factor (vibration exceeding 15 mm / s) = 0

[0090] Default / rated operating parameter value (D-OP1), i.e., the vibration level of the inactive machine is greater than or equal to 0 mm / s and less than or equal to 5 mm / s, preferably less than or equal to 2 mm / s. The vibration of the machine is measured at the control unit 5 of the machine and / or at the bearing 23 of the machine.

[0091] Now refer to Figure 5, which discloses an exemplary illustration of the correlation between adjustment factors of operating parameters that directly affect the runtime until maintenance is carried out. The operating parameter (OP2) that affects the runtime until maintenance is carried out is the operating speed / frequency of the machine.

[0092] According to Figure 5 , the X-axis contains the relative operating speed of the machine with respect to the default / rated operating parameter value, i.e., the value on the X-axis is multiplied by the default / rated operating parameter value. The Y-axis contains the corresponding adjustment factor. When the operating speed of the machine is equal to the default / rated operating speed, the adjustment factor is equal to 1. According to the example shown, the correlation / curve graph can be defined by the following formula, where each term is rounded: Operating speed adjustment factor = -1.48*OS^3 + 2.06*OS^2 – 2.66*OS + 3.08.

[0093] The rated / nominal operating speeds of different machines typically vary in the range of 200 rpm to 6000 rpm. The default / rated operating parameter value (D-OP2) is greater than or equal to 90% of the nominal operating speed of the machine and less than or equal to 110% of the nominal operating speed, preferably greater than or equal to 95% of the nominal operating speed and less than or equal to 105% of the nominal operating speed. In the disclosed embodiment, the default operating parameter value (D-OP2) is 100% of the nominal operating speed of the machine.

[0094] Now refer to Figure 6 , which discloses an example illustration of the correlation between adjustment factors of another operating parameter that directly affects the runtime until maintenance is carried out. The operating parameter (OP2) that affects the runtime until maintenance is carried out is the level of machine vibration when the machine is active.

[0095] According to Figure 6 , the X-axis contains the true vibration of the machine measured in millimeters per second. The Y-axis contains the corresponding adjustment factor. When the vibration when the machine is active is equal to the default / rated vibration, the adjustment factor is equal to 1. The default / rated operating parameter value (D-OP2), i.e., the vibration when the machine is active, is approximately 7 mm / s.

[0096] According to the example shown, the correlation / curve graph can be defined by the following formula, where each term has been rounded: Active vibration adjustment factor = -0.0001*VR^3 + 0.002*VR^2 - 0.017*VR + 1.016.

[0097] Assuming the operating parameter is the vibration level of the machine in operation, the default operating parameter value (D-OP2) is equal to or greater than 5 mm / s and equal to or less than 15 mm / s, preferably equal to or less than 10 mm / s. The vibration of the machine is measured at the control unit 5 of the machine and / or at the bearing 23 of the machine.

[0098] Feasible Modifications of the Present Invention

[0099] The present invention is not limited to the embodiments described above and shown in the drawings, which are mainly for illustrative and exemplary purposes. This patent application aims to cover all adjustments and variations of the preferred embodiments described herein. Therefore, the present invention is defined by the wording of the appended claims, and thus the device can be modified in various ways within the scope of the appended claims.

[0100] It should also be noted that all information regarding terms such as upper, lower, upper part, lower part, etc. should be interpreted / read with the equipment in the orientation of the drawings, and the drawings are oriented such that the reference numerals are correctly read. Therefore, these terms only represent the mutual relationships in the illustrated embodiments, and these relationships may change if the device of the present invention has another structure / design.

[0101] It should also be noted that even if it is not explicitly stated that features from a particular embodiment can be combined with features from another embodiment, if such a combination is feasible, then such a combination should be considered obvious.

Claims

1. A method for periodically determining the maintenance time of a diving machine (1, 2), wherein for each periodic determination, the diving machine is associated with a calendar time until maintenance is carried out and a running time until maintenance is carried out, and wherein the running time until maintenance is carried out is based on the remaining running time before maintenance is required and the historical utilization rate of the diving machine. Among them, The method is characterized in that the following steps are carried out during each periodic determination: - Update at least one of the calendar time until maintenance is carried out and the running time until maintenance is carried out by the following steps: - Monitor a first operating parameter (OP1) that affects the calendar time until maintenance is carried out. - Compare the value of the first operating parameter (OP1) with a default first operating parameter value (D-OP1), wherein the deviation in the comparison provides a calendar time adjustment factor proportional to the deviation. - Adjust the calendar time until maintenance is carried out based on the calendar time adjustment factor. And - Monitor a second operating parameter (OP2) that affects the remaining running time of the diving machine. - Compare the value of the second operating parameter (OP2) with a default second operating parameter value (D-OP2), wherein the deviation in the comparison provides a running time adjustment factor proportional to the deviation. - Adjust the running time until maintenance is carried out based on the running time adjustment factor. - Thereafter, set the maintenance time of the diving machine to the shorter of the calendar time until maintenance is carried out and the running time until maintenance is carried out.

2. The method according to claim 1, characterized in that, During each step of updating the running time until maintenance is carried out, the method includes the following sub-steps: - Monitor a second operating parameter (OP2) that affects the remaining running time of the diving machine. - Compare the value of the second operating parameter (OP2) with a default second operating parameter value (D-OP2), wherein the deviation in the comparison provides a running time adjustment factor proportional to the deviation. - Adjust the running time until maintenance is carried out based on the running time adjustment factor by the following steps: - Adjust the remaining running time based on the running time adjustment factor, and - Adjust the running time until maintenance is carried out based on the adjusted remaining running time and the historical utilization rate of the diving machine.

3. The method according to claim 2, wherein The adjustment of the remaining running time includes multiplying the remaining running time by the running time adjustment factor.

4. The method according to claim 1, wherein The adjustment of the calendar time until maintenance is carried out includes multiplying the calendar time until maintenance is carried out by the calendar time adjustment factor.

5. The method according to any one of the preceding claims, characterized in that, The first operating parameter (OP1) that affects the calendar time until maintenance is carried out is the temperature of the diving machine (1, 2).

6. The method according to claim 5, characterized in that Assuming that the first operating parameter is the temperature of the diving machine, the default first operating parameter value (D-OP1) is equal to or greater than 85 °C and equal to or less than 95 °C.

7. The method according to claim 5 or 6, characterized in that, Measure the temperature at the electric motor (16) of the diving machine, the bearing (23) of the diving machine, or the control unit (5) of the diving machine.

8. The method according to any one of the preceding claims, characterized in that, The first operating parameter (OP1) affecting the calendar time until maintenance is carried out is the vibration level of the submersible machine when the submersible machine is in an inactive state.

9. The method according to claim 8, wherein Assuming that the first operating parameter is the vibration level of the inactive submersible machine, the default first operating parameter value (D-OP1) is greater than or equal to 0 mm / s and less than or equal to 5 mm / s, preferably less than or equal to 2 mm / s.

10. The method according to claim 8 or 9, characterized in that, The vibration level is measured at the control unit (5) of the submersible machine.

11. The method according to any one of the preceding claims, characterized in that The second operating parameter (OP2) affecting the running time until maintenance is carried out is the operating speed of the submersible machine.

12. The method according to claim 11, wherein Assuming that the second operating parameter is the operating speed of the submersible machine, the default second operating parameter value (D-OP2) is equal to or greater than 90% of the rated operating speed and equal to or less than 110% of the rated operating speed, preferably equal to or greater than 95% of the rated operating speed and equal to or less than 105% of the rated operating speed.

13. The method according to any one of the preceding claims, characterized in that, The second operating parameter (OP2) affecting the running time until maintenance is carried out is the vibration level of the submersible machine when the submersible machine is running.

14. The method according to claim 13, wherein Assuming that the second operating parameter is the vibration level of the submersible machine when running, the default second operating parameter value (D-OP2) is equal to or greater than 5 mm / s and equal to or less than 15 mm / s, preferably less than or equal to 10 mm / s.

15. The method according to claim 13 or 14, characterized in that, The vibration level is measured at the control unit (5) of the submersible machine.

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